JPH074051B2 - Active filter with combined use of passive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive active filter which is connected in parallel to a load in a power supply system and compensates a harmonic current flowing into the load to the power supply system.

[Conventional technology]

Three-phase pulse width modulation type power converter composed of high-speed switching elements (hereinafter abbreviated as PWM converter), AC reactor inserted in series in each phase on the AC side of the PWM converter, and PWM converter A DC capacitor connected between the DC terminals, a single-phase diode rectifier circuit connected in parallel with the DC capacitor, a star-star connection (YY) transformer whose secondary side is connected to the AC reactor, and an AC A capacitor connected in parallel to the connection point between the reactor and the transformer,
An active filter that is used in combination with an AC filter connected between the primary side of the transformer and the power supply system and a control device that controls the voltage of the PWM converter is described in "Showa 1988 National Conference of the Industrial Application Society of Japan, Proc. It is publicly known as explained in "Harmonic suppression device based on new principle" and the like.

FIG. 3 shows an example of a three-phase system having a passive active filter.

In FIG. 3, a load 2 such as a thyristor Leonard device is shown.
An AC filter 3 is connected to each phase of the line of the three-phase AC system power supply 1 which supplies power to the system via the system impedance 1 '. Here, the AC filter 3 is a fifth harmonic tuning filter composed of a series circuit of a capacitor 31 and a reactor 32, a seventh harmonic tuning filter composed of a series circuit of a capacitor 33 and a reactor 34, a resistor 35 and a reactor 36.
And a high-order filter composed of a series circuit of a parallel circuit and a capacitor 37. The primary winding of the (Y-Y) transformer 7 is connected to the other end of each phase of the AC filter 3, and the other end of the primary winding of the transformer 7 is star-connected. One end on the secondary side of the transformer 7 is star-connected for each phase, and the other end is connected in series with the AC reactor 4 for each phase. A capacitor 8 is connected to each phase connection point between the secondary side of the transformer 7 and the AC reactor 4.

A PWM converter 5 is connected to the side opposite to the transformer of the AC reactor 4, a DC capacitor 6 is connected between the DC terminals of this PWM converter 5, and a single-phase diode rectifier circuit 9 is connected in parallel to the DC capacitor 6. It is connected. The PWM converter 5 is connected as a three-phase bridge circuit in which diodes D _{1 to} D ₆ are connected in parallel to switching elements S _{1 to} S ₆ that can be turned on and off, and this is a trigger generated by the control device shown in FIG. The signal V _G turns on / off the switching elements S _{1 to} S ₆ to suppress harmonics.

In this way, the active filter that is used in combination with AC is mainly composed of the AC filter 3, the transformer 7, the AC reactor 4, the capacitor 8, the PWM converter 5, the DC capacitor 6, the single-phase diode rectifier circuit 9, and the control device shown in FIG. It is a component.

When the AC filter 3 operates as a phase advancing capacitor and the PWM converter 5 operates as a zero impedance for the fundamental wave, the fundamental wave voltage is not applied to the PWM converter. For harmonics, PWM
The converter 5 generates a harmonic voltage so as to block the harmonic component of the power supply current, and can suppress the problem of the AC filter 3, such as anti-resonance and the inflow of the harmonic current from the upper system. it can.

Therefore, here, the concept of real power and imaginary power is introduced by performing three-phase to two-phase conversion.

That is, the following equation (1) to (3) the power supply current i _su three-phase with, i _sv, i _sw and system voltage V _u, V _v, of the V _w biphasic currents i _sa, i _{S [beta} And the voltages V _α and V _β .

Here, [C] is a three-phase to two-phase conversion matrix.

The instantaneous actual power p and the imaginary power q are obtained from the following equation (4) from the two-phase voltage and current obtained from the equations (1) to (3).

The instantaneous actual power p and the imaginary power q correspond to general active power and reactive power, and the instantaneous actual power p and the imaginary power q are calculated by the following equations (5) and (6), respectively. , And AC components are decomposed.

p = + ... (5) q = + ... (6) where two phases of the power supply current i _sa, fundamental wave component of the i _{S [beta} DC component, the harmonic component is transformed AC components, to these DC The AC and AC components can generally be separated also through a high pass filter.

An example of a control device based on such a technical idea is as shown in FIG.

In FIG. 4, the power calculation circuit 101 has system voltages V _u , V _v , V
_w and the power supply current i _su, i _sv, equation (1) from the detected value of i _sw calculates the instantaneous real power p and imaginary power q according to Formula (4),
These are output to the high pass filter 102. The high-pass filter 102 removes the direct current component from these, and the instantaneous actual power p
And the AC component of the instantaneous imaginary power q are output to the current command value calculation circuit 103 as the actual power command signal p ^* and the imaginary power command signal q ^* , respectively.

p ^* = ... (7) q ^* = ... (8) The current command value calculation circuit 103 receives the actual power command signal p ^* , the imaginary power command signal q ^*, and the system voltages V _u , V _v , V _w , and calculates (1)
And a two-phase current command signal is obtained according to the following equations (9) to (11), two-phase to three-phase conversion is performed, and three-phase current command signals i _u ^* , i _v ^* , i _w ^* are generated. And outputs it to the amplifier circuit 104.

[C] ⁻¹ is the inverse transformation matrix of [C].

The amplifier circuit 104 inputs the current command signals i _u ^* , i _v ^* , i _w ^* , multiplies the gain k to generate the voltage command signals V _u ^* , V _v ^* , V _w ^*, and supplies them to the voltage control circuit 106. Output.

The voltage control circuit 106 inputs the triangular wave carrier voltage S output from the triangular wave generation circuit 105 and the voltage command signals V _u ^* , V _v ^* , V _w ^* , and, for example, (voltage command signal V _u ^* ≧ triangular wave carrier voltage S ), The switching element S ₁ is turned on and S ₆ is turned off. If (voltage command signal V _u ^* <triangular wave carrier voltage S), the switching element S ₁ is turned off and S ₆ is turned on. If the command signal V _v ^* ≧ triangular wave carrier voltage S), a trigger signal V _G for turning on the switching element S ₃ and turning off S ₂ is generated. As a result, the switching elements S _{1 to} S ₆ are turned on and off by the trigger signal V _G , and the instantaneous voltage value of each phase of the PWM converter 5 is controlled.

Since such a PWM converter 5 generates only a harmonic voltage, a harmonic current that cancels the harmonic current of the load 2 and a fundamental wave advance current of the AC filter 3 flow, but the PWM converter 5 No fundamental voltage is applied.

[Problems to be Solved by the Invention]

As described above, in the conventional active active filter with combined use, the switching loss of the PWM converter 5 is supplied and the voltage of the DC capacitor 6 is kept constant by the single-phase diode rectification circuit installed in parallel with the DC capacitor. .

However, in the method of supplying energy in such a single-phase diode rectifier circuit, when the voltage of the DC capacitor transiently rises, there is no method of lowering the voltage, and an excessive voltage is applied to the switching element. There was a problem.

[Means for Solving the Problems]

The present invention has been made in view of the above points,
To facilitate understanding of the present invention, a specific configuration example thereof is as follows.

That is, it is connected in parallel with the load equipment to the power system, between the PWM converter, the AC reactor inserted in series in each phase on the AC side of the PWM converter, and the DC terminal of the PWM exchanger. A connected DC capacitor, a Y-Y transformer whose secondary side is connected to an AC reactor, and a capacitor connected in parallel to the connection point between the AC reactor and the transformer,
An AC filter connected between the primary side of the transformer and the power supply system and a control device that controls the voltage of the PWM converter are provided.The control device detects the power supply current of the power supply system and detects the instantaneous actual power and Means for calculating imaginary power, means for obtaining the AC component of instantaneous real power and imaginary power, means for obtaining the deviation between the DC voltage command value and the actual DC voltage, and amplification of the deviation to obtain the imaginary power DC component Means, means for obtaining an imaginary power command signal by adding the imaginary power DC component and the AC component of the imaginary power, and means for obtaining the current command value by inputting the imaginary power command signal and the AC component of the actual power. , A means for inputting a current command value and outputting a voltage command signal multiplied by a gain, and a means for comparing the voltage command signal with a triangular wave carrier voltage to generate a switch command to the PWM converter are provided. .

[Action]

In the active filter combined with the passive filter configured as above, a phase-advancing current having a 90 ° phase advance with respect to the power supply voltage flows through the PWM converter. Therefore, the voltage of the DC capacitor can be controlled by controlling the voltage in phase with the phase-advancing current, that is, the DC component of the imaginary power.

Hereinafter, the present invention will be described in detail with reference to the drawings.

〔Example〕

FIG. 1 and FIG. 2 are a three-phase system diagram showing a configuration of a main part of an embodiment to which the present invention is applied and a system diagram showing a structure of a main part of a control device thereof.

That is, the one shown in FIG. 1 is obtained by removing the single-phase diode rectifier circuit 9 connected in parallel as shown in FIG. 3 from the DC capacitor 6.

Further, in the one shown in FIG.
Obtains the instantaneous real power and the imaginary power according to the equations (1) to (4), and obtains their AC components by the high-pass filter 102 '.

The subtractor 107 outputs the DC voltage command value V _CD ^* and ΔV of the actual DC voltage V _CD to the amplifier 108. The amplifier 108 has a deviation ΔV
Is amplified and the imaginary power DC component Δq is output to the adder 109.
The adder 109 adds the AC component of the instantaneous imaginary power and the imaginary power DC component Δq of the output of the high-pass filter 102 ′, and outputs the imaginary power command signal.
Output as q ^* to the current command value calculation circuit 103 '. The current command value calculation circuit 103 ′ inputs the imaginary power command signal q ^* and the AC component of the actual power, that is, the actual power command signal p ^*, and according to the equations (9) to (11), the current command values i _u ^* , i _v ^* , I _w ^* are generated and output to the amplifier circuit 104. The amplifier circuit 104 multiplies the current command value input by a gain k to generate voltage command signals V _u ^* , V _v ^* , V _w ^* and outputs them to the voltage control circuit 106.

Therefore, the voltage control circuit 106 outputs the triangular wave carrier voltage S output from the triangular wave generation circuit 105 and the voltage command signals V _u ^* , V _v ^* ,
V _w ^* is input and a trigger signal V _G for turning on / off the switching elements S _{1 to} S ₆ is generated.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a passive combined active filter having a simple structure in which the diode rectifier circuit provided in parallel with the DC capacitor is removed, and the DC capacitor can be charged and the voltage can be controlled together.

[Brief description of drawings]

1 and 2 are a three-phase system diagram showing the configuration of the essential parts of an embodiment to which the present invention is applied, and a system diagram showing the configuration of the essential parts of its control device, and FIGS. 3 and 4 are conventional examples. FIG. 3 is a three-phase system diagram showing the passive combined active filter of FIG. 1 ... Three-phase AC system power supply, 2 ... Load, 3 ... AC filter, 4 ... AC reactor, 5 ... Three-phase pulse width modulation type power converter (PWM converter), 6 ... DC capacitor, 7 ... Transformer, 8 ... Capacitor.

Claims (1)

[Claims] 1. In a passive active filter, which is connected in parallel with a load facility to a power system, a PWM converter, an AC reactor inserted in series with each phase on the AC side of the PWM converter, and the PWM conversion. A DC capacitor connected between the DC terminals of the container, a transformer with a star-star connection whose secondary side is connected to an AC filter, and a capacitor connected in parallel to the connection point between the AC reactor and the transformer,
An AC filter connected between the primary side of the transformer and a power supply system, and a control device that controls the voltage of the PWM converter are provided, and the control device detects the power supply current of the power supply system and instantaneously detects the power supply current. Means for calculating the real power and imaginary power, means for obtaining the AC component of the instantaneous real power and imaginary power, means for obtaining the deviation between the DC voltage command value and the actual DC voltage, and amplifying the deviation to obtain the imaginary power DC component. Obtaining means, means for obtaining an imaginary power command signal by adding the imaginary power direct current component and the imaginary power alternating current component,
A means for obtaining a current command value by inputting the imaginary power command signal and the AC component of the actual power, a means for inputting the current command value and outputting a voltage command value multiplied by a gain, the voltage command signal and the triangular wave carrier voltage By comparison, means for generating a switch command to the PWM converter is provided, and a passive active filter is used in combination.