JP3219098B2 - Control method of transistor converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a transistor converter.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional transistor converter, FIG. 5 is a time chart for explaining the operation of the device of FIG. 4, and FIG. 5 (a) shows the phase voltage of each phase of an AC power supply. FIG. 5 (b) shows the drive signal of the transistor 4, FIG. 5 (c) shows the line voltage, and FIG. 5 (d) compares the maximum line voltage with the output of the transistor converter. FIG. Here, t represents time.

A phase detector 2 is a three-phase AC power supply 1 (hereinafter, referred to as an AC power supply).
Power supply) is detected. 6 tran
Negative switching element 4_U1, Four_U2, Four_V1, Four_V2, Four_W1, Four
_W2 Is a diode 5_U1, Five_U2, Five_V1, Five_V2, Five_W1, Five
_W2 Are connected in anti-parallel to form six main circuit elements.
ing. Each main circuit element is a reactor of each phase._U, 3_V, 3
_W , U of power supply by full-wave rectification connection via phase detector 2,
Connected to V and W phase terminals,
The circuit is configured. Below, transistor switch
The switching element is referred to as a transistor, and the transistor switching
Element 4_U1~Four_W2 Are collectively referred to as transistor 4.
Iod 5_U1~Five_W2 Are collectively referred to as a diode 5. Ko
The inverter control unit 10 determines the phase of FIG.
As shown in FIG.
Signal D_U1, D_U2, D_V1, D_V2, D_W1, D_{W Two} Generate flat
The smoothing capacitor 6 smoothes the output voltage of the main circuit. Inva
Data 7 is a transistor smoothed by the smoothing capacitor 6
The output voltage of the converter is output from the inverter control unit 11.
Drive signal D_I Modulation to the current width corresponding to
Then, the three-phase induction motor 8 is driven.

[0004] The device of FIG. 4 operates as follows. First,
Phase voltage V of each phase_U, V_V, V_W Is shown in Fig. 5 (a).
Line voltage V_UV, V_VW, V_WU, V
_VU, V _WV, V_UW Changes as shown in FIG. 5 (c). here
In V_UV= V_U−V_VTherefore, other line voltages are similarly defined.
Therefore, the voltage of the smoothing capacitor 6, that is, the transformer
Output voltage of the transistor converter V_DCIs greater than the amplitude of the line voltage
Is lower, the largest line voltage among the line voltages is
When the applied circuit is connected, the smoothing capacitor 6
While charging, other circuits are cut off. For example, between lines
V out of voltage_{U- W} Is the largest period Z_UW (FIG. 5
In (c)), the diode 5_U1, Five_{W Two} Has
Voltage is applied to make it conductive, but other diodes
Is applied with a reverse voltage and is shut off. Also Transis
Transistor 4_U1, Four_W2Reverse voltage is applied to
Is turned off, and the forward voltage is applied to the other transistors.
But the drive signal, the base voltage,
Since these are in the arc extinguishing period (see FIG. 5 (b)),
The transistor is shut off. Thus, the smoothing capacitor 6
Is the highest voltage V between line voltages_UVW ((C) in FIG. 5)
Medium, voltage represented by thick curve, below, maximum line voltage
Pressure). Therefore, the transi
V as in the initial operation of the star converter._DCIs V_UVW Compared to
When all are small, the smoothing capacitor 6 is
The battery is initially charged through the node 5. Initialization of smoothing capacitor 6
After the power is turned on, for example, the three-phase induction motor 8 performs light-load operation.
At the time, as shown in FIG._UVW> V
_DC Period and V_UVW<V_DC There is a period. And V_UVW> V
_DC During the period, the smoothing capacitor passes through the diode 5
6 is charged and V_UVW<V_DC , For example, period Z_UW During ~
V_UVW<V_DC In the short period when
Star 4_U1, Four_W2 Forward voltage and base voltage
(Drive signal) is in the firing period.
The current discharged from the transistor 6 is the transistor 4_U1, Four_W2 Through
Is returned to the power supply. At this time, all the diodes
5, a reverse voltage is applied and cut off. Thus, 3
When the phase induction motor 8 is lightly loaded, even during power running operation
There is a period during which current flows through the transistor 4,
Period during which current flows through diode 5 even during operation
There is a pause. However, in general, as described later,
At the time of power running of the motor 7, that is, at the time of power running of the three-phase induction motor.
Means that current mainly flows through the diode 5 and
Power is supplied to the load side. Also, the regeneration of the inverter 7
At the time of regenerative operation of the three-phase induction motor,
The rotational energy of the conductive motive 8 is converted into electric power, and
Power is returned from the load side to the power supply 1 through the transistor 4.
It is.

[0005]

In the above-mentioned conventional transistor converter, the main circuit elements are irrespective of the load state, that is, the load is in a power running state, as shown in FIG. 5 (b). Regardless of whether the vehicle is in the regenerative state or in the power running state or the regenerative state, the power is supplied at a firing angle of 120 degrees in synchronization with the phase of the power supply regardless of the magnitude of the power running power or the regenerative power. As a result, as described below, there is a problem that when power is running with a light load or no load, reactive power is generated to not only lower the power factor of the AC power supply but also cause unnecessary power loss.

FIG. 6 is a time chart for explaining a typical operation of the conventional transistor converter.
(a) and (b), (c) and (d) in FIG. 6, and (e) and (f) in FIG. 6 respectively show (1) when the power running power and the regenerative power of the load are small, and (2) When powering power is large, (3)
Maximum line voltage V _UV when the regenerative power of the load is large
FIG. 3 is a diagram illustrating a relationship between _W and an output voltage _VDC , and a diode current and a transistor current. These voltages,
As is easily understood from the differential equation representing the current relationship, in any of the above cases (1), (2), and (3), the time t _{1 at} which the maximum line voltage V _UVW becomes equal to the output voltage V _DC. , t
_{At 2} , the current takes an extreme value. If dV _DC / dt is negligibly smaller than dV _UVW / dt, the maximum line voltage
There are current inflection points at times t ₃ and t _{4 at} which V _UVW takes extreme values V _A and V _B. In the case of (1) further inflection point of the current coincides with the zero crossing point of approximately current, diode current begins to flow at time t ₃ when the maximum line voltage V _UVW takes a maximum value V _A The transistor current starts flowing at time t ₄ when the maximum line voltage V _UVW takes the minimum value V _B , that is, at the leading edge of the drive signal. As described above, in the case of (1), both the diode current and the transistor current flow, so that when the load is in the power running state, the transistor current becomes reactive power, lowering the power factor of the AC power supply 1 and switching as a switching element. Unnecessary power loss will occur in the transistors used. In the case of (2), since the output voltage V _DC of the transistor converter becomes lower, the maximum line voltage V
_UVW is lower than the output voltage V _DC T _V1 is the circuit time constant τ
= L / R (L is the inductance of the reactor, R is the equivalent load resistance). Therefore, the diode current flows continuously to the load, and the transistor current does not flow. Therefore, in the case of (2), no reactive power is generated, and no power loss occurs in the transistor. In the case of (3), the smoothing capacitor is charged by the regenerative current, and the output voltage V _DC increases, so that the maximum line voltage V _UVW is equal to the output voltage.
The period T _V2 higher than V _DC is shorter than the time constant τ of the circuit. Therefore, the transistor current continuously flows through the load. The AC power supply does a negative job with this transistor current, which becomes an effective regenerative power.

According to the present invention, as described above, when the conventional transistor converter is (1), that is, when the power running light load is applied,
Another object of the present invention is to solve the problem of unnecessarily consuming power when there is no load, and an object of the present invention is to improve the power factor of an AC power supply and reduce the power loss of a transistor.

[0008]

According to a first control method of a transistor converter of the present invention, a diode and a transistor switching element are connected in anti-parallel, and the power is transmitted from an AC power source to the load during a power running operation in which the load performs work. In the regenerative operation, in which the power running operation is interrupted and the power running operation is interrupted and the energy stored in the load is recovered in the AC power supply, the power fed back from the load to the AC power supply is transmitted through the transistor switching element. A plurality of main circuit elements are connected to the AC power supply by full-wave rectification connection, a method of controlling a transistor converter that converts AC power to DC power, wherein the number of phases of the AC power supply is N,
A period of 1 / N cycle centering on the peak time of each phase voltage of the AC power supply is defined as a reference firing period of the phase, and the time when the maximum line voltage takes the minimum value and the maximum When defining the time between the time when the line voltage takes the output voltage value of the transistor converter as the reference shortening time, monitor whether the load is in the powering state or the regenerative state, and when the load is in the powering state, , the reference ignition period of each phase, and shortened by reference shortened time at least from the leading edge, to control the energization of the transistor switching element of the phase the shortened period P _K as ignition period, the load regeneration When in the state, the energization of the transistor switching element of the phase is controlled with the reference ignition period of each phase as the ignition period.

A second control method of a transistor converter according to the present invention detects a powering current and a regenerative current, and when the load shifts from the powering state to the regenerative state, the load is regenerated until the regenerative current reaches a predetermined value. Set the firing period to P _K
To the reference ignition period, and after the regenerative current reaches the predetermined value, the ignition period is fixed at the reference ignition period, and when the load shifts from the regenerative state to the power running state, the ignition period discontinuously change to P _K from the reference ignition period.

[0010]

In order to simplify the explanation, the operation of the present invention will be described in the case of N = 3, that is, an example of a three-phase transistor converter. In the following description, the period of one cycle of 3 minutes around the peak of the phase voltage of the three-phase AC power source is defined as a reference ignition period P _S of the phase, the maximum line voltage has the minimum value and time, then the maximum inter-line voltage is defined as a reference shortened period t _S a period between time to take the output voltage value V _DC transistor converter, it is defined as a reference shorten time reference shortened period time.

FIG. 7 is a diagram for explaining current characteristics when the transistor converter is controlled by a drive signal having a firing period in which the leading edge of the reference firing period is shortened by the reference shortening time, and FIG. Figure 7 shows the standard shortening period t _S
(B) and (c) are diagrams showing the relationship between the maximum line voltage and the diode current when the power running power is small.

As described above, when the powering power is small in the conventional transistor converter (in the case of (1)), the transistor current rises at the leading edge of the 120-degree firing period. Therefore, during a period in which at least the reference shortening time t _S elapses from the leading edge, that is, a period satisfying V _UVW <V _DC , the transistor current is suppressed by suppressing the ignition of the transistor, that is, by shortening the ignition period. It is possible to prevent unnecessary power loss and reduction of the power factor of the AC power supply. Here, no effect on the operation of the transistor converter even time to shorten the reference time savings t _S or more. The reason is that the diode current flows during the period in which the shortening time exceeds the reference shortening time, and is therefore irrelevant to the ON / OFF of the transistor. Similarly, shortening the trailing edge of the conventional ignition period (indicated by the dotted hatching in the drive signal of FIG. 7) does not affect the operation of the transistor converter.

The above shortening of the ignition period is unnecessary when the power running power of the load is large (in the case of (2)) and when the regenerative power is large (in the case of (3)). However, when the power running power of the load is large, the diode current flows exclusively, so that the operation of the transistor converter is not affected even if the firing period of the transistor is shortened. In the present invention, therefore, the load is monitored whether a regenerative state or is in the power running state, when in the power running state regardless of the running power, the reference ignition period P at least a reference shortened time t at the leading edge of the _{S The} ignition period is shortened by _S, and when the load is in a regenerative state, the transistor converter is operated at the conventional ignition angle, that is, the reference ignition period. However, when transitioning from the power running state to the regenerative state, the regenerative current is monitored and the change in regenerative current is monitored to prevent overcurrent from flowing into the AC power supply when the firing period or firing angle is suddenly changed. , The ignition period is gradually increased, and when the regenerative current has reached a predetermined magnitude, the ignition period is controlled so as to become the reference ignition period.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of an induction motor drive system to which a control method of a transistor converter according to the present invention is applied.

The phase detector 2 detects the phase Ph of the three-phase AC power supply 1.
Is detected. 6 transistors 4 _U1, Four_U2, Four_V1, Four_V2,
 Four_W1, Four_W2 Is a diode 5_U1, Five_U2, Five_V1, Five_V2,
 Five_W1, Five_W2 6 main circuit elements are connected in anti-parallel to
Has been established. Each main circuit element is
_U, 3_V, 3_W , AC through full-wave rectification connection via phase detector 2
Connected to U, V, W phase terminals of power supply,
The main circuit of the inverter is configured. Converter control unit 10
Is the phase Ph of the AC power supply 1 and the DC detection signal I_DC(Or i
Converter secondary current command I_2COM) Based on transistor
 Four_U1,Four_U2, Four_V1, Four_V2, Four_W1, Four_W2 Drive to each of
Signal S_U1, S_U2, S_V1, S_V2, S_W1, S_W2 Is output. smooth
The capacitor 6 smoothes the output of the main circuit. Inverter system
The control unit 11 uses the inverter secondary current command I_2COMInn corresponding to
Barter drive signal D_I Generate Inverter 7 is
Inverter drive the output voltage of the transistor converter
Signal D_I PWM modulation to the conduction width corresponding to
The motive 8 is driven. DC detector 9 is a transistor converter
The direction and magnitude of the output current of the
Issue I_DCIs output.

Next, the operation of this embodiment will be described.

[0017] Figure 2 is a diagram showing the relationship between arc period or point firing angle of the direct-current detection signal I _DC and transistor transistor converter, FIG. 3 is a diagram for explaining the operation of the apparatus of FIG. 1,
3 (a) is a drive signal, and FIG. 3 (b) is a maximum line voltage.
FIG. 3C shows V _UVW and U phase diode current Iu.

When the DC detector 9 outputs a positive DC detection signal I _DC indicating the power running state of the load, the converter controller 10
_Are drive signals D _U1 , D _U2 , D _V1 , D _V2 , with a firing angle of 120 degrees (reference firing period P _S ) for driving the transistor 4
D _W1, drive signal D reference shorten time leading and trailing edges of the _W2 t _S only shortened the firing angle theta _K by (or firing period _{P K) S U1, S U2} , S V1, S V2, S _W1 and _SW2 are generated and output to the base of the transistor 4, respectively. This drive signal S
By controlling the main circuit by _U1 to S _W2, when the running power is low, or at the time of no load U-phase diode current-time characteristics, such as (c) in FIG. 3 is obtained. Of FIG.
In (c) represents a direction flowing from the U phase terminal of the AC power source as the positive direction, the symbols (5 _u1, 5 _v2) is diode 5 _u1 flows out from the U-phase terminal of the AC power source, a load, via the diode 5 _v2 The current flowing into the V-phase terminal of the AC power supply is represented by the symbol (5 _v1 , 5 _u2 ). The current flows out of the V-phase terminal of the AC power supply, flows into the U-phase terminal via the diode 5 _v1 , load, and diode 5 _u2. Represents Other symbols are similarly represented. When the powering power is large, a load current / time characteristic as shown in FIG. 6D is obtained regardless of the drive signal. The reason for shortening the trailing edge of the drive signals _DU1 to _DW2 is that the transistors are set to the forward voltage before the reference shortening period starts when there is no load or when the power running power is small due to the selection of circuit constants and other reasons. This is because it may be.
In such a case, the drive signal immediately before the reference shortening period becomes low level due to the shortening of the trailing edge, so that the conduction of the transistor is prevented.

[0019] When the load is shifted from the power running state to the regenerative state, i.e., when the DC detection signal I _DC shifts from positive to negative, converter control unit 10, the set value the absolute value of the direct current detection signal I _DC from 0 - Until I _C , the firing angle of the drive signals S _U1 to S _W2 is extended from θ _K to 120 degrees as a linear function of the absolute value of the DC detection signal I _DC (or the firing period P
Is extended from P _K to one-third cycle), and the absolute value of I _DC is
When I _C is exceeded, the firing angle of drive signals S _U1 to _{SW 2 becomes} 120
Fix every time. By gradually increasing the firing angle in this way, it is possible to prevent an overcurrent from flowing into the AC power supply at the start of regeneration. At this time, if the regenerative power is small and there is no danger of overcurrent flowing to the AC power supply, the firing angle is set to θ _K when the DC detection signal I _DC shifts from positive to negative.
From 120 degrees to discontinuous. Therefore, the direct current detection signal I _DC in this case is only sufficient provide a positive or negative information.

[0020] When the load is transferred from the regeneration state to the power running state, i.e., when the DC detection signal I _DC to positive transition from the negative, the converter control unit 10 from the 120 ° firing angle of the drive signals S _U1 ~ S _W2 θ _K.

Although the direct current detection signal I _DC is used for controlling the converter control unit 10 in the above embodiment, a similar result is obtained by using the inverter secondary current command I _2COM . In FIG. 1, the parenthesized _I2COM is a DC detection signal I _DC
It is shown that it can be used instead of.
Although this embodiment is an example of a three-phase transistor converter, it has been proved that the present invention can be applied to a single-phase transistor converter.

[0022]

As described above, the present invention has the following effects. (1) When the power running is light or no load, the drive signal is shortened so that conduction of the transistor is suppressed during the period when the forward voltage is applied to the transistor. Not only can the rate be prevented from lowering, but also the output voltage ripple is reduced since no discharge from the smoothing capacitor to the AC power supply occurs via the transistor. (2) When the load shifts from the power running state to the regenerative state, it is possible to prevent the overcurrent from flowing into the AC power supply by gradually expanding the ignition period in response to the increase in the regenerative current.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an induction motor drive system to which a transistor converter control method according to the present invention is applied.

2 is a diagram showing the relationship between the transistor converter DC detection signal I _DC and the ignition period of the transistor.

FIG. 3 is a diagram for explaining the operation of the apparatus of FIG. 1, and FIG.
Is the drive signal, FIG. 3 (b) is the maximum line voltage, and FIG.
(c) is a diagram showing a U-phase diode current.

FIG. 4 is a configuration diagram of a conventional transistor converter.

FIG. 5 is a time chart for explaining the operation of the apparatus of FIG. 4; FIG.
(b) is a diagram showing a drive signal of the transistor 4, and FIG.
FIG. 5C is a diagram showing the maximum line voltage, and FIG. 5D is a diagram for comparing the maximum line voltage with the output voltage of the transistor converter.

FIG. 6 is a time chart for explaining a typical operation of the conventional transistor converter.
(b), (c) and (d) of FIG. 6, and (e) and (f) of FIG. 6 show that when the power running power and the regenerative power of the load are small,
FIG. 4 is a diagram illustrating a relationship between a maximum line voltage V _UVW and an output voltage V _DC when a power running power of a load is large and a regenerative power of the load is large, and a diode current and a transistor current.

7A and 7B are diagrams illustrating current characteristics when a transistor converter is controlled by a drive signal having an ignition period obtained by shortening a leading edge of a reference ignition period by a reference shortening time. FIG. FIG. 7B and FIG. 7C show the relationship between the maximum line voltage and the diode current when the power running power is small.

[Explanation of symbols]

1 Three-phase AC power supply 2 Phase detector 3 _U , 3 _V , 3 _W reactor 4 _U1 , 4 _U2 , 4 _V1 , 4 _V2 , 4 _W1 , 4 _W2 Transistor 5 _U1 , 5 _U2 , 5 _V1 , 5 _V2 , 5 _W1 , 5 _W2 diode 6 Smoothing capacitor 7 Inverter 8 Three-phase induction motor 9 DC detector 10 Converter controller 11 Inverter controller

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/219

Claims (2)

(57) [Claims] A diode and a transistor switching element are connected in anti-parallel to each other. In a power running operation in which the load performs work, power transmitted from an AC power supply to the load is transmitted through the diode, and the power running operation is interrupted and the load is interrupted. At the time of regenerative operation for recovering stored energy to the AC power supply, a plurality of main circuit elements that transmit power returned from the load to the AC power supply via the transistor switching element are connected to the AC power supply through full-wave rectification connection. In the method of controlling a transistor converter for converting AC power to DC power, the number of phases of the AC power supply is set to N, and a period of 1 / N cycle around the peak time of each phase voltage of the AC power supply is set to the phase. The time at which the maximum line voltage takes the minimum value and the immediately following maximum line voltage are the output of the transistor converter. When defining the time between the time when the voltage value is taken as the reference shortening time, it monitors whether the load is in the power running state or the regenerative state, and when the load is in the power running state, the reference firing period of each phase and was shortened by reference shortened time at least from the leading edge, to control the energization of the transistor switching element of the phase the shortened period P _K as ignition period, when the load is in a regenerative state, each phase of A control method for a transistor converter, comprising: controlling the energization of a transistor switching element of the phase with a reference ignition period as an ignition period. 2. When the power running current and the regenerative current are detected and the load shifts from the power running state to the regenerative state, the ignition period is set to P corresponding to the regenerative current until the regenerative current reaches a predetermined value.
_K is changed continuously from the reference ignition period, and after the regenerative current reaches the predetermined value, the ignition period is fixed to the reference ignition period, and when the load shifts from the regenerative state to the power running state, the ignition is performed. the method according to claim 1, characterized in that to change discontinuously to P _K a period from the reference ignition period.