CN205911751U - Eliminate high frequency switch EMI's active power filter device - Google Patents

Abstract

The utility model provides an eliminate high frequency switch EMI's active power filter device, including connecting active filter universal control circuit and electric current tracking control algorithm and the PWM module on sampling side electric wire netting, the active filter universal control circuit include harmonic separating module, a serial communication port, the output of electric current tracking control algorithm and PWM module connect generalized type EMI filter module, generalized type EMI filter module including the filter branch that is used for filtering harmonic current, be used for filtering switching frequency harmonic current's the 2nd filter branch and be used for the surge protection circuit of filtering peak and surge, the utility model discloses cover to the surge protection of system with to the generalized type EMI filter module of active filter switching frequency harmonic current's filtering function, can carry out "lower -order harmonic filtering and high frequency and switching frequency harmonic current filtering.

Description

Active filter device for eliminating high frequency switching EMI

technical field

The utility model relates to the power electronic device technology, relates to the technical field of a power electronic device for filtering the switching frequency harmonic current of a high-frequency switch tube (IGBT), in particular to an active filter device for eliminating high-frequency switch EMI.

Background technique

The harmonic content in the distribution network system is an important index to measure the quality of power energy, and it is also an important governance object for promoting clean energy and purifying the power grid in recent years. When the sine wave voltage is applied to the nonlinear load circuit, the current becomes a nonlinear change, causing a non-sinusoidal waveform that is not synchronized with the voltage. The non-sinusoidal current produces a nonlinear voltage drop on the grid system impedance, causing the system voltage The waveform also becomes non-sinusoidal. According to the Fourier series, any non-sinusoidal wave can be decomposed into the same fundamental wave component as the power frequency in the frequency domain, and the harmonic component that is an integer multiple of the fundamental wave component. Harmonic current has many adverse effects on various key electrical equipment and power efficiency of the user system, inaccurate power factor and cause comprehensive protection malfunction, abnormal noise and heating of power distribution system transformers, etc. So far, the power distribution system has introduced a static var generator (Static var Generation-SVG) and an active filter (Active power filter-APF) based on modern power electronics, as a reactive power compensation device and harmonic control. devices, but this kind of equipment is based on high-frequency switching tubes to generate corresponding compensation currents to achieve the purpose of controlling low-order harmonics. However, the high-frequency switching state correspondingly produces harmonic currents of the switching frequency to the grid system. The harmonic current of this switching frequency has great harm to the capacitance of the traditional reactive power compensation device in the distribution network system. The harmonic source and the power capacitor are on the same bus. At this time, the structure of the circuit has the characteristics of a parallel circuit, and the system The impedance changes greatly due to the change of the load on the entire bus. When the system impedance and the power capacitor impedance resonate at a certain harmonic current frequency, it will cause harmonic current amplification, resulting in excessive harmonic current in the power capacitor. Capacitor damage or derating and other phenomena, the skin effect of high-order harmonic current is serious, the effective cross-sectional area of the wire is reduced, and the busbar vibration, abnormal noise and severe heating in the power distribution system are caused.

In addition, with the rapid development and advancement of power electronics technology, computer technology, communication technology and modern precision control technology, the digital control of modern intelligent buildings, the continuous introduction of modern medical equipment in large and medium-sized hospitals, including some fine processing and high-speed railway passenger transport The continuous expansion of the system makes these places use a large number of modern precision electrical equipment and devices, such as digital signal systems, computers, high-end communication systems, network control equipment, various digital office equipment, lighting control systems, fire protection systems, monitoring systems, Frequency conversion systems, CT machines in hospitals, nuclear magnetic resonance machines, electrocardiographs, ventilators, pacemakers, etc. all require high-quality power supply systems and as little high-frequency interference as possible. At present, with the increase of a large number of nonlinear loads, the distortion rate of power supply and current in the distribution network is becoming more and more serious, resulting in a harsh harmonic environment, which poses a great threat to the safe and normal operation of the power system and equipment. It is especially prominent for some places related to personal life safety such as hospitals. So now factories, hospitals, and comprehensive office buildings all use a large number of traditional active filter devices to solve the low-order harmonics (2 to 50th) in the power distribution system. However, this kind of equipment is based on high-frequency switching characteristics, and the general switching frequency is above 10KHz, so the output of the device will contain a large number of high-order harmonics and harmonic currents of the switching frequency. Electronic computers, microprocessors, and other electronic equipment generally have weaknesses such as low insulation, weak resistance to high-frequency interference, high requirements for harmonic environments, and poor overvoltage tolerance. High-order harmonic pollution often causes program operation errors, data errors, time errors, frequent crashes, restarts without reason, malfunctions of precision instruments, and even permanent damage to electrical equipment when these sensitive electronic systems are running. In addition, in the low-voltage power distribution system, most of the nodes of the power grid are equipped with a large number of reactive power compensation devices. When the high-order harmonic current changes in the system impedance, serious high-order voltage will be generated and loaded on the capacitor. , coupled with the severe skin effect of high-order harmonic currents, will cause capacitor overvoltage and overheating and derating or damage. These have all caused huge losses to people's work and daily life. Therefore, the harmonic protection of electrical equipment in the current low-voltage power distribution system has become an urgent problem to be solved, and it is even more important to solve the high-order harmonics and switching frequency harmonic currents of the output of the active filter device.

The existing Chinese patent application with the announcement number CN 103683292 "A Parallel Quasi-Proportional Resonant Active Power Filter and Its Control Method" proposes a parallel-connected quasi-proportional resonant active power filter and its control method. Realize more accurate tracking, solve the problem that PI tracking can't realize no static error tracking to the alternating current, to improve the filter performance of active power filter.The utility model comprises the following steps: 1) the network voltage signal that will obtain is passed software The phase-locked loop monitors the frequency of the power grid in real time and obtains the phase angle of the positive sequence voltage of phase A; 2) real-time modification of the resonant angular frequency for quasi-proportional resonance control, so that the resonant angular frequency of quasi-proportional resonance always maintains a fixed proportional relationship with the grid frequency ; 3) According to the resonant angular frequency of real-time modification and the load current signal obtained, carry out quasi-proportional resonance control, and take out the reference current of the selected filtering frequency; 4) compare the output reference current with the actual output of the active power filter The current difference is subjected to quasi-proportional resonance control, and the drive signal is output to drive the IGBT to turn on." However, the above-mentioned utility model still has defects, and cannot perform surge protection for the system and filter the switching frequency harmonic current of the active filter , for low-order harmonic filtering and high-frequency and switching frequency harmonic current filtering. The above-mentioned utility model is only for the control system algorithm, not for the configuration of peripheral hardware parameters to filter the high-frequency harmonic current and the switching frequency harmonic current, so as to reduce the high-order harmonic and switching frequency sub-harmonic current injected into the power grid. The above-mentioned utility model cannot effectively filter out high-order harmonics and switching frequency sub-harmonics, and the filtering branch does not adopt closed-loop control, so it is easy to form resonance and amplify harmonics with system impedance.

Utility model content

The technical problem to be solved by the utility model is to solve the above-mentioned problems in the prior art, and provide an active filter device and a control method for eliminating high-frequency switch EMI, filter out low-order harmonic currents, and effectively eliminate switching frequency at the same time Harmonic current and load high-order harmonic current, reduce the interference and harm caused by high-frequency harmonics in the system to electrical equipment, especially precision loads.

For solving the above problems, a kind of technical scheme of the utility model is:

The utility model comprises a general control circuit of an active filter connected to the grid on the sampling side, a current tracking control algorithm and a PWM module, and the general control circuit of the active filter includes a harmonic separation module; it is characterized in that the The current tracking control algorithm and the output end of the PWM module are connected to a comprehensive EMI filter module, and the comprehensive EMI filter module includes a first filter branch for filtering out harmonic currents, and a first filter branch for filtering out switching frequency harmonic currents. The second filtering branch and a surge protection circuit for filtering peaks and surges.

Further, the first filtering branch includes a smoothing reactance connected to the inverter side of the power grid, a grid-connected reactance connected to the load side of the power grid, and a first filtering branch capacitor connected between the power grid and the neutral line.

Further, the grid-connected reactance includes a reactor LA connected in series with phase A of the power grid, a reactor LB connected in series with phase B of the power grid, and a reactor LC connected in series with phase C of the power grid; The smoothing reactance La of the phase, the smoothing reactance Lb connected in series with the B phase, and the smoothing reactance Lc connected in series with the C phase; the first filter branch capacitor includes a capacitor Ca1 connected to the grid A phase and the N line, and connected to the grid The capacitor Cb1 between phase B and N wire is connected to the capacitor Cc1 between phase C and N wire of the power grid.

Further, the second filtering branch includes a capacitor Ca2 connecting phase A and N wire of the grid, a capacitor Cb2 connecting phase B of the grid and N wire, and a capacitor Cc2 connecting phase C and N wire of the grid.

Further, the capacitor Ca2 is connected in series with the reactor La1, the capacitor Cb2 is connected in series with the reactor Lb1, and the capacitor Cc2 is connected in series with the reactor Lc1.

Further, the surge protection circuit includes a varistor Rva connecting phase A of the power grid and the PE line, a varistor Rvb of a phase B of the power grid and the PE line, and a varistor Rvc of a phase C of the power grid and the PE line; The varistor Rvab of the AB phase, the varistor Rvbc connected with the BC phase of the power grid, the varistor Rvca connected with the CA phase of the power grid, and the varistor Rvng connected with the N line and the PE line.

Further, it also includes a first filtering branch closed-loop control system. The first filtering branch closed-loop control system includes a filtering branch current sampling module and a feedback control algorithm conversion module; the sampling of the filtering branch current sampling module The terminal is connected to the first filter branch of the integrated EMI filter, and the output end of the filter branch current sampling module is connected to the described feedback control algorithm conversion module; the feedback control algorithm conversion module outputs the feedback current It is used for summing the harmonic current separated from the general control circuit of the active filter to obtain the reference command current for closed-loop control.

Compared with the prior art, the utility model aims at the defects of the prior art,

The utility model includes an active filter general control circuit (not within the control scope of the utility model), a comprehensive EMI filter module and a first filter branch control system. The general control of the active filter is mainly aimed at absorbing the 2nd to 50th harmonic current; the comprehensive EMI filter module is mainly aimed at the switching frequency harmonic current generated by the active filter, including the high frequency absorption filter module, the switching frequency harmonic current filter In addition to the module and surge protection circuit. It can fully filter out the high-frequency and switching frequency harmonic current injected by the high-frequency switching tube into the power distribution system, and reduce the high-frequency interference in the system and the impact of high-frequency harmonics on electrical equipment, especially precision loads. harm.

Aiming at the deficiencies of the existing active filter for high-frequency switching frequency, the utility model covers the surge protection of the system and the comprehensive EMI filter module with the function of filtering the switching frequency harmonic current of the active filter, which can Perform low-order harmonic filtering and high-frequency and switching frequency harmonic current filtering.

The first filtering branch and the second filtering branch have the functions of suppressing and completely absorbing high-order harmonics and switching frequency harmonics, pulse spikes, surges and other interferences, and can track the output waveform and System voltage waveform, instantaneously filter out switching harmonics output by high-frequency switching tubes and peaks, surges, and clutter in the system power supply and filter out harmonic currents in the system, so that the waveform of the grid power supply is close to the waveform of the system voltage, Improve power quality and purify power grid.

The EMI filter module based on the elimination of switching frequency harmonic current provided by the utility model adopts digital control for the general control circuit of low-order high-current harmonic active filter, and injects vector values opposite to the harmonic direction in the grid system, real-time Eliminate low-order harmonic currents.

The first filter branch of the utility model adopts the high-pass filter design of the active damping system to reduce the loss of the system, improve the working efficiency of the whole machine and fully filter out the high-frequency harmonic current. Through the real-time sampling and feedback of the three-phase current of the first filtering branch, closed-loop control is performed to avoid resonance with the system current and reduce harmonic amplification caused by resonance.

The second filtering branch adopts the principle of single tuning to aim at the switching frequency harmonic current of the high-speed switching tube, making it resonate at the switching frequency and reach the ideal zero impedance state of resonance impedance, providing a circuit for the switching frequency current that is not injected into the grid system at all design.

The utility model mainly filters high-frequency harmonic current and switching frequency harmonic current according to peripheral hardware parameter configuration, and reduces high-order harmonic and switching frequency sub-harmonic current injected into the power grid. The utility model adopts a high-pass filter plus a switching frequency sub-filter, and is used as a closed-loop control system. Once there is a resonance frequency, the processor immediately changes the output of the filter current to control the amplification of the resonance current.

Description of drawings

1. Figure 1 is a schematic diagram of the overall structure of the active filter device for eliminating high-frequency switch EMI of the present invention.

2. Fig. 2 is a circuit schematic diagram of the comprehensive EMI filter module of the present invention.

Three, Fig. 3 is the used software phase-locked loop control flowchart of the utility model.

Four, Fig. 4 is the overall working principle block diagram involved in the utility model.

5. Fig. 5 is the 2 to 50 low-order harmonic filter module involved in the utility model.

detailed description

The utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the utility model is not limited thereto.

Referring to Fig. 1, it is a structural schematic diagram of the overall system control of a comprehensive EMI parallel active filter based on eliminating high-frequency harmonics and switching frequency harmonics of the present invention. As shown in Figure 4, this kind of comprehensive parallel active filter includes signal acquisition and conditioning module, FPGA module, DSP module, peripheral IGBT driver module and corresponding upper computer display interface.

The working principle of the general control circuit of the active filter is as follows: the so-called general control circuit of the active filter means that the load current and voltage in the power distribution system reach the input range of the relevant AD sampling after passing through the corresponding signal acquisition and conditioning circuit, Convert the system voltage and current signals into corresponding digital signals, and send the digital signals to the FPGA module. The values processed by the FPGA module are sent to the DSP module through the address bus and data bus. The DSP module calculates and For the same phase angle of the positive sequence component of the system, according to the different phase angles of each harmonic current, DQ is used to separate the harmonic current in the load current, and then the harmonic current is compared with the output current of the device, and the error value error is controlled by traditional PI The device outputs the corresponding modulation wave, generates the corresponding driving signal through the PWM generator, drives the IGBT to turn on, and passes through the low-order harmonic filter module to output the filter current used to filter the load harmonics, but at the same time it also generates The harmonic current of the switching frequency is injected into the grid system.

Load current signals ILa, ILb, ILc, filtered branch current signals ITa, ITb, ITc, and system voltage signals Ua, Ub, Uc, after passing through the acquisition circuit and conditioning circuit, are processed by FPGA module and DSP module, and software phase-locked The loop obtains the phase angle of the positive sequence voltage of phase A, modifies the phase angle parameters in real time according to the different harmonic phase angles of each harmonic, and separates the harmonics of the load current to obtain the harmonic current values I _a , I _b , and I of each harmonic _c , the currents ITa, ITb, and ITc of the filter branch are converted into feedforward currents through the relevant transformation control algorithm With each harmonic current I _a , I _b , I _c obtained, the result of the sum operation is taken as the command current command current with the actual output current of the device The difference value is used for PI current tracking control, and the output driving signal is sent to the driving circuit through corresponding isolation and level conversion, driving the IGBT to turn on, and generating a current that filters out the low-order harmonics of the system.

Fig. 2 is a circuit schematic diagram of the comprehensive EMI filter module of the present invention. The comprehensive EMI filter module mainly covers surge protection circuit, high frequency filter circuit and switching frequency harmonic current filter circuit. The main component of the surge protection circuit is the varistor. The filter circuit mainly includes the first filter branch capacitor and the Capacitors and reactors of the second filter branch.

The three-phase varistor Rva in Figure 2 is connected to the output end of La of the smoothing reactor, Rvb is connected to the output end of Lb of the smoothing reactor, Rvc is connected to the output end of Lc of the smoothing reactor, Rva, The other ends of Rvb and Rvc are respectively connected to the protective zero line PE; one end of Rvab is connected between the smoothing reactance on the inverter side of phase A and the grid reactance, and the other end is connected to the smoothing reactance on the inverter side and the grid reactance On the B phase between, make one end of Rvbc connected between the B-phase inverter side smoothing reactance and the grid reactance, and the other end connect to the C phase between the inverter side smoothing reactance and the grid reactance, so that One end of Rvca is connected between the phase C inverter side smoothing reactance and the grid reactance, and the other end is connected to the A phase between the inverter side smoothing reactance and the grid reactance. A surge protection circuit is formed, which can avoid the impact on electrical equipment caused by the instantaneous overvoltage of the system voltage or device voltage exceeding the normal working voltage, and instantaneously filter the peak and surge in the system power supply or device output.

The first filtering branch in Fig. 2 includes the smoothing reactance La of phase A, the filter capacitor Ca1, the network filter reactance LA, the smoothing reactance Lb of the B phase, the filter capacitor Cb1, the network filter reactance LB, the leveling reactance of the C phase Wave reactance Lc, filter capacitor Cc1, network filter reactance LC, the three phases respectively constitute the corresponding first filter branch LCL low-pass filter, high-order harmonics enter the N line through the filter capacitor, so that the high-order harmonics are no longer injected power grid. Moreover, the first filtering branch adopts current feedback closed-loop control, which can fully reduce the loss of the system and avoid the possibility of resonance due to the transformation of the system impedance.

The second filter branch in Fig. 2 includes the second filter capacitor Ca2 of phase A, the second filter reactor La1,

The second filter capacitor Cb2 of phase B, the second filter reactor Lb1, the second filter capacitor Cc2 of C phase, and the second filter reactor Lc1, the three phases respectively constitute a single tuning filter, and the parameters are adjusted to make its resonance point At the switching frequency of the IGBT switching tube, it completely absorbs the switching frequency harmonic current, avoiding the injection of switching sub-harmonics into the grid by conventional active filters, which seriously affects other electrical equipment in the system.

Fig. 3 is the schematic diagram of the software phase-locked loop used in the utility model, mainly comprises following same:

1.1. Firstly, the system grid voltage collection signal is processed, the collected three-phase system voltage Usc, Usb, Usc is discretized, and the Clarke transformation of abc_to_αβ is performed to obtain the static components Usα and Usβ of the two-phase plane Cartesian coordinate system;

1.2. The Usα and Usβ in the static rectangular coordinate system are changed through the rotated rectangular coordinate system, that is, the Park transformation of αβ_to_dq, and the active component Usd and the reactive component Usq in the dynamic rotating rectangular coordinate system are obtained.

1.3. The Usq component in the dynamic Cartesian coordinate system is subjected to a shifted mean value low-pass filter and Usq ^* = 0 to make a difference Error, and the PI controller corrected by Error is used to obtain the phase tracking output error value Δω and the phase difference signal Δω is calculated with the rated angular frequency ω ₁ of the power grid to obtain the angular frequency ω of the positive sequence voltage of phase A in the three-phase system, and then through Then get the phase angle θ of the positive sequence voltage of phase A; then take the sine sinθ and cosine cosθ respectively for θ, and feed back to abc_to_αβ and αβ_to_dq for loop control, so as to stably obtain the phase angle of the positive sequence voltage of the system A phase.

The parallel active filter device based on eliminating switching frequency EMI includes a general control circuit for active filters. Its working principle is as follows: the so-called active filter general control circuit means that the load current and voltage in the power distribution system reach the input range of relevant AD sampling after passing through the corresponding signal acquisition and conditioning circuit, and convert the system voltage and current signal For the corresponding digital signal, the digital signal is sent to the FPGA, and the value processed by the FPGA is sent to the DSP through the address bus and data bus. The DSP calculates the same phase angle as the positive sequence component of the system through the software phase-locked loop function. Different phase angles of the sub-harmonic current, use DQ to separate the harmonic current in the load current, and then make a difference between the harmonic current and the output current of the device, the error value error passes through the traditional PI controller, outputs the corresponding modulation wave, and generates it through PWM The device generates the corresponding driving signal to drive the IGBT to turn on, so as to output the filter current used to filter the load harmonic, but at the same time, the harmonic current of the switching frequency is also generated and injected into the grid system.

Aiming at the shortcomings of the above-mentioned active filter for high-frequency switching frequency, the utility model covers a comprehensive EMI filter module for system surge protection and filtering of active filter switching frequency harmonic current. The filter covers the A-phase reactor LA connected to the system grid, the B-phase reactor LB connected to the system grid, the C-phase reactor LC connected to the system grid, and the A-phase smoothing reactor on the active filter side. La, B-phase smoothing reactance Lb of the active filter side, C-phase smoothing reactance Lc of the active filter side; Ca1 of the first filter branch of the A-phase, Cb1 of the first filter branch of the B-phase, C-phase Cc1 of the first filtering branch; Ca2 of the second filtering branch of A phase, Cb2 of the second filtering branch of B phase, Cc2 of the second filtering branch of C phase, reactor La1 of the second filtering branch of A phase, The reactor Lb1 of the second filter branch of the B phase, the reactor Lc1 of the second filter branch of the C phase; the varistor Rva of the A surge protection circuit, the varistor Rvb of the B surge protection circuit, and the C surge protection The varistor Rvc of the circuit; the varistor Rvab of the AB phase surge protection circuit, the varistor Rvbc of the BC phase surge protection circuit, the varistor Rvca of the CA phase surge protection circuit, N and the system protection zero line PE The varistor Rvng of the surge protection circuit. The grid-connected reactance and inverter-side smoothing reactance of the integrated grid distribution system, as well as the two filtering branches and the surge protection circuit together constitute a comprehensive EMI filter for low-order harmonic filtering and high-frequency and switching frequency harmonic current filtering. filter module.

The utility model eliminates the active filtering device of the high-frequency switch EMI, including the following two parts:

1. Comprehensive EMI filter module. The filter includes a high-order harmonic absorbing circuit, a switching frequency harmonic current filtering circuit and related surge protection circuits.

2. The closed-loop control system of the first filtering branch. Based on the phase-locked loop module of the general control circuit of the active filter and the reference command current module, the current of the first filter branch adopts a feedback closed-loop control system.

In the comprehensive EMI filtering module:

1) The grid-connected reactance, the inverter-side reactance and the first filter capacitor constitute the first filter branch with a certain corner frequency.

1.1. When the current from the device passes through the inverter-side smoothing reactance, the grid reactor and the capacitor of the first filter branch, a low-pass filter of the first filter branch LCL is formed. That is, the first filter branch of phase A includes smoothing reactor La, network reactor LA and capacitor Ca1 of first filter branch of phase A; the first filter branch of phase B includes smoothing reactor Lb and network reactor LB And the B-phase first filter branch capacitor Cb1; the C-phase first filter branch includes a smoothing reactor Lc, a grid reactor LC, and a C-phase first filter branch capacitor Cc1.

1.2. The pulse voltage signal generated by the general control circuit of the active filter passes through the LCL filter branch composed of the inverter-side smoothing reactance, the grid reactance and the first filter branch capacitor, and some of the high voltage signals above the corner frequency (f _ref ) The high-frequency signal enters the N line through the capacitor of the first filter branch, and the low-order harmonic current below the corner frequency (f _ref ) is transmitted to the grid through the grid-connected reactance to offset the harmonic current in the system.

1.3. The current of the first filter branch is controlled by an active damping system, and the capacitive currents ITa, ITb, and ITc of the first filter branch are introduced to feed back to the general control circuit of the active filter for closed-loop control to enhance the suppression effect of resonance and reduce system loss , effectively inhibit the oscillation of low-order harmonic current.

2) Aiming at the high-speed turn-on of the switching tube of the active filter, a large amount of harmonic current of the switching frequency is generated, and the second filter branch of the utility model is adopted.

2.1. In order to improve the compensation effect, the switching frequency design of the general control circuit of the active filter is relatively high, basically above 10KHz, or even higher. The ability to track and compensate low-order harmonics is improved, but the harmonic current of the switching frequency far exceeds the filtering bandwidth of the first filtering branch LCL low-pass filter, resulting in the injection of switching frequency harmonics into the grid. Therefore, for switching frequency Harmonic current utility model second filter branch.

2.2. The second filter branch adopts the single tuning principle to aim at the switching frequency harmonic current of the high-speed switching tube, so that it resonates at the switching frequency and reaches the ideal zero impedance state of resonance impedance, providing a switching frequency current that does not inject into the grid system at all The circuit, so that the switching frequency current passes through the capacitor and reactor of the second filtering branch and is no longer injected into the grid system to circulate.

3) Surge protection circuit: Considering the high-speed switching tube output of the device and the flicker in the system, so in the comprehensive filter module, a response strategy for high-frequency flicker is added to improve the safety of the power distribution system and the protection of the device. The protective function also increases the control of the device on the stability of the system, so as to avoid the flickering of the device due to various reasons from affecting the power grid system. When the system voltage flickers or the device output has flicker after the smoothing reactance, the circuit directly absorbs the flicker waveform, making it completely enter the system's protective zero line PE, and no longer exists through the load and system cycle, perfect Power quality and self-protection devices.

In the first filtering branch closed-loop control system:

1) The phase-locked loop module of the general control circuit of the active filter

1.1. Firstly, the system grid voltage acquisition signal is processed, the collected three-phase system voltage Usa, Usd, Usc is discretized, and the Clarke transformation of abc_to_αβ is performed to obtain the static components Usα and Usβ of the two-phase plane Cartesian coordinate system;

1.2. The Usα and Usβ in the static rectangular coordinate system are changed through the rotated rectangular coordinate system, that is, the Park transformation of αβ_to_dq, and the components Usd and Usq in the dynamic rotating rectangular coordinate system are obtained.

1.3. The Usq component in the dynamic Cartesian coordinate system, the output after the shifted mean value low-pass filter and Usq ^* = 0 are used as the difference Error, and the PI controller after Error is corrected to obtain the phase tracking output error value Δω , the phase difference signal Δω is calculated with the rated angular frequency ω ₁ of the power grid to obtain the angular frequency ω of the positive sequence voltage of phase A in the three-phase system, and then through After that, the phase angle θ of the positive sequence voltage of phase A is obtained; then the sine sinθ and cosine cosθ are respectively taken for θ, and fed back to abc_to_αβ and αβ_to_dq for loop control, and also for the separation of harmonic current and the first filter branch capacitor current feedback Prepare for closed-loop control.

2) The first filter branch current feedback closed-loop control system

1.4. According to the obtained sinθ and cosθ of the positive sequence of the A phase, based on the positive sequence phase angle ω of the A phase, the dq and dq_to_abc transformation operations are performed on the sampling currents ITa, ITb, and ITc of the first filter branch to obtain the first filter branch feedback current The harmonic current separated from the general control circuit of the active filter is summed to obtain the reference command current and the output current of the device is compared, and the obtained error component is corrected by the PI regulator as a modulation wave, which is sent to the PWM generator to generate The PWM signal drives the high-speed switching tube to output harmonic current, so as to offset the load harmonic current in the system.

In summary, the utility model proposes an active filter device for eliminating high-frequency switch EMI, which is mainly aimed at injecting high-order harmonics and switching frequency harmonic currents into the power grid by active filter devices on the existing market. With the continuous expansion of the power electronics market and the diversification of electrical equipment in recent years, a large number of non-linear loads have poured into the electrical system, generating a large number of harmonics that seriously pollute the grid system. The situation brings great harm.

The utility model is connected in parallel in the power supply of the grid system, which can perfectly solve the harmonic problem, not only filter out the low-order harmonic current, but also no longer inject high-order harmonic and switching frequency sub-harmonic current into the grid, and fully purify the grid. Solve power quality problems.

The above only illustrates the best embodiments of the present utility model, but should not be construed as a limitation on the claims. The utility model is not limited to the above embodiments, and all the various changes made within the protection scope of the independent claims of the utility model are all within the protection scope of the utility model.

Claims (7)

1. a kind of active filter of elimination HF switch emi, leads to including the active filter being connected on the electrical network of sampling side With control circuit and current follow-up control algorithm and pwm module, described active filter universal control circuit includes harmonic wave and divides From module；It is characterized in that, the outfan of described current follow-up control algorithm and pwm module connects comprehensive emi and filters mould Block, described comprehensive emi filtration module include for filter harmonic current the first filter branch, be used for filtering switching frequency Second filter branch of harmonic current and the surge protection circuit for filtering spike and surge.

2. the active filter of elimination HF switch emi according to claim 1 is it is characterised in that described first Filter branch includes the flat ripple reactance being connected to electrical network inverter side, the networking reactance being connected to network load side, and is connected to The first filter branch capacitor between electrical network and zero line.

3. the active filter of elimination HF switch emi according to claim 2 is it is characterised in that described networking Reactance includes being connected on the reactor la of electrical network a phase, is connected on the reactor lb of electrical network b phase, is connected on the reactor of electrical network c phase lc；Described flat ripple reactance includes being connected on the flat ripple reactance la of a phase, is connected on the flat ripple reactance lb of b phase, is connected on c phase Flat ripple reactance lc；The first described filter branch capacitor includes connecting the electric capacity ca1 of electrical network a phase and n line, connects electrical network b phase With the electric capacity cb1 of n line, connect the electric capacity cc1 of electrical network c phase and n line.

4. the active filter of elimination HF switch emi according to claim 1 is it is characterised in that described second Filter branch includes the electric capacity ca2 connecting electrical network a phase and n line, the electric capacity cb2 being connected electrical network b phase and n line, connection electrical network c phase and The electric capacity cc2 of n line.

5. the active filter of elimination HF switch emi according to claim 4 is it is characterised in that described electric capacity Ca2 current-limiting reactor la1, described electric capacity cb2 current-limiting reactor lb1, described electric capacity cc2 current-limiting reactor lc1.

6. the active filter of elimination HF switch emi according to claim 1 is it is characterised in that described surge Protection circuit includes varistor rvb, the electrical network c phase connecting electrical network a phase and the varistor rva, electrical network b phase and pe line of pe line Varistor rvc with pe line；The varistor rvab connecting electrical network ab phase, the varistor rvbc connecting electrical network bc phase, company The varistor rvng of the varistor rvca of the ca phase that gets access to grid, connection n line and pe line.

7. the active filter of elimination HF switch emi according to claim 1 is it is characterised in that also include first Filter branch closed-loop control system, the first described filter branch closed-loop control system include filter branch current sample module and Feedback control algorithm modular converter；The sampling end of described filter branch current sample module connects described comprehensive emi filter First filter branch of ripple device, the outfan of described filter branch current sample module connects described feedback control algorithm and turns Die change block.