JPH061983B2 - Power converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power converter, and more particularly to a power converter suitable for a converter that performs pulse width control.

[Conventional technology]

From the viewpoint of improving the power factor of a converter, Japanese Patent Laid-Open No. 56-162976 discloses a method in which a controllable switching element having a current interruption function is connected to an arm and pulse width control and phase control are used together. Annual Meeting of the Institute of Electrical Engineers of Japan No.45
3, a method using only pulse width control is proposed. However, in both cases, it is necessary to synchronize with the power supply voltage for converter control. In the conventional technology, as a means for performing this synchronous pull-in, a pulse train is generated by using a synchronization signal generated when one phase of the AC power supply voltage changes from negative to positive and crosses zero voltage as a trigger (only pulse width control). In this case, a method of executing a series of pulse generation processing in synchronization with a synchronization signal has been used, such as activating a phase control system prior to pulse train generation (when phase control is also used). However, in such a synchronization technique, when the synchronization signal is generated, the synchronization is forcibly performed regardless of what kind of pulse train is currently generated. However, there is a sufficient situation in which a firing command is generated for a certain converter element, but the firing command must be immediately generated by the synchronization process. From the point of securing the minimum pulse width given to the converter element ( (Because it is necessary to prevent), JP-A-59-103579
There is room for improvement in simplicity in constructing a system, such as the need to provide an additional circuit as shown in the publication.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, the simplicity of the entire system including the minimum pulse width ensuring circuit is not taken into consideration, and there is a problem that the minimum pulse width ensuring circuit is indispensable for the system.

An object of the present invention is to provide a power converter that can eliminate the need for a complicated minimum pulse width ensuring circuit.

[Means for solving problems]

The above-mentioned object is a converter that converts direct current into alternating current power,
A pattern generator for giving a pulse pattern to the converter at a constant cycle asynchronously with the power source, and a synchronizer for correcting the numerical value used in the pattern generator according to a synchronization signal obtained from the AC power source. age,
The pulse pattern generation process is performed asynchronously with the synchronization process, and the phase value for pulse pattern calculation is initialized according to the elapsed time from the generation of the synchronization signal.

[Operation] The pulse pattern generation process operates as if it is unrelated to the synchronization process. As a result, the pulse pattern generation process does not perform synchronization instantaneously but executes it with some dead time, so that an additional circuit such as a pulse width securing circuit is unnecessary.

〔Example〕

Hereinafter, the present invention will be described with reference to FIGS. 1, 2, 6, 8 and 10.
~ The embodiment shown in Fig. 13 and Figs. 3 to 5 and 7
This will be described in detail with reference to FIGS.

FIG. 1 is an overall configuration diagram showing an embodiment of a power conversion device of the present invention. Moreover, the whole structure is demonstrated. 1
Is an AC power supply for supplying power to the converter 2, 3 is a current detector for detecting the DC output current of the converter 2, and 4 is L
-R load, 5 is an input terminal of the direct current command I *, 6 is a comparator for obtaining a deviation Δi between the command I * and the feedback value _if , 7 is a voltage detector for detecting an AC voltage level, 8 is an AC voltage A waveform shaping circuit that generates a pulse when the value crosses zero,
9 is the pattern generator 1 when the zero-cross pulse U ↑ is generated.
A synchronizing device 10 for correcting the contents of the integrated value storage register of the frequency command ω * inside 0 is a pattern generating device 10 for generating an extinguishing pattern in the constituent elements of the converter 2. The pattern generator 10 integrates the function generator 110 for generating the second phase command PH ₂ * and the conduction ratio command PU * according to the current deviation Δi, and the power supply frequency command ω * at regular intervals,
While creating a first phase command PH ₁ *, theta depending on overall phase generating means 120, total phase command theta _T * values to create a total phase command theta _T * from the second phase command PH ₂ * _T * is 0
60 °, 60-120 °, 120-180 °, 180-
Of the six regions of 240 °, 240 to 300 °, and 300 to 360 °, the region determination means 130 for determining which region is included, the determination information Mo, the total phase command θ _T *, the flow rate command PU *. It is composed of a distribution device 140 and the like which decides which pulse pattern should be given to which control element. 21 to 26 are control elements of the converter 2.

Next, the operation will be specifically described. Since each device and means is realized by a microcomputer, the operation of each device and means will be described with reference to a flowchart.

FIG. 2 is a schematic flow chart showing an embodiment of the processing of the synchronization device 9 and the pattern generation device 10 of FIG. 1, which are the two main processes, (a) is a synchronization process, and (b) is a pattern. The generation process is shown.

First, the synchronization processing will be described. Since the synchronization process is started by the zero-cross pulse U ↑ of the power supply, if there is no fluctuation in the power supply and a 50Hz power supply is used,
This subroutine will be executed every 20 msec. The main processing of this subroutine is that the data necessary for initializing the _first phase command PH ₁ * obtained by integrating the frequency command ω * of the power source for each constant time Δt, that is, the zero-cross pulse of the power source is It is to save the time when it occurred. How to use the data stored by this synchronization processing to create the initialization data of the _first phase command PH ₁ * will be described in detail in the pattern generation processing.

Further, in this synchronization processing, the zero-cross pulse may be taken into the microprocessor as an interrupt signal and operated as the interrupt processing, or the edge of the zero-cross pulse is detected by the transient detector, and the time at this time is checked by the separate timer, The value is stored in FIFO RAM (f
The processing to be stored in the irst in first out RAM) may be non-interrupt processing that causes the peripheral circuit unit to be executed. In the following description, the case of interrupt processing will be described as an example.

Process 91 is an additional process for making it difficult for the synchronization process to malfunction with respect to the disturbance. That is, when the ideal zero-cross pulse is input, the phase command PH ₁ * should approach the electrical angle of 360 °. This PH ₁ *
The interrupt received when the value of is far from 360 ° is returned to the interrupt waiting state without performing the synchronization process. This additional processing can prevent malfunction of the synchronization processing.

FIG. 3 is a diagram showing an example in which such a phenomenon occurs,
(A) shows an ideal case and (b) shows a case where an erroneous zero-cross pulse is generated. There is no guarantee that the power supply voltage waveform v _U is always in the state as shown in (a), and it is fully conceivable that noise is superimposed as shown in (b), and the erroneous zero-cross pulse at this time causes the synchronization processing to be performed each time. If done, normal pattern generation cannot be expected.

Process 92 is a process of storing the time of occurrence of the zero-cross pulse.

Next, the pattern generation process will be described. This pattern generation process is a timer interrupt task that is activated almost every fixed time Δt. By this task, the converter element is turned on and off every Δt, so the switching frequency of the converter 2 is determined by this value, and 1 / Δt
(Hz).

Furthermore, if Δt is determined so that 20 msec / Δt becomes an integer, a timer interrupt is set so as to synchronize with the zero-cross pulse, and if the power supply does not cause frequency fluctuation, this pattern generation process is synchronized with the synchronization process. However, this pattern generation process can be said to be activated asynchronously with the power supply, since frequency fluctuations and the like will always occur.

The activation timing of both tasks is shown in FIG. FIG. 4A shows a pulse signal from the pattern generator 10, FIG. 4B shows a pulse signal from the synchronizer 9, and T ₁
The pulse signal from the synchronization device 9 at the time point interrupts the pattern generation device 10 to hold the time of zero cross generation. If this interrupt is before the calculation of the total phase command θ _T * in the pattern generation device 10, Synchronous operation is shown in Figure 4 (a) *
After the calculation of θ _T *, the synchronous operation is delayed by the timer interrupt, and is reflected in the pattern generation at * 2. Then, so that Again if the time held in the zero crossing occurs at T ₂ time is performed * 3 pattern generating synchronization is reflected.

Next, the processing content will be described in detail. Fig. 2 (b)
The process 110 is a function generating process for generating the conduction coefficient command PU * and the second phase command PH ₂ * according to the current deviation Δi, as shown in FIG. The phase control operates in the region β in which Δi is small, and the pulse width control operates in the region α in which the absolute value of Δi is large. Further, here, the minimum conduction ratio PU _min is set, but this value is a numerical value linked to the above-mentioned minimum pulse width. Since this value itself is not affected by the synchronization processing, if PU * _min is secured, the minimum pulse width can be secured without an additional circuit. Needless to say, the second phase command PH ₂ * is not necessary for applications in which phase control is unnecessary only by pulse width control, and the essence of the present invention regarding synchronization is not affected.

The process 120 is a total phase creation process, and details thereof will be described in the sixth section.
An example is shown in the figure. Process 121 determines whether or not a zero-cross pulse is generated, and if not, process 1
At 22, the power phase frequency command ω * multiplied by the gain k is added to the previous phase command PH ₁ * to obtain the current phase command PH 1
Ask for ₁ *. On the other hand, when there is the generation of the zero cross pulse, calculates the elapsed time T _p up to the current zero-crossing occurs in the processing 123. At this time, the zero-cross pulse generation time data stored by the interrupt or the function of the peripheral circuit unit when the zero-cross pulse is generated is used. Next, in process 124, initial data for the phase command PH ₁ * is created by the following equation.

PH ₁ * = T _p / Δt · k · ω * (1) where Δt; integration interval process 125 rewrites the previous PH ₁ * to the current PH ₁ * and prepares for the next integration. . Then, in process 126, the total phase command θ _T * is obtained from the current first phase command PH ₁ * and second phase command PH ₂ *. Here, the power supply frequency command ω * is 50 Hz or 60 Hz because it is the power supply frequency. Furthermore, when only pulse width control is used and phase control is not performed,
The process 126 becomes unnecessary.

FIG. 7 is an explanatory diagram of a state in which the phase command PH ₁ * is created. FIG. 7 (a) shows a state in which the phase command PH ₁ * is integrated by kω * in the pattern generation process that is started every Δt. On the other hand, FIG. 7 (b) shows the state of the phase command PH ₁ * when the synchronization processing occurs on the way, and the elapsed time T _P from the generation of the synchronization processing to the next pattern generation processing is shown. Corresponding to the initial data (T _P / Δt · kω
By storing *) in the phase command PH ₁ *, synchronization is performed, and in the subsequent pattern generation processing, k · ω * is added and integration is performed based on this. In this way, the generation of the synchronization signal and the pattern generation processing are operated asynchronously, and the synchronization with the power supply is realized by correcting the phase command PH ₁ *.

The process 130 of FIG. 2B is a process of determining which region of the electrical angle 360 ° the pulse should be issued by using the total phase command θ _T *. An example of the detailed processing is shown in the flowchart of FIG. First, process 1
In (31), it is checked (Mo) in which 60 ° section of the electrical angle 360 ° the value of the total phase command θ _T * lies. According to this determination, among the converter constituent elements, the element to be continuously fired for Δt, the element to be short-circuited, the short-circuiting element is extinguished, and the first ignition element and the first ignition element to be subsequently fired. An element to be extinguished during this Δt time is determined, such as a second ignition element to extinguish the element and then fire again. Further, processing 13
Or 2 theta _T * exists in which Δt interval of 60 ° interval examined (st). If Δt = 555.6 μsec, it can be seen that there are 6 Δt sections within the 60 ° section (when the power source is 50 Hz). If you know this st,
You will know which data table to use when searching for the extinction time. Although a method capable of realizing sinusoidalization (unequal pulse) has been described here as an example, this processing 132 is not necessary when equal pulses are sufficient.

Next, the pulse distribution processing 140 of FIG. 2B will be described. First, if the 60 ° region of the total phase command θ _T * is known by the region determination processing 130, the element to be extinguished can be known as shown in Table 1. next,
It suffices to know the time of the extinguishing, but the conduction ratio command PU * is used for this. Here, the total phase command θ _T * is 0
An example will be described in the case of being in the -60 ° section. Further, if the switching frequency is 1.8 kHz, the 60 ° section is further composed of six stages. If θ _T * is on the first stage, Assuming that the flow rate command PU * = 0.6, by referring to the flow rate versus extinction ignition time table shown in FIG. 9, the contents of the distribution processing of the following (1) to (4) can be understood. .

(1) The element 25 is constantly fired during Δt (2) The short-circuit element 22 is fired while t <t ₁ and the elements 21, 2
3, 24 and 26 are extinguished (3) The element 23 is ignited while t ₁ ≤t ≤t ₂ and the elements 21, 2 and
2, 24 and 26 are extinguished (4) The element 21 is ignited while t ₂ ≤t <Δt, and the elements 22 and 2 are turned on.
Arcs 3, 24 and 26 are extinguished. The set values of l _{1 to} l ₆ are data obtained by calculation in advance in order to convert the output into a sine wave, but this value limits the essence of the present invention. Not a thing.

As described above, in the pulse distribution processing 140, the element to be extinguished is checked in the processing 141, the specific time is checked in the processing 142, and output in the processing 143 as in the flowchart shown in the embodiment of FIG. Performs pulse distribution by scheduling ports.

Thus, according to the present embodiment, the pattern generation process is
Although the data is modified based on the power supply synchronization process, it is not affected by the pattern generation itself, so the minimum pulse width determined in the pattern generation process is not affected by the synchronization process. Absent. As a result, in the present embodiment, there is an effect that no additional circuit such as the minimum pulse width ensuring circuit is required.

11 to 13 show another embodiment of the present invention, which corresponds to FIG. 1 and FIG. 2, respectively, and processing 1 of FIG.
It is a flowchart which shows the detail of 50. In this embodiment, the synchronization process is performed every 60 electrical degrees. The circuit configuration is as shown in FIG.
The power supply voltage is taken in as three phases, and different from FIG. 1 in that the zero-cross points of rising and falling of the voltage of each phase are used as triggers for the synchronization processing, and the other points are the same.

FIG. 12 is a flow chart showing an embodiment of processing in the synchronization device 9 and the pattern generation device 10 in FIG.
12A shows the processing in the synchronizing device 9, and FIG. 12B shows the processing in the pattern generating device 10. The difference from FIG. 2 is that in FIG. 12A, the processing 91 in FIG. In the process 93, the synchronization process is performed once for the electrical angle of 360 ° in the process 91, whereas the zero cross pulse is input for each 60 ° of the electrical angle in the process 93.
A process 92 for validating the storage process of the zero-cross pulse generation time is performed in the vicinity thereof, and a process 150 is added in FIG.
_{The 1} * initialization has a base phase value of 0 °,
60 °, 120 °, 180 °, 240 °, 300 ° and 6
However, since the PH ₁ * correction processing of the processing 150 is somewhat complicated, the synchronization is performed once every 3.3 msec as compared with the method described above, which only synchronizes once every 20 msec. Therefore, the effect is increased to reduce the ripple of the output current.

FIG. 13 is a flow chart showing a specific example of initialization creation of the phase command PH ₁ * in the process 150 of FIG. 12 (b). In process 1501, the elapsed time T _p from the occurrence of the zero cross is obtained, and in process 1502 the variable data PH ₁₀ * of the initialization data is obtained. Up to this point, the process is the same as the processes 123 and 124 in FIG. 6, but the process is slightly different. In process 1503, it is checked whether the phase command PH ₁ * is smaller than the electrical angle of 30 °. If it is smaller, the variable command data PH _{10 is} added to the phase command PH ₁ * in processing 1504.
Add * and 0 ° and substitute. If not smaller, process 1
At 505, it is compared whether or not PH ₁ * is smaller than 90 °.
It is determined that it is the fall of the W phase that occurs in the vicinity of °, and the phase command PH ₁ * is substituted with PH ₁₀ * and 60 °. Similarly, processes 1508, 1510, 151 corresponding to zero-cross signals of V phase rising, U phase falling, W phase rising, V phase falling, and U phase rising.
2, 1513, the initial data set of the phase command PH ₁ * is executed.

As described above, according to this embodiment, although the soft processing is slightly complicated, the synchronization is frequently performed, so that the improvement of the output current characteristic can be expected.

〔The invention's effect〕

As described above, according to the present invention, since the pulse generation process can achieve the synchronization without being directly influenced by the synchronization process, it is not necessary to provide an additional circuit such as a minimum pulse width ensuring circuit. There is an effect.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a power conversion device of the present invention, FIG. 2 is a schematic flow chart showing an embodiment of processing of a synchronization device and a pattern generation device of FIG. 1, and FIG. FIG. 5 is a diagram showing power supply voltage waveforms, FIG. 4 is a diagram showing start timings of the synchronizing device and the pattern generating device of FIG. 1, and FIG.
FIG. 7 is an explanatory diagram of the process 110 in FIG. 2, FIG. 6 is a flowchart showing an example of the details of the process 120 in FIG. 2, and FIG.
FIG. 8 is an explanatory view showing a state in which the phase command PH ₁ * is created, FIG. 8 is a flowchart showing an embodiment of the details of the processing 130 of FIG. 2, and FIG. 9 is a conduction ratio vs extinction ignition time table. FIG. 10 is a flow chart showing an example of details of the process 140 of FIG. 2, FIG. 11 is an overall configuration diagram corresponding to FIG. 1 showing another embodiment of the present invention, and FIG. In the case of the figure, a schematic flow chart corresponding to FIG. 2 is shown, and FIG. 13 is a flow chart showing a concrete example of initialization creation of the phase command PH ₁ * in the process 150 of FIG. 2 ... converter, 7 ... voltage detector, 8 ... waveform shaping circuit,
9 ... Synchronizing device, 10 ... Pattern generating device, 110 ... Function generating means, 120 ... Total phase creating means, 130 ... Region determination means, 140 ... Distributing device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Sasaki 4026 Kujimachi, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Ltd. (72) Masayuki Hirose 1070 Ichige, Katsuta City, Ibaraki Hitachi Ltd. Mito Corporation In the factory (56) Reference JP 62-171470 (JP, A) JP 56-162976 (JP, A) JP 59-103579 (JP, A)

Claims (7)

[Claims] 1. A converter for converting an AC power supply into a DC power,
A pattern generator that gives a pulse pattern to the converter at a constant cycle asynchronously with the AC power source, and a synchronizer that corrects a numerical value used in the pattern generator according to a synchronization signal obtained from the AC power source. A power conversion device characterized by the following. 2. The numerical value corrected by the synchronizer is
The power conversion device according to claim 1, wherein the phase angle is a phase angle from a synchronization point at which the synchronization signal is generated. 3. The power converter according to claim 2, wherein the phase angle is a numerical value obtained by integrating the power supply frequency of the AC power supply at regular intervals. 4. The synchronization signal is a signal generated at a moment when one phase of the AC power supply crosses a zero voltage from a negative voltage to a positive voltage, and the synchronization signal is a signal according to claim 1, claim 2, or claim 3.
The power converter according to the item. 5. The pattern generator includes phase information including the phase angle of electrical angles 0 to 60 °, 60 to 120 °, 12
0-180 °, 180-240 °, 240-300 °,
Region determination means for determining which region of 300 to 360 ° is included, deviation between the current command and the feedback value of the DC current converted by the converter, and converter configuration to be extinguished from the region determination means The power conversion device according to claim 1, comprising a device and a distribution device that determines an extinction period. 6. The power conversion device according to claim 2, wherein the phase angle correction means sets a value according to an elapsed time from the generation of the synchronization signal to the integration processing. 7. The power conversion device according to claim 5, wherein the phase information is a sum of a phase angle from the synchronization point and a second phase angle determined according to the current deviation.