JP2926931B2 - Harmonic suppression device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic suppression device, and more particularly to a harmonic suppression device that suppresses harmonics of a power supply system using a harmonic suppression inverter. is there.

B. Summary of the Invention The present invention relates to a harmonic suppression device that suppresses harmonics of a power supply system using a harmonic suppression inverter. An inverter with a harmonic suppression function is connected in parallel between the load to be suppressed and the power supply side. In this case, a control circuit for the harmonic suppression capacity is provided in the forward converter control circuit of each inverter, and the harmonics of the power supply current are finally compensated by sequentially performing the harmonic compensation from the inverter on the load side.

C. Prior Art In order to suppress harmonics, various types of harmonic suppression devices have been proposed which suppress harmonics using an inverter having a harmonic suppression function.

The configuration of the main circuit section of the harmonic suppression inverter is the same as that of the voltage source power regeneration inverter. Therefore, the forward conversion unit capacity is also selected according to the inverse conversion unit capacity.

D. Problems to be Solved by the Invention When the harmonic generation load has a large capacity, it is necessary to increase the capacity of the forward converter in order to completely compensate for the harmonic.

The problem here is when the harmonic generation load becomes very light. In other words, a large-capacity forward converter is operated to drive a small-capacity motor or the like, and the utilization rate of the device is poor.

Also, during operation of the harmonic suppression inverter, it is necessary to protect the forward conversion unit when the system load to be compensated for harmonics increases and exceeds the allowable amount. There are two types, one due to an increase in system load and one due to a motor load. In order to distinguish this, it is necessary to limit the overcurrent in the instantaneous power calculation unit.

The present invention has been made in view of the above-described problems, and an object of the present invention is to connect a plurality of inverters with a harmonic suppression function in parallel between a load to be harmonic-suppressed and a power supply side, and to connect each of the inverters. An object of the present invention is to provide a harmonic suppression device which has a function of limiting a harmonic capacity in a control circuit unit, thereby improving the utilization rate of the device and performing high-performance harmonic compensation.

E. Means and Action for Solving the Problems To achieve the above object, the present invention provides a forward converter that converts AC power to DC power, and converts the DC power by the forward converter to AC power of a predetermined frequency. A plurality of inverting converters for converting, and a plurality of harmonic suppressing inverters each comprising a control circuit unit for controlling the forward converting unit are connected in parallel between a load to be harmonic-suppressed and a power supply side, and each of the harmonic suppressing inverters is connected. By providing the limiting circuit means for limiting the harmonic compensation capacity in the control circuit section, the harmonic compensation is sequentially performed from the inverter on the load side to be the target of harmonic suppression.

In addition, a self-extinguishing device is used as the main circuit switch for PW
A forward conversion circuit that enables power regeneration by M control, a reverse conversion circuit that supplies DC power from the forward conversion circuit and supplies AC power to a load, and a control circuit unit that performs PWM control of the forward conversion circuit A harmonic suppression device having a harmonic suppression inverter, wherein the control circuit unit obtains respective harmonic components of instantaneous real power and instantaneous imaginary power from a load current and a phase voltage of an AC system of a forward conversion circuit; and Real power calculating means for obtaining the real power of the load from the DC voltage and the DC current of the inverting circuit, and adding the DC power calculated based on the real power of the load and the loss power of the self-extinguishing device. An instantaneous power limiting means for limiting the instantaneous real power and imaginary power of the harmonic component in accordance with the amount of power, and a means for obtaining a current command for the forward conversion circuit from the real power and imaginary power limited by the instantaneous power limiting means. And the instantaneous real power and imaginary power of the harmonic compensation component according to the power amount obtained by adding the DC power calculated by the inverter DC voltage detection and the DC current detection and the power corresponding to the switching element loss of the forward converter. Add restrictions.

F. Embodiment An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a harmonic suppression device according to an embodiment of the present invention, wherein 1 is a power supply, 2 is a load for generating harmonics, and 3a to 3c.
Is a harmonic suppression inverter for compensating harmonics, 4a to 4c are motors connected to the harmonic suppression inverters 3a to 3c, respectively, and are loads of these harmonic suppression inverters, and 5a to 5c are current detectors.

In harmonics suppression device shown in FIG. 1, the power supply current I _s is shunted to the current I _1a flows a current I _1b flowing into the inverter 3a in the direction of the load 2. Current detector 5a detects the current I _1a, and inputs the detection signal to the inverter 3a. The inverter 3a compensates for a harmonic component included in the current _I1b based on the detection signal of the current detector 5a. Current I _1a is shunted to the current I _2a flowing current I _2b shunting the inverter 3b load two directions. Current detector 5b detects a current I _2a, guides the detection signal to the inverter 3b. The inverter 3b similarly compensates for a harmonic component included in the current _I2b based on the detection signal of the current detector 5b. Further, the current I _2a is divided into a current I _3b flowing into the inverter 3c and a current I _3a flowing through the load 2. Similarly, with the current detector 5c directs the detected signal to detect ultimately load current I _3a to the inverter 3c, inverter 3c is a harmonic component of the current I _3a based on the detection signal of the current detector 5c Compensate.

That is, the inverter 3a~3c is intended to be operated in parallel, first inverter 3c do harmonic compensation by detecting the harmonic components included in the current I _3a. If the compensation amount exceeds the allowable range, the compensation amount is cut by a control circuit described later, and no compensation is performed. Therefore, the current I _2a
Is not a sinusoidal current because perfect harmonic compensation is not performed.

Then, the inverter 3b is to compensate for the harmonic current contained in the I _2a, it will compensate for those that can not be compensated for by the inverter 3b. However, if the amount of compensation exceeds the allowable range in the inverter 3b as well, the compensation is limited, and harmonics remain in the current _I1a .

Further, inverter 3a detects harmonic currents I _1a, performs harmonic compensation. Here, if all of the harmonics of the current I _3a is compensated, the power supply current I _S is a sinusoidal current.

As described above, the power supply side current is made to be a sine wave by performing compensation in order from the inverter close to the harmonic generation load. In addition, the amount of compensation is automatically shared, and a large amount of harmonics can be compensated in total.

Furthermore, when harmonics included in the current I _3a are small and harmonic compensation can be performed only with the inverter 3c, the current
Both I _S , I _1a and I _2a are sinusoidal currents. Inverter
The maximum amount of total harmonic compensation of 3a to 3c is
4c is all stopped. Conversely, when all the motors 4a to 4c are at full load, the amount of harmonic compensation becomes minimum. Also,
When harmonic compensation is performed by a large number of units, the harmonic content decreases and approaches a sine wave as it approaches the power supply side.

FIG. 2 shows a harmonic suppression inverter, 6 is a reactor, 7 is a capacitor, and the reactor 6 and the capacitor 7 form a carrier removal filter 8. 9
Is an AC reactor, and 10 is a forward converter, which is connected to the AC power supply 1 via a carrier wave removing filter 8 and an AC reactor 9. The forward converter 10 has a bridge connection of a transistor 11, which is a self-extinguishing switching element, and a diode 12 is connected to the transistor 11 in anti-parallel. Reference numeral 13 denotes a capacitor, and reference numeral 14 denotes an inverse converter, which is configured by bridge-connecting a diode 15 to which an inverse-parallel-connected transistor 15 is connected.

17 is a transformer which is a voltage detector, and 18 is a current transformer which is a current detector, which detects an inverter current. 19 is a current detector for detecting a DC current. Reference numeral 20 denotes a control circuit for controlling the forward converter 10, which includes a synchronizing signal S1 from the transformer 17 and a current transformer 5 (5a
5c), the gate signal S6 is output by inputting the load current detection signal S2, the inverter current detection signal S3 of the converter 18, the DC voltage detection signal S4, and the DC current detection signal S5. Thus, the forward inverter 10, the inverse converter 14, and the control circuit 20 constitute an active inverter.

In the harmonic suppression inverter shown in FIG.
Converts AC power from AC power supply 1 to DC power. The DC power of the forward converter 10 is supplied to the induction motor 4a after being converted into AC power of a predetermined frequency by the inverse converter 14.
The control circuit unit 20 receives the synchronization signal S1, the load current detection signal S2, the inverter current detection signal S3, the DC voltage detection signal S4, and the DC current detection signal S5, and performs PWM based on these signals.
A signal is output, and the transistor 11 of the forward conversion unit 10 is controlled. In other words, the main circuit section including the forward conversion section 10 and the inverse conversion section 14 is the same as the conventional voltage-source power regeneration inverter, and the AC reactor 9 is connected to the input side.
10 uses a self-extinguishing type switching element. The control circuit unit 20 controls the load current to be suppressed in order to provide the conventional inverter with the function of suppressing the harmonic current of the system.
Detects I _L and calculates the harmonic compensation current command value for the target load current I _{L. If the} compensation amount exceeds the allowable range as described above, cut off that amount. A new function has been added to prevent this from being performed.
Accordingly, even when not operating the induction motor 4a, it is intended to compensate for the harmonic of the system load current I _L by controlling the switching elements of the rectifier unit 10.

FIG. 3 is a control circuit diagram. 3-phase / 2-phase converter 21, a three-phase load current of the system I _U, I _V, 2-phase currents on the orthogonal alpha-beta coordinates I _W I _alpha, converted to I beta.

Similarly, the three-phase / two-phase conversion unit 22 outputs the system phase voltages E _U , E _V , and E _W
Into two-phase voltages E _α and E _β on the orthogonal α-β coordinates.

2-phase currents I _alpha described above, I _beta and 2-phase voltage E _alpha, and E _beta alpha-
The instantaneous power on the β coordinate axis is obtained, and the instantaneous power calculator 23 obtains the instantaneous real power P and the instantaneous imaginary power q as the sum of the scalar products of the two-phase voltage and the current.

The AC component calculation units 24 and 25 have a high-pass filter function by an adder of a low-pass filter, and obtain the respective AC components (harmonic instantaneous power) P _h , q from the instantaneous real power P and the instantaneous imaginary power q.
_{Find h} .

That, P _h is the instantaneous power components of the system load, although q _h is the instantaneous imaginary power components, by providing a limit to, perform restriction of the harmonic compensation current to increase in system load. Real power limiter 31 is the instantaneous power components P _h and P _hb, imaginary power limiter 32 the instantaneous imaginary power component q and q _ha. P ₁ is a loss of the rectifier unit transistors, P ₂ is the active ingredient of each of the motor load. Here, P ₃ = When P ₁ + P _2, limiter 3 instantaneous power limit calculating unit 33 according to the size of the P ₃
Determine the limit value of 1,32.

 Focusing on the real power portion, it is as follows.

_{P ha = P 1 + P 2} + P hb = P 3 + P hb ... (4) ∴P hb = P ha -P 3 ... (5) Now, when trying to limit the input current is used in the current command value computing P _h and q _h may be limited. However
Limiting the _{P 3 (= P 1 + P} 2) component of P _h component performs restriction on q _h components for P _h component since drop of the DC voltage is expected. Specifically, the limit value of P _h increases in the case when P ₃ is close to zero (the motor is lightly loaded), smaller in the case P ₃ is maximum (motor full load). The restriction of q _h is performed in the same manner.

If the motor is in a stopped state can afford Viewed from P _ha ≒ P _h, and the device rating of the input current effective value is small transistor. Motor in the state of full load, at _{P ha = P 3 + P h} , P
₃ is supplied as a fundamental component of the input current, and _Ph is a harmonic component. In this case, there is no room in the compensation amount of the P _h because P ₃ is large.

The current command calculator 26 calculates the instantaneous powers P _ha , q _ha and the phase voltages E _α , E
instantaneous current on the orthogonal α-β coordinates from the _β Ask for.

The two-phase / three-phase converter 27 is a two-phase instantaneous current Is the three-phase instantaneous current Convert to

The PWM control unit 28 is a three-phase instantaneous current And the compensation current detection signals I _R , I _S , and I _T and obtain a PWM waveform gate signal by a comparison method with a carrier by a comparator, and the self-extinguishing element of the forward conversion circuit 10 is switched by the gate signal. I do.

With the configuration described above, the harmonic component included in the system load current is supplied from the forward conversion circuit 10 to the AC power supply 1 as a current to be compensated.

Here, it supplies the current calculation unit 26 instantaneously real power P _hb inverse transform circuit 14 adds the real power P ₂ to be supplied to the electric motor. Voltage E _d and the inverse conversion circuit of the real power P ₂ is condenser 13
Obtains a DC load by multiplying the 14 respective detection signals of the direct current I _d in is determined by the real power calculating section 29 with a first-order lag by the filter if necessary. Further, the instantaneous real power P _hb are added loss power P ₁ to compensate for the loss in the switching loss or the like of the forward transform circuit 10. The loss power P ₁ is a DC voltage command of the detection signal and the capacitor 13 of the capacitor voltage E _d From the voltage control circuit 30 in comparison with

According to this embodiment, the instantaneous real power P and the imaginary power q are sequentially obtained from the system load current, and the harmonic instantaneous real power is obtained from these powers.
P _ha and the imaginary power q _ha are obtained, and the real power P _ha is added to the real power P ₂ supplied to the load by the inverse conversion circuit 14 and the conversion loss P ₁ of the A control signal of the instantaneous real power P is converted from the real power P and the instantaneous imaginary power _qha into a current command, and a PWM control signal is obtained by two-phase / three-phase conversion and current feedback control.

Therefore, in order to suppress harmonics, a current component to the forward conversion circuit 10 is obtained by obtaining a harmonic component from the instantaneous real power and the imaginary power,
To obtain the current command to the forward conversion circuit 10 by adding the actual power of the load of the inverse conversion circuit 14 to this current command, it is necessary to supply a stable power to the load of the reverse conversion circuit without lowering the harmonic suppression function. Can be. Further, since the power to be supplied to the load of the inverse conversion circuit 14 is obtained from only the DC voltage and the DC current, the actual power calculation unit 29 is simplified. In addition, an inverse conversion circuit
The power supplied to the load from the inverse conversion circuit 14 has a power factor of 1 because the real power of ₁₄ is added to the real harmonic power P _hb for suppressing harmonics and the power is controlled by the forward conversion circuit 10. Similarly, the power factor is controlled to 1 during the regenerative operation.

G. Effects of the Invention As described above, according to the present invention, a large number of inverters having a harmonic suppression function are connected in parallel with the power supply side of the load to be subjected to harmonic suppression, and the forward converter of each inverter is connected. The control circuit is provided with a control circuit section for the harmonic compensation capacity, and the control circuit section adds the DC power calculated from the inverter DC voltage and DC current detection to the power obtained by adding the power for the switching element loss of the forward converter. Since the instantaneous real power and imaginary power for harmonic compensation are limited according to the amount, the following effects can be obtained.

(1) When operating multiple harmonic suppression inverters,
Since each inverter shares harmonic compensation, large-capacity compensation is possible in total.

(2) When each inverter exceeds the allowable compensation amount, it does not compensate any more, and the next inverter automatically compensates for it. There is no need to exchange information between the inverters, so that the equipment is simplified, and no special consideration is required when increasing the equipment.

[Brief description of the drawings]

1 is a block diagram of a harmonic suppression device according to an embodiment of the present invention, FIG. 2 is a block diagram of a harmonic suppression inverter of the device of FIG. 1, and FIG. 3 is a control of the harmonic suppression inverter of FIG. It is a block diagram of a circuit part. 1 ... power supply 2 ... harmonic generation load, 3a-3c ... harmonic suppression inverter, 4a-4c ... motor, 5a-5c ... current detector, 10 ... forward converter, 14 ... reverse Conversion unit, 20 Control circuit unit.

Claims (2)

(57) [Claims] A forward converter for converting AC power from an AC power supply into DC power, respectively, and converts the DC power by the forward converter into AC power of a predetermined frequency to supply the AC power to a motor as a load. Inverting section, and the AC input current and AC input voltage of the forward conversion section, respectively, the difference current between the power supply current of the AC power supply and the AC input current of the forward conversion section,
And based on the DC input current and the DC input voltage of the inverse conversion unit, a plurality of harmonic suppression inverters comprising a control circuit unit that controls the forward conversion unit, a load to be harmonic suppression target and the AC power supply And a limiting circuit means for limiting a harmonic compensation capacity in a control circuit section of each harmonic suppression inverter. 2. A forward conversion circuit that enables power regeneration by PWM control using a self-extinguishing type device as a main circuit switch;
In a harmonic suppression device having a harmonic suppression inverter including a reverse conversion circuit that is supplied with DC power from the forward conversion circuit and supplies AC power to a load, and a control circuit unit that performs PWM control on the forward conversion circuit, The control circuit section is means for obtaining respective harmonic components of instantaneous real power and instantaneous imaginary power from the load current and the phase voltage of the AC system of the forward conversion circuit, and converts the DC voltage of the inverse conversion circuit from the DC current to the actual load. Real power calculating means for calculating the power, and the instantaneous real power of the harmonic component according to the power amount obtained by adding the DC power calculated based on the real power of the load and the loss power of the self-extinguishing device. A harmonic suppression device comprising: an instantaneous power limiter that limits imaginary power; and a unit that obtains a current command for the forward conversion circuit from the real power and the imaginary power limited by the instantaneous power limiter.