JP4066156B2 - Power converter - Google Patents

Description

なお、図４は、図８のＡ〜Ｆ領域からＡ領域のみを例にとって説明しているが、他の領域の場合には、その領域の図形を回転又は対称に変換して考えればよい。
（３）、領域の判定２。
続いて、Ｓｔｅｐ３として、Ａ領域を更にＡ１〜Ａ４に分割した小領域と過変調領域のＡ５に関して、更に、密な領域判定を行う。
電圧指令ベクトルが１〜５（Ａ領域ならＡ１〜Ａ５）のどの領域に存在するか判定する。
１、Ｖａ＋Ｖｂ≦０．５ ならば、１領域
２、Ｖａ＋Ｖｂ＞１ ならば、第５領域（過変調領域）
０．５≦Ｖａ＋Ｖｂ≦１で、
３、Ｖａ＞０．５ ならば、２領域
４、Ｖｂ＞０．５ ならば、４領域
５、１〜４以外 ならば、３領域
と領域を細かく判定する。
（４）、各ベクトルの出力時間幅の計算。
Ｓｔｅｐ４として、出力時間幅の計算を行う。
Ｔａ：ａベクトルの出力時間
Ｔｂ：ｂベクトルの出力時間
Ｔｃ：ｃベクトルの出力時間
Ｔａｐ：ａｐベクトルの出力時間
Ｔａｎ：ａｎベクトルの出力時間
Ｔｂｐ：ｂｐベクトルの出力時間
Ｔｂｎ：ｂｎベクトルの出力時間
Ｔ０ｐ：０ｐベクトルの出力時間
Ｔ０ｏ：０ｏベクトルの出力時間
Ｔ０ｎ：０ｎベクトルの出力時間
とし、各時間はＰＷＭキャリヤ周期で正規化されているとする。
【０００８】
Ａ１領域の計算。
2レベルインバータならば、１の長さを持つａベクトルをＴａ＝Ｖａ時間出力し、１の長さを持つｂベクトルをＴｂ＝Ｖｂ出力すれば良いが、3レベルインバータではＡ１領域でａｐ、ａｎ、ｂｐ、ｂｎベクトルを使って電圧を出力しなければならない。従って、図４より、ａｐ、ａｎ、ｂｐ、ｂｎベクトルは０．５の長さとなるので、比率で考えれば、ａｐ、ａｎベクトルの時間はＶａの2倍と等しく、ｂｐ、ｂｎベクトルの時間はＶｂの2倍と等しくなる。
従って、各ベクトルの時間は、
Ｔａｐ＋Ｔａｎ＝２×Ｖａ
Ｔｂｐ＋Ｔｂｎ＝２×Ｖｂ
Ｔｏｐ＋Ｔｏｏ＋Ｔｏｎ＝１−２（Ｖａ＋Ｖｂ）
その他のベクトルの時間は零、と演算する。
【０００９】
Ａ２領域の計算。
Ａ２領域の計算は、図５よりｂベクトル方向の成分をｃベクトルで出力するには、ｃベクトル方向の成分はＶｂの２倍と同じ比率とする必要があり、ａベクトル成分はｃベクトルによるａベクトル成分の値を引き算してＶａ−Ｖｂとする必要があるから、時間の関係は、
（Ｔａｐ＋Ｔａｎ）／２ ＋Ｔａ＝Ｖａ−Ｖｂ
Ｔａｐ＋Ｔａｎ＋Ｔａ＋Ｔｃ＝１
となるので、各ベクトルの時間は、
Ｔｃ ＝２×Ｖｂ
Ｔａｐ＋Ｔａｎ＝２（１−Ｖａ−Ｖｂ）
Ｔａ ＝２×Ｖａ−１
その他のベクトルの時間は零と演算する。
【００１０】
Ａ４領域の計算。
Ａ４領域の計算は、Ａ２領域の考え方と同じで、Ｖａ、Ｖｂが逆転するだけであるから、各ベクトルの時間は、
Ｔｃ ＝２×Ｖａ
Ｔｂｐ＋Ｔｂｎ＝２（１−Ｖａ−Ｖｂ）
Ｔｂ ＝２×Ｖｂ−１
その他のベクトルの時間は零と演算する。
【００１１】
Ａ３領域の計算。
Ａ３領域の計算は、図６よりｃベクトルに垂直な成分から、

ｃベクトル成分から、
（Ｔａｐ＋Ｔａｎ）／２＋（Ｔｂｐ＋Ｔｂｎ）／２＋Ｔｃ＝Ｖａ＋Ｖｂ
各ベクトルの時間和は１であるから、
Ｔａｐ＋Ｔａｎ＋Ｔｂｐ＋Ｔｂｎ＝１
より、各ベクトルの時間は、
Ｔｃ ＝２（Ｖａ＋Ｖｂ）−１
Ｔａｐ＋Ｔａｎ ＝１−２×Ｖｂ
Ｔｂｐ＋Ｔｂｎ ＝１−２×Ｖａ
その他のベクトルの時間は零と演算する。
Ａ５（過変調領域）の計算。
Ａ５領域の計算は、Ａ５領域ではａ、ｂ、ｃベクトルを選択して電圧を出力するが、この領域では指令と同じ電圧を電力変換装置が出力できないので、出力電圧は歪んだ電圧となってしまう。歪みを少なくする場合、出力電圧をなるだけ高くする場合で、各ベクトルの時間は変わってくるので、ここでは例として出力電圧をなるだけ高くする場合で説明する。
（１）Ｖａ≧Ｖｂならば、
Ｔａ＝Ｖａ（ただしＴａを１以下に制限）、
Ｔｃ＝１−Ｔａ
その他のベクトルの時間は零と演算する。
（２）Ｖａ＜Ｖｂならば、
Ｔｂ＝Ｖｂ（ただしＴｂを１以下に制限）、
Ｔｃ＝１−Ｔｂ
その他のベクトルの時間は零と演算する。
とする。
このように、本発明によれば、指令電圧ベクトルの位置判定と、３つのベクトルの出力時間演算が、ｓｉｎ、ｃｏｓの演算を使わず非常に簡単な手法により、高速、効率的に行うことが可能になる。また、これらの演算をＣＰＵを使わずロジック回路のみで安価に構成することも可能である。
【００１２】
【発明の効果】
以上説明したように、本発明によれば、電圧指令を３相の電圧指令で与え３相電圧指令の中で最大値Ｖｍａｘ、中間値Ｖｍｉｄ、最低値Ｖｍｉｎとなる相から電気角を判断して、ＡＢＣＤＥＦ等の電圧指令の在る領域を判定し、Ｖａ＝Ｖｍａｘ−Ｖｍｉｄ、Ｖｂ＝Ｖｍｉｄ−Ｖｍａｘを演算して、Ｖａ、Ｖｂを基に、各領域を更に４領域に再分割して、その領域毎に演算方法を切替えるので、簡単、且つ、高速にＰＷＭパルス幅の演算が可能になり、サーボの高速な演算周期にも適応できて、安価で高速な３レベルサーボアンプを実現できる効果がある。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る電力変換装置のＰＷＭ発生器の構成図である。
【図２】図１に示すＰＷＭ発生器の相電圧指令と三角波キャリヤの関係図である。
【図３】図１に示すＰＷＭ発生器の領域判定テーブルを示す図である。
【図４】図１に示すＰＷＭ発生器の空間ベクトルと電圧の関係を示す図である。
【図５】図４に示す空間ベクトルのＡ２領域の説明図である。
【図６】図４に示す空間ベクトルのＡ３領域の説明図である。
【図７】従来の３レベルインバータの回路図である。
【図８】図７に示す３レベルインバータの空間ベクトル図である。
【符号の説明】
１ ＰＷＭ発生器
２ Ｕ相電圧指令
３ Ｖ相電圧指令
４ Ｗ相電圧指令
５ Ｕ１相ＰＷＭパルス
６ Ｖ１相ＰＷＭパルス
７ Ｗ１相ＰＷＭパルス
８ Ｕ２相ＰＷＭパルス
９ Ｖ２相ＰＷＭパルス
１０ Ｗ２相ＰＷＭパルス[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter / servo drive that performs variable speed control of a motor and a power converter linked to a system.
[0002]
[Prior art]
A conventional three-phase three-level inverter is shown in FIG.
This three-phase three-level inverter is a circuit that generates a PWM pulse based on the command voltage output from the host controller and outputs a signal for turning on / off the switch element.
As a PWM pulse generation method of the PWM pulse generation circuit, a triangular wave comparison type PWM method that creates a PWM pulse by comparing a three-phase voltage command and two triangular wave carriers, or a space disclosed in Japanese Patent Laid-Open No. 05-292754. A space vector type PWM system is generally used in which a command voltage is given as a vector quantity using the concept of vector to create a PWM pulse of a desired output voltage.
[0003]
In the case of Japanese Patent Laid-Open No. 05-292754, when the upper two of the four switching elements connected in series in the PWM inverter are turned on, the phase output terminal is connected to the positive electrode P of the DC power supply (P state), When two SWs are turned on, the phase output terminal is connected to the neutral point output terminal 0 of the DC power supply via the clamp element (diode) (0 state). When the two lower SWs are turned on, the phase output terminal is FIG. 8 shows a vector that can be output as a state (N state) connected to the negative electrode N of the DC power supply. FIG. 8 shows 27 vector symbols (27 vector symbols PNN, PPN, P0N, P00, PP0, 0NN, 00N, PPP, 000, NNN,..., 10 vector names a, b, c, aP, bP. , AN, bN, 0P, 00, 0N), and a total of 24 areas A1 to F4 obtained by dividing the areas A to F into four parts.
Then, it is determined in which of the regions A to F the given command voltage vector is present, at least three vectors close to the tip of the command voltage vector are selected, and the output time of each voltage vector Is an average of the PWM period and is calculated so as to coincide with the command voltage vector.
Now, it is determined in which section of ABCDEF the voltage command in the polar coordinate format represented by (θ, k) as the degree of modulation k, and if it is in the A1 region, the voltage command vector has an amplitude V and an angle θ Then, the voltage time product of the voltage command vector during the carrier period T is VTexp (jθ) = VTcosθ + jVsinθ by complex number calculation.
On the other hand, when the three vectors V0, V1, and V2 in the region A1 are generated for the time T1, T2, and T3, respectively, the voltage-time product is V0 · T1 + V1 · T2 + V2 · T3.
V0 is a vector in which all the complex number representations of zero vector 0P = PPP, 00 = 000, 0N = NNN shown in FIG.
V1 is a vector in which the complex number representation of the voltage vectors aP = P00 and aN = 0NN is halved.
V2 represents a vector in which the complex number representations of the voltage vectors bP = PP0 and bN = 00N are both 1/4 + j · 3/4.
Therefore, the pulse generation times T1, T2, T3 are
VO T1 + V1 T2 + V2 T3 = VT cos θ + jVT sin θ
T1 + T2 + T3 = T
If the preconditions V0 = 0, V1 = 1/2, V2 = 1/4 + .3 / 4 are substituted and arranged,
(1/2) T2 + (1/4) T3 = VTcosθ (· 3/4) T3 = VTsinθ
T1 = T (1-2 ksin (θ + π / 3))
T2 = 2kTsin (π / 3−θ)
T3 = 2ktsin θ,
Is required. These T1, T2, and T3 are common to the areas A1, B1, D1, D1, E1, and F1.
Similarly, T1, T2, and T3 of the regions A2 to F2 are obtained as follows.
T1 = 2T (1-ksin (θ + π / 3))
T2 = T (2 ksin (π / 3−θ) −1)
T3 = 2kTsinθ
Similarly, the generation times of the four regions A3 to F3 and regions A4 to F4 can be determined.
[0004]
[Problems to be solved by the invention]
However, in the above conventional example, in the case of PWM that compares a sinusoidal voltage command as shown in FIG. 7 and a triangular wave, it is not necessary to calculate the PWM pulse width, so that a PWM pulse can be output at a high speed. In order to generate an efficient PWM pulse, it is better to use a PWM generation method using the concept of a space vector as disclosed in Japanese Patent Application Laid-Open No. 05-292754.
However, if the concept of the space vector is used, the 27 output voltage vectors shown in FIG. 8 are output as PWM pulses. Therefore, it is necessary to calculate the PWM pulse width and to determine a number of cases. There has been a problem that the calculation time of becomes longer.
Furthermore, the PWM generator is often input with a three-phase output voltage command as a command. In this case, an operation for converting the three-phase output voltage command into a vector is required, and the calculation time is increased. There was a problem.
Therefore, the present invention can be applied to a high-speed calculation cycle as a calculation method for calculating the same PWM pulse as a space vector method from a three-phase voltage command, and can realize an inexpensive and high-speed three-level inverter and servo amplifier. The object is to provide a conversion device.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 relates to a power converter, comprising a PWM generator for inputting a three-phase voltage command, calculating a pulse width and outputting a PWM pulse, Among them, the electrical angle of the output voltage is determined from the phase having the maximum value Vmax, the intermediate value Vmid, and the minimum value Vmin, and the differential voltage 1, Va (Va = Vmax−Vmid), and the differential voltage 2, Vb (Vb = Vmid−). Vmin), when Va and Vb are values normalized by the maximum value of the line-to-line output voltage of the power converter, if Va + Vb ≦ 0.5, the first region, and if Va + Vb> 1.0, the fifth region (Overmodulation region), 0.5 ≦ Va + Vb ≦ 1.0, Va> 0.5, second region; Vb> 0.5, fourth region; Three-phase three-level power variation to determine area In the device, 27 vectors that can be output from the three-phase three-level power conversion device are made to correspond to 10 vector names, and a value obtained by normalizing each vector output time width by the carrier cycle is output as the Ta: a vector output time. , Tb: b vector output time, Tc: c vector output time, Tap: ap vector output time, Tan: an vector output time, Tbp: bp vector output time, Tbn: bn vector output time, Top : 0p vector output time, Too: 0o vector output time, Ton: 0n vector output time, and in the first region, Tap + Tan = 2 × Va, Tbp + Tbn = 2 × Vb, Top + Too + Ton = 1−2 (Va + Vb) ), The vector output time is determined so as to satisfy the relational expression, and other vector times are set to zero. In the region, the vector output time is determined so as to satisfy the relational expressions of Tc = 2 × Vb, Tap + Tan = 2 (1−Va−Vb), Ta = 2 × Va−1, and other vector times are set to zero. In the third region, the vector output time is determined so as to satisfy the relational expressions Tc = 2 (Va + Vb) -1, Tap + Tan = 1−2 × Vb, Tbp + Tbn = 1−2 × Va, and the other vector times are In the fourth region, the vector output time is determined so as to satisfy the relational expressions of Tc = 2 × Va, Tbp + Tbn = 2 (1−Va−Vb), Tb = 2 × Vb−1, The vector time is zero, and the PWM pulse width calculation method is switched.
The invention according to claim 2 is the power conversion device according to claim 1, wherein in the fifth region, if Va ≧ Vb, Ta = Va (however, Ta is limited to 1 or less), Tc = 1−Ta, If Va <Vb, the vector output time is determined so as to satisfy the relational expression of Tb = Vb (where Tb is limited to 1 or less) and Tc = 1−Tb, the other vector times are set to zero, and the PWM pulse width This is characterized in that the calculation method is switched.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a PWM generator of a power conversion device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between the phase voltage command of the PWM generator shown in FIG. 1 and a triangular wave carrier.
FIG. 3 is a diagram showing a region determination table of the PWM generator shown in FIG.
A PWM generator (PWM pulse calculator) 1 shown in FIG. 1 receives three-phase output voltage commands Vu1, Vv2, and Vw3 from a host controller.
The three-phase output voltage commands Vu1, Vv2, and Vw3 are given as shown in FIG. 2 based on the concept of the triangular wave comparison PWM generation method of the two-level inverter, and are used as a complement to the upper switch signal among the four switch elements in each phase. Six types of PWM pulses 5 to 10 necessary for switching of the three-level inverter are generated by a method of generating a lower switch signal.
Hereinafter, assuming that the three-phase voltage commands Vu1, Vv2, and Vw3 are normalized so as to be compared with the triangular wave as shown in FIG. 2, the maximum value of the line output voltage of the power converter becomes 1.0. The actual maximum value is equal to the bus voltage 2 × Ed in FIG.
[0007]
Next, the operation of the PWM pulse width will be described in detail according to the procedure.
(1) Region determination 1.
First, as Step 1, a rough region determination process is performed.
It is determined in which area A to F the voltage vector area of the voltage command is present in the space vector area shown in FIG.
Specifically, from the phase having the maximum value and the phase having the lowest value among the instantaneous phase voltages of each Vu1, Vv2, and Vw3 as shown in FIG. 2, using the determination table of FIG. When the maximum value is Vu1 and the minimum value is Vw3, it is determined that the region is A or the like.
(2) Calculation of line voltage.
Next, as Step 2, the line voltage is calculated.
The phase voltage having the maximum value is Vmax, the intermediate phase voltage is Vmid, the lowest phase voltage is Vmin, the magnitude of the line voltage in the a vector direction in FIG. 8 is Va, and the magnitude of the line voltage in the b vector direction. Is Vb,
Va = Vmax−Vmid
Vb = Vmid−Vmin.
[Expression 1]

4 illustrates only the A region from the A to F regions of FIG. 8 as an example, but in the case of other regions, the figure in that region may be converted into rotation or symmetry.
(3) Region determination 2.
Subsequently, as Step 3, denser area determination is performed with respect to the small area obtained by further dividing the A area into A1 to A4 and the overmodulation area A5.
It is determined in which region the voltage command vector is 1 to 5 (A1 to A5 if the region is A).
1, if Va + Vb ≦ 0.5, 1 region 2; if Va + Vb> 1, 5th region (overmodulation region)
0.5 ≦ Va + Vb ≦ 1,
3. If Va> 0.5, 2 regions 4; if Vb> 0.5, then 4 regions 5, except 1 to 4;
(4) Calculation of the output time width of each vector.
As Step 4, the output time width is calculated.
Ta: a vector output time Tb: b vector output time Tc: c vector output time Tap: ap vector output time Tan: an vector output time Tbp: bp vector output time Tbn: bn vector output time T0p : 0p vector output time T0o: 0o vector output time T0n: 0n vector output time, and each time is normalized by the PWM carrier period.
[0008]
Calculation of A1 area.
In the case of a two-level inverter, an a vector having a length of 1 may be output for Ta = Va time, and a b vector having a length of 1 may be output by Tb = Vb. , Bp, bn vectors must be used to output the voltage. Therefore, from FIG. 4, the ap, an, bp, and bn vectors have a length of 0.5. Therefore, considering the ratio, the times of the ap and an vectors are equal to twice Va, and the times of the bp and bn vectors are It is equal to twice Vb.
Therefore, the time of each vector is
Tap + Tan = 2 × Va
Tbp + Tbn = 2 × Vb
Top + Too + Ton = 1−2 ( Va + Vb )
The other vector time is calculated as zero.
[0009]
Calculation of A2 area.
In the calculation of the A2 region, in order to output the component in the b vector direction as a c vector from FIG. 5, the component in the c vector direction needs to have the same ratio as twice Vb. Since it is necessary to subtract the vector component value to Va-Vb, the time relationship is
(Tap + Tan) / 2 + Ta = Va-Vb
Tap + Tan + Ta + Tc = 1
Therefore, the time of each vector is
Tc = 2 × Vb
Tap + Tan = 2 (1-Va-Vb)
Ta = 2 × Va−1
The time of other vectors is calculated as zero.
[0010]
Calculation of A4 area.
The calculation of the A4 region is the same as the idea of the A2 region, and Va and Vb are only reversed, so the time of each vector is
Tc = 2 × Va
Tbp + Tbn = 2 (1-Va-Vb)
Tb = 2 × Vb−1
The time of other vectors is calculated as zero.
[0011]
Calculation of A3 area.
The calculation of the A3 region is based on the component perpendicular to the c vector from FIG.

From the c vector component,
(Tap + Tan) / 2 + (Tbp + Tbn) / 2 + Tc = Va + Vb
Since the time sum of each vector is 1,
Tap + Tan + Tbp + Tbn = 1
Therefore, the time of each vector is
Tc = 2 (Va + Vb) -1
Tap + Tan = 1-2 × Vb
Tbp + Tbn = 1−2 × Va
The time of other vectors is calculated as zero.
Calculation of A5 (overmodulation region).
In the calculation of the A5 region, the a, b, and c vectors are selected and the voltage is output in the A5 region. However, since the power converter cannot output the same voltage as the command in this region, the output voltage becomes a distorted voltage. End up. When the distortion is reduced, the time of each vector changes when the output voltage is increased as much as possible. Therefore, here, the case where the output voltage is increased as much as possible will be described as an example.
(1) If Va ≧ Vb,
Ta = Va (however, Ta is limited to 1 or less),
Tc = 1-Ta
The time of other vectors is calculated as zero.
(2) If Va <Vb,
Tb = Vb (however, Tb is limited to 1 or less),
Tc = 1-Tb
The time of other vectors is calculated as zero.
And
As described above, according to the present invention, the position determination of the command voltage vector and the output time calculation of the three vectors can be performed at high speed and efficiently by a very simple method without using the calculation of sin and cos. It becomes possible. It is also possible to configure these operations at low cost using only a logic circuit without using a CPU.
[0012]
【The invention's effect】
As described above, according to the present invention, the voltage command is given as a three-phase voltage command, and the electrical angle is determined from the phase having the maximum value Vmax, the intermediate value Vmid, and the minimum value Vmin in the three-phase voltage command. , Determine the area where the voltage command such as ABCDEF is present, calculate Va = Vmax−Vmid, Vb = Vmid−Vmax, and further subdivide each area into 4 areas based on Va and Vb. Since the calculation method is switched for each region, the PWM pulse width can be calculated easily and at high speed, and it can be applied to a high-speed servo calculation cycle, thus realizing an inexpensive and high-speed 3-level servo amplifier. is there.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a PWM generator of a power conversion device according to an embodiment of the present invention.
FIG. 2 is a relationship diagram between a phase voltage command of the PWM generator shown in FIG. 1 and a triangular wave carrier.
FIG. 3 is a diagram showing a region determination table of the PWM generator shown in FIG. 1;
4 is a diagram showing a relationship between a space vector and a voltage of the PWM generator shown in FIG. 1; FIG.
FIG. 5 is an explanatory diagram of an A2 area of the space vector shown in FIG. 4;
6 is an explanatory diagram of an A3 area of the space vector shown in FIG. 4. FIG.
FIG. 7 is a circuit diagram of a conventional three-level inverter.
FIG. 8 is a space vector diagram of the three-level inverter shown in FIG. 7;
[Explanation of symbols]
1 PWM generator 2 U phase voltage command 3 V phase voltage command 4 W phase voltage command 5 U1 phase PWM pulse 6 V1 phase PWM pulse 7 W1 phase PWM pulse 8 U2 phase PWM pulse 9 V2 phase PWM pulse 10 W2 phase PWM pulse

Claims (2)

A PWM generator for inputting a three-phase voltage command to calculate a pulse width and outputting a PWM pulse;
The electrical angle of the output voltage is determined from the phase having the maximum value Vmax, the intermediate value Vmid, and the minimum value Vmin in the three-phase voltage command,
From the differential voltage 1, Va (Va = Vmax−Vmid), and the differential voltage 2, Vb (Vb = Vmid−Vmin),
When the Va and Vb are normalized by the maximum value of the line output voltage of the power converter,
If Va + Vb ≦ 0.5, the first region,
If Va + Vb> 1.0, the fifth region (overmodulation region),
0.5 ≦ Va + Vb ≦ 1.0,
In the three-phase three-level power converter that determines the third region and the five regions if Va> 0.5, the second region Vb> 0.5, and the fourth region other than the above,
The 27 vectors that can be output from the three-phase three-level power conversion device are associated with 10 vector names, and the values obtained by normalizing the output time widths of the vectors with the carrier period are output times of the Ta: a vector Tb: b vector. Output time Tc: c vector output time Tap: ap vector output time Tan: an vector output time Tbp: bp vector output time Tbn: bn vector output time Top: 0p vector output time Too: 0o vector Output time Ton: 0n vector output time,
In the first region, Tap + Tan = 2 × Va,
Tbp + Tbn = 2 × Vb,
Top + Too + Ton = 1−2 (Va + Vb)
The vector output time is determined so that the relational expression is satisfied, and other vector times are set to zero.
In the second region, Tc = 2 × Vb
Tap + Tan = 2 (1-Va-Vb)
Ta = 2 × Va−1
The vector output time is determined so that the relational expression is satisfied, and other vector times are set to zero.
In the third region,
Tc = 2 (Va + Vb) -1
Tap + Tan = 1−2 × Vb
Tbp + Tbn = 1−2 × Va
The vector output time is determined so that the relational expression is satisfied, and other vector times are set to zero.
In the fourth region,
Tc = 2 × Va
Tbp + Tbn = 2 (1-Va-Vb)
Tb = 2 × Vb−1
The vector output time is determined so that the relational expression is satisfied, and other vector times are set to zero.
A power converter that switches a method of calculating a PWM pulse width. In the power converter according to claim 1, in the 5th field,
If Va ≧ Vb,
Ta = Va (However, Ta is limited to 1 or less)
Tc = 1-Ta
If Va <Vb,
Tb = Vb (however, Tb is limited to 1 or less)
Tc = 1-Tb
The vector output time is determined so that the relational expression is satisfied, and other vector times are set to zero.
A power converter that switches a method of calculating a PWM pulse width.

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