CN107248743A - A kind of active electric filter device for specifying subharmonic - Google Patents
A kind of active electric filter device for specifying subharmonic Download PDFInfo
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- H—ELECTRICITY
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Abstract
The invention discloses a kind of active electric filter device for specifying subharmonic, it is adaptable to includes the circuit of the harmonious carrier load of system power supply, including：Transformer, inverter, modulated signal generation module；The first side winding of transformer is connected with the harmonic load, accesses the loop that the harmonious carrier load of the system power supply is constituted；The primary side that modulated signal generation module is used for after the modulated signal for generating the inverter, primary side fundamental current of the modulated signal after reversely amplifying and positive amplification specifies the superposition generation of n-th harmonic electric current；Inverter is used to direct current signal is transformed into the ac current signal with the modulated signal same frequency and the Circuit Fault on Secondary Transformer winding is injected, so that the transformer primary side fundamental wave equiva lent impedance is Z1+(1‑α)Zm, transformer primary side n-th harmonic equiva lent impedance is nZ1+(1+β)nZm.The present invention is based on fundamental wave and the mixing control of specified subharmonic magnetic flux so that transformer primary side is short-circuit with respect to fundamental wave and specifies subharmonic open circuit relatively.
Description
Technical Field
The invention belongs to the technical field of active power filtering, and particularly relates to an active power filtering device for specific subharmonics.
Background
With the wider application of power electronic nonlinear load in industrial and civil fields, the current waveform distortion in the power grid is more serious, and the problems of harmonic wave and reactive power are more and more obvious. For the harmonic and power factor problem, the industry has proposed various solutions, wherein the main filtering solutions include a conventional passive LC filter, a conventional parallel active power filter, a series hybrid active power filter, an injection hybrid active power filter, and a unified power quality regulator.
The passive filter has larger volume and weight and can only filter out harmonic waves of specific frequency; of all power filters, the series hybrid active power filter has attracted much attention because it can greatly increase the harmonic impedance (function as a "harmonic isolator"). However, at present, a harmonic current full compensation mode is adopted, and the required transformer capacity is large, so that a series of problems exist in the aspects of protection strategy, stability and the like, and the method specifically comprises the following steps:
1) the overall system of series active power filters requires a customized protection strategy. The inverter assembly is connected in series between a power supply and a load and cannot be directly protected by a power supply contactor, a circuit breaker or a fuse and other devices;
2) the filtering performance of the device conflicts with the transformer capacity. The traditional series hybrid active power filter based on fundamental wave magnetic flux compensation only compensates the fundamental wave magnetic flux and only can reduce the equivalent impedance of the fundamental wave, and after a used transformer is determined, the equivalent impedance of the harmonic wave is fixed and is the excitation impedance of the transformer; the design of the rated capacity of the transformer depends on the excitation impedance under the consideration of the system protection strategy, and the design capacity of the series transformer is that the fundamental wave flux of the transformer is not compensated at all under the consideration of the extreme conditionTo reduce this rated capacity, the transformer excitation impedance must be reduced; in summary, better filtering performance requires a larger capacity transformer.
3) The protection strategy and reliability of the device conflict with the transformer capacity. In order to protect and improve the reliability of the device, the transformer excitation impedance should be designed to be small, otherwise, once the device is in an abnormal operation state, the output voltage of the inverter will be very high.
4) When the harmonic current is fully compensated, the system stability is reduced. Generally, the higher harmonic and some lower harmonics (determined according to specific application occasions) have lower amplitudes, and when the harmonics are filtered by adopting more economical and simple methods such as a passive filter, a more satisfactory effect can be obtained; when the harmonic current full compensation is adopted, the capacity of an active power filter is occupied, the cost is increased, and the system stability is seriously reduced.
In conclusion, the passive filter has large volume and weight and can only filter out harmonic waves of specific frequency; the existing series hybrid active power filter has attracted much attention because it acts as a "harmonic isolator" to perform real-time filtering. On one hand, the harmonic equivalent impedance of the transformer is a fixed value after the transformer is determined, and a transformer with larger capacity is needed to obtain better filtering effect; on the other hand, the existing series hybrid active power filter adopts a current full compensation mode, so that the system stability is greatly reduced, and the cost is increased due to the increase of the capacities of the transformer and each switching device of the system.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to solve the problems that the prior active power filter only compensates the fundamental wave magnetic flux, so that only the equivalent impedance of the fundamental wave can be reduced, after the used transformer is determined, the equivalent impedance of the harmonic wave is a fixed value, and a transformer with larger capacity is needed to obtain better filtering effect; and the existing active power filter adopts a current full compensation mode, so that the system stability is greatly reduced, and the technical problem of cost increase due to the increase of the capacities of the transformer and each switching device of the system is solved.
To achieve the above object, the present invention provides an active power filter device for a specific subharmonic, suitable for a circuit including a system power supply and a harmonic load, the deviceThe device comprises: transformer, inverter, modulation signal generation module. A primary side winding of the transformer is connected with the harmonic load in series and is connected into a loop formed by the system power supply and the harmonic load, and current flowing through the primary side winding of the transformer comprises fundamental current and harmonic current; the modulation signal generation module is used for generating a modulation signal of the inverter, and the modulation signal is generated by superposing a primary side fundamental current after reverse amplification and a primary side appointed subharmonic current after forward amplification; the inverter is used for converting the direct current signal into an alternating current signal with the same frequency as the modulation signal and injecting the alternating current signal into the secondary side winding of the transformer so as to enable the primary side fundamental wave equivalent impedance of the transformer to be Z1+(1-α)ZmThe primary side of the transformer is assigned subharmonic equivalent impedance as nZ1+(1+β)nZmWherein Z is1Is the primary side leakage reactance of the transformer, ZmFor the excitation impedance of the transformer, n is a designated subharmonic number, and α and β are a fundamental wave control coefficient and a designated subharmonic control coefficient, respectively, which are adjusted by the amplification factor of the primary side fundamental wave current and the amplification factor of the primary side designated subharmonic current, respectively, in the modulation signal.
The invention makes the equivalent impedance of the fundamental wave and the appointed subharmonic of the primary side winding separately controllable by the mixed control of the fundamental wave and the appointed subharmonic magnetic flux based on the primary side of the transformer. The equivalent impedance of primary side fundamental wave of the transformer is Z1+(1-α)ZmThe nth harmonic equivalent impedance on the primary side of the transformer is nZ1+(1+β)nZmThe active power filter device provided by the invention can enable the equivalent impedance of the primary side fundamental wave of the transformer to be 0 (relatively short circuit with respect to the fundamental wave) and the equivalent impedance of the primary side appointed subharmonic to be very large (relatively open circuit with respect to the appointed subharmonic) by controlling α and β.
Optionally, the modulation signal generating module includes: a fundamental current detection unit, a harmonic current detection unit, a fundamental current amplifier, a harmonic current amplifier, and a superposition unit. A fundamental wave current detection unit for detecting a fundamental wave current on the primary side from a current flowing through a primary winding of the transformer; a harmonic current detection unit for detecting a specified subharmonic current on the primary side from a current flowing through a primary winding of the transformer; a fundamental wave current amplifier for inversely amplifying the fundamental wave current on the primary side; the harmonic current amplifier is used for carrying out positive amplification on the specified subharmonic current on the primary side; and the superposition unit is used for superposing the fundamental wave current on the primary side after reverse amplification and the appointed subharmonic current on the primary side after forward amplification to generate a modulation signal.
Optionally, modulating the signal IrefComprises the following steps:
wherein,for the primary side current I of the transformer1The fundamental component in (1) is the primary side fundamental current,for the primary side current I of the transformer1Of (b) the nth harmonic component, ki-k gain of a current transformer for determining a current through a primary winding of said transformer1Is the amplification factor, k, of a fundamental current amplifier2To specify the amplification of the subharmonic current amplifier.
Optionally, the current I of the secondary side of the transformer2Comprises the following steps:KPWMis the gain of the inverter; the current of the secondary side winding of the transformer is equivalent to the current of the primary side of the transformerI2' is:
wherein k isTFor the coupling transformation ratio of the transformer,
optionally, the transformer primary side fundamental equivalent impedance and the transformer primary side specified subharmonic equivalent impedance are determined by: the voltage equation phasors of the transformer are: u shape1＝Z1I1+Zm(I1+I2′)，U1The voltage across the primary winding of the transformer; primary side fundamental equivalent impedance of transformerComprises the following steps:
primary side nth harmonic equivalent impedance of transformerComprises the following steps:
wherein,is the fundamental voltage across the primary winding of the transformer,is the nth harmonic voltage across the primary winding of the transformer,
U1 (1)＝Z1 (1)I1 (1)+Zm (1)(I1 (1)+I2′(1))，U1 (n)＝Z1 (n)I1 (n)+Zm (n)(I1 (n)+I2′(n))；
I2′(1)and I2′(n)A fundamental component and an nth harmonic component, I, respectively, in a current equivalent to a primary side of the transformer for a secondary side winding current of the transformer2′(1)＝-αI1 (1)，I2′(n)＝βI1 (n)；
Z1 (1)Is the leakage reactance, Z, of the primary side of the transformer with respect to the fundamental wave1 (1)＝Z1，Zm (1)Is the excitation impedance of the transformer with respect to the fundamental wave, Zm (1)＝Zm，Z1 (n)Leakage reactance, Z, of the primary side of the transformer with respect to the nth harmonic1 (n)＝nZ1，Zm (n)For the excitation impedance of the transformer with respect to the nth harmonic, Zm (n)＝nZm。
Alternatively, ifThenAt this time, the primary side winding of the transformer is equivalently short-circuited to the fundamental wave.
Optionally, the value of β is set so that the equivalent impedance of the nth harmonic wave on the primary side of the transformer is equal to that of the nth harmonic wave on the primary side of the transformerThe primary side winding of the transformer is equivalent to the nth harmonic wave at the time of high resistanceAnd (4) opening the circuit.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
1) based on the flux mixing control of the fundamental wave and the appointed subharmonic wave, the equivalent impedance of the fundamental wave and the appointed subharmonic wave of the primary side winding of the series transformer are respectively and independently controllable.
2) By controlling the designated subharmonic control coefficient to be large enough, a transformer with smaller excitation impedance can be selected under the condition that the designated subharmonic equivalent impedance is not changed, namely, by reasonably designing the designated subharmonic control coefficient, the required transformer excitation impedance (transformer capacity) of a primary side winding of the transformer is smaller under the condition that the primary side winding of the transformer has the same harmonic equivalent impedance (an active filter has similar filtering performance); when the transformer with the same capacity is adopted, the filtering effect is better.
3) The invention only compensates the appointed subharmonic current with larger amplitude, and general higher harmonic and lower subharmonic (determined according to specific application occasions) with lower amplitude are filtered by adopting more economic modes such as a passive filter, and the like, thereby increasing the system stability and reducing the filtering cost.
4) The simplified passive filter design has better filtering performance when the same transformer is adopted, so the capacity and the volume of the passive filter can be greatly reduced.
Drawings
Fig. 1 is a schematic diagram illustrating a single-phase principle of an active power filter device connected to a power grid according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of the active power filter device connected to the three-phase system according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 1 is a schematic diagram of a single-phase principle of an active power filter device provided by an embodiment of the present invention accessing a power grid. As shown in fig. 1, the power grid may include an active power filter device and a passive power filter device 200, wherein the active power filter device includes: transformer 101, inverter 102 and modulation signal generation module 103.
In order to reduce the capacity of the active power filter device and improve the stability of the active power filter device, the active power filter device can be appointed to filter certain harmonic waves with higher amplitude, the passive power filter device can be appointed to filter low-order harmonic waves and high-order harmonic waves with lower amplitude, and the active power filter device and the passive power filter device can work cooperatively to complete filtering. In particular, the passive power filter device 200 may include a plurality of harmonic filter branches, for example, a 3 rd harmonic filter branch: inductor L3And a capacitor C3Series branch, 5 th harmonic filtering branch: inductor L5And a capacitor C5And (4) connecting branches in series. It is understood that the passive filter device may further include more or less filter branches according to actual needs, and the embodiment of the present invention is not limited thereto, and is only used for illustrating the present invention.
As shown in FIG. 1, USRepresenting an ideal system voltage source, UhIs a harmonic source and represents various distortions (such as voltage drop, harmonic wave, etc.) of the system power supply, LSRepresenting the impedance of the system voltage source. The current at the primary side of the transformer is I1。CdAnd LdAn LC filter current is constructed for filtering out harmonics at the switching frequency of the inverter 102. The primary port of the transformer 101 is an AX port, and the secondary port is an AX port.
The inverter 102 takes triangular waves as carriers, adopts a Sinusoidal Pulse Width Modulation (SPWM) control strategy, controls a voltage source inverter to generate a controllable current along with a modulation signal, and the controllable current is filtered by an LC filter and then injected into a secondary side winding of a coupling transformer, so that the secondary side winding current of the transformer simultaneously contains fundamental wave current and harmonic current with different control coefficients. DC side voltage U of inverterdThere are three sources: 1) a capacitor is connected to the direct current side, and the voltage of the direct current side is stabilized by controlling an inverter; 2) a storage battery is connected to the direct current side, and stable direct current side voltage is obtained by controlling an inverter; 3) the power is obtained through induction of a power system, and stable direct-current side voltage is obtained through rectification.
The primary side winding of the transformer 101 is connected with the harmonic load in series and is connected to a system power supply USAnd a harmonic load, the current flowing through the primary winding of the transformer includes a primary side fundamental currentAnd harmonic current of primary sidek is the harmonic order, k>0, and k ≠ 1.
The modulation signal generation module 103 is used for generating a modulation signal I of the inverter 102ref，IrefBy the primary side fundamental current after reverse amplificationAnd a forward amplified primary side specified subharmonic currentSuperposition generation, n is a designated subharmonic order, n>0, and n ≠ 1.
Inverter 102 for converting UdThe provided DC signal is converted into ANDrefAC current signal I with same frequency2And injecting the secondary side winding of the transformer to make the primary side fundamental wave equivalent impedance of the transformer beZ1+(1-α)ZmThe nth harmonic equivalent impedance on the primary side of the transformer is nZ1+(1+β)nZmWherein Z is1Is the primary side leakage reactance of the transformer, ZmFor the excitation impedance of the transformer, α and β are the fundamental wave control coefficient and the specified subharmonic control coefficient, respectively, which are adjusted by the amplification factor of the primary side fundamental wave current and the amplification factor of the primary side harmonic current, respectively, in the modulation signal.
The modulation signal generation module 103 includes: a fundamental current detection unit, a harmonic current detection unit, a fundamental current amplifier, a harmonic current amplifier, and a superposition unit.
A fundamental wave current detection unit for detecting a fundamental wave current on the primary sideA harmonic current detection unit for detecting a specified subharmonic current on the primary sideWherein, the transfer functions of the fundamental current and the nth harmonic current detection link are respectively Gfund(s) and Ghn(s)，
In addition, a current I flowing through a primary winding of the transformer is determined1The gain of the current transformer used is ki，GdiAnd(s) represents a filtering element after detecting the primary side current.
The fundamental current detection unit and the harmonic current detection unit comprise current transformers and fundamental waves and designated subharmonic current detection links, the current transformers are connected in series with a system bus supplying power to a load, line current is induced and sent to the current detection link, and the fundamental current detection link detects required fundamental components from the system bus current; the designated subharmonic current detection section detects a desired designated subharmonic current component from the system current.
A fundamental wave current amplifier for inversely amplifying the fundamental wave current on the primary side; and the harmonic current amplifier is used for positively amplifying the specified subharmonic current on the primary side. The fundamental and harmonic amplifiers have amplification factors (gains) of-k1And k2。
A superposition unit for superposing the reversely amplified primary side fundamental wave current and the forward amplified primary side specified subharmonic current to generate a modulation signal Iref，
Wherein,for the primary side current I of the transformer1The fundamental component in (1) is the primary side fundamental current,for the primary side current I of the transformer1The nth harmonic component, -k1Is the amplification factor, k, of a fundamental current amplifier2To specify the amplification of the subharmonic current amplifier.
The inverter 102 is equivalent to a first-order small inertia element, the transfer function G of a voltage source type inverterPWM(s) isKPWMFor inverter gain, TPWMFor inverter delay, s is an s-domain operator, for simplifying analysis, neglecting the inverter delay, the inverter is equivalent to gain KPWMThe ratio of (a) to (b).
Current I on the secondary side of transformer 1012Comprises the following steps:KPWMis the gain of the inverter; transformer deviceThe current of the secondary side winding is equivalent to the current I of the primary side of the transformer2' is:
wherein k isTFor the coupling transformation ratio of the transformer,
optionally, the transformer primary side fundamental equivalent impedance and the transformer primary side harmonic equivalent impedance are determined by:
the voltage equation phasors of the transformer are: u shape1＝Z1I1+Zm(I1+I2′)，U2′＝Z2′I2′+Zm(I1+I2′)；
Wherein, U1Is the voltage across the primary winding of the transformer, U2' is the voltage equivalent of the two ends of the secondary winding of the transformer to the voltage of the primary side, Z2' is the leakage reactance of the secondary side of the transformer equivalent to the primary side.
Transformer primary side fundamental equivalent impedance seen from AX portComprises the following steps:
primary side nth harmonic equivalent impedance of transformerComprises the following steps:
is the fundamental voltage across the primary winding of the transformer,for the nth harmonic voltage across the primary winding of the transformer:
U1 (1)＝Z1 (1)I1 (1)+Zm (1)(I1 (1)+I2′(1))，U1 (n)＝Z1 (n)I1 (n)+Zm (n)(I1 (n)+I2′(n))；
I2′(1)and I2′(n)A fundamental component and an nth harmonic component, I, respectively, in a current equivalent to a primary side of the transformer for a secondary side winding current of the transformer2′(1)＝-αI1 (1)，I2′(n)＝βI1 (n)；
Z1 (1)Is the leakage reactance, Z, of the primary side of the transformer with respect to the fundamental wave1 (1)＝Z1，Zm (1)Is the excitation impedance of the transformer with respect to the fundamental wave, Zm (1)＝Zm，Z1 (n)Leakage reactance, Z, of the primary side of the transformer with respect to the nth harmonic1 (n)＝nZ1，Zm (n)For the excitation impedance of the transformer with respect to the nth harmonic, Zm (n)＝nZm。
Alternatively, ifThenAt this time, the primary side winding of the transformer is equivalently short-circuited to the fundamental wave.
Optionally, the value of β is set so that the equivalent impedance of the nth harmonic wave on the primary side of the transformer is equal to that of the nth harmonic wave on the primary side of the transformerThe impedance is high, and the primary side winding of the transformer is equivalently open to the nth harmonic wave.
By reasonably setting the harmonic control coefficient β, the primary side winding of the transformer is equivalent to a high impedance for a designated subharmonic, and can play a very good role in attenuating the designated subharmonic when being matched with a passive filtering branch (namely, the passive filtering branch is applied to the structure of the series hybrid active power filter)1+nZm) Series hybrid active power filter based on fundamental wave and harmonic flux hybrid compensation (designating subharmonic equivalent impedance as nZ)1+(1+β)nZm) The coefficient (1+ β) is introduced into the harmonic equivalent impedance, so that when the transformer with the same capacity is adopted, the filtering performance is better (on the premise of meeting the same filtering effect, the transformer with the smaller capacity can be selected), the appointed subharmonic compensation is adopted, the active filtering part only compensates the appointed subharmonic current with the larger amplitude, and the general higher harmonic and the lower subharmonic with the lower amplitude (determined according to the specific application occasion) are filtered in a more economic mode such as a passive filter, so that the system stability is improved, and the filtering cost is reduced.
Thus, the transformer may be a low capacity coupling transformer that couples the output current of the voltage source inverter in series between the system power supply and the harmonic load through an LC filter. Due to the bilateral excitation of the primary and secondary (primary and secondary) side windings of the transformer, the primary side winding of the transformer is equivalent to two adjustable reactances with different control coefficients for fundamental waves and harmonic waves respectively. The fundamental wave and harmonic gain coefficient of the amplifier unit are controlled, and the fundamental wave and harmonic flux compensation condition of the transformer unit is changed. The primary side winding of the transformer is enabled to be short-circuited (low resistance) to the fundamental wave, and the appointed subharmonic current is forced to flow into the passive branch circuit (high resistance) to the appointed subharmonic, so that the active filtering function is achieved.
When the specified compensation is carried out on a plurality of harmonic currents, a plurality of specified subharmonic current detection links can be adopted and integrated into one specified subharmonic current detection unit. With reference to a single-phase system, an active power filter with specified sub-harmonic compensation using a small capacity transformer can be used on each phase separately in a three-phase system. All amplifier units on the three-phase line are controlled independently and are not affected when a fault occurs. Referring specifically to fig. 2, a schematic circuit diagram of an active power filter device connected to a three-phase system is shown.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. An active power filter device for a specified subharmonic, adapted for use in a circuit including a system power supply and a harmonic load, comprising: the device comprises a transformer, an inverter and a modulation signal generation module;
the primary side winding of the transformer is connected with the harmonic load in series and is connected into a loop formed by the system power supply and the harmonic load, and the current flowing through the primary side winding of the transformer comprises fundamental current and harmonic current;
the modulation signal generation module is used for generating a modulation signal of the inverter, and the modulation signal is generated by superposing a primary side fundamental current after reverse amplification and a primary side appointed subharmonic current after forward amplification;
the inverter is used for converting the direct current signal into an alternating current signal with the same frequency as the modulation signal and injecting the alternating current signal into the secondary side winding of the transformer, so that the primary side fundamental wave equivalent impedance of the transformer is Z1+(1-α)ZmThe primary side of the transformer is assigned subharmonic equivalent impedance as nZ1+(1+β)nZmWherein Z is1Is the primary side leakage reactance of the transformer, ZmFor the excitation impedance of the transformer, n is a designated subharmonic number, and α and β are a fundamental wave control coefficient and a designated subharmonic control coefficient, respectively, which are adjusted by the amplification factor of the primary side fundamental wave current and the amplification factor of the primary side designated subharmonic current, respectively, in the modulation signal.
2. The active power filtering device of claim 1, wherein the modulation signal generation module comprises: the harmonic current detection circuit comprises a fundamental current detection unit, a specified subharmonic current detection unit, a fundamental current amplifier, a harmonic current amplifier and a superposition unit;
the fundamental current detection unit is configured to detect a fundamental current on the primary side from a current flowing through a primary winding of the transformer;
the specified subharmonic current detection unit is used for detecting the specified subharmonic current on the primary side from the current flowing through the primary side winding of the transformer;
the fundamental current amplifier is used for reversely amplifying the fundamental current on the primary side;
the harmonic current amplifier is used for carrying out positive amplification on the specified subharmonic current on the primary side;
the superposition unit is used for superposing the fundamental wave current on the primary side after reverse amplification and the appointed subharmonic current on the primary side after forward amplification to generate a modulation signal.
3. The method of claim 2Active power filter device, characterized in that the modulation signal IrefComprises the following steps:
<mrow> <msub> <mi>I</mi> <mrow> <mi>r</mi> <mi>e</mi> <mi>f</mi> </mrow> </msub> <mo>=</mo> <mo>-</mo> <msub> <mi>k</mi> <mi>i</mi> </msub> <msub> <mi>k</mi> <mn>1</mn> </msub> <msubsup> <mi>I</mi> <mn>1</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> <mo>+</mo> <msub> <mi>k</mi> <mi>i</mi> </msub> <msub> <mi>k</mi> <mn>2</mn> </msub> <msubsup> <mi>I</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> <mo>;</mo> </mrow>
wherein,for the primary side current I of the transformer1The fundamental component in (1) is the primary side fundamental current,for the primary side current I of the transformer1Of (b) the nth harmonic component, ki-k gain of a current transformer for determining a current through a primary winding of said transformer1Is the amplification factor, k, of a fundamental current amplifier2To specify the amplification of the subharmonic current amplifier.
4. The active power filter of claim 3, wherein the current I on the secondary side of the transformer2Comprises the following steps:KPWMis the gain of the inverter; the current of the secondary side winding of the transformer is equivalent to the current I of the primary side of the transformer2' is:
<mrow> <msup> <msub> <mi>I</mi> <mn>2</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mn>1</mn> <msub> <mi>k</mi> <mi>T</mi> </msub> </mfrac> <msub> <mi>I</mi> <mn>2</mn> </msub> <mo>=</mo> <mo>-</mo> <msubsup> <mi>&alpha;I</mi> <mn>1</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> <mo>+</mo> <msubsup> <mi>&beta;I</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> <mo>;</mo> </mrow>
wherein k isTFor the coupling transformation ratio of the transformer,
5. the active power filter arrangement of claim 4 wherein the transformer primary side fundamental equivalent impedance and transformer primary side specified subharmonic equivalent impedance are determined by:
the voltage equation phasors of the transformer are: u shape1＝Z1I1+Zm(I1+I2′)，U1The voltage across the primary winding of the transformer;
primary side fundamental equivalent impedance of transformerComprises the following steps:
<mrow> <msubsup> <mi>Z</mi> <mrow> <mi>A</mi> <mi>X</mi> </mrow> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mfrac> <msubsup> <mi>U</mi> <mn>1</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> <msubsup> <mi>I</mi> <mn>1</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> </mfrac> <mo>=</mo> <msubsup> <mi>Z</mi> <mn>1</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> <mo>+</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mi>&alpha;</mi> <mo>)</mo> </mrow> <msubsup> <mi>Z</mi> <mi>m</mi> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>Z</mi> <mn>1</mn> </msub> <mo>+</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mi>&alpha;</mi> <mo>)</mo> </mrow> <msub> <mi>Z</mi> <mi>m</mi> </msub> <mo>;</mo> </mrow>
primary side nth harmonic equivalent impedance of transformerComprises the following steps:
<mrow> <msubsup> <mi>Z</mi> <mrow> <mi>A</mi> <mi>X</mi> </mrow> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mfrac> <msubsup> <mi>U</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> <msubsup> <mi>I</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> </mfrac> <mo>=</mo> <msubsup> <mi>Z</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> <mo>+</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <mi>&beta;</mi> <mo>)</mo> </mrow> <msubsup> <mi>Z</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>nZ</mi> <mn>1</mn> </msub> <mo>+</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <mi>&beta;</mi> <mo>)</mo> </mrow> <msub> <mi>nZ</mi> <mi>m</mi> </msub> </mrow>
wherein,is the fundamental voltage across the primary winding of the transformer,is the nth harmonic voltage across the primary winding of the transformer,
<mrow> <msup> <msub> <mi>U</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msup> <mo>=</mo> <msup> <msub> <mi>Z</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msup> <msup> <msub> <mi>I</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msup> <mo>+</mo> <msup> <msub> <mi>Z</mi> <mi>m</mi> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msup> <mrow> <mo>(</mo> <msup> <msub> <mi>I</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </msup> <mo>+</mo> <msup> <msub> <mi>I</mi> <mn>2</mn> </msub> <mrow> <mo>&prime;</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </msup> <mo>)</mo> </mrow> <mo>,</mo> <msup> <msub> <mi>U</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msup> <mo>=</mo> <msup> <msub> <mi>Z</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msup> <msup> <msub> <mi>I</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msup> <mo>+</mo> <msup> <msub> <mi>Z</mi> <mi>m</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msup> <mrow> <mo>(</mo> <msup> <msub> <mi>I</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </msup> <mo>+</mo> <msup> <msub> <mi>I</mi> <mn>2</mn> </msub> <mrow> <mo>&prime;</mo> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </msup> <mo>)</mo> </mrow> <mo>;</mo> </mrow>
andrespectively a fundamental component and an nth harmonic component in the current equivalent to the primary side of the transformer for the secondary side winding current of the transformer,
Z1 (1)is the leakage reactance, Z, of the primary side of the transformer with respect to the fundamental wave1 (1)＝Z1，Zm (1)Is the excitation impedance of the transformer with respect to the fundamental wave, Zm (1)＝Zm，Z1 (n)Leakage reactance, Z, of the primary side of the transformer with respect to the nth harmonic1 (n)＝nZ1，Zm (n)For the excitation impedance of the transformer with respect to the nth harmonic, Zm (n)＝nZm。
6. Active power filter device according to any of claims 1 to 5, characterized in that ifThenAt this time, the primary side winding of the transformer is equivalently short-circuited to the fundamental wave.
7. The active power filter device of any one of claims 1 to 5, wherein the value of β is set such that the nth harmonic equivalent impedance of the primary side of the transformer is setThe impedance is high, and the primary side winding of the transformer is equivalently open to the nth harmonic wave.
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| CN107370153A (en) * | 2017-07-21 | 2017-11-21 | 华中科技大学 | A kind of active electric filter device |
| CN108462177A (en) * | 2018-01-30 | 2018-08-28 | 华中科技大学 | A kind of serial active filter and system of gird-connected inverter |
| CN109873423A (en) * | 2019-03-21 | 2019-06-11 | 华中科技大学 | A kind of series hybrid electric energy quality controller |
| CN110718931A (en) * | 2019-09-19 | 2020-01-21 | 国电南瑞科技股份有限公司 | Novel direct current transmission system suitable for offshore wind power grid connection |
| CN111244959A (en) * | 2020-03-13 | 2020-06-05 | 西南交通大学 | Low-order harmonic filtering method for three-phase alternating current signals |
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| WO2023231278A1 (en) * | 2022-06-02 | 2023-12-07 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Vacuum on-load tap changer test system and harmonic current source |
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| CN111244959A (en) * | 2020-03-13 | 2020-06-05 | 西南交通大学 | Low-order harmonic filtering method for three-phase alternating current signals |
| CN112531730A (en) * | 2020-12-07 | 2021-03-19 | 广东电网有限责任公司清远供电局 | Ice melting device with reactive compensation and adjustable output current |
| CN112531730B (en) * | 2020-12-07 | 2023-02-17 | 广东电网有限责任公司清远供电局 | Ice melting device with reactive compensation and adjustable output current |
| WO2023231278A1 (en) * | 2022-06-02 | 2023-12-07 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Vacuum on-load tap changer test system and harmonic current source |
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