JP3113117B2 - Power converter control method and control device thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse width modulation control (PWM control) converter for converting AC power to DC power, and a power converter applied to a PWM control inverter for converting DC power to AC power. The present invention relates to a control method and a control device thereof.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration diagram of one phase (U phase) of a PWM control inverter. In the case of a three-phase output inverter, the V and W phases are similarly configured.

In the figure, Vd1 and Vd2 are DC voltage sources, S1 and Sd.
2 is a self-extinguishing element, D1 and D2 are freewheeling diodes, LOAD is a load, CTU is a current detector, C1
, C2 are comparators, GU (S) is a current control circuit, PWM
C is a pulse width modulation control circuit, TRG is a carrier generator, S
M is a Schmitt circuit. The load current IU is detected by the current detector CTU, and the current command value IU is detected by the comparator C1.
^* ΕU = IU ^* -Find IU. This deviation εU is amplified by the current control circuit GU (S) to obtain eU
= GU (S) · εU is input to the pulse width modulation control circuit PWMC.

In the pulse width modulation control circuit PWMC, the carrier generator TRG generates a triangular wave X, which is compared with the input signal eU by the comparator C2 and the gates of the self-extinguishing elements S1 and S2 via the Schmitt circuit SM. Generate a signal gU.
FIG. 6 is a time chart for explaining the operation of the PWM control circuit PWMC of FIG. 5, that is, when eU ≧ X, gu = 1, S1: on (S2: off), and eU <X When gu = 0, S1 is off (S2: on). At this time, when the DC power supply voltage is Vd1 = Vd2 = Vd / 2, the output voltage VU of the inverter is VU = + Vd / 2 when S1 is on (S2 is off) and S1 is off (S2 is on) In this case, VU = -Vd / 2, and the average value VU (shown by a broken line) is a value proportional to the input signal eU. Therefore, this input signal eU becomes the voltage command value of the inverter.

[0005] IU ^* > IU, deviation εU = IU ^* −
IU becomes a positive value, and the voltage command value eu increases. Therefore, the output voltage Vu of the inverter increases in proportion to eU, and the load current IU increases.

On the contrary, IU ^* If <IU, the deviation ε
U = IU ^* −IU becomes a negative value, and the voltage command value eU decreases. Therefore, the output voltage VU of the inverter decreases, and the load current IU decreases. Finally, IU = IU ^* It is controlled so that Current command value IU ^* Is changed in the form of a sine wave, the load current IU is also controlled to follow the change, and a sine wave current can be supplied to the load LAOD.

As described above, the PWM control inverter can obtain the output voltage VU proportional to the voltage command value eU,
It is widely used as a variable voltage variable frequency power supply in AC motor drive devices and the like.

[0008]

However, the conventional PWM
The control inverter has the following problems. A gate turn-off thyristor (GTO) or the like is used as an element constituting the inverter. A snubber circuit is connected in parallel with the element to protect the element. In order to initialize (discharge) the capacitor of this snubber circuit, once the element is turned on, it must be kept on for a certain period of time. Further, the minimum on / off time is determined from the characteristics of the element itself, and the pulse width of the gate signal is given to satisfy the minimum on / off time.

In FIG. 6, + kmax and -kmax represent an upper limit value and a lower limit value of the voltage command value eU.
An output voltage VU proportional to the voltage command value eU can be generated in a range of max≥eU≥-kmax.

When eU = + kmax, the gate signal gU =
The period of 0 is toff, which satisfies the minimum off time of the element S2 (minimum on time of the element S1). Similarly, e
When u = −kmax, the period of the gate signal gU = 1 is tof
f, which satisfies the minimum on-time of the element S1 (the minimum off-time of the element S2).

When eU> + kmax or eU <-kmax, the period of the gate signal gU = 0 or gU = 1 is toff.
And the minimum on or off time of the device cannot be satisfied. Therefore, a limiter circuit or the like is provided to change the voltage command value eU to + kmax ≧ eU ≧ −kmax.
Limited to the range.

For example, carrier frequency fc = 500 Hz
In this case, the cycle T of the triangular wave X is 2 msec, and to satisfy the minimum off-time (or minimum on-time) toff = 200 μsec, kmax = 0.8. That is, the utilization rate of the inverter in this case is 80%, and the remaining 2
0% is wasted. A large inverter capacity must be prepared for the reduced utilization, and the conventional P
The WM control inverter was an uneconomical system.

The present invention has been made in view of the above problems, and has a minimum ON time of an element (a minimum OFF time of an element S2).
Power conversion that can increase the utilization factor of the converter to 100% while ensuring that the output voltage is proportional to the input signal even when the absolute value of the input signal (voltage command value) e is large. It is an object of the present invention to provide a method of controlling a vessel and a control device thereof.

[0014]

According to a first aspect of the present invention, there is provided a power converter of pulse width modulation control, wherein a voltage command value given to the power converter is e (-1). ≦ e ≦ + 1), when the maximum modulation rate of the PWM control is kmax, and when −kmax ≦ e ≦ + kmax, the output voltage of the power converter is controlled by ordinary pulse width modulation control.

When e <-kmax, the error time .DELTA.t is added to the width ti of the control pulse Pi to obtain a new control pulse width ti '= ti + .DELTA.t, and the pulse width ti' is set to the set time ts. On the other hand, when ti'≥ts, the control pulse with the pulse width ti 'is output as it is, the error time .DELTA.t = 0 is stored in the memory, and the error time .DELTA.t is added to the next control pulse. This is a method for controlling the power converter. To achieve the above objective,
According to a second aspect of the present invention, in the power converter of the pulse width modulation control, the voltage command value given to the power converter is e (−1 ≦ e ≦ + 1), and the maximum modulation rate of the PWM control is k.
When −kmax ≦ e ≦ + kmax, the output voltage of the power converter is controlled by ordinary pulse width modulation control,

When + kmax <e, the error time .DELTA.t is added to the width ti of the control pulse Pi to obtain a new control pulse width ti '= ti + .DELTA.t, and the pulse width ti' is set at the set time ts. On the other hand, when ti '<ts, the power converter is configured to store the error time .DELTA.t = ti' in the memory without an output pulse and to control the error time .DELTA.t to be added to the next control pulse. Is a control method.

According to a third aspect of the present invention, there is provided a power converter for controlling based on a control pulse obtained by comparing an input signal of pulse width modulation control with a carrier signal.

When the pulse from the pulse transmission circuit and the control pulse are input and the control pulse is shorter than a set time, a memory for storing the error signal Δt and a logical operation are performed to constitute the power converter. And an arithmetic circuit for obtaining an output signal to be given to the element performing the arithmetic operation.
The voltage command value given to the power converter is e (−1 ≦ e
≤ +1), where the maximum modulation rate of the PWM control is kmax, and when -kmax ≤ e ≤ + kmax, the output voltage of the power converter is controlled by ordinary pulse width modulation control,

When e <-kmax or + kmax <e, the error time .DELTA.t is added to the width ti of the control pulse Pi to obtain a new control pulse width ti '= ti + .DELTA.t, and the pulse width ti' is set. For a given time ts, ti
When '≧ ts, a control pulse having a pulse width ti' is output as it is, and the error time Δt = 0 is stored in a memory.
When ti '<ts, the error time .DELTA.t = ti' is stored in the memory without an output pulse, and the control is performed by adding the error time .DELTA.t to the next control pulse. It is a control device of a power converter.

[0020]

According to the invention described in any one of the first to third aspects, the following effects can be obtained. That is,-
When kmax ≦ e ≦ + kmax, the output voltage of the power converter is controlled by ordinary pulse width modulation control, and e <−k
max or + kmax <e, width t of control pulse Pi
i, the error time Δt is added, and a new control pulse ti '= ti
+ .DELTA.t is obtained, the ti 'is compared with a set time ts, and when ti'≥ts, an output pulse is output to ti'.
When '<ts, no output pulse is issued and Δt = ti
'Is stored in the memory, and control is performed so that Δt is reflected in the next control pulse. As a result, an output voltage proportional to the voltage command value can be obtained, and the minimum off time (or minimum on time) toff of the element can be satisfied. Therefore, the utilization factor of the converter can be increased to 100%, and the conventional problems can be solved.

[0021]

1 shows a pulse width modulation control (PWM) according to the present invention.
2 shows only a part of a circuit for implementing the PWM control method of the power converter of FIG.

In the figure, Ga is a discriminating circuit that outputs 1 when the voltage command value eU is positive and outputs 0 when it is negative, and SW1 and SW2 are switches that operate in accordance with the output signal of the discriminating circuit Ga. Circuit, CAL is an arithmetic circuit having a memory for storing the error time Δt when the width ti of the control pulse Pi is smaller than the set time ts, TCONT is a pulse circuit for outputting a pulse Ps having a width of the set time ts, as will be described later. INV1, INV2, and INV3 are composed of inverting circuits. This configuration is the same for the V and W phases. Next, the control operation will be described. However, the determination is performed with the discrimination signal Sk = 1 when the voltage command value eU is positive.

In FIG. 5, a voltage command value eU and a control pulse Pi (gU) obtained by comparing the triangular wave X by the carrier generator TRG are inputted to the terminal b of the switch SW1 and the inverting circuit INV1 in FIG. The value eU is determined by the discriminating circuit Ga.
Is input to The output IPi of INV1 is the switch S
W1 is input to terminal c, and Ga output signal Sk is applied to switch S
Input to W1 and SW2.

Next, the switch SW1 is connected to the terminal b when the signal Sk = 1, and the output Pi of the terminal a is connected to the arithmetic circuit CAL.
Is input to the pulse circuit TCONT. TCONT outputs a pulse Ps synchronized with the input pulse Pi, and outputs
Input to AL. The arithmetic circuit CAL receives the input Pi and P
s, a logical operation is performed to output a pulse Po, and the pulse Po is input to the e terminal of the switch SW2 and the inverting circuit INV2.
The output IPo of V2 is input to the f terminal of the switch SW2.
The switch SW2 is connected to the terminal e (Sk = 1), and its output terminal d outputs S1, and one outputs an output signal S2 via the inverting circuit INV3. When the signal Sk = 0, the switches SW1 and SW2 are connected to the terminals c and f, and the signal IP
i and IPo are used. FIG. 2 shows a calculation flowchart of the calculation circuit CAL. In the figure, ti (Iti) indicates the pulse width of the input pulse Pi (IPi) selected by the switch SW1, and ts indicates the width of the set time pulse Ps.

First, when the pulse width ti (Iti) is input, Δt obtained in the memory (Process 1) is added, and
The added value ti '= ti + .DELTA.t is input to the comparing section.
The comparison unit outputs a control pulse having a pulse width of ti 'as it is when ti'≥ts with respect to the set time ts,
Storing the error time Δt = 0 in the memory;

When ti '<ts, without output pulse,
The error time .DELTA.t = ti 'is stored in the memory. That is,
The calculation is performed so that the error time Δt is added to the next control pulse to generate a new control pulse. Next, the PWM control operation waveform of the present invention is shown. FIG. 3 shows the voltage command value eU.
Is positive and Sk = 1.

In the figure, tin is the pulse width of the control pulse Pi obtained by comparing the voltage command value eU and the triangular wave X, and
s represents a set time (= toff: minimum off time of the element) (n is an input pulse width number).

First, when Δt = 0 (initial value) and the first control pulse width ti1 is input, the control pulse width is modified to a new control pulse width ti1 = ti1 + Δt, and when ti1 ′ <ts, the control pulse width is changed. ti1 'is not output. As a result, Δt = ti
1 'and stored in the memory. Next, when the second control pulse width ti2 is input, it is corrected to ti2 '= ti2 + .DELTA.t, and when ti2'≥ts, the control pulse width ti2' is output, and .DELTA.t = 0.

When the third control pulse width ti3 is input, the control pulse width t is corrected as in the first control pulse width t i3.
For i3 ', when ti3'<ts, the control pulse ti3 'is not output and .DELTA.t = ti3'. Fourth control pulse width ti4
Is input, ti4 is corrected to ti4 '= ti4 + .DELTA.t, but ti4' is not output because ti4 '<ts. As a result, Δt becomes a new error time Δt ′ = Δt + ti4.

The fifth control pulse width ti5 is equal to the set time t.
wider than s, but ti5 is modified to ti5 '= ti5 + .DELTA.t', and if ti5'≥ts, a control pulse ti5 is output, and .DELTA.t
= 0. FIG. 4 shows a case where the voltage command value eU is negative and Sk = 0.

The input pulse Pi is inverted by INV1 and input to the arithmetic circuit CAL as IPi to perform the same operation as in FIG. The output pulse Po is inverted by INV2 to produce gate signals S1 and S2 from IPo.

As described above, the modified control pulse Pi
Is compared with the set time ts. If ti'≥ts, the control pulse ti 'is output as it is, and ti'<ts
In this case, the control pulse ti 'is not output and the error time .DELTA.
It is stored in the memory as t = ti '. By reflecting the Δt in the next control pulse, an output voltage proportional to the voltage command value eU can be obtained, and the utilization rate of the power converter can be improved.

[0033]

According to the power converter control method and control apparatus of the present invention, the error time .DELTA.t is added to the width ti of the control pulse Pi to obtain a new control pulse ti '= ti + .DELTA.t. By comparing the set time ts with the set time ts and outputting a control pulse according to the result, the voltage command value eU is continuously proportional to the voltage command value eU even in a region where the voltage command value eU is larger than the maximum modulation rate kmax of the PWM control. Output voltage V
U can be obtained, and the minimum on-time or minimum off-time of the elements constituting the converter can be satisfied. As a result, when PWM control is performed on a power converter such as an inverter or a converter, the utilization factor of the converter can be significantly improved, and the voltage Vd of the DC power supply can be reduced accordingly, and the Small size, light weight, efficiency improvement and cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing one embodiment of a control device for a power converter according to the present invention.

FIG. 2 is a flowchart for explaining the calculation processing of FIG. 1;

FIG. 3 is a diagram for explaining a PWM control operation when a voltage command value is positive in FIG. 1;

FIG. 4 is a diagram for explaining a PWM control operation when the voltage command value is negative in FIG.

FIGS. 5A and 5B are diagrams showing a main circuit and a load current control block of the power converter, respectively.

FIG. 6 is a diagram for explaining a conventional PWM control operation.

[Explanation of symbols]

Vd1, Vd2: DC voltage source, S1, S2: self-extinguishing element,
D1, D2 ... free-wheeling diode, LOAD ...
Load, CTU: Current detector, CU1, CU2: Comparator, GU
(S): current control compensation circuit, PWMC: PWM control circuit, TRG: triangular wave generator, SM: Schmitt circuit, G
a: discrimination circuit, SW1, SW2: switch circuit, TCONT
... Pulse circuit, CAL ... Calculation circuit, INV1, INV
2, INV3 ... inverting circuit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02M 7/515 H02M 7/537

Claims (3)

(57) [Claims] 1. A power converter of pulse width modulation control, wherein a voltage command value given to the power converter is e (−1 ≦ e
≤ +1), where the maximum modulation rate of the PWM control is kmax, the output voltage of the power converter is controlled by the normal pulse width modulation control when -kmax ≤ e ≤ + kmax, and when e <-kmax The error time Δt is added to the width ti of the control pulse Pi, and the pulse width ti '=
ti + .DELTA.t is obtained. When ti'≥ts with respect to the time ts at which the pulse width ti 'is set, a control pulse having the pulse width ti' is output as it is, and the error time .DELTA.t = 0
Is stored in a memory, and control is performed by adding the error time Δt to a next control pulse. 2. A power converter of pulse width modulation control, wherein a voltage command value given to the power converter is e (−1 ≦ e
≤ +1), where the maximum modulation rate of the PWM control is kmax, the output voltage of the power converter is controlled by the normal pulse width modulation control when -kmmax ≤ e ≤ + kmmax, and the control is performed when + kmmax <e. The error time Δt is added to the width ti of the pulse Pi, and the pulse width ti '=
ti + .DELTA.t, and when the pulse width ti 'is ti'<ts with respect to the set time ts, the error time .DELTA.t = ti 'is stored in the memory without an output pulse;
A control method for a power converter, wherein the control is performed by adding the error time Δt to a next control pulse. 3. A power converter for performing control based on a control pulse obtained by comparing an input signal of pulse width modulation control with a carrier signal, comprising the steps of: receiving a pulse from the pulse transmission circuit and the control pulse; Is smaller than the set time,
A memory for storing the error signal Δt, and an arithmetic circuit for performing a logical operation to obtain an output signal to be applied to the elements constituting the power converter, and the arithmetic circuit includes a voltage command applied to the power converter. When the value is e (−1 ≦ e ≦ + 1) and the maximum modulation rate of the PWM control is kmax, the output voltage of the power converter is controlled by the normal pulse width modulation control when −kmax ≦ e ≦ + kmmax. , E <−kmax or + kmax <e, the control pulse P
The error time .DELTA.t is added to the width ti of i to obtain a pulse width ti '= ti + .DELTA.t of a new control pulse.
When ti'≥ts with respect to the set time ts for i ', the control pulse having the pulse width ti' is output as it is, the error time .DELTA.t = 0 is stored in the memory, and ti '<t
s, the error time Δt = ti without an output pulse
′ Is stored in the memory, and the error time Δt is added to the next control pulse for control.