JP3156478B2 - Control device for pulse width modulation type inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a three-level inverter, and more particularly to a control device for a pulse width modulation type inverter.

[0002]

2. Description of the Related Art A so-called inverter train which drives an induction motor by controlling a variable voltage / variable frequency (VVVF) inverter by a pulse width modulation method has been put into practical use. The drive system is becoming mainstream.

In a current inverter system for driving a vehicle, a so-called pulse width modulation (PWM) control system in which a pulse signal is generated by comparing a modulated wave signal which is a basic component of an output voltage with a carrier signal such as a triangular wave is used. It has been conventionally used.

In the PWM control system, there are a synchronous modulation system in which the zero-cross point of the modulated wave signal and the carrier signal are controlled so as to always coincide with each other, and an asynchronous modulation system in which the carrier is fixed irrespective of the modulated wave.

[0005] At present, most vehicles use a two-level inverter that controls a two-level voltage using a GTO thyristor. However, in the two-level GTO inverter, there is a restriction on the switching frequency, and asynchronous modulation is performed in a minute voltage region including zero voltage, and the synchronous modulation method is switched in other voltage regions. It is also a big problem, and the change in sound quality accompanying the pulse mode switching is also a problem.

On the other hand, the three-level inverter has a feature that the number of steps of the output voltage has an apparent higher switching frequency than that of the two-level inverter, and can solve the problems in the two-level inverter such as reduction of electromagnetic noise. Therefore, a three-level inverter system for vehicles using a high-voltage IGBT as a main circuit element has been developed.

FIG. 3 shows PWM control of a three-level IGBT inverter. That is, a dipolar modulation that outputs pulses alternately through a zero voltage to control a minute voltage is introduced, and a unipolar that outputs a pulse train of the same polarity every half cycle, which is the most common PWM control of a three-level inverter, is introduced. In order to achieve a smooth transition by suppressing fluctuations in the inverter output current, a partial dipolar control in which dipolar modulation and unipolar modulation are mixed during one cycle is introduced. Further, over-modulation is employed to control the output voltage continuously up to one pulse region.

Thus, (a) dipolar modulation, (b)
By performing partial dipolar modulation, (c) unipolar modulation, (d) overmodulation, and (e) one-pulse control, the voltage can be continuously controlled over the entire region. In this case, as the switching frequency becomes higher, the asynchronous modulation method is used in (a) to (d), and only one pulse in (e) is the synchronous modulation method.
Controls (a) to (d) are called multi-pulse control in contrast to one-pulse control.

[0009]

As described above, since the three-level IBGT inverter performs asynchronous modulation by multi-pulse control and synchronous modulation by one-pulse control, the switching frequency between asynchronous modulation and synchronous modulation is high and accurate. Switching control is required.

An object of the present invention is to provide a pulse width modulation type inverter control device which can smoothly switch between asynchronous modulation and synchronous modulation, continuously control the output voltage in all control areas, and obtain a smooth ride. To provide.

[0011]

In order to achieve the above object, the present invention sets the phase angle of the fundamental modulation wave of the inverter to 1/1 / the sampling period of the phase angle calculation when switching from multi-pulse control to single-pulse control. The phase is delayed by subtracting a period equivalent to two cycles, and when switching from one-pulse control to multi-pulse control, １ ／ of the sampling cycle of the phase angle calculation is performed.
The phase is advanced by adding the period equivalent.

[0012]

The time delay in the sampling operation can be corrected by adjusting the phase angle of the basic modulated wave when switching between the multi-pulse control and the one-pulse control, so that smooth control can be realized.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a control apparatus for a pulse width modulation type inverter according to the present invention.

FIG. 1 shows a main circuit configuration (in the case of three phases) of a three-level inverter device for driving a vehicle to which a control device for a pulse width modulation type inverter according to the present invention is applied. In FIG. 1, reference numeral 60 denotes a train line which is a DC voltage source; 61 and 62, capacitors which are divided (divided) to generate an intermediate point N (hereinafter, referred to as a neutral point) from the voltage of the DC voltage source 60;
-73,80-83,90-93 are self-extinguishing switching elements provided with a rectifying element for reflux (in this example, I
Although the GBT is used, a GTO thyristor, a transistor, or the like may be used), 74, 75, 84, 85, 94, and 95 are auxiliary rectifying elements for deriving a neutral point potential of the capacitor.
Also, the load is shown for the case of the induction motor 10.

The operation of the switching arms 7 to 9 which can be operated independently for each phase is
Will be described as an example.

The voltages ed ₁ and ed _{2 of the} capacitors 61 and 62
Is a completely smooth DC voltage source, and ed ₁ = ed ₂ = Ed /
2 (Ed: total DC voltage).

At this time, three-level output voltages e of Ed / 2, 0, and -Ed / 2 are obtained at the AC output terminal U by controlling the on / off of the switching elements 70 to 73 as shown in Table 1. .

[0018]

[Table 1]

S _p , S _o , S _n, and S are switching functions expressing the conduction state of the switching elements 70 to 73 as 1, 0, −1, and the output voltage e is

[0020]

(Equation 1)

## EQU2 ##

E has a waveform obtained by combining pulse-like voltages having magnitudes of Ed / 2, 0, and -Ed / 2.
e is pulse width modulation (PWM) of S so that it approaches a sine wave
Control.

Here, prior to describing the present embodiment, the PWM control will be described.

As described above, the PWM control of the three-level inverter is performed by (a) dipolar modulation, (b) partial dipolar modulation, (c) unipolar modulation, (d) overmodulation, and (e).
One pulse control is performed, and the output voltage is controlled almost continuously from 0 to 100%.

Generally, the inverter output voltage command E * is
It is set as shown by the solid line in FIG. 3 according to the inverter frequency command Fi *. This inverter output voltage command E *
From the DC voltage Ed, the fundamental wave amplitude command (modulation rate) A (0 ≦ A ≦ 1) in the sine wave modulation region is

[0026]

(Equation 2)

Is given by From this, the basic modulation wave command a
From the modulation rate A and the phase θ

[0028]

A = A sin θ (Formula 3) θ = 2πFi * t Fi *: inverter frequency command, t: time

In order to enable continuous transition between the dipolar modulation of (a) and the unipolar modulation of (c), the basic modulation wave command a of Equation 3 is divided into two, and the positive bias modulation wave command a _bp , A negative bias modulation wave command a _bn is created as in the following equation.

[0030]

(Equation 4)

By setting the bias amount B, (a) dipolar modulation to (c) unipolar modulation are realized.
Next, each modulation will be described.

FIG. 4 illustrates the dipolar modulation.

When the bias amount B is in the range of A / 2 ≦ B <0.5, positive and negative pulses are generated by two layers of positive and negative bias modulation wave commands a _bp and a _bn. As a result, a predetermined minimum on-pulse width can be ensured, and the inverter output voltage can be controlled to zero.

The partial dipolar modulation will be described with reference to FIG.

Partial dipolar modulation is performed when the bias amount B is in the range of 0 <B <A / 2. Depending on the magnitude of the bias amount B, the bias modulation wave commands a _bp and a _bn cross zero, but in this period, a negative (or positive) voltage is realized by a positive (or negative) pulse. Since it cannot be performed, the output voltage decreases as compared with the fundamental modulation wave. Therefore, during this period, the positive and negative modulation wave commands a _p and an _n are set as follows to compensate for the insufficient voltage.

[0036]

(Equation 5)

[0037]

(Equation 6)

[0038] However, a _p for clarity in FIG. 5, displaying a a _n a positive signal. Here, period I
Is dipolar modulation, and period II is unipolar modulation. By this correction, an output voltage equal to the fundamental modulation wave is obtained,
Partial dipolar modulation in which dipolar modulation and unipolar modulation coexist can be realized.

FIG. 6 illustrates unipolar modulation.

The bias amount B = 0 is in the unipolar modulation region, and the positive and negative bias modulation wave commands a _bp and a _bn coincide. Positive, negative modulated wave instruction a _p, a _n becomes the following equation.

[0041]

(Equation 7)

[0042]

(Equation 8)

[0043] However, in FIG. 6 a _p, are displayed so as to be both a _n a positive signal. Note that overmodulation control also belongs to this area.

The overmodulation control will be described with reference to FIG.

In the overmodulation control, the positive and negative modulation wave commands a _p ,
in which the amplitude of a _n exists one or more regions, in this one or more regions, eliminating the drop to zero duration of the pulse, perform the PWM control only near the zero cross of the modulation wave.
However, the actual output voltage is smaller than the basic modulation wave, and the output voltage does not increase linearly with the linear increase of the modulation factor A.

Therefore, the output voltage is corrected by making the setting of the modulation factor A non-linear. If the switching frequency in the PWM control portion of the overmodulation is sufficiently high, the relationship between the fundamental wave effective value E of the output voltage and the modulation factor A can be expressed by the following equation.

[0047]

(Equation 9)

If the required modulation rate A is calculated in advance from Equation 9 and the modulation rate A is changed non-linearly with respect to the output voltage command E * of the inverter as shown in FIG. The output voltage command E * can be controlled linearly.

From the above (a) dipolar modulation to (d) overmodulation, the change of the bias amount B, the correction of the modulation wave command,
Although there are factors such as non-linearity of the modulation factor, the method of creating the PWM signal is basically the same.

FIG. 9 illustrates one-pulse control.

In the three-level PWM control, the width of the zero voltage period can be set arbitrarily, so that the output voltage can be adjusted during one-pulse control. Assuming that the timing angle at which the output voltage rises is α, the fundamental wave effective value E of the inverter output voltage
Can be expressed by the following equation using α.

[0052]

E = E _max · cosα (Equation 10) The voltage coverage range for α ≦ 30 ° is 86.6% to 100.
%, And in the range of α ≦ 30 °, the output voltage can be continuously controlled from the above-mentioned overmodulation.

As shown in FIG. 9, the setting of the pulse width is such that the intersection between the output voltage command E * of the inverter and cos θ is the timing angle α of the rise of the output voltage, and the intersection with −cos θ is
This is the falling timing angle β. As described above, the method of generating the PWM signal of one pulse control is completely different from (a) dipolar modulation to (d) overmodulation.

Next, FIG. 2 shows an embodiment in which the present invention is applied to control of a three-level inverter device for driving a vehicle.
In FIG. 2, 1 is based on the inverter frequency command Fi *.
This is a phase calculation unit that calculates the fundamental wave phase of the output voltage of the inverter. The inverter frequency command Fi * is obtained by calculating the rotation frequency of the electric motor from the output of the rotation frequency detector attached to the wheel (not shown) and adding it to the slip frequency command. The output 101 of the phase calculation unit 1 is input to a phase adjustment unit 17 described later, and the output 117 is converted into a sine wave signal 102 by the sine wave conversion unit 2. Reference numeral 3 denotes a calculation unit for calculating a modulation factor A for obtaining a required instantaneous output voltage of the inverter from the output voltage command E * of the inverter. The output voltage command E * is a command value of the inverter output voltage determined from the inverter frequency command Fi * and a filter capacitor voltage and a motor current (not shown) so that the V / F characteristic is constant. is there. As shown in FIG. 8, the modulation factor A has a non-linear relationship with the output voltage command E * in the overmodulation region. An output 103 of the modulation factor calculator 3;
The sine wave signal 102 is multiplied by the multiplier 4 to obtain a basic modulation wave command 104. Reference numeral 5 denotes a bias setting unit that adds / subtracts the basic modulation wave command 104 to / from the modulation rate A output 103 and sets a bias amount B for continuously realizing dipolar modulation, partial dipolar modulation, and unipolar modulation.
Adder 6 adds basic modulation wave command 104 and bias amount 105
And the subtractor 7 subtracts to obtain a negative bias modulation wave command 107. In order to correct the output voltage described above, the positive bias modulation wave command 106 is divided into positive and negative signals by a distributor 601 for obtaining a positive signal 1061 and a distributor 602 for obtaining a negative signal 1062, and the negative bias modulation wave command 107 is 701 that obtains a negative signal 1072
2, the signal is divided into positive and negative signals.
071 adds the positive side modulation wave instruction a _p 108 and adds a negative signal 1062,1072 in the adder 9, to create a negative-side modulation wave instruction _a n 109. 10 is a pulse timing calculation unit, positive, based on the negative side modulation wave instruction 109, the switching function S _p, calculates the pulse timing of S _n.

[0055] The timer output unit 11 to be described later is a timer part for creating a pulse, creating a normal pulse, the rising or falling edge of the pulse, means for setting at every sampling period T _s are common. The T _S generator 18 outputs a sampling period T _S 118 from the clock CLK of the control device. This T _S is also an element that determines the switching frequency of the inverter, and the switching frequency F of the inverter
_sw is given by the following equation.

[0056]

Equation 11] _{F sw = 1 / (2 ×} T s) ... ( Equation 11) FIG. 10 is a switching function S _p in dipolar modulation (region I) and the unipolar modulation (region II), the method for generating the timing of S _n Is shown. Setting the rise and fall of the pulse timing for each sampling period T _S is, first, in time T _1, the rise timing T _pup of S _p, S _n
The falling timing T _ndn of the positive and negative modulation wave commands 10
It is obtained by the following equation using 8,109.

[0057]

(Equation 12)

[0058]

(Equation 13)

[0059] In the next time T _2, obtains the falling timing T _pdn of S _p, the rising timing T _Nup of S _n by the following equation.

[0060]

[Equation 14]

[0061]

(Equation 15)

The processing of T ₁ and T ₂ is performed at the sampling period T
S _p, can create S _n by performing alternately every _s.

However, T _pup , T _dnn , T _pdn , and T _nup correspond to the output 100 of the pulse timing calculator 10 in FIG.
Is sent to the timer output unit 11 via Timer output unit 1
1 also operates in synchronization with the sampling period T _s , the operation results T _pup , T _ndn , T _pdn , and T _nup are calculated at the next time, for example, the operation result at time T ₁ is the time T ₂ . Timer output will be performed. Therefore, the output voltage is as shown in FIG. 10, it becomes delayed by a sampling period T _s. This is a delay that occurs when the timer operates in synchronization with the sampling period.

Returning to FIG. One pulse control, as described above, in synchronization with the fundamental modulation wave, in the half cycle, the switching function S _p, sets the timing angle of the rising and falling of S _n. In the 12 cos ^-1 E * calculation unit, the output voltage command E
In order to find the intersection between * and cos θ, cos ⁻¹ E * is found.
In step 12, the calculation may be performed or a table may be prepared in advance. The output 112 of 12 is the switching function S _p , S _n
Are the rising angle α and the falling angle β. This is shown in FIG. Output 112 to phase timing calculator 1
At 3, it is converted into time data. In this case, in the timing generation method such as the pulse timing calculation unit 10, for example, a delay of the sampling period T _s occurs from the determination of α to the output from the timer output unit 11, so that the synchronous modulation Cannot be realized. Accordingly, the phase timing calculation unit 13 monitors the fundamental wave phase, and if it is determined that it reaches α or β within the next sampling cycle, the amount of time from the increase rate of the past fundamental wave phase to α Operate on data. That is, the fundamental wave phase at the current sampling theta, pulse S _p rise angle alpha _p of the increase in the basic phase of the sampling period in cos ^-1 E * calculation of Δθ12 from previous falling angle the When beta _p, rising timing T _pup switching function S _p, the fall timing T _pdn is as follows.

[0065]

(Equation 16)

On the other hand, in the case of the switching function S _n , similarly, if the rising angle is α _n and the falling angle is β _n , the following equation can be used.

[0067]

[Equation 17]

The above output 113 is sent to the timer output unit 11 via the changeover switch 15. The pulse mode switching unit 14 determines switching between (a) dipolar modulation to (d) overmodulation and one-pulse control based on the magnitude of the output voltage command E *.
5 to switch the control mode. Further, the switching signal 114 is sent to the phase correction unit 16 to calculate the correction amount and the direction of the fundamental wave phase at the time of switching the pulse mode.
6 is input to the phase adjustment unit 17 to correct the fundamental wave phase 101. The portion 100 surrounded by the dotted line is a portion common to the three phases, and the other portions are required for each phase.

Next, the operation of the phase correction section 16 will be described with reference to FIG. FIG. 11 shows a case where the overmodulation is switched to one pulse and the phase is switched at 180 °.
Figure fundamental modulation wave instruction in FIG. (A) is positive, modulated wave instruction a _p negative side is shown superimposed with a _n. In one pulse control is determined by calculating the rising timing alpha _n, the negative-side modulation wave instruction a
_With respect to _n , a negative-side pulse can be generated without a time delay. On the other hand, in overmodulation, which is multi-pulse control, since there is a time delay in the creation of a positive-side pulse as shown in FIG. The fundamental wave is as _ap 'shown by a dotted line. Therefore, the fundamental wave becomes discontinuous for shifting to a _n from a _p 'is at the time of switching, an overcurrent is generated.

[0070] Therefore, in the phase correction unit 16, as the phase command of the fundamental wave is continuous, in the case of FIG. 10 delays the negative side modulation wave instruction a _n, is a continuous transition of a _n from a _p '.
At the time of switching from one pulse to overmodulation, there is a time delay in pulse generation on the overmodulation side, so that the phase command of the fundamental wave on the overmodulation side is advanced. Table 2 shows the relationship of the correction directions arranged in correspondence with the phase order.

[0071]

[Table 2]

The correction amount will be described. As in this embodiment, when the sample value control for controlling each sampling time, the frequency response of the sampling period T _s 1/2
Becomes Therefore, the phase output of the fundamental modulation wave is calculated for each sampling period, 1/2 × T _s equivalent may be corrected phase angle.

[0073] The basic modulation wave of the phase is obtained by integrating the increment Δθ of each sampling period T _s of the inverter frequency command Fi *. If the current phase is θ _n and the phase at the previous sampling is θ _n-1

[0074]

[Number 18] _{θ n = θ n-1 +} Δθ ... ( number _{18) Δθ = k × T s} × Fi * Here k: because it is the relationship of the conversion factor, 1 / 2Δ at the time of the pulse mode switching
The correction amount of θ is calculated and the correction is performed.

[0075]

According to the present invention, the output voltage can be controlled continuously by correcting the phase delay of the fundamental modulation wave between the asynchronous modulation and the synchronous modulation, so that the output current does not fluctuate due to the switching of the modulation mode. , Smooth control can be performed.

[Brief description of the drawings]

FIG. 1 is a main circuit diagram of a three-level inverter device for driving a vehicle to which the present invention is applied.

FIG. 2 is a control block diagram showing one embodiment of the present invention.

FIG. 3 is a PWM control characteristic diagram of a three-level inverter.

FIG. 4 is a pulse waveform diagram of a basic modulation wave command and output voltage of dipolar modulation.

FIG. 5 is a pulse waveform diagram of a basic modulation wave command and output voltage of partial dipolar modulation.

FIG. 6 is a pulse waveform diagram of a basic modulation wave command and output voltage of unipolar modulation.

FIG. 7 is a pulse waveform chart of an overmodulation basic modulation wave command and an output voltage.

FIG. 8 is an explanatory diagram showing a relationship between an inverter output voltage command and a modulation factor.

FIG. 9 is an explanatory diagram showing a pulse waveform of an output voltage of one-pulse control.

FIG. 10 is an explanatory diagram showing a pulse timing generation direction during multi-pulse control.

FIG. 11 is an explanatory diagram of a transition from overmodulation to one-pulse control.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Phase calculation part, 3 ... Modulation rate calculation part, 5 ... Bias setting part, 10 ... Pulse timing calculation part, 11 ... Timer output part, 12 ... Cos ^-1 E * calculation part, 13 ... Phase timing calculation part, 14 ... Pulse mode switching unit, 16 ... Phase correction unit, 1
7: phase adjustment unit, 18: sampling setting unit.

Continuation of the front page (56) References JP-A-5-146160 (JP, A) JP-A-5-344739 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7 / 48 H02M 7/5387

Claims (2)

(57) [Claims] A DC voltage is changed to a three-phase three-phase by turning on and off a plurality of switching elements by a pulse control signal.
An inverter for converting to an AC voltage , wherein the inverter generates a basic modulation wave command proportional to a phase voltage of an AC output of the inverter .
Means for sampling the basic modulation wave command at a predetermined sampling cycle asynchronously with respect to the phase of the basic modulation wave command, and setting the pulse rise and fall of a pulse width corresponding to the magnitude of the basic modulation wave command. A multi-pulse control mode that generates the pulse control signals of a plurality of pulse trains in a half cycle of the basic modulation wave command by a pulse width modulation method that calculates a timing angle, and a sampling cycle is synchronized with the phase of the basic modulation wave command. It is allowed rise of one pulse in the half cycle of the fundamental modulation wave instruction and calculates the angle of the falling timing, and the one-pulse control mode for generating the pulse control signal of one pulse half cycle of the fundamental modulation wave instruction switching of the inverter control device for controlling said inverter, and said multi-pulse control mode and the one-pulse control mode by Sometimes, the phase of the basic modulation wave command is made to correspond to the phase sequence for a predetermined period depending on the sampling period.
A control device for a pulse width modulation type inverter, comprising: means for making a correction for advancing or delaying . 2. The control device for a pulse width modulation type inverter according to claim 1, wherein the correction for the predetermined period is performed for a half of the sampling period.