JP2002300782A - Multiple inverter and its control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple inverter which makes a stable operation without requiring a large reactor. SOLUTION: An output-current balance control part 4 is made on by an output-current balance control on-off part 7 when a switch 8 is switched off and switches 9 and 10 are switched on while an output-voltage instruction 5 is low not exceeding amplitude range of a PWM delta wave carrier signal, and the output-current balance control part 4 is switched off when the output voltage instruction is raised. The output-current balance control can always be made when the switch 8 is switched on and the switches 9 and 10 are switched off, since the output-voltage instruction 5 does not exceed the amplitude range of the PWM delta wave carrier signal by an output-voltage instruction limit control part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a voltage-type pulse (PW).
M) The present invention relates to a method for controlling a multiplex inverter device including a plurality of inverters (hereinafter, simply referred to as inverters).

[0002]

2. Description of the Related Art FIG. 2 shows a basic circuit diagram of a multiplex inverter device in which two single-phase inverters are multiplex-connected in parallel.

[0003] The single-phase inverter 1 comprises a DC voltage source V1;
Switching elements (IGBT) S1 to S4 and diodes D1 to D4 connected in antiparallel to switching elements S1 to S4
And output reactors L1 and L2, which are also connected in parallel to a single-phase inverter 2 composed of a DC voltage source V2, switching elements S5 to S8, diodes D5 to D8, and output reactors L3 and L4. ing.

In this circuit, as shown in FIG.
The switching elements S1 and S2 of the inverter 1 are switched on and off alternately by comparing the output voltage command of the PWM generation unit and the triangular wave carrier signal, and between the on of the switching element S1 and the on of S2. A both-on section called an on-delay time is provided to prevent a vertical short circuit.

FIG. 4 shows an example of output current balance control in the multiplex inverter device of FIG. In the figure, 5 is an output voltage command of the inverter, 11 is a PWM generation unit, 21 is an on-delay time setting unit, 4 is an output current balance control unit,
Reference numeral 31 denotes a drive circuit unit for V1, S1-S4, and D1-D4 described with reference to FIG.

The switching elements S5 and S of the inverter 2
6 is basically the switching elements S1, S2 of the inverter 1.
When the output current is unbalanced due to a switching timing shift or a difference in the ON voltage of the transistor, the output current is balanced by the output current balance control loop by the output current balance control unit 4. Then, the output voltage command is corrected.

That is, when the output currents of the inverters 1 and 2 are lu1 and lu2, respectively, the output current balance controller 4 calculates an average value by dividing the sum of the two output currents by the number of inverters. (Proportional or integral) control the difference between the output currents lu1 and lu2 of the inverters to be balanced and if the output current is larger than the average current value, lower the output current command and reduce the output current to the average current value. If smaller, the output current command is increased to control the output currents lu1 and lu2 so that they are balanced by the average value.

[0008]

However, as shown in FIG. 5, when the output voltage command of the PWM generator of the multiplex inverter is going to exceed the amplitude range of the triangular carrier signal,
If only one of the voltage commands first exceeds the triangular wave carrier signal by the output current balance control, only one of the inverters may perform switching. A switching difference in delay time occurs between the inverter 1 and the inverter 2. Due to the switching difference of the on-delay time, the balance of the output current is lost. For this reason, in order to suppress the circulating current flowing between the inverters, the AC reactor becomes large.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a control method of a multiplex inverter and a multiplex inverter apparatus that do not require a large-sized reactor and perform stable operation.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method in which an output of a PWM is made to be the same for a plurality of inverters before an output voltage command of a PWM generator exceeds an amplitude range of a triangular wave carrier signal. Alternatively, the output voltage command of the PWM generator is limited so that the output voltage command does not exceed the amplitude of the triangular carrier signal, and the output current balance control is always performed.

In the control of the multiplex inverter according to the present invention, if a method is used in which the output of the PWM is the same for a plurality of inverters before the output voltage command of the PWM generator exceeds the amplitude range of the triangular carrier signal, a low frequency In this case, the output current balance control works, so that the output reactor can be reduced in size. In addition, since the output voltage command of the inverter can be output to a point beyond the amplitude range of the triangular wave carrier signal, there is an advantage that the output voltage can be increased. In addition, the number of times of PWM switching is reduced, and the generation loss of the inverter (loss of IGBT). Can also be suppressed.

If a method is used in which the output voltage command of the PWM generator is limited so that the output voltage command does not exceed the amplitude range of the triangular wave carrier signal and the output current balance control can be always performed, the output current balance control is always performed. As a result, the circulating current is reduced, and the output reactor can be reduced in size.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a multiplex inverter device according to one embodiment of the present invention.

The multiplex inverter device of this embodiment is configured by adding an output voltage command limit control unit 6, an output current balance control on / off unit 7, and switches 8, 9, and 10 to the conventional device of FIG. . Switching of the switches 8 to 10 is performed by a soft parameter (constant setting) of the inverter.

When the switch 8 is turned off and the switches 9 and 10 are turned on, while the output voltage command unit 5 is low and does not exceed the amplitude range of the PWM triangular carrier signal, the output current balance control on / off unit 7 controls the output current. The balance control unit 4 is turned on, and when the output voltage command rises and exceeds the amplitude of the triangular carrier signal, the output current balance control unit 4 is turned off. Since the output frequency command generally increases as the output voltage command of the inverter increases, the impedance of the reactor connected to the output increases when the output voltage command increases, and the output current balances.

When the switch 8 is turned on and the switches 9 and 10 are turned off, the output voltage command limit control unit 6 does not cause the output voltage command 5 to exceed the amplitude range of the PWM triangular carrier signal, so that the output current balance control can always be performed.

It is needless to say that the present invention can be applied to a multiplex inverter device having three or more inverters. Also, multiple inverters can be connected using the impedance of a transformer instead of the reactors L1, L2, L3, and L4. Further, the inverter may have three phases.

[0019]

As described above, according to the present invention, in a multiple inverter device, disturbance of output current balance control due to the influence of the ON delay time can be prevented, and an excessive AC reactor for preventing circulating current. Therefore, there is an effect that a stable and inexpensive multiplex inverter device can be manufactured without requiring any of the above.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a multiplex inverter device according to an embodiment of the present invention.

FIG. 2 is a basic circuit diagram of a multiplex inverter device in which two single-phase inverters are multiplex-connected in parallel.

FIG. 3 is a waveform diagram showing an operation of a PWM generator.

FIG. 4 is a diagram illustrating an example of output current balance control;

FIG. 5 shows a case where an output voltage command exceeds a triangular wave carrier.
FIG. 6 is a diagram illustrating a PWM output.

[Explanation of symbols]

 1, 2 Inverter 4 Output current balance control unit 5 Inverter output voltage command 6 Output voltage command limit control unit 7 Output current balance control on / off unit 8 to 10 switch 11, 12 PWM generation unit 21, 22 On delay time setting unit 31 , 32 Drive circuit V1, V2 DC voltage source S1 to S8 IGBT T1 to T4 Current detector L1 to L4 Correlation reactor

Claims (5)

[Claims] In a multiplex inverter device having a plurality of voltage-type pulse modulation inverters whose outputs are connected via a reactor or a transformer, when an imbalance occurs in the output current of each inverter, the PW of each inverter is reduced.
In a control method of a multiplex inverter device, which performs output current balance control for balancing output currents between inverters by controlling the width of M, the output voltage command is low, and the output voltage command is not exceeded when the amplitude does not exceed the amplitude range of the PWM triangular wave carrier. A control method of a multiplex inverter device, wherein output current balance control is performed, and when an output voltage command rises, an output of a PWM generator is made the same for a plurality of inverters. 2. In a multiplex inverter device having a plurality of voltage-type pulse modulation inverters whose outputs are connected via a reactor or a transformer, when an imbalance occurs in the output current of each inverter, the PW of each inverter is reduced.
An output current balance control that balances the output currents of the inverters by controlling the width of M. In the control method of a multiplex inverter device, the output voltage command of the PWM generator is output so that it does not exceed the amplitude of the triangular wave carrier. A control method for a multiplex inverter device, wherein a limit is set for a voltage command and output balance control is always performed. 3. An output comprising a plurality of voltage-type pulse modulation inverters connected via a reactor or a transformer, and when an imbalance occurs in the output current of each inverter, controlling the PWM width of each inverter. In a multiplex inverter device having an output current balance control unit for performing output current balance control for balancing output currents between inverters, the output current balance control is performed while the output voltage command is low and does not exceed the amplitude range of the PWM triangular wave carrier. Activate the part,
A multiplex inverter device comprising an output current balance control on / off unit that deactivates the output balance control unit when an output voltage command increases. 4. An output comprising a plurality of voltage-type pulse modulation inverters connected via a reactor or a transformer, and when an imbalance occurs in the output current of each inverter, controlling the PWM width of each inverter. In a multiplex inverter device with an output current balance control unit that performs output current balance control that balances the output current between inverters, the output voltage command of the PWM generation unit is limited to the output voltage command so that it does not exceed the amplitude of the triangular wave carrier A multiplex inverter device comprising an output voltage command limit control unit for applying a voltage. 5. An output comprising a plurality of voltage-type pulse-modulated inverters connected via a reactor or a transformer, and when an imbalance occurs in the output current of each inverter, controlling the PWM width of each inverter. In a multiplex inverter device having an output current balance control unit for performing output current balance control for balancing output currents between inverters, the output current balance control is performed as long as the output voltage command is low and does not exceed the amplitude range of the PWM triangular wave carrier. Activate the part,
When the output voltage command rises, an output current balance control on / off section that deactivates the output balance section, and limits the output voltage command so that the output voltage command of the PWM generation section does not exceed the amplitude of the triangular wave carrier. An output voltage command limit control unit; between the output current balance control unit and the output current balance control on / off unit;
A first switch, a second switch, and a third switch provided between the output voltage command limit control unit and the PWM generation unit of each inverter during the PWM generation unit; and when the first and second switches are turned on. And a switch setting unit for turning on the third switch when the third switch is off and the first and second switches are off.