JP2008131770A - Power converting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a harmonic component while DC busbar current is highly precisely detected. <P>SOLUTION: A power converting device is provided with a PWM control part 9 comparing three-phase AC signals Vum<SP>*</SP>, Vvm<SP>*</SP>and Vwm<SP>*</SP>with a triangular wave carrier signal and generating a pulse width modulation wave, a power converter main circuit part 3 driving a switching element by a pulse width modulation wave and converting a DC voltage into a three-phase AC voltage and DC detecting parts 5 and 6 detecting the DC busbar current and reproducing a phase current on a DC input side of the power converter main circuit part. The device is also provided with a voltage command change part 8 adding a correction signal causing an average value of correction quantity at a voltage command change period to be zero or almost zero to the three-phase AC signal by setting an odd number of three or more unit periods when the triangular wave carrier signal monotonously increases or monotonously decreases as a voltage command change period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power conversion device that detects a DC bus current and obtains AC-side current information.

In power converters such as inverters and converters, DC-AC conversion or AC-DC conversion functions are realized by pulse width modulation (hereinafter referred to as “PWM”). Inverters are used in drive systems for AC motors (hereinafter referred to as “motors”) such as synchronous motors and induction motors, and converters are widely used as power supply devices such as inverters.
When driving an electric motor using an inverter, it is necessary to extract only the fundamental wave component included in the alternating current with high accuracy in order to control the generated torque of the electric motor with high accuracy. In general, since a high-frequency pulsation component by PWM is superimposed on the alternating current, only the fundamental wave component is extracted by, for example, a method using an alternating current sensor (Patent Document 1).
In recent years, a technique has been proposed in which a DC bus current of a power converter is detected without using an AC current sensor, and information on the AC current is extracted from the detected value (Patent Document 2, Patent Document 3, Patent). Document 4, Patent Document 5, and Non-Patent Document 1). According to these technologies, it is not necessary to use an alternating current sensor such as a current transformer (CT) using a Hall element, the configuration of the apparatus is simple and space-saving, and the manufacturing cost can be reduced.
JP-A-6-189578 JP 2002-119062 A JP 2004-64903 A JP 2001-327173 A JP-A-10-155278 Tetsuya Fukumoto, Yukie Watanabe, Hiroto Sone, Yoichi Hayashi: “Improvement of waveform distortion by AC current calculation and ripple correction in 1-shunt resistance method” Semiconductor Power Conversion / Industrial Power Electrical Application Joint Study Group, SPC-05-99, pp. 1-6 (2005)

In the method according to Patent Document 4, one period of a triangular wave carrier signal for generating a PWM signal is divided into a first half period and a second half period, and a DC bus current is detected in any one of these periods. This DC bus current is detected more difficult as the AC output voltage of the power converter becomes lower. Therefore, the correction voltage is added to the AC output voltage in the first half, and the output voltage value itself is increased to detect the DC bus current. I have to. In the second half, the correction voltage added in the first half is subtracted so that the average output voltage in the first half and the second half is not affected.
However, when an alternating current is detected using this technique, torque pulsation may occur or accuracy may deteriorate. By applying the correction voltage, an unnecessarily current change occurs, and this current change becomes an "error" and affects the current detection value. As a result, torque pulsation and torque accuracy are reduced. Causes deterioration. In particular, when the inductance of the motor is small or when the carrier frequency is low, a current error due to the correction voltage tends to occur, which is a problem.

In addition, the bias of the current detection value caused by detecting the DC bus current in only one of the first half and the second half is a problem. This problem is caused by the fact that the detection timing is different between the first half and the second half when the DC bus current is detected in a time-sharing manner. That is, since the value of the current ripple generated due to PWM switching differs at two timings, if current is detected in only one of the periods, a bias will occur. This is particularly noticeable when the current ripple is large, and is problematic because it promotes the current error caused by the correction voltage.
Further, there is a method according to Non-Patent Document 1 for distortion compensation of the AC current reproduction value. However, in this method, it is necessary to perform the compensation calculation every time it is detected, which may increase the calculation load. Non-Patent Document 1 also shows a simple compensation method with a reduced calculation load. This is applicable only when the detection timing is fixed at a timing that matches the maximum value and the minimum value of the triangular wave carrier signal, and is difficult to apply to systems with different detection timings.

  Further, in the method according to Patent Document 5, about 1 / integer of the carrier frequency period is defined as a “dependent period”, and DC bus current measurement (detection) and compensation are performed within this period. Also in this method, as in the technique of Patent Document 4, correction and correction of the output voltage and detection of the DC bus current are performed during the dependent period. As a result, a frequency component that coincides with the period of the dependent period is superimposed on the voltage command value, and a frequency component lower than the frequency component of the carrier signal is generated in the alternating current. Since this low frequency component is 1 / integer of the carrier frequency, there is a high possibility that it will be in the audible range. For example, IGBT is widely used as a semiconductor device provided in an inverter, and the upper limit of the carrier frequency is about 20 kHz. Therefore, if it is 1 / integer, it becomes 10 kHz or less and becomes an audible range. The audible component becomes electromagnetic noise and becomes annoying noise, and if the frequency component of the alternating current matches the resonance frequency of the mechanical system, excessive vibration may occur, which may cause malfunction of the device. is there.

  Then, this invention makes it a subject to provide the power converter device which can suppress a harmonic component, detecting a DC bus current with high precision.

  In order to solve the above problems, a power converter according to the present invention compares a three-phase alternating current signal and a triangular wave carrier signal to generate a pulse width modulated wave, and a switching element using the pulse width modulated wave. A power converter circuit unit that drives and converts a DC voltage into a three-phase AC voltage, and a current detection unit that detects a DC bus current and reproduces a phase current on the DC input side of the power converter circuit unit; In the power converter provided, the average value of the correction amount in the voltage command change cycle is substantially zero as the voltage command change cycle in which the unit period in which the triangular wave carrier signal monotonously increases or decreases is an odd number of 3 or more. And a voltage command changing unit for adding such a correction signal to the three-phase AC signal.

  By adding a correction amount to the voltage command value with a period in which the triangular wave carrier signal monotonously increases or decreases as a unit period, and an odd number of periods in which the unit period continues for 3 or more as one cycle, The width of the pulsed current flowing in the current is widened, and highly accurate current detection becomes possible. Also, it is not an integral multiple of the period of the triangular wave carrier signal. For this reason, a harmonic component is suppressed and generation | occurrence | production of electromagnetic noise can be reduced.

  According to the present invention, harmonic components can be suppressed while detecting a DC bus current with high accuracy.

(First embodiment)
A first embodiment of the present invention will be described with reference to the configuration diagram of FIG. A power converter 100 in FIG. 1 includes a DC power source 1, a smoothing capacitor 2 connected in parallel, and a power converter main circuit unit in which a voltage across the smoothing capacitor 2 is applied to the input side via a shunt resistor 5 ( A power converter circuit unit) 3, an AC motor 4 connected to an AC output of the power converter main circuit unit 3, a rotor position sensor 12 attached to the AC motor 4 and outputting a rotor angle signal θ, And a microcomputer (hereinafter referred to as “microcomputer”).

The microcomputer 8 receives the DC bus current IDC flowing through the shunt resistor 5 and reproduces the phase currents Iuc, Ivc, and Iwc, and the reproduced phase currents Iuc, Ivc, and Iwc, and the current arbitrarily given from the outside. The command values Id ^* and Iq ^* are input, and the voltage command value creating unit 7 that outputs the first voltage command values Vu ^* , Vv ^* , and Vw ^* according to the rotor angle signal θ, and the first voltage command A voltage command change unit 8 that outputs the second voltage command values Vum ^* , Vvm ^* , Vwm ^* by adding the values Vu ^* , Vv ^* , Vw ^* and the voltage command change values ΔVuc, ΔVvc, ΔVwc; a phase AC signal second voltage command value ^{Vum *,} Vvm ^*, by comparing the triangular wave carrier signal Vwm ^* and the triangular wave carrier signal generator 9a is generated, PWM system for generating a switching signal It has functions such as control unit 9.

  The power converter main circuit unit 3 outputs a three-phase AC voltage by switching the semiconductor element based on the switching signal, and three-phase currents Iu, Iv, and Iw flow. The switching signal is also supplied to the current detection unit 6 to determine the detection timing of the DC bus current IDC.

First, the voltage command change part 8 which is the characteristic structure of this embodiment is described.
The voltage command change period is defined as one period that is a sum of these consecutive odd number (n), with the monotone increasing period or the monotonic decreasing period of the triangular wave carrier as one unit period (FIG. 2 ( a)). The voltage command change cycle has n carrier cycle half-cycle periods, and in order to identify them, an ordinal number k is defined as “kth half-cycle period” (k = 1, 2, 3,. .., n). FIG. 2 is a timing chart in the case of n = 3. 2A is a waveform of a triangular wave carrier signal, FIG. 2B is a time change of ordinal number k indicating the order of half-cycle periods, FIG. 2C is a voltage command change value ΔVuc, 2 (d) is the first voltage command value Vu ^* , Vv ^* , Vw ^* and the second voltage command value Vum ^* , Vvm ^* , Vwm ^* .

The final voltage command for performing PWM modulation is the second voltage command values Vum ^* , Vvm ^* , Vwm ^* , which are expressed by the following equations.

これは、電圧指令値作成部７が出力する第１の電圧指令値Ｖu^＊、Ｖv^＊、Ｖw^＊と交流電動機４への印加電圧とに差異を生じさせないためである。
なお、図２（ｄ）では、Ｕ相のみに電圧指令変更値ΔＶucが加算されている例であり、Ｖ相とＷ相とに関しては、何も補正がなされず、Ｖ_ｖｍ ^＊＝Ｖ_Ｖ ^＊、ならびに、Ｖ_ｗｍ ^＊＝Ｖ_ｗ ^＊となっている。 Further, the voltage command change value has a time average value of zero or substantially zero in one cycle of the voltage command change cycle based on the equation (2).

This is because there is no difference between the first voltage command values Vu ^* , Vv ^* , Vw ^* output from the voltage command value creation unit 7 and the voltage applied to the AC motor 4.
FIG. 2D shows an example in which the voltage command change value ΔVuc is added only to the U phase. No correction is made for the V phase and the W phase, and V _vm ^* = V _V ^*. , as _well, and has a _^V wm ^* ₌ ^{V w} *.

Next, a voltage command change value addition method that is the most characteristic feature of the present embodiment will be described. For simplicity of explanation, it is assumed that the voltage command change value ΔVuc is added only to the U phase.
First, in order to detect the DC bus current IDC, it is necessary to add a correction amount ΔEuc to the first voltage command value Vu ^* (a method for determining ΔEuc will be described later). .

として、電圧指令値を変更する。直流母線電流ＩＤＣの検出は、序数ｋ＝２の期間で行い、このときには、必要な補正電圧ΔＥucが加算される。この序数ｋ＝２におけるキャリア半周期を「フル電圧補正期間」とする。また、ΔＥuc／２が加算される序数ｋ＝１、ならびに、序数ｋ＝３の期間を「ハーフ電圧補正期間」とする。なお、序数ｋ＝２ではΔＥｕｃが必要となるが、序数ｋ＝１と序数ｋ＝３との補正電圧の合計が−ΔＥｕｃになればよく、厳密性は問われない。 In the present embodiment, it is important that n is an odd number, and n = 3 as an example. In that case,

As a result, the voltage command value is changed. The detection of the DC bus current IDC is performed in the period of the ordinal number k = 2. At this time, the necessary correction voltage ΔEuc is added. The carrier half cycle in the ordinal number k = 2 is defined as a “full voltage correction period”. Further, the period of the ordinal number k = 1 and the ordinal number k = 3 to which ΔEuc / 2 is added is defined as a “half voltage correction period”. Note that ΔEuc is required when the ordinal number k = 2, but the sum of the correction voltages of the ordinal number k = 1 and the ordinal number k = 3 only needs to be −ΔEuc, and the strictness is not questioned.

  In a method such as Patent Document 4, for example, ΔEuc is added during a monotone increasing period of a triangular wave to detect the DC bus current IDC, and −ΔEuc is added (subtracted the added amount) during the next monotonic decreasing period. The generation of errors from the original voltage command is suppressed. In the present embodiment, it seems that the correction voltage is applied to detect the DC bus current IDC. However, the correction voltage is divided in half, and the divided correction voltages are respectively set before and after the detection period. It differs in that it adds.

あるいは、

のように電圧指令変更値を与える。この場合、式（４）では、序数ｋ＝２、あるいは序数ｋ＝４にて、電流検出を行うことが可能であり、式（５)では、序数ｋ＝３にて電流検出を行うことが可能である。いずれも、電圧指令変更周期の開始時（序数ｋ＝１）と終了時（序数ｋ＝ｎ）とを「ハーフ電圧補正期間」とし、それ以外は「フル電圧補正期間」としている。 From the same idea, when n = 5,

Or

The voltage command change value is given as follows. In this case, current detection can be performed with ordinal number k = 2 or ordinal number k = 4 in equation (4), and current detection can be performed with ordinal number k = 3 in equation (5). Is possible. In both cases, the start time (ordinal number k = 1) and the end time (ordinal number k = n) of the voltage command change period are set as “half voltage correction period”, and other times are set as “full voltage correction period”.

Next, the effect of this embodiment is demonstrated using FIG.
Based on the second voltage command values Vum ^* , Vvm ^* , and Vwm ^* obtained by the voltage command changing unit 8, the PWM control unit 9 performs PWM control based on triangular wave comparison. FIG. 3D shows a current pulse generated in the DC bus current IDC as a result of the PWM control.
If the three-phase voltage command value to be compared with the triangular wave carrier signal is defined as a voltage maximum phase, a voltage intermediate phase, and a voltage minimum phase in descending order of values, in FIG.
• Maximum voltage phase → U phase • Intermediate voltage phase → V phase • Minimum voltage phase → W phase Note that which of the three phases (U phase, V phase, and W phase) is the maximum voltage phase, intermediate voltage phase, or minimum voltage phase changes every 60 degrees depending on the AC phase.

  It is known that the maximum voltage phase current and the minimum voltage phase current are generated in the DC bus current IDC in a time-sharing manner. In the monotonically increasing period of the triangular wave carrier signal (FIG. 3A), the current IDC1 of the minimum voltage phase appears first, followed by the current IDC2 of the maximum voltage phase (FIG. 3D). In the monotonously decreasing period (FIG. 3A), the reverse is true, and the current IDC1 of the maximum voltage phase appears first, followed by the current IDC2 of the minimum voltage phase.

  In the example of FIG. 3, n = 3, ΔVuc is added to the U phase, ΔVwc is added to the W phase, and the voltage command value is changed. As a result, it can be seen that the pulse width of the DC bus current IDC is widened in the period of the ordinal number k = 2. Furthermore, it can be seen that the triangular wave carrier signal when the ordinal number k = 2 is alternately switched between monotonic increase and monotonic decrease (FIGS. 3A and 3B). This is because the voltage command change period is set to “odd number (n = 3 in FIG. 3)” between half cycles of the carrier. As a result, the triangular wave carrier signal at the time of detection of the DC bus current IDC is not unique ("only detected when monotonically increasing or monotonically decreasing" is said to be unambiguous) and balanced. Current detection is possible. As a result, the problem as in Patent Document 4 is eliminated, and the current detection accuracy is greatly improved.

式（６）より、重畳される周波数成分をｆａとすれば、Ｔａの逆数になり、式（７）で示される。

なお、式（３）〜式（５）における補正量ΔＥucは、以下に示すように、特許文献４と同様の考え方で求めればよい。 Further, if n = 3, the voltage command change cycle is 1.5 times the triangular wave carrier cycle, and is not an integral multiple as in Patent Document 5. That is, if the carrier frequency is 20 kHz, the harmonic component added by the voltage command changing unit 8 is a component of 13.3 kHz (= 20 kHz / 1.5). Although this value is in the audible range, it is difficult for the human ear to hear, and the silent effect is great.
Further, if n = 5, the harmonic component is a component of 8 kHz (= 20 kHz / 2.5). This value is audible and can be heard by the human ear, so the silent effect is sacrificed. However, if it is assumed that the mechanical resonance frequency of the device is in the vicinity of 13 kHz, the frequency of the harmonic component can be shifted, and problems due to vibration of the device can be avoided.
As described above, the frequency component having the voltage command change period as one period is superimposed on the harmonic component added by the voltage command change unit 8. When one cycle of the voltage command change cycle is Ta, one cycle of the triangular wave carrier signal is Tc, and expressed as n, Equation (6) is obtained.

From Equation (6), if the frequency component to be superimposed is fa, it becomes the reciprocal of Ta and is represented by Equation (7).

In addition, what is necessary is just to obtain | require the correction amount (DELTA) Euc in Formula (3)-Formula (5) by the same view as patent document 4, as shown below.

The current pulse widths of the maximum voltage phase current and the minimum voltage phase current flowing as the DC bus current IDC are determined by the difference between the voltage intermediate phase and the command value, respectively. The current cannot be detected unless the current pulse width has a predetermined value or more.
Here, the “predetermined value” means a dead time period for preventing an arm short circuit of a semiconductor element, a period in which ringing due to switching occurs, a sample hold time of an A / D converter, or the like. It is the minimum width considered, and it can be considered that it is determined by hardware constraints. The minimum value of the current detection detectable width is defined as the minimum pulse width Tpw.

の関係になる。各電圧指令値の差分が最小パルス幅Ｔｐｗに相当する電圧Ｖ（Ｔｐｗ）以上の大きさであれば、補正量を加える必要はない。
また、本実施形態の方法によれば、最大で２相の電流値しか得られないが、三相交流電動機の場合は、中性点電圧をオープンにするのが一般的であるため、キルヒホッフの第１法則により、式９の関係式を用いて残り１相の電流値を求めることができる。

As described above, by correcting so that the voltage difference between the two phases of the voltage command value is always equal to or greater than the voltage corresponding to the minimum pulse width Tpw, the current of the maximum voltage phase and the minimum voltage phase can be detected. Become. Therefore, the correction amounts ΔEuc, ΔEvc, ΔEwc added as voltage command change values are respectively

It becomes a relationship. If the difference between the voltage command values is not less than the voltage V (Tpw) corresponding to the minimum pulse width Tpw, there is no need to add a correction amount.
Further, according to the method of the present embodiment, only a maximum of two-phase current values can be obtained. However, in the case of a three-phase AC motor, it is common to open the neutral voltage, so Kirchhoff's According to the first law, the current value of the remaining one phase can be obtained using the relational expression of Expression 9.

Moreover, the voltage command value preparation part 7 is taken as the general operation | movement used for the conventional alternating current motor control. That is, in the voltage command value creation unit 7, the first voltage command values Vu ^* and Vv are obtained from the reproduced currents Iuc, Ivc and Iwc obtained by the current detection unit 6 and the current command values Id ^* and Iq ^{* which} are arbitrarily given. ^{* And} Vw ^* are output. Since the reproduction currents Iuc, Ivc, and Iwc here are AC amounts in the stator coordinate system, generally, rotational coordinate conversion (dq conversion) is introduced to treat the current as a DC amount and follow the current command value. To achieve current control. The values on the first voltage command coordinates (rotation coordinates), which are AC amounts, are calculated by inversely converting the output of the current controller by dq, and the first voltage command values Vu ^* , Vv ^* , Vw ^* are calculated ^. Get.
In addition, in order to perform coordinate conversion, AC motor control requires phase information. In the case of a synchronous motor, a rotor position sensor is essential. Further, the shunt resistor 5 shown in FIG. 1 only needs to detect the DC bus current IDC, and may be a DC current sensor (DCCT) or the like instead of the shunt resistor 5.

The waveform of the DC bus current IDC when n = 5 will be described with reference to FIG. 4A shows the waveform of the triangular carrier signal, FIG. 4B shows the time change of the ordinal number k, FIG. 4C shows the waveform of the voltage command change value ΔVuc, and FIG. It is a waveform of DC bus current IDC. In the DC bus current IDC, a voltage maximum phase pulse and a voltage minimum phase pulse respectively corresponding to the AC current of the maximum voltage phase and the minimum voltage phase are generated. In FIG. 4, the voltage command change value ΔVuc is added based on the equation (5). That is, by adding the correction amount ΔEuc with the ordinal number k = 3, the pulse width of the voltage maximum phase pulse is matched with the minimum pulse width Tpw. From FIG. 4 (d), voltage maximum phase pulses (reference numerals 1 to 5) having a minimum pulse width Tpw or more appear every five (that is, n), and the pulse frequency of the DC bus current IDC is 1 / n frequency components. In addition, since the number of voltage maximum phase pulses having a pulse width equal to or greater than the minimum pulse width Tpw in one cycle of the voltage command change cycle is equal to the number of ΔVuc = ΔEuc, two in the case of Expression (4) In the case of equation (5), the number changes to one.
In FIG. 4, the voltage maximum phase pulse and the voltage minimum phase pulse are discriminated from the monotone increase period and the monotone decrease period of the triangular wave carrier signal. However, if the switching state of the semiconductor element of the power converter main circuit unit 3 is observed, it can be similarly determined.

  According to the present embodiment, a period in which the triangular wave carrier signal is monotonously increased or monotonously decreased is defined as a unit period, and an odd number of periods in which the unit period is three or more consecutive is defined as one period, and the correction amount is set in the voltage command value. to add. As a result, the pulse width of the DC bus current IDC is increased, and highly accurate current detection is possible. That is, even if only the DC bus current detection sensor is used, the current detection accuracy can be improved, so that accurate position estimation is possible, and unprecedented torque accuracy can be realized. Moreover, since it is not an integral multiple of the period of the triangular wave carrier signal, the generation of electromagnetic noise can be reduced. Furthermore, the correction amount for all periods is averaged by subtracting 1/2 of the correction amount of the voltage command value in the unit period before and after the added unit period.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the configuration diagram of FIG. In FIG. 5, the power conversion device 110 deletes the rotor position sensor 12 from the configuration of the power conversion device 100 of the first embodiment, and instead estimates the rotor position of the AC motor 4. The operation unit 10 is added.

The rotor position estimation calculation unit 10 receives the reproduction currents Iuc, Ivc, and Iwc reproducing the motor currents Iu, Iv, and Iw, performs the rotor position estimation calculation, and outputs the rotor estimated position phase signal θc. The rotor position estimation calculation is performed using the first voltage command values Vu ^* , Vv ^* , Vw ^* , and motor constant values such as the internal resistance and inductance of the AC motor 4. The voltage command value creation unit 7 determines the phase of the AC output of the power converter main circuit unit 3 by obtaining the phase signal θc of the rotor estimated position from the rotor position estimation calculation unit 10, and is fixed to the rotor coordinate system. Perform mutual conversion with the child coordinate system. In the position sensorless control, the position is estimated based on the current of the AC motor 4, and therefore the accuracy of the detection current is extremely important.

(Third embodiment)
A third embodiment of the present invention will be described with reference to the configuration diagram of FIG. In FIG. 6, the power conversion device 120 is configured by adding a speed control unit 11 to the configuration of the power conversion device 110 of the second embodiment to configure a speed control system. The speed control unit 11 receives the estimated speed value ωc output from the rotor position estimation calculation unit 10 and an arbitrarily given speed command value ω1 ^*, and receives the d-axis current command value Id ^* and the q-axis current command value Iq ^*. Is output. The estimated speed value ωc is a differential value of the phase signal θc of the estimated rotor position calculated by the estimated rotor position estimation unit 10. The speed controller 11 compares the speed command value ω1 ^* with the estimated speed value ωc to perform speed control.

  When the speed control system is configured, a rotor angle signal (phase signal) θ obtained from a rotor position sensor 12 (see FIG. 1) attached to the AC motor 4 is detected, and this rotation is detected. The detected speed value ωr obtained by differentiating the child angle signal θ may be used instead of the estimated speed value ωc. In the present embodiment, since the torque accuracy is improved by improving the current detection accuracy, the followability of the speed is improved even in the configuration of the speed control system. As a result, an unprecedented speed control response can be realized.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. The configuration of this embodiment is the same as that of the first embodiment shown in FIG. 1 except that the voltage command value creating unit 7 is different. The first voltage command value in the first embodiment is based on a modulation system that switches all three phases of the semiconductor elements of the power converter main circuit unit 3 by comparing the three-phase voltage command value with the triangular wave carrier signal. Yes. However, in this modulation method, there is a problem that switching loss of the semiconductor element is generated for three phases, which may hinder high-efficiency operation. Therefore, a two-phase modulation method that reduces loss by reducing the number of switching operations is generally known. The two-phase modulation method is a method that reduces the switching loss and enables high-efficiency operation by turning on the upper or lower arm of one phase and switching the remaining two phases. In the present embodiment, the voltage command value creation unit 7 creates the first voltage command values Vu ^* , Vv ^* , Vw ^* based on the two-phase modulation method.

Of the first voltage command values Vu ^* , Vv ^* , and Vw ^* in the present embodiment, one phase matches the amplitude value of the triangular wave carrier signal, so that the phase is not switched. From this, the waveform of the pulse current of the DC bus current IDC is different from that of the first embodiment. FIG. 7 shows the waveform of the DC bus current IDC when the phase that is not switched is defined as the minimum voltage phase and n = 5. FIG. 7A shows the waveform of the triangular carrier signal, FIG. 7B shows the time change of ordinal number k, FIG. 7C shows the voltage command change value ΔVuc, and FIG. 7D shows the DC bus. Current IDC. In FIG. 7, the maximum voltage phase is the U phase, and ΔVuc is determined based on the equation (5) in consideration of detecting the maximum voltage phase pulse.

  It can be seen from the waveform of the DC bus current IDC shown in FIG. 7 that the voltage minimum phase pulse is generated across the monotone increasing period and the monotonic decreasing period. On the other hand, the voltage maximum phase pulse generates one pulse in each period. The voltage maximum phase pulse has an ordinal number k = 3 and the correction amount ΔEuc is added to set the pulse width to Tpw. From the figure, the point that the maximum voltage phase pulse having the minimum pulse width Tpw or more is generated every fifth pulse, that is, every n pulses, is the same as in the first embodiment, but 2 for the pulse frequency of the DC bus current IDC. / N frequency component. Further, the number of maximum voltage phase pulses having a pulse width equal to or greater than Tpw generated in one cycle of the voltage command change cycle is one in FIG. Since this number is equal to the number that satisfies ΔVuc = ΔEuc, when ΔVuc is determined based on Equation (4), the number is two.

In addition, a frequency component having a voltage command change period as one period is superimposed on the harmonic component added by the voltage command change unit 8. This is the same as in the first embodiment. Therefore, also in this embodiment, the harmonic component shown in Formula (7) is superimposed.
The present embodiment is the same as the first embodiment except that the modulation method of the voltage command value creation unit 7 is different from that of the first embodiment. Therefore, the method of the present embodiment can be applied to the configurations shown in the second embodiment and the third embodiment.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications such as the following are possible.
(1) Although each said embodiment converted the DC voltage into the three-phase alternating voltage, it can be applied to the circuit which converts the three-phase alternating voltage into the direct-current voltage. In this case, the direct current on the output side is detected, and the current detection unit reproduces the phase current on the input side. Note that a circuit for converting an AC voltage into a DC voltage is described in, for example, Japanese Patent Application Laid-Open No. 2006-67754.

It is a block diagram in 1st Embodiment of this invention. It is explanatory drawing regarding the change method of the voltage command value of 1st Embodiment of this invention. It is a related figure of voltage command value and direct-current bus current of a 1st embodiment of the present invention. It is explanatory drawing regarding generation | occurrence | production of the DC bus current pulse with the minimum pulse width of 1st Embodiment of this invention. It is a block diagram in 2nd Embodiment of this invention. It is a block diagram in 3rd Embodiment of this invention. It is explanatory drawing regarding the change method of the voltage command value in 4th Embodiment of this invention.

Explanation of symbols

1 DC power supply 2 Smoothing capacitor 3 Power converter main circuit section (power converter circuit section)
DESCRIPTION OF SYMBOLS 4 AC motor 5 Shunt resistance 6 Current detection part 7 Voltage command value preparation part 8 Voltage command change part 9 PWM control part 9a Triangular wave carrier signal generation part 10 Rotor position estimation calculation part 11 Speed control part 12 Rotor position sensor 100,110 , 120 Power converter

Claims (9)

A PWM controller that compares a three-phase AC signal with a triangular wave carrier signal to generate a pulse-width modulated wave, and a power converter that drives a switching element with this pulse-width modulated wave and converts a DC voltage into a three-phase AC voltage In a power converter comprising: a circuit unit; and a current detection unit that detects a DC bus current and reproduces a phase current on a DC input side of the power converter circuit unit,
A voltage command change period is an odd number of unit periods in which the triangular wave carrier signal monotonously increases or monotonously decreases by 3 or more.
A power conversion device, further comprising: a voltage command change unit that adds a correction signal to the three-phase AC signal so that an average value of correction amounts in the voltage command change period is zero or substantially zero. The correction amount of the three-phase AC signal is:
At least one of the odd number of correction amounts in the voltage command change period is
The power converter according to claim 1, wherein a duration of a pulsed current generated in the DC bus current is ensured to be equal to or greater than a predetermined value. A width equal to or greater than a predetermined value for ensuring a period for passing the pulsed current is:
3. The pulse width obtained by summing a ringing period resulting from switching of a semiconductor element constituting the power converter circuit unit and a sample hold period for detecting the DC bus current. Power converter. For n correction amounts in the voltage command change period,
The power conversion device according to claim 2, wherein a correction amount of the {(n + 1) / 2} -th unit period is a correction amount equal to or greater than the predetermined value. Among the n correction amounts of the unit period that are odd numbers in the voltage command change cycle, the magnitudes of the first correction amount and the nth correction amount are:
The power conversion device according to claim 2, wherein the power conversion device is approximately ½ of a correction amount in another period.   2. The power conversion device according to claim 1, wherein a three-phase current output from the power converter circuit unit is controlled based on the phase current reproduced by the current detection unit. With the reproduced phase current as an input, a rotor position estimation calculation unit that estimates a rotor position of an AC motor driven by the three-phase AC voltage,
The power converter according to claim 1, wherein the phase of the three-phase AC voltage is determined based on the estimated rotor position. A power converter circuit unit for driving a switching element by a pulse width modulation wave, converting from DC to AC, or converting power from AC to DC;
In a power converter comprising: a current detection unit that detects a current on a DC side of the power converter circuit unit and reproduces an AC side phase current;
An electric power characterized by including an average pulse frequency of the pulse width modulated wave and a 1 / n frequency component of the pulse frequency as harmonic components generated on the AC side of the power converter circuit unit Conversion device. A power converter circuit unit that drives the switching element by a pulse width modulation wave, converts power from direct current to alternating current, or converts power from alternating current to direct current; and
In a power converter comprising a current detection unit that detects a DC bus current on the DC side of the power converter circuit unit and reproduces a phase current,
While the power converter circuit unit stops the switching operation of any one of the three phases, the other two phases perform the switching operation,
The power converter circuit unit includes an average pulse frequency of the pulse width modulated wave and a 2 / n frequency component of the pulse frequency as harmonic components generated on the AC side. Conversion device.

Images