阅读说明：本技术 电力变换装置 (power conversion device ) 是由 埴冈翔太 家泽雅宏 于 2017-05-09 设计创作，主要内容包括：控制电力变换电路(1)内的开关元件(2、3)的控制装置(20)具备：模式生成部(20),生成频率变化模式(25)；以及控制器(22)。模式生成部(20)使用n个第一频率fc和比该n个第一频率fc彼此之差的最小值小的第二频率fdef,对于2n个开关频率f,以转变前后的两个开关频率f的中值与各所述开关频率f的值不重叠的方式决定转变顺序而生成频率变化模式(25),所述2n个开关频率f是对各第一频率fc加上第二频率fdef以及从各第一频率fc减去第二频率fdef而决定的。控制器(22)根据频率变化模式(25),将2n个开关频率f各个使用不同的持续时间,生成对开关元件(2、3)的控制信号G。(A control device (20) for controlling switching elements (2, 3) in a power conversion circuit (1) is provided with: a pattern generation unit (20) that generates a frequency change pattern (25); and a controller (22). A pattern generation unit (20) generates a frequency variation pattern (25) by determining a transition order of 2n switching frequencies f, using n first frequencies fc and a second frequency fdef that is smaller than the minimum value of the difference between the n first frequencies fc, wherein the 2n switching frequencies f are determined by adding the second frequency fdef to each first frequency fc and subtracting the second frequency fdef from each first frequency fc, so that the median of the two switching frequencies f before and after the transition does not overlap the value of each switching frequency f. The controller (22) generates control signals G for the switching elements (2, 3) by using 2n switching frequencies f for different durations in accordance with a frequency variation pattern (25).)

1. A power conversion device is provided with: a power conversion circuit having a switching element, which converts input power into electric power by switching operation of the switching element and outputs the converted electric power; and a control device for controlling the power conversion circuit,

The control device is provided with: a pattern generation unit that generates a frequency change pattern by changing 2n switching frequencies f, with n being an integer of 2 or more; and a controller for generating a control signal for switching the switching element by using the 2n switching frequencies f for different durations in accordance with the generated frequency variation pattern,

The pattern generation unit includes:

a frequency determination unit that determines the 2n switching frequencies f using n first frequencies fc and a second frequency fdef that is smaller than a minimum value of a difference between the n first frequencies fc, the 2n switching frequencies f being generated by adding the second frequency fdef to each of the first frequencies fc so as to sandwich the first frequency fc and subtracting the second frequency fdef from each of the first frequencies fc;

A transition determination unit that determines a transition order of the 2n switching frequencies f so that a median value of two switching frequencies f before and after the transition does not overlap with a value of each switching frequency f,

The controller uses carriers each having the switching frequency f as a carrier frequency, and changes each carrier frequency in synchronization with any of upper and lower peaks of the carrier.

2. the power conversion device according to claim 1,

The controller uses at least one of the 2n switching frequencies f for more than two cycles.

3. The power conversion device according to claim 2,

The controller uses all of the 2n switching frequencies f for two or more cycles.

4. The power conversion device according to any one of claims 1 to 3,

The second frequency fdef to be added or subtracted to each of the first frequencies fc is common.

5. The power conversion device according to claim 4,

The second frequency fdef is decided based on (1/(m · Tf)), where (1/(m · Tf) is calculated using a period Tf of a pattern that causes each of the 2n switching frequencies f to continue for the duration and a number m of times of a reduction target in a harmonic component of the switching frequency f).

6. The power conversion device according to claim 4,

The 2n switching frequencies f continue for the same cycle number λ, i.e., the duration, and the second frequency fdef is determined based on (1/(2m · Tfc)), where (1/(2m · Tfc) is calculated using the cycle number Tfc of the pattern in which the n first frequencies fc continue for the cycle number λ and the number m of times of reduction targets in the harmonic component of the switching frequency f, respectively.

7. The power conversion device according to any one of claims 1 to 6,

When the first frequency fc when n is 2 is set to fc1 or fc2, the transition order in which the 2n switching frequencies f are repeated is one of the forward order and the reverse order of fc2+ fdef, fc 1-fdef, fc 2-fdef, and fc1+ fdef.

8. The power conversion device according to any one of claims 1 to 6,

The transition sequence in which the 2n switching frequencies f are repeated when n is 3 or more is set to fc (k), where k is an integer of 1 to n, is one of a positive sequence and a negative sequence that satisfies the sequence of fc (n) -fdef, fc (n-1) + fdef, fc (n) + fdef, fc (1) -fdef, fc (2) -fdef, and that satisfies the sequence of fc (k +1) -fdef, fc (k) + fdef, fc (k +2) -fdef when k is 1 to n-2.

9. The power conversion device according to any one of claims 1 to 8,

The pattern generation unit generates the frequency variation pattern in which the 2n switching frequencies f are shifted in the shift order using different durations.

10. The power conversion device according to any one of claims 1 to 8,

The pattern generating section generates the frequency variation pattern in which the 2n switching frequencies f are shifted in the shift order,

The controller generates the control signal at a control cycle of a period equivalent to each of the durations corresponding to each of the carrier frequencies.

11. The power conversion device according to any one of claims 1 to 10,

the reciprocal of the period Tf of the pattern in which each of the 2n switching frequencies f continues for the duration is equal to or more than the resolution bandwidth of a spectrum analyzer for measuring the spectrum of the switching noise.

12. The power conversion device according to any one of claims 1 to 11,

The pattern generation unit holds a table showing a correspondence between a change width of the switching frequency and a reduction amount of the harmonic component in the frequency change pattern, determines the change width corresponding to a desired reduction amount of the harmonic component of the reduction target order using the table, and generates the frequency change pattern based on the determined change width.

13. The power conversion device according to any one of claims 1 to 12,

The power conversion circuit is configured by arranging a first power conversion circuit and a second power conversion circuit in parallel,

The control device generates the frequency variation pattern as a first pattern and a second pattern to control the first power conversion circuit and the second power conversion circuit,

the minimum switching frequency f in the second mode is greater than the maximum switching frequency f within the first mode.

14. The power conversion device according to claim 13,

The frequency difference between the minimum switching frequency f in the second mode and the maximum switching frequency f in the first mode is determined according to the desired attenuation amount of the harmonic component of the reduction target order.

Technical Field

The present invention relates to a power conversion device including a switching element, and more particularly to a switching frequency when controlling the switching element.

Background

In a power converter that converts power by a switching operation in which a switching element is turned on and off, when switching control is performed at a constant switching frequency, electromagnetic noise occurs that is generated in a constant frequency component and harmonic components thereof.

Since the standards of electromagnetic noise are specified in accordance with product classification, countermeasures need to be taken in the case where the electromagnetic noise generated by the power converter exceeds the standards. It is generally considered to provide noise countermeasure means such as a noise filter, but this leads to an increase in size and cost of the device structure.

In order to solve the above problem, a conventional power conversion device includes: a frequency changing device for repeatedly outputting a frequency changing pattern including a plurality of frequency values; and a controller that performs on/off control of the switching element at a switching frequency corresponding to the frequency variation pattern (see, for example, patent document 1).

In a conventional power converter based on another example, the switching cycle number is diffused in a switching frequency diffusion pattern in which a main diffusion pattern (main diffusion pattern) in which a basic pattern defining a plurality of frequencies with respect to time is repeated for each repetition time and a sub diffusion pattern (sub diffusion pattern) in which the interval between adjacent frequencies is smaller than that in the main diffusion pattern and the frequency is switched for each repetition time are synthesized (see, for example, patent document 2).

Disclosure of Invention

Technical problem to be solved by the invention

In these power converters, electromagnetic noise is reduced by using a plurality of switching frequencies, but depending on the frequency band, particularly in the AM (amplitude modulation) band, in order to obtain a sufficient noise reduction effect, the variation width (variation width) of the switching frequency needs to be increased. Therefore, there is a problem that the load of the arithmetic processing of the high-frequency switching control increases.

In the power converter described in patent document 2, since the plurality of switching frequencies are switched at the same time interval, the duration of each switching frequency may be too long when the current ripple at the time of switching is to be suppressed.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power conversion device capable of effectively reducing electromagnetic noise in a wide frequency band by suppressing an increase in the variation width of a switching frequency and preventing an excessively long duration time per switching frequency in switching control using a plurality of switching frequencies.

Means for solving the problems

The power conversion device of the present invention includes: a power conversion circuit having a switching element, which converts input power into electric power by switching operation of the switching element and outputs the converted electric power; and a control device for controlling the power conversion circuit. The control device includes: a pattern generation unit that generates a frequency change pattern by changing 2n switching frequencies f, with n being an integer of 2 or more; and a controller for generating a control signal for switching the switching element by using the 2n switching frequencies f for different durations in accordance with the generated frequency change pattern. The pattern generation unit includes: a frequency determination unit that determines the 2n switching frequencies f using n first frequencies fc and a second frequency fdef that is smaller than a minimum value of a difference between the n first frequencies fc, the 2n switching frequencies f being generated by adding the second frequency fdef to each of the first frequencies fc so as to sandwich the first frequency fc and subtracting the second frequency fdef from each of the first frequencies fc; and a transition determination unit configured to determine a transition order of the 2n switching frequencies f such that a median of two switching frequencies f before and after the transition does not overlap with a value of each of the switching frequencies f, wherein the controller uses a carrier having each of the switching frequencies f as a carrier frequency, and changes each of the carrier frequencies in synchronization with any of upper and lower peaks of the carrier.

Effects of the invention

According to the power conversion device of the present invention, since the switching control is performed using the 2n switching frequencies f each having a different duration, and the 2n switching frequencies f are determined so that the median of the two switching frequencies f before and after the transition does not overlap with the value of the other switching frequency f, it is possible to suppress an increase in the variation width of the switching frequency and effectively reduce the electromagnetic noise in a wide frequency band. In addition, the duration of each switching frequency can be prevented from being excessively long.

Drawings

Fig. 1 is a diagram showing a configuration of a power conversion device according to embodiment 1 of the present invention.

Fig. 2 is a diagram for explaining the switching frequency and the transition procedure in embodiment 1 of the present invention.

Fig. 3 is a diagram showing a carrier wave according to embodiment 1 of the present invention.

Fig. 4 is a diagram illustrating a spectrum of a harmonic component with respect to a switching frequency in embodiment 1 of the present invention.

Fig. 5 is a graph showing the frequency characteristics of electromagnetic noise in the case where a fixed switching frequency is used.

Fig. 6 is a graph showing the frequency characteristics of electromagnetic noise in the case where two switching frequencies are used every 1 cycle.

Fig. 7 is a graph showing the frequency characteristics of electromagnetic noise in the case where two switching frequencies are used every 10 cycles.

Fig. 8 is a diagram showing carriers of comparative example a of embodiment 1 of the present invention.

Fig. 9 is a diagram for explaining the effect of reducing electromagnetic noise according to embodiment 1 of the present invention.

Fig. 10 is a partially enlarged view of fig. 9.

Fig. 11 is a flowchart showing generation of a frequency change pattern according to embodiment 1 of the present invention.

Fig. 12 is a flowchart showing generation of a frequency change pattern according to another example of embodiment 1 of the present invention.

Fig. 13 is a diagram showing a configuration of a power conversion device according to embodiment 2 of the present invention.

Fig. 14 is a diagram showing a configuration of a power conversion device according to embodiment 4 of the present invention.

Fig. 15 is a diagram showing a configuration of a power conversion device according to embodiment 5 of the present invention.

Fig. 16 is a diagram showing the frequency characteristics of a gaussian filter that realizes the frequency resolution of the spectrum analyzer.

Fig. 17 is a conceptual diagram of the frequency characteristics of electromagnetic noise in the case of using two switching frequencies having a frequency difference in embodiment 5 of the present invention.

Fig. 18 is a conceptual diagram of the measurement results of the frequency characteristics of electromagnetic noise in the case of using two switching frequencies having a frequency difference according to embodiment 5 of the present invention.

Fig. 19 is a diagram showing a synthesized wave in the case where the frequency difference is 0 in embodiment 5 of the present invention.

Fig. 20 is a diagram showing a composite wave according to embodiment 5 of the present invention.

Fig. 21 is a diagram showing a configuration of a power conversion device according to embodiment 6 of the present invention.

Fig. 22 is a waveform diagram showing the amount of reduction of harmonic components in embodiment 6 of the present invention.

Fig. 23 is a diagram showing a change in switching frequency in an application example of embodiment 6 of the present invention.

Detailed Description