JPH0496626A - Harmonic suppressor - Google Patents

Abstract

PURPOSE:To finally compensate harmonic of a power supply current by connecting a plurality of harmonic suppression inverters in parallel, and providing limiter means for limiting a harmonic compensating capacity in a controller of each inverter. CONSTITUTION:Inverter 3a-3c are operated in parallel, the inverter 3c first detects a harmonic component contained in a current I3a and compensates the harmonic. Then, the inverter 3b compensates a harmonic current contained in a current I2a, and compensates for that which cannot be sufficiently compensates by the inverter 3b, Further, the inverter 3a detects the harmonic of the current I1a and compensates for the harmonic. If all the harmonic contained in the current I3a are compensated, a power supply current Is becomes a sine wave current.

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a harmonic suppression device, and particularly relates to a harmonic suppression device that uses a harmonic suppression inverter to suppress harmonics in a power supply system. be.

B0 Summary of the Invention The present invention is a harmonic suppression device that suppresses harmonics in a power supply system using a harmonic suppression inverter, in which an inverter with a harmonic suppression function is connected in parallel between a load to be suppressed and a power source. However, by providing a control circuit for harmonic suppression capacitance in the forward conversion section control circuit of each inverter and sequentially compensating for harmonics starting from the inverter on the load side, harmonics of the power supply current are finally compensated.

C0 Prior Art In order to suppress harmonics, various harmonic suppression devices have been proposed that suppress harmonics using an inverter equipped with 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 regeneration inverter. Therefore, the capacity of the forward transformer is also selected depending on the capacity of the inverse transformer.

D1 Problems to be Solved by the Invention When the harmonic generation load has a large capacity, in order to completely compensate for the harmonics, it is necessary to increase the capacity of the forward conversion section.

The problem here arises when the harmonic generation load becomes a very light load. In other words, in order to drive a small capacity motor etc., a large capacity forward conversion section must be operated.
This will result in poor equipment utilization.

In addition, it is necessary to protect the forward conversion section in the event that the system load subject to high frequency compensation increases and exceeds the permissible amount while the harmonic suppression inverter is operating. There are two types: one due to an increase in load and one due to motor load. In order to distinguish this, it is necessary to perform overcurrent limitation in the instantaneous power calculation section.

The present invention has been made in view of the above-mentioned problems, and its purpose is to connect a plurality of inverters with a harmonic suppression function in parallel between the load to be harmonic suppressed and the power supply side,
It is an object of the present invention to provide a harmonic suppression device that has a high utilization rate and can perform harmonic compensation with high performance by providing a control circuit section of each inverter with a function of limiting harmonic capacity.

88 Means and Effects for Solving the Problems In order to achieve the above object, the present invention includes a forward converter that converts AC power into DC power, and a forward converter that converts the DC power into AC power of a predetermined frequency. A plurality of harmonic suppression inverters each consisting of an inverse conversion section to control the forward conversion section and a control circuit section to control the forward conversion section are connected in parallel between the load to be harmonic suppressed and the power supply side, and each harmonic suppression inverter is By providing a limiting circuit means for limiting the harmonic compensation capacity in the control circuit section, harmonic compensation is sequentially performed starting from the load-side inverter that is to be subjected to harmonic suppression.

In addition, a self-extinguishing device can be used as a main circuit switch for PW.
A forward conversion circuit that enables power regeneration through M control, an inverse conversion circuit that receives DC power from the forward conversion circuit and supplies AC power to a load, and a control circuit section that performs PWM control on the forward conversion circuit. In the harmonic suppression device having a harmonic suppression inverter, the control circuit unit includes means for determining harmonic components of the instantaneous real power and the instantaneous imaginary power from the load current and phase voltage of the AC system of the forward conversion circuit; Actual power calculation means for calculating the actual power of the load from the DC voltage and DC current of the inversion circuit, and the DC power calculated based on the actual power of the load and the power loss of the self-extinguishing device are added together. Instantaneous power limiting means for limiting the instantaneous real power and imaginary power of harmonic components according to the amount of power; and means for determining the current command of the forward conversion circuit from the real power and imaginary power limited by the instantaneous power limiting means. and is limited to the instantaneous real power and imaginary power of the harmonic compensation component according to the amount of power that is the sum of the DC power calculated by inverter DC voltage detection and DC current detection and the power for switching element loss in the forward conversion section. Add.

F. EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows a harmonic suppression device according to an embodiment of the present invention, in which 1 is a power supply, 2 is a load that generates harmonics, and 3a to 3
c is a harmonic suppression inverter that compensates for harmonics; 4a to 4;
C is a motor which is also a load of the harmonic suppression inverters 3a to 3C, and 5a to 5c are current detectors.

In the harmonic suppression device shown in FIG. 1, a power supply current I is divided into currents I and b flowing into the inverter 3a and currents I and a flowing toward the load 2. Current detector 5a detects current B
a and inputs the detection signal to the inverter 3a. Inverter 3a compensates for harmonic components contained in current 11b based on the detection signal of current detector 5a. Current ■1.
is divided into a current 12b which is divided into the inverter 3b and a current I2m which flows in two directions of the load. The current detector 5b is connected to the current detector 2. is detected, and the detection signal is guided to the inverter 3b.

Inverter 3b similarly compensates for harmonic components contained in current I2b based on the detection signal of current detector 5b.

Furthermore, electrician 2. is the current I flowing into the inverter 3c
Current flowing through 3b and load 2■3. Divided into. Similarly, the current detector 5c ultimately detects the load current ■3. , and guides the detection signal to the inverter 3C, and the inverter 3c generates the current I3. based on the detection signal of the current detector 5C.
Compensates for harmonic components.

That is, inverters 3a to 3c are operated in parallel, and first, inverter 3C detects harmonic components contained in current I3m and performs harmonic compensation.

If the amount of compensation exceeds the allowable range, that amount is cut by a control circuit, which will be described later, and no compensation is performed. Therefore, the current I2. does not have complete harmonic compensation, so it does not become a sinusoidal current.

Next, inverter 3b receives current I2. The harmonic current contained in the inverter 3b is compensated for, but the harmonic current that cannot be compensated for by the inverter 3b is compensated for. However, inverter 3b
Also, if the amount of compensation exceeds the allowable range, compensation is limited and harmonics remain in the current 11m.

Furthermore, the inverter 3a has a current of 1. The harmonics of a are detected and harmonic compensation is performed. Here, if all harmonics included in the current 13m are compensated for, the power supply current Ig becomes a sine wave current.

In this way, by sequentially performing compensation from the inverter close to the harmonic generating load, the power supply side current is made to be a sine wave. Furthermore, the amount of compensation is automatically shared, making it possible to compensate for a large amount of harmonics in total.

Furthermore, when the harmonics contained in the current 13m are small and harmonic compensation is possible only with the inverter 3C, both the currents I Sr I l'' + I2' are sinusoidal currents. The total amount of harmonic compensation is maximum when all motors 4a to 4C are stopped. Conversely, when all motors 4a to 4C are under full load, the amount of harmonic compensation is minimum.

Furthermore, when harmonic compensation is performed using a large number of units, the closer the harmonics are to the power supply side, the lower the harmonic content rate becomes, approaching a sine wave.

FIG. 2 shows a harmonic suppression inverter, in which 6 is a reactor, 7 is a capacitor, and these reactor 6 and capacitor 7 form a carrier wave removal filter 8. 9 is an AC reactor, and 10 is a forward converter, which is connected to the AC power source 1 via the carrier removal filter 8 and the AC reactor 9. The forward conversion section 10 is formed by bridge-connecting a transistor 11 which is a self-extinguishing switching element, and a diode 12 is connected to the transistor 11 in antiparallel. 13 is a capacitor, and 14 is an inverse conversion section, which is constructed by bridge-connecting transistors 15 to which a diode 16 is connected in antiparallel.

A transformer 17 is a voltage detector, and a current transformer 18 is a current detector to detect the inverter current.

A current detector 19 detects direct current. 20 is a control circuit unit that controls the forward conversion unit 10, and receives a synchronization signal SL from the transformer 17, a load current detection signal S2. Inverter current detection signal S3 of current transformer 18. It inputs the DC voltage detection signal S4 and the DC current detection signal S5 and outputs the gate signal S6. In this way, the forward conversion section IO1 and the inverse conversion section 14 and the control circuit section 20 constitute an active inverter.

In the harmonic suppression inverter shown in FIG.
converts AC power from AC power supply 1 into DC power. The DC power of the forward converter 10 is converted into AC power of a predetermined frequency by the inverse converter 14, and then supplied to the induction motor 4a. The control circuit section 20 receives a synchronization signal Sl, a load current detection signal S2. Inverter current detection signal S3. It inputs the DC voltage detection signal S4 and the DC current detection signal S5, outputs a PWM signal based on these signals, and controls the transistor 11 of the forward conversion unit 10. That is, the forward conversion unit 10
The main circuit section, which consists of the
is connected, and a self-extinguishing switching element is used in the forward conversion section 10. In order to provide the conventional inverter with the function of suppressing harmonic current in the grid, the control circuit unit 20 detects the load current IL to be suppressed and performs harmonic compensation for the target load current IL. New functions have been added: a function to calculate the current command value, and a function to cut the amount of compensation and prevent it from being performed if the amount of compensation exceeds the allowable range as described above. Therefore, even when the induction motor 4a is not operating, by controlling the switching elements of the forward converter 10, the system load current I
This is to compensate for the harmonics of L.

FIG. 3 is a control circuit diagram. The three-phase/two-phase conversion section 21 is
The three-phase load currents Iu, Iv, and Iw of the grid are orthogonal α
-Two-phase current on β coordinate 1. , Iβ.

Convert to E,,E,.

The above two-phase current 1. ,I, and the two-phase voltage E, ,E, are α
- Becomes an instantaneous vector on the β coordinate axis, and the instantaneous power calculation unit 2
3 is the instantaneous actual power P as the sum of the scalar products of two-phase voltage and current.
and find the instantaneous imaginary power q.

Similarly, the three-phase/two-phase converter 22 converts the system phase voltage Eu,
The calculation units 24 and 25 for Ev and Ew are two-phase voltage AC components on orthogonal α-β coordinates, and have a bypass filter function using a low-pass filter and an adder. Wave instantaneous power) Ph, qh are determined.

That is, Ph is the instantaneous power component of the system load, q,
are instantaneous imaginary power components, and by placing limits on these, the harmonic compensation current is limited in response to an increase in system load. The actual power limiter 31 sets the instantaneous power component P, P bb
The imaginary power limiter 32 sets the instantaneous imaginary power component q to qha
shall be. Pl is the loss of the forward converter transistor, and P2 is the respective effective component of the motor load. Here, p3=p
, +p2, the instantaneous power limit calculation unit 33 calculates P3.
The limit value of the limiter 31□382 is determined according to the size of the limiter 31□382.

Focusing on the actual power part, we get the following.

Pha=P1+P2+Phb=P3+Phb...
(4),', Phb-Pha-P3 −
(5) If it is desired to limit the input current, it is sufficient to limit Pl and qh used in current command value calculation.

However, if the P3 (-P, +P2) component of the Ph component is restricted, a drop in DC voltage is expected, so the qh acid component is restricted for the P component. in particular,
When P3 is close to zero (motor is lightly loaded), P,
The limit value becomes larger, and P3 is the maximum (motor at full load)
It becomes smaller in the case of . A similar method is used to limit qh.

When the motor is stopped, p , , = p ,
The effective value of the input current is small and there is plenty of room considering the element rating of the transistor. When the motor is fully loaded, P b-
−P 3+ Ph h, P3 is supplied by the fundamental component of the input current, and Ph is the harmonic component.

In this case, since P3 is large, there is not enough compensation for P.

The current command calculation unit 26 calculates the instantaneous power P ha,q @@
The instantaneous current 1 on the orthogonal α-β coordinates from the phase voltages E, , E, and
, I,” is found.

The two-phase/three-phase converter 27 generates a two-phase adjacent current I4■,! 3
Adjacent current I. .

eb ■,. 'to Convert.

The PWM control unit 28 controls the three-phase adjacent current I. .

■. 1. ■. . ' and compensation current detection signals In, Is.

A PWM waveform gate signal is obtained by comparison with a carrier wave using a comparator, and this gate signal controls the switching of the self-extinguishing element of the forward conversion circuit 10.

With the configuration described above, the harmonic components included in the system load current are supplied from the forward conversion circuit 10 to the AC power supply 1 side as a current for compensating.

Here, real power P2 supplied to the motor by the inverse conversion circuit 14 is added to the instantaneous actual power Phb, and the added value is supplied to the current command calculation section 26. This actual power P2 is the voltage Ed of the capacitor 13
The DC load is determined by multiplying the detection signals of the DC current (6) and the DC current (6) of the inverse conversion circuit 14, and is determined by the actual power calculation unit 29 with a first-order delay due to a filter as necessary. Further, loss power P1 for compensating for losses such as switching loss of the forward conversion circuit 10 is added to the instantaneous actual power Phb. This loss power P, is the capacitor voltage E,
It is determined by the voltage control circuit 30 by matching the detection signal of 1 with the DC voltage command E d'' of the capacitor 13.

According to this embodiment, the instantaneous real power P and the instantaneous imaginary power q are obtained from the grid load current, and the harmonic instantaneous real power P is obtained from these powers.
ha and imaginary power qha are calculated, and among these, the real power P2 supplied to the load by the inverse conversion circuit 14 and the conversion loss P1 of the forward conversion circuit 10 are added to the real power Pha to calculate the instantaneous actual power P of the forward conversion circuit 10. The actual power P and instantaneous imaginary power qba are converted into a current command as a control signal, and a PWM control signal is obtained by 2-phase/3-phase conversion and current feedback control.

Therefore, in order to suppress harmonics, the harmonic branch is determined from the instantaneous real power and the imaginary power, and the current command to the forward conversion circuit 10 is determined.
Since the current command to the forward conversion circuit 10 is obtained by adding the load actual power of the inverse conversion circuit 14 to this current command, stable power can be supplied to the load of the inverse conversion circuit without reducing the harmonic suppression function. I can do it. Furthermore, since the power to be supplied to the load of the inverse conversion circuit 14 is calculated from only the DC voltage and DC current, the actual power calculation unit 29 is simplified. Furthermore, the actual power of the inverse conversion circuit 14 is added to the harmonic actual power Phb for harmonic suppression to control the power of the forward conversion circuit 1°, so the power supplied from the inverse conversion circuit 14 to the load is The power factor becomes 1, and the power factor is similarly controlled to 1 during regenerative operation.

G1 Effects of the Invention As described above, according to the present invention, a large number of inverters with a harmonic suppression function are connected in parallel between the load to be suppressed and the power supply side, and the forward conversion section of each inverter is controlled. The circuit is provided with a control circuit for harmonic compensation capacity, and this control circuit calculates the amount of power that is the sum of the DC power calculated from the inverter DC voltage and DC current detection and the power for the switching element loss in the forward conversion section. By setting limits on the instantaneous real power and imaginary power for harmonic compensation according to the following, the following effects can be obtained.

(1) When operating multiple harmonic suppression inverters,
Since each inverter performs harmonic compensation, a large amount of compensation can be achieved in total.

(2) If each inverter exceeds the allowable compensation amount, it will not compensate any more and the next inverter will automatically compensate for this, so each harmonic suppression inverter will There is no need to exchange information between inverters, so the equipment is simple and no special consideration is required when increasing equipment.

[Brief explanation of the drawing]

FIG. 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. 2. FIG. 3 is a block diagram of a circuit section. 1... Power supply, 2... Harmonic generation load, 3a to 3c.
...Harmonic suppression inverter, 4a to 4c...motor,
5a-5C... Current detector, 10... Forward conversion unit, 1
4... Inverse conversion section, 20... Control circuit section. Figure 1 Example harmonic suppression device

Claims (2)

[Claims] (1) A harmonic system consisting of a forward converter that converts AC power into DC power, an inverse converter that converts the DC power generated by the forward converter into AC power of a predetermined frequency, and a control circuit that controls the forward converter. A plurality of wave suppression inverters are connected in parallel between the load to be harmonic suppressed and the power supply side, and a limiting circuit means for limiting harmonic compensation capacity is provided in the control circuit section of each harmonic suppression inverter. A harmonic suppression device characterized by: (2) PW using self-extinguishing device as main circuit switch
A forward conversion circuit that enables power regeneration through M control, an inverse conversion circuit that receives DC power from the forward conversion circuit and supplies AC power to a load, and a control circuit section that performs PWM control on the forward conversion circuit. In the harmonic suppression device having a harmonic suppression inverter, the control circuit unit includes means for determining harmonic components of the instantaneous real power and the instantaneous imaginary power from the load current and phase voltage of the AC system of the forward conversion circuit; Actual power calculation means for calculating the actual power of the load from the DC voltage and DC current of the inversion circuit, and the DC power calculated based on the actual power of the load and the power loss of the self-extinguishing device are added together. Instantaneous power limiting means for limiting the instantaneous real power and imaginary power of harmonic components according to the amount of power; and means for determining the current command of the forward conversion circuit from the real power and imaginary power limited by the instantaneous power limiting means. A harmonic suppression device characterized by comprising: