KR100766718B1 - Single phase Active Filter for Computer Server - Google Patents

Abstract

The present invention relates to an active power filter for a computer server, a voltage detector for receiving the power supply voltage of the server, a current detector for receiving the load current of the server, a DC voltage detector for detecting the DC voltage of the DC capacitor, the voltage detector and the current detector The digital output of the control unit, including a digital converter for converting the compensation value calculated in the digital processor and the digital processor for calculating the compensation value using the AD converter and the digital signal to convert the signal received from the digital signal into a pulse A gate drive for supplying a signal from the unit to the inverter, an inverter unit for receiving the signal of the gate drive to output the compensation voltage to the filter unit, and an LCL filter unit for converting the compensation voltage generated in the inverter unit to the compensation current to supply to the power supply of the server.

Computer Server, Reactive Power, Harmonics, Inverter, Single Phase

Description

Single phase active filter device for computer server

1 is a waveform of current generated in a computer server.

2 is a basic diagram of a single-phase active filter device for a computer server.

3 is a basic algorithm of a single phase active filter device for a computer server.

4 are experimental waveforms of the single-phase active filter for the computer server of the present invention.

Waveform 1 of Figure 4 is a load current waveform containing a harmonic current.

Waveform 2 of FIG. 4 is a power supply voltage waveform.

Waveform 3 of FIG. 4 is an inverter output compensation current waveform.

Waveform 4 of FIG. 4 is a power supply current waveform in which harmonic currents are removed.

The graph of FIG. 5 simulates the case where the inverter output coupling reactor is in the L-C form, and implements the result waveform as an FFT.

The graph of FIG. 6 simulates the case where the inverter output side coupling reactor is in the form of L-C-L, and implements the resultant waveform as an FFT.

The present invention relates to a device for compensating for harmonic current and reactive power generated in using a computer server, and effectively cuts out harmonics and reactive power generated by a DC rectifier used in a computer server, thereby improving power quality at the power supply side. Device.

With the recent surge in the use of computers, IT companies continue to expand servers, and the power quality continues to deteriorate due to the harmonics and reactive power generated by the servers. Due to deterioration of power quality, malfunctions and lifespan of surrounding electric machines are shortened.

For example, due to the increase of harmonic voltage, current and reactive power, only 60% of the noise and overheating and actual capacity of the switchboard transformer can be used. In some cases, due to power quality deterioration, the precision equipment of the peripheral system is malfunctioning, the server is stopped or a fire occurs, causing huge damage.

In order to prevent such server accidents, IT companies have made a lot of efforts. For example, three-phase four-wire image split harmonic filters or three-phase four-wire active power filters are installed in switchboards.

However, the 3-phase 4-wire harmonic filter can reduce only the harmonic currents of the 3rd, 6th, and 9th orders generated in the system, and the 3-phase 4-wire active power filter has a disadvantage of being expensive. Since it can only be installed in a wired switchboard, it eliminates harmonics by integrating multiple devices, so it is impossible to reduce the harmonics generated after the filter before the switchboard.

Accordingly, the present invention has been developed a single-phase active filter device for a computer server to improve the power quality of the server without affecting the peripheral devices before the switchboard.

In order to simplify the control and to reduce the weight and size of the product, the controller uses a digital processor, and the LCL at the inverter output stage can be prevented from being contaminated by the inverter switching voltage ripple of the active filter and improving efficiency. A filter was used.

In order to achieve the above object, the present invention provides a voltage detector for receiving a power supply voltage of a server, a current detector for receiving a load current of a server, a DC voltage detector for detecting a DC voltage of a DC capacitor, and in the voltage detector and the current detector. AD converter for converting the received signal into a digital signal, a digital processor for calculating a compensation value using the digital signal, a digital output unit for converting the compensation value calculated by the digital processor into a pulse, a signal from the digital output unit to an inverter It includes a gate drive to supply a, a drive unit for receiving the signal of the gate drive outputting the compensation voltage to the filter unit, the LCL filter unit for converting the compensation voltage generated in the inverter unit to the compensation current to supply to the power supply of the server.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings and test waveforms.

1 is a measured current waveform including harmonic currents generated by a computer server.

As shown in the figure, the current waveform of the computer is significantly distorted by the SMPS power supply, and the third harmonic current is included most. A single phase active power filter device for a computer server is used to make these current waveforms into clean waveforms to improve power quality.

2 is a system configuration diagram of the present invention.

There is a single phase active filter 3 connected in parallel between the main power supply 1 for supplying power to the computer server 2.

AC voltage detector (4) for measuring the power supply voltage, current detector (5) for measuring the load current of the computer server, current detector (6) for measuring the compensation current from the single-phase active filter, and voltage state of the DC capacitor on the inverter side Signals measured by the four voltage and current detectors of the DC voltage detector 11 measuring the signal to the digital signal processor 15 using the A / D converter 14 of the control board 13. Calculate and compute the compensation waveform. The calculated compensation waveform is sent to the full bridge type inverter IGBT stack 9 through the digital signal output unit 16 and the gate drive 12.

When the first single-phase active filter is operated, the DC capacitor is initially charged through the resistor 7-1 to prevent inrush current flowing into the DC capacitor on the inverter side, and when the initial charging is completed, the control board ( By using the relay 17 of 13), the magnetic switch 7 is turned on, and the single-phase active filter 3 starts to compensate from the time when the magnetic switch is turned on. At the start of the compensation, the inverter of the single-phase active filter is a voltage source inverter, which compensates using the voltage stored in the DC capacitor 10. The LCL filter is used to convert the compensation voltage output from the ripple and inverter into the compensation current waveform. Use (8).

An algorithm for controlling a single phase active filter for a computer server is shown in FIG. 3.

The voltage V measured by the power supply voltage detector 4 detects the reference SIN and COS necessary for the algorithm through the PLL. Using the SIN and COS, the current value IL measured by the load current detector 5 is used to detect the effective portion (IL real) and the invalid portion (IL img). (IL img) is used for the discrete Fourier series (DFT) to detect the fundamental wave current IL src ref of the load current and the reactive fundamental wave current IL src_re ref.

The fundamental wave current (IL src ref) is a current including the fundamental wave active current and reactive current.

Subtract the fundamental wave current (IL src ref) from the load current (IL), and set the gain k of the invalid fundamental wave current to 0 to compensate only the harmonic current components of the load current, and set the gain k to 1 to make it invalid. A compensation current IF src that can also compensate for power is detected.

 In the operation of a single-phase active filter, the voltage of the DC capacitor should always be maintained at a constant voltage, so that the capacitor voltage (Vdc) measured by the DC voltage detector 11 and the reference voltage (Vdc *) as a reference are subtracted, After converting AC waveform by multiplying reference SIN through PI controller, add to compensation current waveform. In this way, the DC capacitor voltage is charged when the reference voltage falls below the reference voltage, and discharges when the DC capacitor voltage is above the reference voltage to maintain a constant voltage.

  When the compensation waveform IF src and the DC capacitor constant voltage maintenance algorithm waveform are added up, subtracted from the current waveform detected by the filter-side current detector 6, and then compared with a triangular wave through a P controller, In addition, a compensation PWM waveform to be exported through the digital signal output unit 16 is generated.

On the inverter output side, the LCL filter using the combination of the reactor (8-1), the ripple removing capacitor (8-2), and the inverter side reactor (8-3) is used instead of the reactor using the conventional active filters. Used.

Active filters using only conventional coupling reactors do not effectively remove high frequency ripple voltages generated by the inverter's PWM voltage waveforms, which in turn lowers the power quality of the system. Due to the high reactor capacity, the coupling reactors High heat and noise were also generated. However, in the active filter proposed in the present invention, the inverter side reactor 8-3 of the inverter stage generates a harmonic compensation current due to the voltage difference between the power supply voltage and the inverter output voltage, and the ripple removing capacitor 8-2. And the power supply side reactor (8-1) serves to remove the high frequency ripple voltage, it is effective to remove the harmonics and improve the power quality than the active filter only the coupling reactor with only a small capacity reactor. Conventional coupling reactors are made of reactors with a capacity of about 5% of the inverter capacity in consideration of the voltage drop and the compensation efficiency of the inverter, but the L-C-L filter can be miniaturized to about 3% of the inverter capacity.

The following formula calculates the capacity value of the coupling reactor using the inverter capacity. If we know the capacity and rated current of the inverter, we can get the reactor's impedance (Z). When the impedance Z is obtained, the reactor value [H] with respect to the fundamental frequency (60 Hz) can be obtained.

The above L value is a reactor value obtained by adding the reactor side reactor and the power source side reactor, and simulation and actual results show the best ripple reduction ratio. The capacitor C value can be obtained using the reactor L value and the cutoff frequency of the inverter switching frequency. The cutoff frequency is typically one half the inverter switching frequency.

4 are experimental waveforms of the single-phase active filter for the computer server of the present invention.

Waveform 1 of Figure 4 is a load current waveform containing a harmonic current.

Waveform 2 of FIG. 4 is a power supply voltage waveform.

Waveform 3 of FIG. 4 is an inverter output compensation current waveform.

Waveform 4 of FIG. 4 is a power supply current waveform in which harmonic currents are removed.

5 and 6 illustrate the case where the inverter output filter is L-C type and L-C-L type, and the voltage ripple is converted to FFT. The inverter switching frequency was set to 2 kHz.

Simulation simulation condition Mock condition L-C filter L-C-L filter  Switching frequency: 2 kHz Cutoff frequency: 1.2 kHz Inverter side reactor 1265 uH 1265 uH Ripple Elimination Capacitor 9.14 uF 13.9 uF Power Side Reactor 140 uH

The graph of FIG. 5 simulates the case where the inverter output coupling reactor is in the L-C form, and implements the result waveform as an FFT.

The graph of FIG. 6 simulates the case where the inverter output side coupling reactor is in the form of L-C-L, and implements the resultant waveform as an FFT.

It can be seen that the harmonic voltage in the graph of FIG. 6 is much smaller.

The present invention measures harmonics and reactive power generated by a computer server with a voltage and current detector, calculates a control algorithm with a digital processor, and quickly drives an IGBT, thereby enabling fast and accurate compensation of harmonics and reactive power.

Since the control method is not an analog implementation of the algorithm, but an algorithm implementation using a digital processor, it is easy to control any load or system change.

By using two reactors and one capacitor in the coupling reactor, high frequency ripple voltage can be minimized and a clean, stable compensation current waveform can be output.

Claims (4)

In the single-phase active filter device for a computer server, The power supply voltage detector 4 for sending the power supply voltage signal of the single-phase power supply 1 to the A / D converter 14 of the control board 13 and the load current signal of the computer server 2 to the A of the control board 13. A load current detector 5 for sending to the / D converter 14, a filter current detector 6 for sending the compensation current signal of the single-phase active filter device for the computer server to the A / D converter 14 of the control board 13, A DC voltage detector 11 for sending the voltage signal of the DC capacitor portion of the inverter portion to the A / D converter 14 of the control board 13; Converting the voltage and current signals received from the power supply voltage detector 4, the load current detector 5, the filter current detector 6, and the DC voltage detector 11 into digital signals that the digital processor 15 can recognize. A digital processor 15 for calculating a compensation value using an A / D converter 14, a digital signal of the A / D converter, and a compensation value calculated by the digital processor 15 are converted into a signal. A control board 13 including a digital output 16 and A gate drive 12 to supply a signal from the digital output 16 of the control board 13 to the IGBT stack 9 of the inverter section; An inverter unit receiving the signal of the gate drive 12 and outputting a compensation voltage to the L-C-L filter unit 8; The L-C-L filter unit 8 converts the compensation voltage generated by the inverter unit into a compensation current and supplies it to the power supply unit of the server. Single-phase active filter device for a computer server, characterized in that configured to include. 2. The inverter of claim 1, wherein the inverter unit comprises a full bridge type IGBT stack 9 having four IGBTs and a DC capacitor connected in series to at least two series to charge and discharge the DC voltage through the IGBT stack 9; Single-phase active filter device for a computer server, characterized in that it comprises a DC capacitor unit (10) and a DC voltage detector (11) for measuring the voltage signal of the DC capacitor unit (10). delete 2. The reactor according to claim 1, wherein the LCL filter unit (8) includes an inverter side reactor (8-3), a ripple removing capacitor (8-2), and a power source side reactor (8-1). 3) and the ripple cancellation capacitor 8-2 set the capacity of the inverter side reactor 8-3 and the ripple cancellation capacitor 8-2 by adjusting the cutoff frequency to 1/2 of the switching frequency of the inverter section. A single-phase active filter device for a computer server in which the capacity of the power supply-side reactor 8-1 is 1: 9 ratio with the inverter-side reactor 8-3.

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