JPS5886873A - Controller for inverter during instantaneous power failure - Google Patents

Abstract

PURPOSE:To make it possible to control an inverter even during a prolonged instantaneous power failure, by a method wherein a smoothing capacitor of an inverter main circuit is constituted by two series-connected capacitors, and the voltage between the neutral point thereof and one phase line of output lines of the inverter is employed as an inverter control power source. CONSTITUTION:The voltage generated an AC power source 1 is insulated by a transformer 6, which a connected to a power failure detecting circuit 27. To form a power source for an inverter control circuit 140, the AC power source 1 is connected to the primary side of a transformer 26 through a-contacts 321, 323 of a changeover relay 32, and connection is made such that a DC voltage of an inverter main circuit, i.e., the voltage between a neutral point 300 formed by capacitors 3A, 3B and one of inverter output terminals, e.g., the U phase is supplied to other taps on the primary side of the transformer 26 through b-contacts 322, 324 of the changeover relay 32. The voltage provided by a secondary winding of the transformer 26 is rectified as well as smoothed and supplied to the inverter control circuit 140.

Description

DETAILED DESCRIPTION OF THE INVENTION /) Technical Field of the Invention The present invention relates to an instantaneous power failure control device for an inverter that allows continuous operation even in the event of a power outage of a commercial AC power source.

J) Prior art In recent years, control of AC motors using inverters has been widely adopted. However, in voltage source inverters, when an instantaneous power failure occurs in the AC control power supply while the AC motor is running, and the inverter is temporarily stopped.

If the AC motor is restarted while rotating after power is restored, if the inverter is not started in accordance with the back electromotive force and phase of the AC motor, 'rtFEv, an excessive current will flow and the inverter restart will fail.

Therefore, conventionally, as a method for continuing the operation of the inverter even in the event of a momentary power failure, a means of configuring the circuit as shown in FIG. 1 has been adopted.

The inverter's main circuit converts the AC that is applied to AC into DC using a rectifier (converter), smoothes it through a capacitor J, converts it back to AC through an inverter, converter, and converts it back into AC to drive an AC motor. ! Power is supplied to the

The power supply voltage for the inverter control circuit and the inverter bridge drive circuit is applied from the AC power source 1 via six transformers. The alternating current voltage applied to the transformer 184 is converted to direct current voltage by a rectifier, and the electric charge is stored in a large capacity capacitor ytt.

Transistor! , a reactor 10, a capacitor 11, a chip circuit consisting of an 11° diode, and a voltage control circuit/
, 7 constitute a constant voltage circuit. The pulse transformer/j'7 transistor/AK is driven by the output of the inverter control circuit/41, and the inverter bridge 4t is driven by the base drive circuit/2.

An example of a detailed diagram of the inverter control circuit No. 7 is shown in FIG. 1. The inverter frequency is set by a frequency setter 100 consisting of a variable resistor and a constant power source. operational amplifier IO,
10:l, 10 da, resistance 10/.

A well-known acceleration/deceleration limiting circuit is configured by iot, iot, iot, iot, capacitor/lO1 variable resistor ios, and a usable resistor 101 adjusts the rate of frequency change. This addition/subtraction control@circuit output becomes the frequency reference f", and a frequency proportional to the inverter frequency is input to the waveform synthesis circuit /'/ by the voltage → frequency converter //, and -1
Pulse width variation Wj4 (PWM) by triangular wave generator //3
The output of the acceleration/deceleration limiting circuit is compared with the triangular wave by a comparator /# using the output of the acceleration/deceleration limiting circuit as an inverter voltage reference, and the pulse width modulation output is input to the waveform synthesis circuit //.

This waveform synthesis circuit combines the inverter frequency and pulse width modulation output, and outputs an inverter bridge drive signal.

In an inverter circuit like Jin, the voltage and frequency of the inverter output are simultaneously controlled by the pulse width variation t14 that controls the energization time of the inverter bridge, and generally the ratio of the voltage V and frequency 1 is controlled to be constant fi3F. /y
It's called control.

If a momentary power outage occurs in a system in which an AC motor is operated by such an inverter, k.

There is a demand for continuous operation of the AC motor without stopping 1. For example, when this system is used for a water supply pump and the rotation of the pump is stopped due to a momentary power outage, the filth that has adhered to the pipes will flow back into the water. This causes problems such as peeling and cloudy water. Therefore, it is desirable to continue operating the AC motor even during momentary power outages.

In the conventional device shown in FIG. 1, the charge stored in the capacitor t is used as the control/control power source during a momentary power outage.

This operation is shown in the time chart of FIG.

When a power outage occurs at time tll (AC power supply voltage V
,. from on to off), the capacitor voltage V. l is chi1
The control power supply voltage V is discharged down through the collar circuit, and its charge is used. , is kept constant at 1 time 1. When the power is restored (AC power supply voltage 'AO goes from off to off), the condensing voltage V. will recover, so the control power supply voltage V during a short momentary power outage. , it is possible to continue operating the inverter without any inconvenience.

J) Problems with conventional contact However, the problem with this conventional method is that as the W4 stop time increases, the capacitor voltage v0 decreases, resulting in a decrease in Vo8. 11, the control power supply voltage V'll drops and the control circuit no longer operates normally.

Therefore, in the past, the instantaneous power outage time was generally θ, 5 seconds or less kll
An interlock was installed that would stop the inverter in the event of a momentary power outage.

In addition, if the time when the AC 1 source is completely zero for a long time, the voltage of the smoothing capacitor J in the inverter main circuit will also drop, and the AC motor S of the load will be overloaded, so the AC power supply voltage should be kept at 5096 or higher. In addition, there are restrictions such that funds can be cut off for no more than 0,000 seconds. Therefore, in order to perform such instantaneous power failure control, a capacitor J with a large capacity is required, resulting in a large-sized device.

Furthermore, in order to be able to control even if the instantaneous power outage time becomes longer, the capacitor t for instantaneous power outage control in the inverter control 11 circuit needs to have a very large capacity of several hundred thousand μF 81 degrees. The size of the device housing the main circuit and the capacitor t is now the same, making the entire device large and expensive, making it practically impossible. 'tei)
OBJECTS OF THE INVENTION The present invention has been made to eliminate the drawbacks of the above-mentioned conventional devices, and provides instantaneous power failure control for a small and economical inverter that is capable of controlling even when the instantaneous power failure time is relatively long. Its purpose is to provide a device V.

S) Structure of the invention The present invention provides a smoothing capacitor 3 in an inverter main circuit.
is a series-connected capacitor, and the voltage between the neutral point of the connected capacitor and the melting point of the l-phase of the inverter's output line is used as the inverter control power source. .

4) Embodiments of the Invention Let's talk about the Suhars convergence change PLK, Figure D-)
, (b) shows the operating waveform of the pulse Iil'Th.

Triangular wave AT for pulse width modulation and voltage reference.

(U phase) is compared with the comparator, and the output is used to select the switching element (transistor) of the inverter bridge in Fig. 1.
/, + Turn on and off.

The voltage between the load terminal υ phase and the neutral point of the DC power supply formed by the rectifier and capacitor J is vTJ-0. Similarly, the voltage between the load terminal V phase and the neutral point is muff-0, so the voltage between the U-4 terminals is V. -7 waveform. When the effective voltage is changed by adjusting the magnitude of the voltage reference erj, the voltage V. -v fi waveform does not have a peak value of voltage, but a voltage having the same peak value as the KTII flow side voltage is output, but the width of the pulse changes and the average value of the output voltage changes. This control will be referred to as pulse width modulation control from now on.Furthermore, the voltage V when the magnitude of the voltage reference eo becomes zero, that is, the output voltage is zero. -0 is a vertically symmetrical waveform represented by K (see Figures ~).

The present invention utilizes the fact that the voltage between the inverter output terminal and the DC voltage neutral point is almost unaffected by the inverter output voltage or its frequency, and has an alternating waveform that constantly switches.

In the drawings, the same reference numerals indicate the same or similar parts.

FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention;
FIG. 4 is a detailed view of a part thereof.

The voltage of the AC power supply l is disconnected by the transformer 6 and connected to the power failure detection circuit a7, while the inverter control circuit via
is the a-closing J-co 1,3 of the Ray J-co that is cut off from the AC 1 source.
Go through Ko3v! Connect to the primary side of the inverter's main circuit, create a neutral point J00 vk from JBK, and use a relay to switch the voltage between this neutral point JOO and the seven inverter output terminals, for example, υ phase 1. 3a
KII is connected to supply another tap on the primary side of the transformer 6 through the b contacts J here and J here.

Connect the secondary winding mK rectifier Jj a 1jt with 6 transformers to convert it to direct current, smooth it with a capacitor Co/1, and supply the stabilized control power supply voltage from the constant voltage circuit nK to the inverter control ID circuit l 〇11C do.

The voltage detection circuit JjK connected to the secondary winding of the transformer M detects the voltage and supplies it to the inverter control circuit 1, and the output and the presence/absence of the start signal 11T are detected via the level detector 2D. The logical product is calculated using the conditional logical product circuit J0, and the relay Jlv is turned on (that one point J// is) I!
Therefore, in the case of preparation for operation, since the conditions for the start signal 8T have not been input, relay J/ is turned off, switching relay here is turned on, and AC power supply l is connected to transformer M.

Next, when starting signal 8te is input, the inverter starts and relay si turns on at the same time.

゛ The switching relay 31 is turned off, and the envoy ROM is turned off.

3, the voltage between the neutral point sea of JB and the inverter output terminal 8 is supplied. Since the peak value of voltage B is about % compared to AC power supply l, connect it to the tap with the lower voltage on the primary side of the transformer, and adjust the secondary voltage of the transformer by turning on/off switching relay JJ. I try not to change it regardless of the situation.

With such a connection, the control power supply voltage during inverter operation is obtained from the inverter output rather than being directly connected to the AC power supply I. A power outage detection circuit detects a momentary power outage, a voltage detection circuit detects a voltage proportional to the DC side voltage of the inverter main circuit, and controls the frequency of the inverter during a power outage to control the AC motor of the load! The regenerated energy of the inverter main circuit plane voltage is controlled to be constant y.The transistor nails 1Q and nails that constitute the two arms of the clay figurine of the inverter bridge.

Each is the second volume of the transformation ROM! ! &C connected rectifier aa
b, capacitor J/ b, rectifier c, capacitor J/
A drive circuit J41tl to which a DC voltage is supplied from a DC power supply consisting of a, a rectifier d, and a capacitor/d, 30. μ
Upon receiving the signal from the inverter control circuit l#O from dK,
Further, the lower three arms of the inverter bridge constitute transistors ←, 6. What is the bias?

A rectifier Jje connected to the secondary winding II of the smart voltage regulator.

The drive circuit μ is supplied with a DC voltage from a DC power supply consisting of a capacitor collector, and is operated in response to a signal from an inverter control circuit.

FIG. 6 is a block diagram showing details of the power failure detection circuit, voltage detection circuit, and inverter control circuit i+o of this embodiment.

The voltage of AC power supply l is detected by transformer 6.

The detected voltage is rectified and filtered through a rectifier 4 and a 271° resistor Jv.
When the level detector fJK detects a power outage or an abnormal drop in the AC power supply l, K operates the switch drive circuit//'l and switches the contacts to be driven.
When ie is turned on, the output of operational amplifier io becomes zero,
The output of the operational amplifier ioJ constituting the integrating circuit is in a hold state, and the inverter frequency reference f6 is also in a hold state.

On the other hand, during inverter operation, the inverter output terminal (U phase)
The voltage between the neutral point SOo and the DC side is connected to the voltage detection circuit via the voltage regulator, and the rectifier is connected to a 10° capacitor, 2t/
, the peak voltage value is detected from the configuration of the resistor, 'tl-, and in the inverter control circuit 11C, the voltage reference value /20 and the resistor //? , /J/, and the error is amplified through W
17.7 is entered. As a result, when the DC side voltage of the inverter main circuit drops, the inverter frequency is lowered and the rotational energy of the AC motor I is
Mmm... 7! To regenerate IK, the capacitor voltage (J) is increased and the capacitor voltage, that is, the peak value of the voltage between the capacitor neutral point and the inverter specific power (control voltage) is kept constant.

Considering the operating polarity of this circuit, 1 frequency setter 1
The output fR of 00 is (→ and when increasing the frequency by 1, the output of amplifier io- is ←), the output of amplifier 103 changes in the direction of (→, and the output of amplifier 10 is (-)
With the polarity of , outputs 1 based on the inverter frequency.

In steady state, the sum of the 18 wave number setter output f1 and the inverter station wave number base flkf is zero, and the output of the amplifier 102 is zero, and the outputs of the amplifiers io and y, which are the outputs of the integrating circuit, are held in a state where they do not become buds. ing.

Now, during a power outage, the output of the amplifier 10J is forced to zero by turning on the contact llj, and the output of the inverter DC side voltage control circuit (amplifier tit) is forced to zero.

11M, 10) is activated and the voltage of capacitor 1/ of voltage detection circuit X becomes lower than the value set by basic power supply iJo, the output of amplifier//1 becomes ←).

Its output is given to amplifier lO3 via contact //4,
The output of the amplifier/It becomes (+), which lowers the output of the amplifier tOS, so the magnitude of `` on the frequency basis decreases, lowering the inverter frequency.Then, the energy of the AC motor j is regenerated, and the DC side capacitor 3 , JB'@Charges and the voltage increases.

In this way, during a power outage, the inverter DC side voltage, that is, the output peak voltage of the transformer proportional to this, is kept constant.

Next, let's consider when the inverter starts up. Start signal BT
If the voltage detection value of the voltage detection circuit is within the normal range, the level detector signal is output.

With both of them, the output vO1 of the AND circuit/JJ is operated by the output of one of them, and the switch saw j
When a signal of (-υ is given to the frequency tIjl #3I setter 10O from K to increase the number of inverters MItfI, the number of inverters MItfI is increased.

By the output of the other of the AND circuit 1, the AND circuit 1
A switch drive signal for the inverter bridge is output through the inverter to put the inverter into operation.

However, if the inverter frequency is lowered, it becomes an AC motor! energy is recovered and the motor speed decreases to near zero.
Since the DC voltage of the inverter decreases, the voltage of the voltage detection circuit λg is detected by a level detector, and the output of the AND circuit stops and the inverter stops.

At the same time, relay 31 in Fig. 3 turns off. If the AC power is restored in this state, relay 3λ is on and its contacts J and 3 are connected to transformer 6 as shown in the figure. Connected, waiting for inverter startup, startup signal 8? If it is installed, it will start automatically.

FIG. 7 is a time chart showing this activation state.

At time t, when start signal 8T is turned on, relay J
Time 1. ), the primary voltage V of the transformer M is from the AC voltage II/ to one of the inverter output lines and the neutral point 30
Voltage switching between 0 and 0.

At the same time, the frequency base #f" increases by 1, and the motor S accelerates. At time t, the inverter increases to the set frequency. At time t4, an instantaneous power failure occurs, and the power failure detection circuit core turns off. Inverter DC @ voltage v0
The frequency standard f" is lowered so that the rotational energy of the negative-impact motor is regenerated so that
Since the amount of regenerative energy is about l- of the inverter cylinder, a small amount of regenerative energy is sufficient.

When the power is turned on at time t, the inverter frequency standard increases toward the set value and returns to the normal value Kal at time t.

In this way, the power supply for the circuit that controls and drives the inverter shown in Figure 3 uses the voltage between one of the inverter output lines and the capacitor neutral point soo while the inverter is being driven, so it is possible to avoid power outages. The motor continues to operate as long as there is rotational energy in the motor, and after 0111, it automatically accelerates to the set frequency.

FIG. 5 shows an example of the base drive circuit for the transistors in the inverter bridge of this embodiment.

When a DC voltage is received from the capacitor /b and an on signal is obtained from the inverter control circuit l da θ by the photocoupler 200, the resistance koda/ is 1! pressure is generated and the transistor λ is
is turned on, and the base current is limited by resistor 4. The resistor is connected between the pace and emitter of the transistors in the inverter bridge.

(2) Cost example of the invention However, the voltage detection circuit between the inverter output and the neutral point 300 in Figures J and #6 is as shown in Figure 9. Detector 3111
The effect is the same even with the method of detecting and controlling from C.

Furthermore, as shown in Figure 1, the conventional circuit (Figure 1)
As the control power supply voltage, a transformer 2411C is supplied through the relay 3- in Fig. 3, and a rectifier is connected to the secondary @ of this transformer -6σ, and a capacitor l/ is connected to obtain the DC power supply voltage. It is also possible to operate while maintaining the control power supply voltage even during a power outage by using control similar to that shown in diagram S.

Further, although the above description has been made regarding a J-phase inverter, it goes without saying that the invention is applicable regardless of the number of phases of the inverter or the elements used.

The same applies to multi-phase transformers instead of single-phase transformers.

In addition, in Fig. 3, relay 3.2 that supplies the power supply voltage of the pressure limiter is always on the inverter side (voltage between the inverter a'''1 line of force and the capacitor neutral point 300) during inverter operation.
K is switched, but it is switched to inverter 914 only when AC power supply l is out of power.

Other controls may be similar to those shown in FIG. 3.

t) Effects of the Invention As explained above, according to the present invention, during a power outage, the energy of the AC motor of the jI load is regenerated, the inverter DC side voltage vnr is controlled to be constant, and the inverter is operated or the AC power supply is out of power. Invert the circuit power supply that controls the inverter inside! By switching from the AC power supply and using it to obtain the voltage between the seven output lines and the capacitor's neutral point,
Provides power to the control circuit even during momentary power outages.

By adding elements that make it easy to continue operating the inverter, it is compact and economical.

Furthermore, even if the motor stops during a long-term power outage, it can be automatically restarted after power is restored, providing a highly reliable and high-performance inverter instantaneous power failure control device.

[Brief explanation of drawings]

Figure 1 is a pull diagram of a conventional lid, Figure 1 is a detailed diagram of its control circuit, and Figure 3 is an explanatory diagram of its operation. Figures D&L) and (b) are explanatory diagrams of the output waveform of the pulse width modulation inverter, Figure S is a block diagram 1w showing the configuration of an embodiment of the present invention, Figure 1 is a detailed diagram of its control circuit, and Figure 1 is a detailed diagram of the control circuit. Figure 7 is a time chart showing the operation of this embodiment), II
IE&' is a detailed diagram of the base drive circuit of this embodiment, and FIGS. 9 and 10 are route diagrams of other embodiments of the present invention. l...AC power supply, c...rectifier (conver/). ,7. ．． 7A,, 7B... Capacitor, D... Inverme bridge s! ...AC motor, 6. Coro...
transformer. io, tdaO...Inverter control circuit, Koku...Power failure detection circuit, K...Voltage detection circuit, K9...Level detector. 3θ10. AND circuit, 3/, 3 pieces...relay, group
S-da6...Switch element. Applicant's agent Inomata Kiyoma 1 figure r4 Band 2 figure 3 figure Atsushi 4 figure (5) (6) Horse 5 figure 6 figure Rei 7 figure Haruma-

Claims (1)

[Scope of Claims] 1. An AC power source, a converter that converts the AC from the AC into DC, and an inverter in which a DC @ terminal is connected to the output terminal of the inverter and an AC motor as a load is connected to the AC side terminal. In a device provided with an output m of the converter
Connect one capacitor of equal capacity in series in K parallel. 4I means that the voltage between the series-connected neutral point and the AC side terminal is set as the control power supply voltage of the inverter.
Instantaneous power failure control device for inverters. When the voltage between the neutral point and one of the AC side terminals drops or when the inverter is stopped, the control power supply voltage of the inverter is taken from the AC power supply, and after the inverter is started, the voltage between the neutral point and the AC 11m is 8. The instantaneous power failure control device for an inverter according to claim 7, further comprising a switching circuit that uses the voltage between the inverter and one of the inverter as the control power supply voltage of the inverter. J. A power outage detection circuit is provided to detect a drop in the AC power supply, thereby detecting an instantaneous power outage, and lowering the inverter frequency so that the voltage across the capacitor remains constant. The instantaneous power failure and control device for an inverter according to claim 1, characterized in that the device is configured to regenerate electric power from an electric motor.