JPH08251933A - Controller and control method for inverter - Google Patents

Abstract

PURPOSE: To suppress the inrush current flowing into a transformer connected to the output side at the time of starting an inverter by comparing a reference sine wave signal subjected to phase regulation with a zero potential to produce a phase regulated gate signal. CONSTITUTION: One of two reference sine wave signals Q1 , Q2 for setting the ON-OFF timing of each switching element S1 -S4 in an inverter is subjected to amplitude regulation and added to the other before being subjected to phase regulation. The reference sine wave signals Q1 ', Q2 ' are then compared with a zero potential to produce phase regulated gate signals G1 ', G2 '. Consequently, the effective value of output voltage from the inverter can be regulated through phase regulation of gate signals G1 , G2 . In particular, inrush current flowing into a transformer on the output side of the inverter can be suppressed at the time of starting the inverter by decreasing the gain of the reference sine wave signals Q1 , Q2 for regulating the amplitude gradually thereby increasing the effective value of output voltage from the inverter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device and control method for an inverter, and more particularly, to a system interconnection of a self-excited reactive power compensator (SVC), a variable voltage variable frequency power supply (VVVF), a solar power generation system, and the like. The present invention relates to a control device and control method for an inverter used in a system or the like.

[0002]

2. Description of the Related Art For example, a self-excited var compensator (SV)
C), a variable voltage variable frequency power source (VVVF), a square wave inverter 2 used in a grid interconnection system such as a solar power generation system, and the like as shown in FIG. On the other hand, a plurality (four in the figure) of switching elements S _{1 to} S ₄ are connected in a full-bridge configuration, and a transformer 3 is connected to the output side of this inverter 2 and via the transformer 3. It is connected to the load [system]. In this inverter 2, the switching element S
_The DC power from the DC power supply 1 is AC-converted and supplied to the load by alternately turning ON / OFF ₁ , S ₄ and S ₃ , S ₂ .

The ON-OFF control of the switching elements S _{1 to} S ₄ in this inverter 2 is shown in FIG.
As shown in (d), each of the switching elements S _{1 to} S ₄ is repeatedly turned on or off with a conduction angle of 180 °, and the switching elements S ₁ and S _{3 have a} phase of 60 ° with respect to the electrical angle of the output voltage fundamental wave. Shift [Fig. 5 (a) (c)]
, And the gate signals G _{1 to} G ₄ are generated by inverting the switching elements S ₂ and S ₄ with respect to the switching elements S ₁ and S ₃ , respectively (see FIGS. 5B and 5D).

By applying these gate signals G _{1 to} G ₄ to the switching elements S _{1 to} S ₄ to operate them,
An output voltage Vout having a 120 ° conduction width having a rectangular waveform is obtained [see FIG. 5 (e)]. Low order in this output voltage Vout,
In particular, in order to suppress the appearance of the third harmonic component, the inverter 2 is operated with the conduction angles of the switching elements S _{1 to} S ₄ fixed as described above.

[0005]

By the way, as described above, the inverter 2 is operated with the conduction angles of the switching elements S _{1 to} S ₄ fixed in order to obtain the output voltage Vout having the 120 ° conduction width. And when the inverter 2 starts up,
An excessive rush current may flow in the transformer 3 connected to the output side of the inverter 2, and when the magnetic flux saturation region in the transformer 3 is reached, an overcurrent may occur, and the inverter 2
There is a risk of abnormal stop.

Therefore, the present invention has been proposed in view of the above problems, and an object thereof is to allow an inrush current to flow into a transformer connected to the output side of the inverter when the inverter is started. An object of the present invention is to provide a control device and a control method of an inverter that can be suppressed as much as possible.

[0007]

As a technical means for achieving the above object, the method of the present invention comprises a full bridge connection by a plurality of switching elements, a transformer is connected to the output side thereof, and the switching is performed. ON-O of element
Regarding the square wave inverter that converts the direct current from the direct current power source into the alternating current by the FF operation, the switching elements are turned on.
In the method of controlling the -OFF operation by a gate signal, one of the two reference sine wave signals having a predetermined phase difference for setting the ON-OFF timing of each of the switching elements is controlled by an arbitrary gain. Amplitude is adjusted, one amplitude-adjusted reference sine wave signal is added to the other reference sine wave signal, the phase is adjusted, and the phase adjusted reference sine wave signal is compared with the zero potential to obtain the phase-adjusted gate signal. It is characterized by generating.

It is desirable that the effective value of the output voltage of the inverter is increased by adjusting the phase of the gate signal by gradually decreasing the gain of the reference sine wave signal whose amplitude is adjusted when the inverter is started.

Further, the device of the present invention is constituted by a full bridge connection by a plurality of switching elements, a transformer is connected to the output side thereof, and the ON-OF of the switching elements is connected.
Regarding the square wave inverter that converts the direct current from the direct current power source into the alternating current by the F operation, turning on each of the switching elements
A device for controlling an OFF operation by a gate signal,
Of the two reference sine wave signals having a predetermined phase difference for setting the ON-OFF timing of each switching element, one reference sine wave signal is multiplied by an arbitrary gain to adjust the amplitude, and the multiplication circuit. An adder circuit that adds one reference sine wave signal whose amplitude is adjusted to the other reference sine wave signal to adjust the phase, and a gate signal that is phase-adjusted by comparing the reference sine wave signal whose phase is adjusted by the addition with a zero potential. And a comparison circuit for generating

[0010]

In the present invention, of the two reference sine wave signals having a predetermined phase difference for setting the ON-OFF timing of each switching element of the inverter, one reference sine wave signal is amplitude-adjusted with an arbitrary gain, One of the amplitude-adjusted reference sine wave signals is added to the other reference sine wave signal for phase adjustment, and the phase adjusted reference sine wave signal is compared with zero potential to generate a phase adjusted gate signal. Therefore, the effective value of the output voltage of the inverter can be adjusted by adjusting the phase of the gate signal. In particular, when the inverter is started up, the gain of the reference sine wave signal for amplitude adjustment is gradually decreased to increase the effective value of the output voltage of the inverter by adjusting the phase of the gate signal. It is possible to suppress the inrush current from flowing into.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to the square wave inverter shown in FIG. 4 will be described with reference to FIGS. The same or corresponding parts as those in FIGS. 4 and 5 are designated by the same reference numerals.

The inverter 2 to which the present invention is applied is used, for example, in a self-excited reactive power compensator (SVC), a variable voltage variable frequency power supply (VVVF), a grid interconnection system such as a solar power generation system, and the like. Then, as in the conventional case, as shown in FIG. 4, a plurality of (four in the figure) switching elements S _{1 to} S are provided for the DC power source 1 such as a solar cell and a fuel cell.
₄ are connected in a full bridge configuration, and a load [system] is connected to the AC output side via a transformer 3.

In the inverter 2, the switching elements S ₁ , S ₄ and S ₃ , S ₂ are alternately turned on and off on the basis of gate signals G _{1 to} G ₄ [described later], as in the conventional case. DC power from the power supply 1 is converted into AC power and supplied to the load via the transformer 3.

In the present invention, the gate signals G _{1 to} G ₄ for operating the inverter 2 are shown in FIG. 1 on the basis of reference sine wave signals Q ₁ and Q ₂ [described later] having a phase difference of 120 °. It is generated by the control circuit 4 having the circuit configuration shown.

The control circuit 4 has two reference sine wave signals Q ₁ and Q ₂ having a phase difference of 120 ° for setting ON-OFF timings of the switching elements S _{1 to} S ₄ as shown in FIG. Of the reference sine wave signal Q ₁ (Q
The other ₂₎ the multiplication circuit A ₁ to multiply each amplitude adjustment any gain G (A _2), the multiplication of the gain G amplitude adjusted one reference sine wave signal Q ₁ * a (Q ₂ *) and the reference sine wave signal Q ₂ (Q ₁₎ to be added addition circuit B ₁ to the phase adjustment (B _2), and the zero potential reference sine wave signal Q ₁ and phase adjustment '(Q _2') by the addition Comparison circuit C ₁ for generating gate signal G ₁ ′ (G ₃ ′) whose phase is adjusted by comparison
(C ₂ ) and. The comparison circuit C ₁ (C ₂ )
The gate signal G ₁ '(G ₃ ') output from the inverting circuit D ₁
By inversion at (D ₂ ), the phase-adjusted gate signal G ₂ ′ (G ₄ ′) can be obtained.

Under normal operating conditions, the other reference sine wave signal
Issue Q₂ (Q₁ ) For one reference sine wave signal Q₁ 
(Q₂ ) Is multiplied by a gain G to a multiplication circuit A₁ (A₂ ) Multiplied by
I do. At this time, the gain G is set to 0, and the gain G is
One multiplied reference sinusoidal signal Q₁* (Q₂*) Is the other group
Quasi-sine wave signal Q₂ (Q₁ ) Is the addition circuit B₁ (B₂ ) Added
Calculate In this case, the gain G is 0 as described above.
Therefore, the adder circuit B₁ (B ₂ ) From the one reference sine wave
Signal Q₁ (Q₂ ) Is output as it is [Fig. 2 (a) Actual
See line]. This one reference sine wave signal Q₁ (Q₂ ) Ratio
Comparison circuit C₁ (C₂) Switch to zero potential
Element S₁ (S₃ ) ON / OFF gate signal
No.G₁ (G₃ ) Is generated [see the solid lines in FIGS.
See). Also, this gate signal G₁ (G₃ ) Inversion circuit D
₁ (D₂ ) Switching element
S₂ (S_Four ) ON-OFF gate signal G₂ 
(G_Four) Is generated [see solid lines in FIGS. 2 (c) and 2 (e)].

These gate signals G _{1 to} G ₄ are the same as those in the prior art, and by applying these gate signals G _{1 to} G ₄ to the switching elements S _{1 to} S ₄ , the inverter 2 is made to have a rectangular wave. Output voltage V of 120 ° conduction width with
You will drive out.

According to the present invention, when the inverter 2 is started, in order to prevent an excessive inrush current from flowing through the transformer 3 connected to the output side thereof, the reference sine wave signals Q ₁ and Q ₂ are set as follows. And adjust the amplitude and phase.

That is, when the inverter 2 is started, the other reference
Sine wave signal Q₂ (Q₁ ) For one reference sine wave
Issue Q₁ (Q₂ ) Is multiplied by a gain G to a multiplication circuit A₁ (A₂ ) Squared
At this time, the gain G is set to 1. That gay
One reference sine wave signal Q whose amplitude is adjusted by multiplying
₁* (Q₂*) Is the other reference sine wave signal Q₂ (Q₁ ) Added
Circuit B₁ (B₂ ) The reference sine wave signal whose phase is adjusted by adding
Issue Q₁'(Q₂') Is generated [see the broken line in Fig. 2 (a) and Fig. 3].
See). Then, the reference sine wave whose phase is adjusted by this addition
Signal Q₁'(Q₂') Is the comparison circuit C₁ (C₂ ) Due to zero potential
Switching element S compared to₁ (S₃ ) ON-OF
Phase-adjusted gate signal G for F ₁'(G₃') Raw
(Refer to broken lines in FIGS. 2B and 2D). Also, this game
Signal G ₁'(G₃') Inversion circuit D₁ (D₂ )
The switching element S₂ (S_Four ) ON-
Gate signal G whose phase is adjusted to turn off₂'(G_Four')
Is generated [see the broken line in FIGS. 2 (c) and (e)].

These gate signals G ₁ 'to G ₄ ' are out of phase with each other, unlike the case of the normal operating state [solid line in FIG. 2], and these gate signals G ₁ 'to G ₄ ' are switched. By providing the elements S _{1 to} S ₄ with the inverter 2
Can be started with an output voltage Vout ′ having an effective value smaller than that in the normal operating state [see the broken line in FIG. 2 (f)]. As a result, an excessive rush current does not flow in the transformer 3 connected to the output side of the inverter 2, and there is no risk of causing an overcurrent and causing the inverter 2 to abnormally stop.

After starting the inverter 2, the gain G
Is gradually decreased from 1 to 0, and the reference sine wave signals Q ₁ 'and Q ₂ ' whose phases are adjusted as shown by the arrow in FIG. The phase is adjusted so as to become the previous reference sine wave signals Q ₁ and Q ₂ [see FIG. 3], and as a result, FIG.
As shown by the arrow in (e), each switching element S _{1 to} S _{1
When the} phase of the gate signal G of ₄ is adjusted and the effective value of the output voltage Vout ′ at startup is gradually increased as shown by the arrow in FIG. 2 (f), and finally the gain G becomes 0, When the reference sine wave signals Q ₁ and Q ₂ are in a normal operating state, 1
An output voltage Vout of the inverter 2 having a 20 ° conduction width can be obtained [see solid lines in FIGS. 2 (a) to 2 (f)].

In the above embodiment, the case where the effective value of the output voltage Vout is gradually increased at the time of starting the inverter 2 has been described, but the present invention is not limited to this, and the inverter 2 is in operation. At its output voltage V
Of course, it is also applicable to the case where the effective value of out is gradually increased or decreased to be adjusted.

[0023]

According to the present invention, of the two reference sine wave signals having a predetermined phase difference for setting the ON-OFF timing of each switching element of the inverter, one of the reference sine wave signals has an arbitrary gain. A gate signal whose amplitude is adjusted, one of the amplitude-adjusted reference sine wave signals is added to the other reference sine wave signal, and the phase is adjusted, and the phase-adjusted reference sine wave signal is compared with the zero potential. Therefore, the effective value of the output voltage of the inverter can be adjusted. Particularly, when the inverter is started, the effective value of the output voltage can be reduced by gradually decreasing the gain of the reference sine wave signal. Can be gradually increased, and the inrush current can be suppressed from flowing into the transformer on the output side of the inverter, preventing abnormal stoppage of the inverter due to overcurrent. It can and reliability is greatly improved.

[Brief description of drawings]

FIG. 1 is a control block diagram for obtaining a gate signal and an output voltage of an inverter for explaining an embodiment of the present invention.

FIG. 2A is a waveform diagram showing a reference sine wave signal for generating a gate signal, and FIGS. 2B to 2E are waveform diagrams showing a gate signal for turning ON / OFF a switching element.
(F) is a waveform diagram showing the output voltage of the inverter

FIG. 3 is a vector diagram of the reference sine wave signal of FIG. 2 (a) and the phase-adjusted reference sine wave signal.

FIG. 4 is a circuit diagram showing an inverter having a full bridge configuration of a plurality of switching elements.

FIG. 5 is for explaining a conventional example, and includes (a) to
(D) is a waveform diagram showing a gate signal for turning on / off the switching element, and (e) is a waveform diagram showing an output voltage of the inverter.

[Explanation of symbols]

1 DC power source 2 square wave inverter 3 transformers S ₁ to S ₄ switching elements G ₁ ~G ₄ gate signal G ₁ '~G _4' gate signals Q ₁ and phase adjustment, Q ₂ reference sine wave signal Q ₁ *, Q ₂ * Amplitude adjusted reference sine wave signal Q ₁ ', Q ₂ ' Phase adjusted reference sine wave signal Vout Output voltage Vout 'Output voltage

Claims (3)

[Claims] 1. A full bridge connection comprising a plurality of switching elements, the output side of which is connected to a transformer,
Regarding a square wave inverter for converting a direct current from a direct current power source into an alternating current by an on-off operation of the switching element, a method of controlling an on-off operation of each of the switching elements by a gate signal, an on-off timing of each of the switching elements. Of the two reference sine wave signals with the specified phase difference, set the amplitude of one of the reference sine wave signals with an arbitrary gain, and then adjust the amplitude of the reference sine wave signal of the other And a phase adjustment is performed, and the phase adjusted reference sine wave signal is compared with a zero potential to generate a phase adjusted gate signal. 2. The effective value of the output voltage of the inverter is increased by adjusting the phase of the gate signal by gradually decreasing the gain of the reference sine wave signal whose amplitude is adjusted when the inverter is started. The control method of the inverter of claim | item 1. 3. A full bridge connection comprising a plurality of switching elements, the output side of which is connected to a transformer,
A square wave inverter for converting a direct current from a direct current power source into an alternating current by an on-off operation of the switching element, which is a device for controlling an on-off operation of each of the switching elements by a gate signal. Of two reference sine wave signals having a predetermined phase difference for setting the OFF timing, one reference sine wave signal is multiplied by an arbitrary gain to adjust the amplitude, and one reference whose amplitude is adjusted by the multiplication An addition circuit that adds a sine wave signal to the other reference sine wave signal to adjust the phase, and a comparison circuit that compares the reference sine wave signal whose phase has been adjusted by the addition with a zero potential to generate a phase-adjusted gate signal. An inverter control device characterized by being provided.