KR101039310B1 - Hybrid Active Power Filter - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid active power filter, comprising: providing a low band filter between a supply power supply and a nonlinear load to filter high frequency components other than the fundamental wave, whereby the resonance phenomenon of the low band filter is suppressed and the low frequency band harmonic current It is a hybrid active power filter that connects an active power filter to the low pass filter that can provide a compensation current for filtering the PSA.

Active Power Filter, Low Band Filter, L-C Filter, Nonlinear Load

Description

Hybrid Active Power Filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid active power filter, and in particular, a passive filter without resistance is used to remove high frequencies generated between a supply power supply and a nonlinear load, and the resonance frequency component and the nonlinear load generated by the passive filter are used. The present invention relates to a complex active power filter capable of miniaturizing and reducing overall weight by minimizing the volume, weight, and loss power of a passive filter by appropriately removing the generated low frequency band harmonic flow components from an active filter.

Since the development of electricity, devices using electricity have also been developed in various ways. These various devices can be divided into a device having a large linear load characteristics and a non-linear load characteristic with respect to electricity. Devices having a linear load characteristic have a disadvantage in that the size of the device is very large because the characteristics are linear and the characteristics are easy to predict and easy to compensate. In addition, devices having a non-linear load characteristic is a trend that is widely used in various industrial fields because the characteristics appear non-linear, but the component is small and easy to configure compared to the passive element.

However, since devices having nonlinear load characteristics inevitably generate distortions due to power stages, transmission lines, and other peripheral devices, various types of passive power filters and active power filters must be provided to solve such distortions.

For this reason, active power filters are placed in devices with nonlinear loads, and function to remove harmonic currents contained in the load current to improve power quality. Active power filters are classified into circuits, and may be classified into a current type active power filter using a current type inverter and a voltage type active filter using a voltage type inverter. Current type active filter has the advantage of fast compensation speed, but many filters of R // L-C type (5th order tuning filter, 7th order tuning filter, 7th order high pass to filter high frequency components included in compensation current) Filter) in parallel. As a result, current-type active filters suffer from a fundamental power factor drop in the 60-Hz power system, additional power loss in the resistors, and bulkiness.

Meanwhile, the voltage type active filter removes harmonic currents included in the load current by adding an inductor serving as an impedance buffer between the power system and the inverter and controlling the inverter so that the current flowing through the inductor is a harmonic current to be removed. Accordingly, the harmonic current compensation performance of the voltage type active filter is determined by the inverter's current control speed. As a result, the voltage-type active filter has a disadvantage in that the compensation performance for higher-order harmonic currents is lower than that of the current inverter. However, the voltage-type active filter does not use an additional filter, so the circuit configuration is simpler than the current-type active filter.

1 is a circuit diagram illustrating a conventional hybrid active power filter.

As shown in FIG. 1, the conventional hybrid active power filter includes a supply power source 10 and a non-linear load 20 to prevent the distorted current generated from the nonlinear load 20 from flowing into the supply power source 10. An active filter 30 and a passive filter 40 are employed between them.

In this case, the passive filter 40 is an eleventh order and a tuning filter (for example, a fifth order shunt, a seventh order shunt, and an 11th order shunt) in which an inductor and a capacitor are connected in series to remove harmonic components of a specific order. A high order filter is included to remove the above high order components. In addition, the conventional hybrid active power filter employs the active filter 30 to remove components other than the harmonic components removed by the passive filter 40.

In the conventional hybrid active power filter having such a configuration, the higher order filter is configured by inserting a resistor to remove various higher order components. In this case, since the inserted resistor acts as a resistance to the power supply, the conventional hybrid active power filter may cause power loss due to the inserted resistor.

In order to solve the problem of power loss described above, it may be considered to remove the resistance from the higher order filter. However, when the resistance is removed from the higher order filter, the higher order filter operates as a tuning filter that removes only specific harmonic components, and thus operates as a filter only for harmonic currents of a specific order. In addition, the higher-order filter with the resistance removed short-circuits the system for other specific order voltages, thereby degrading the stability of the system.

Accordingly, the present invention has been devised to solve the necessity of the above-described prior art, and an object of the present invention is to adopt a passive filter having a high cutoff frequency capable of reducing the volume of a high pass filter including a resistor and having no resistance. In addition, the present invention provides a hybrid active power filter including an active filter capable of acting as a damper against a resonance phenomenon of a passive filter that may occur at light load.

In accordance with another aspect of the present invention, a hybrid active power filter includes: a low pass filter disposed between a supply power supply and a nonlinear load; And an active filter connected to the low pass filter to provide a resonance suppression loop generated by the low pass filter.

Wherein the low pass filter comprises an inductor connected in series between the supply power and the nonlinear load; A node between the inductor and the nonlinear load; And a capacitor connected to the node.

The active filter is connected to the node to generate and deliver a compensation current for the load current generated from the power supply, and the compensation current generated by the active filter is generated at a resonance frequency generated by the low pass filter. The controller may further include a controller configured to generate a corresponding harmonic signal.

The controller includes a harmonic signal detector for detecting a load current at the node; A moving average calculator for calculating a moving average for the voltage detected at the node; A subtractor for subtracting the output of the moving average calculator from the voltage detected at the node; A gain adjuster for adjusting a gain output from the subtractor to correspond to a resonance frequency of the low pass filter; A summer for adding up the compensation current reference signal output from the harmonic signal detector and the output from the gain regulator; And a current controller controlling the active filter to generate a compensation current provided to the node based on the summer output.

의 배수가 될 것이다.On the other hand, if the inductor is L and the capacitor is C, the resonance frequency included in the output of the low pass filter is

Will be a multiple of.

A hybrid active power filter according to an embodiment of the present invention for achieving the above object, the low-pass filter disposed between the supply power supply and the non-linear load to filter the higher order components; And an active filter configured to generate a compensation current corresponding to a virtual resistor for removing a load current corresponding to a resonance frequency included in an output of the low pass filter.

Wherein the active filter further comprises a controller for controlling to generate the compensation current, the controller comprising: a harmonic signal detector for detecting a load current at a node located between the supply power supply and the nonlinear load; A moving average calculator for calculating a moving average for the voltage detected at the node; A subtractor for subtracting the output of the moving average calculator from the voltage detected at the node; A gain adjuster for adjusting a gain output from the subtractor to correspond to a resonance frequency of the low pass filter; A summer for adding up the compensation current reference signal output from the harmonic signal detector and the output from the gain regulator; And a current controller that removes the active filter to become a virtual resistance for a specific order among harmonic components generated from the supply power based on the summer output.

As described above, according to the hybrid active power filter of the present invention, there is little self energy consumption without using an energy element such as a resistor, the ability of the passive filter to filter in a wide range, and the resonance phenomenon of the passive filter. By providing an active filter that eliminates these components, the entire system can be designed appropriately, minimizing the volume, weight, and power dissipation of passive filters.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, and descriptions of other parts will be omitted so as not to obscure the subject matter of the present invention.

The terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors are appropriate to the concept of terms in order to explain their invention in the best way. It should be interpreted as meanings and concepts in accordance with the technical spirit of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The hybrid active power filter described below is characterized by providing a passive filter acting as a low band filter between the supply power supply and the nonlinear load, and providing an active filter to eliminate resonance of the passive filter. Here, the passive filter is arranged in parallel with the inductor and the capacitor to act as a low pass filter for the load current between the supply and the nonlinear load. In the present invention, each capacitance value of the inductor and the capacitor may be different values depending on the power supply and the nonlinear load used, and thus, the quantitative value thereof will not be limited.

Meanwhile, since the resonant frequency value generated according to the capacitance values of the inductor and the capacitor used in the passive filter is changed, the compensation current value of the active filter for preventing the resonance phenomenon of the passive filter may also vary according to the characteristics of the passive filter. . In more detail, the controller controlling the active filter provides the compensation current to the voltage node of a specific node of the passive filter when the compensation current generated in the active filter is generated. The error of compensation current at a particular node can be reduced. The controller then uses the moving average operation to apply the current load current to the compensation current immediately along with the previously detected signal values.

Hereinafter, a hybrid active power filter according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The drawing of the hybrid active power filter described below describes an example applied to the three-phase power system, but the present invention is not limited thereto.

2 schematically illustrates a configuration of a hybrid active power filter that can be applied to a three-phase power system according to an embodiment of the present invention.

Referring to FIG. 2, the hybrid active power filter of the present invention includes a supply power source 110 and a nonlinear load 120, and passively acts as a low band filter between the supply power source 110 and the nonlinear load 120. The filter 130 includes an active filter 140 connected to the passive filter 130.

The passive filter 130 acts as a low band filter by connecting an inductor and a capacitor in parallel between the power supply 110 and the nonlinear load 120. Accordingly, the passive filter 130 may remove a wide range of harmonic components between the power supply 110 and the nonlinear load 120.

The active filter 140 is connected between the inductor and the capacitor of the passive filter 130 to eliminate voltage distortion that may occur at the output of the passive filter 130. To this end, the active filter 140 includes an inductor disposed between the inductor and the capacitor of the passive filter 130, a converter connected in series with the inductor, and a supply power supply for supplying power to the converter. Here, the converter's power can be removed if the converter maintains a DC-link voltage that can power itself without a separate power supply.

As described above, the hybrid active power filter of the present invention provides a low-pass filter between the power supply 110 and the nonlinear load 120 to remove high order components, but does not use resistors, inductors and capacitors. By implementing using, it is possible to minimize the loss power.

This hybrid active power filter will be described in more detail with reference to FIG. 3. FIG. 3 is a block diagram generalizing the three-phase power system of FIG. 2.

Referring to FIG. 3, a hybrid active power filter includes an inductor L between a power supply 110 and a nonlinear load 120, a node between the inductor L and a nonlinear load 120, that is, a voltage node V _a. ) included, and the voltage node (V _a), the inductor (L) and the active filter 140, an active filter connected to the capacitor (C), the voltage node (V _a) are connected in parallel in parallel with the capacitor (C) in the Controller 150 to control the output of 140.

The inductor L and the capacitor C are connected in parallel to form a passive filter 130 having the characteristics of a low pass filter. Accordingly, the inductor L and the capacitor C operating as the low pass filter with respect to the power system may filter the higher order component of the load current I _load flowing to the power supply 110. On the other hand, since the passive filter 130 is configured in parallel with the inductor (L) and the capacitor (C), a resonance frequency may occur accordingly. That is, the passive filter 130 has a resonance phenomenon caused by the inductor (L) and the capacitor (C) at light load or transient state and has a resonance frequency as shown in Equation (1).

The active filter 140 is controlled such that a virtual resistor is formed with respect to components other than the fundamental wave of the current generated from the power supply to suppress the resonance phenomenon of the passive filter 130. In other words, the active filter 140 may remove a component other than the fundamental wave generated by the resonance phenomenon by supplying a constant compensation current I _com to the power system.

The controller 150 generates and provides a specific control signal to the switch, or converter, of the active filter 140 so that the active filter 140 can detect and remove high-order components other than the fundamental wave generated by the resonance phenomenon. At this time, the controller 150 is a signal corresponding to the resonant frequency of the passive filter and the multiple of the resonant frequency in order to eliminate the resonance phenomenon generated at the output of the passive filter, the compensation current (I _com ) provided by the active filter 140 It is preferable to become.

This controller 150 will be described in more detail with reference to FIG. 4. 4 schematically shows the configuration of the controller 150 of the present invention.

Referring to FIG. 4, the controller 150 of the present invention includes a harmonic signal detector 151, a moving average calculator 153, an adder 154, a gain adjuster 155, a subtractor 152, and a current controller 157. It may include.

The harmonic signal detector 151 detects a harmonic signal generated from the power supply 110, that is, a _load current I _load . The harmonic signal detector 151 generates a reference signal I _com * so that the active filter 140 can generate a compensation current for canceling the harmonic signal corresponding to the detected load current. The reference signal I _com * of the generated compensation current is transmitted to the summer 154.

Moving average (Moving Average) computing unit 153 computes a moving average of the voltage detected at the voltage node (V _a). The moving average calculator 153 may adjust the number of points of the moving average according to the power supply size of the power supply or the characteristics of the nonlinear load. For example, if the moving average point 5, the moving average output of the computing unit 153 detects the five power by detecting the power detected by the voltage node (V _a) by a predetermined time, calculated after dividing them into 5 Can be a moving average. Through this process, the moving average computing unit 153 may remove the high-order component in the voltage node (V _a). The output of the moving average calculator 153 is passed to the subtractor 152.

The subtractor 152 subtracts the output of the moving average computing unit 153 from the electrical current which is detected by the voltage node (V _a). Accordingly, the node voltage (V _a), it is possible to detect a higher-order component generated by the power supply 110. The output of subtractor 152 is delivered to gain adjuster 155.

The gain adjuster 155 adjusts the gain of the signal output from the subtractor 152 and delivers it to the summer 154. The gain value K of the gain adjuster 155 may be changed according to the resonance frequency formed by the inductor L and the capacitor C constituting the harmonic signal and the low band filter generated from the power supply 110. The gain adjuster 155 applies a gain of a predetermined value to the signal received from the subtractor 152 and then transfers the gain to the summer 154.

The summer 154 gain-adjusts the reference signal I _com * of the compensation current received from the harmonic signal detector 151 and the higher order component at the voltage node V _a received from the gain adjuster 155. After summation, it is passed to the current controller 157.

The current controller 157 is provided to adjust a converter of the active filter in accordance with the signal to generate a compensating current, and this means that the power system, the voltage node (V _a) delivered from the summer 154. The Accordingly, the active filter 140 may generate an effect of virtually inserting a resistor only for a specific higher order component of the load current (I _load ), thereby forming a resonance suppression loop as a whole.

As described above, the hybrid active power filter of the present invention provides a low-pass passive filter using an inductor and a capacitor (C) between the supply power source 110 and the nonlinear load 120 to provide a wide range of load currents (I _load ). Higher order components can be filtered out. And then subtracting the hybrid active power filter is a signal output by the moving average operation on the voltage generated at the voltage node (V _a) in order to remove the resonance phenomenon occurring in passive filter 130 in the source signal, the appropriate The gain, that is, the gain for removing the resonance phenomenon corresponding to the resonance frequency generated by the inductor L and the capacitor C, is applied, and then the compensation current reference signal I _com * detected by the harmonic signal detector 151. ) To the current controller 157. Then, the current controller 157 may generate a compensation current capable of removing a higher order component corresponding to the resonance phenomenon from the load current I _load and provide it to the power meter. As a result, the hybrid active power filter can be configured by linking the passive filter and the active filter to each other, thereby optimizing the weight and weight of the system as a whole and minimizing power loss.

5A and 5B illustrate a process before and after using an active filter applied to a load used in a three-phase four-wire type according to an exemplary embodiment of the present invention.

5A shows a state in which an inductor and a capacitor are connected and form a low pass filter between a supply power supply and a non-charge load. As shown, it can be seen that the load current passing through the low pass filter contains a lot of noise of higher order components in the waveform. By providing an active filter connected to the low band filter in such a power meter, a waveform in which higher-order components are removed as shown in FIG. 5B can be obtained. That is, the hybrid active power filter of the present invention can remove the resonance phenomenon caused by the output of the passive filter by filtering the signal generated from the power supply and passed through the low pass filter in the active filter. Accordingly, the hybrid active power filter can obtain a relatively stable signal waveform from which high-order component noise is removed, as shown in FIG. 5B.

Table 1 shows quantitatively the harmonic reduction effect shown in FIG. 5B.

Frequency [kHz] 0.3 0.42 0.66 0.78 3.84 3.96 4.08 Before reward [A] 3.37 2.02 1.586 1.229 1.476 2.72 1.94 After compensation [A] 1.6 0.45 0.35 0.16 0.005 0.006 0.008

In Table 1, the reference frequencies are 0.3, 0.42, 0.66, 0.78, 3.84, 3.96, 4.08 and the like and the unit is Khz. At each of these frequencies, the precompensation characteristic is represented by 3.37, 2.02, 1.586, 1.229, 1.476, 2.72, and 1.94, while the postcompensation characteristic is 1.6, 0.45, 0.35, 0.16, 0.005, 0.006, and 0.008, which corresponds to the harmonic components. It can be seen that the minimum is 53% to 95%.

As described above, in the detailed description of the present invention has been described with respect to specific embodiments, various modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below, but also by the equivalents of the claims.

1 illustrates a conventional hybrid active power filter.

2 is a view schematically showing the structure of a hybrid active power filter according to an embodiment of the present invention.

FIG. 3 is a generalized view of the composite active power filter structure of FIG. 2. FIG.

4 is a block diagram illustrating the controller structure of FIG. 3 in more detail.

5A and 5B show waveforms before and after the application of the composite active power filter of the present invention.

Claims (10)

A passive filter disposed between a supply power supply and a nonlinear load, the inductor being connected in series between the supply power supply and the nonlinear load, a node between the inductor and the nonlinear load, and a capacitor connected to the node; An active filter coupled to the passive filter to provide a resonance suppression loop generated by the passive filter; And And a controller for controlling a compensation current generated by the active filter to be generated as a harmonic signal corresponding to a resonance frequency generated by the passive filter. The controller comprising: A harmonic signal detector for detecting a load current at the node; A moving average calculator for calculating a moving average for the voltage detected at the node; A subtractor for subtracting the output of the moving average calculator from the voltage detected at the node; A gain adjuster for adjusting a gain of the signal output from the subtractor to correspond to a resonance frequency of the passive filter; A summer for adding up the compensation current reference signal output from the harmonic signal detector and the output from the gain regulator; And A current controller for controlling an active filter to become a virtual resistance for a specific order among harmonic components generated from the power supply based on the summer output; A hybrid active power filter comprising a. delete The method of claim 1, wherein the active filter And a compensating current connected to the node to generate a compensation current for removing a resonance phenomenon output from the passive filter in a light load or a transient state of the supply power, and delivering the compensation current to the node. The method of claim 1, wherein the moving average calculator A hybrid active power filter, characterized in that the number of points of the moving average is adjusted according to the size of the power supply or the characteristics of the nonlinear load. 5. The method of claim 4, The output of the moving average calculator is a moving average calculated after detecting the power of the number of points for each predetermined time by the power detected by the node, and dividing the power of the detected number of points by the number of points. Active power filter. The method of claim 1, When the inductor is L and the capacitor is C, Resonance frequency included in the output of the passive filter is

Hybrid active power filter, characterized in that multiple of. 5. The method of claim 4, The active filter An inductor connected to the node; And And a converter coupled to the inductor. Disposed between a supply power supply and a nonlinear load, the inductor connected in series between the supply power supply and the nonlinear load, a node between the inductor and the nonlinear load, and a capacitor connected to the node; A manual filter for filtering; An active filter generating and providing a compensation current corresponding to a virtual resistor for removing a load current corresponding to a resonance frequency included in an output of the passive filter; And A controller for controlling to generate the compensation current; The controller comprising: A harmonic signal detector for detecting a load current at the node; A moving average calculator for calculating a moving average for the voltage detected at the node; A subtractor for subtracting the output of the moving average calculator from the voltage detected at the node; A gain adjuster for adjusting a gain of the signal output from the subtractor to correspond to a resonance frequency of the passive filter; A summer for adding up the compensation current reference signal output from the harmonic signal detector and the output from the gain regulator; And A current controller for controlling an active filter to become a virtual resistance for a specific order among harmonic components generated from the power supply based on the summer output; A hybrid active power filter comprising a. 10. The apparatus of claim 8, wherein the moving average calculator A hybrid active power filter, characterized in that the number of points of the moving average is adjusted according to the size of the power supply or the characteristics of the nonlinear load. 10. The method of claim 9, wherein the output of the moving average calculator And a moving average calculated after detecting the power of the number of points for a predetermined time by dividing the power detected by the node, and dividing the power of the detected number of points by the number of points.

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