CN103036236B - Control method of wide frequency range multi-type harmonic comprehensive governance system - Google Patents

Abstract

The invention discloses a control method of a wide frequency range multi-type harmonic comprehensive governance system. The control method of the wide frequency range multi-type harmonic comprehensive governance system comprises the wide frequency range multi-type harmonic comprehensive governance system. The wide frequency range multi-type harmonic comprehensive governance system comprises a series active power filter and a parallel passive power filter. The series active power filter comprises an inverter, a filter circuit, and a series transformer. The inverter is connected with a secondary side of the series transformer through the filter circuit. A primary side of the transformer is in series connection with grid lines. The parallel passive power filter is in parallel connection with a load side of the series active power filter. The control method of the wide frequency range multi-type harmonic comprehensive governance system is based on a control method of a fundamental wave magnetic flux compensation principle of the transformer. A fundamental wave compensating current is injected at the secondary side of the transformer. The size of the fundamental wave compensating current is k times larger or smaller than a power system current, and the direction of the fundamental wave compensating current is opposite to that of the power system current. Impedance of the series transformer to a fundamental wave is zero. Normal operation of the power system cannot be influenced. High impedance to the harmonic wave is presented. Filtering effect of a passive power filter can be improved. A harmonic voltage is compensated. Simultaneously, resonance of power harmonic in series or parallel connection can be well restrained.

Description

control method of wide frequency domain multi-type harmonic comprehensive treatment system

Technical Field

The invention relates to an active power filter, in particular to a control method of a wide-frequency-domain multi-type harmonic comprehensive treatment system.

Background

With the increasing application of power electronic devices, the types of harmonic sources are increased, and the harmonic environment of a power grid is more and more complex. A grid rectifier is a typical harmonic source, and can be roughly classified into a current-type harmonic source and a voltage-type harmonic source depending on a dc-side filter element thereof. The rectifying device with inductive filtering on the direct current side can be regarded as a current type harmonic source, and the rectifying device with capacitive filtering on the direct current side can be regarded as a voltage type harmonic source. Because the early current mode rectifying device is widely applied, domestic and foreign researches on the governing method of the current mode harmonic source are more, and the researches on the governing scheme of the voltage mode harmonic source are relatively less. In recent years, with increasing applications of power electronic devices such as inverters, switching power supplies, uninterruptible power supplies, and electronic ballasts, voltage type harmonic sources in a power grid are increasing, and the voltage type harmonic sources become another main harmonic source. In addition, loads in some occasions may contain current type harmonic sources and voltage type harmonic sources, the harmonic problem is serious, and different types of harmonic sources need to be comprehensively managed.

At present, a lot of researches are carried out on the governance methods of current-mode and voltage-mode harmonic sources at home and abroad, and the researches on the comprehensive governance methods of different types of harmonic sources are few. Some research conclusions show that the parallel active power filter is suitable for compensating current type harmonic sources, and the series active power filter is suitable for compensating voltage type harmonic sources, but the parallel active power filter is adopted for compensating the voltage type harmonic sources, and when the series active power filter is adopted for compensating the current type harmonic sources, harmonic amplification phenomena can be caused, and the compensation effect is not good. The conventional series hybrid active power filter can compensate current type harmonic sources, but a passive part generally adopts a plurality of groups of single series resonance passive power filters, and when the load side contains harmonic voltages, the harmonic currents flowing through the passive power filters are easily overlarge, so that the passive power filter is not suitable for occasions with harmonic voltage distortion on the load side. The hybrid passive filter composed of the series passive filter and the parallel passive filter can realize the comprehensive compensation of voltage type and current type harmonic waves, but the influence of filter internal resistance and filter partial resonance caused by the parameter change of the series resonance passive filter and the frequency deviation of a power grid can generate larger fundamental voltage drop to influence the normal operation of the power grid. The traditional series active power filter adopts control methods such as load voltage detection, power current detection, composite detection and the like, because harmonic signals with different frequencies are directly and uniformly controlled, amplitude and phase errors are easily generated in a steady state, the errors are not easy to adjust and correct, and the steady-state control accuracy is not high enough.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a control method of a broadband multi-type harmonic comprehensive treatment system aiming at the defects of the prior art, realize the comprehensive treatment of current type and voltage type harmonic sources, effectively inhibit the series and parallel resonance of the harmonic of a power grid, enhance the filtering effect and improve the steady-state control precision.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a control method of a wide frequency domain multi-type harmonic comprehensive treatment system comprises the wide frequency domain multi-type harmonic comprehensive treatment system, wherein the wide frequency domain multi-type harmonic comprehensive treatment system comprises a series active power filter and a parallel passive power filter, the series active power filter comprises an inverter, a filter circuit and a transformer, the inverter is connected to the secondary side of the transformer through the filter circuit, the primary side of the transformer is connected in a power grid line in series, the parallel passive power filter is connected to the load side of the series active power filter in parallel, and the method comprises the following steps:

1) detecting three-phase current i of power grid_sa、i_sb、i_scMultiplying the three-phase current of the power grid by the primary-secondary side transformation ratio of the transformer and inverting the phase, namely multiplying the three-phase current by-k, so that the obtained current contains a secondary-side fundamental wave compensation current signal;

2) subtracting the output current i of the inverter from the current signal obtained in the step 1)_ca、i_cb、i_ccObtaining a fundamental wave compensation current error signal;

3) ip-plus for fundamental compensation current error signaliq positive conversion is carried out, and active components of the error signals are extracted through a low-pass filterAnd a reactive component

4) Calculating amplitude I of fundamental wave compensation current error signal₁Angle of sumPI regulation is carried out on the amplitude value, delay compensation is carried out on the phase angle, and the reference quantity of the amplitude value and the phase angle is obtainedAnd

5) calculating current modulation reference active component according to reference quantity of amplitude value and phase angleAnd a reactive component

6) Carrying out ip-iq inverse transformation to obtain a three-phase current modulation control signal i^*And controlling the voltage type inverter to output fundamental wave compensation current.

The parallel passive filter is a fundamental wave parallel resonance passive band elimination filter formed by an inductor and a capacitor.

Compared with the prior art, the invention has the beneficial effects that: the parallel passive filter adopts a fundamental wave parallel resonance passive filter, has small impedance to higher harmonic waves and low-order characteristic harmonic waves, can effectively limit the low-order harmonic current flowing through PPF when harmonic voltage on the load side is distorted, and does not influence the suppression effect of the harmonic current. The wide-frequency-domain multi-type harmonic comprehensive treatment system can be applied to occasions with harmonic voltage distortion on the load side, and comprehensive compensation of current-type and voltage-type harmonic sources is realized; by adopting a control method based on a transformer fundamental wave magnetic flux compensation principle, fundamental wave compensation current which is k times as large as power grid current and has opposite directions is injected into the secondary side of the transformer, so that the impedance of the series transformer to the fundamental wave is zero, the normal operation of the power grid is not influenced, meanwhile, the harmonic wave presents very high impedance, the filtering effect of a passive power filter can be improved, the harmonic voltage is compensated, and the series and parallel resonance of the harmonic wave of the power grid is well inhibited; the fundamental wave compensation current of the series active filter adopts a static-error-free PI control method, only carries out proportional integral control on the amplitude of the command signal without influencing the phase, and has the advantages of good dynamic performance, no steady-state error, fixed switching frequency, simplicity and easiness in implementation.

Drawings

FIG. 1 is a topological structure diagram of a broadband domain multi-type harmonic comprehensive treatment system according to an embodiment of the present invention;

fig. 2 is a detection control block diagram of the broadband multi-type harmonic comprehensive treatment system according to an embodiment of the present invention.

Detailed Description

As shown in fig. 1, the broadband multi-type harmonic comprehensive treatment system according to an embodiment of the present invention includes a series active power filter and a parallel resonant passive filter, the parallel resonant passive filter is a fundamental wave parallel resonant passive band elimination filter formed by an inductor and a capacitor, the series active power filter is connected to one end of a secondary side of a series transformer after passing through an LC output filter circuit from each ac output end of a three-phase voltage type inverter, wherein the capacitor of the LC output filter circuit is connected in parallel with the secondary side of the transformer, a series transformer on three phases of a power grid is connected in a Y-connection manner, and a series transformer is connected in seriesThe other end of the secondary side of the transformer is used as a three-phase neutral point, the primary side of the series transformer is connected in series between a power grid and a harmonic source, and the parallel resonance type passive power filter is connected to the load side of the series type active power filter in parallel. The series active power filter adopts a control method based on the fundamental wave flux compensation principle of the transformer, if the primary-secondary side transformation ratio of the series transformer in figure 1 is k, according to the fundamental wave flux compensation principle of the transformer, when the current i injected into the secondary side of the transformer_cIs a primary side fundamental current i_sfThe primary flux of the fundamental wave of the transformer is zero when the voltage is multiplied by-k. At the moment, the transformer shows very low primary side leakage impedance to fundamental waves when looking into the primary side of the transformer, and normal operation of a power grid is not influenced; the impedance presented to the nth harmonic wave is about n times of the fundamental wave excitation impedance, the impedance of the transformer to the nth harmonic wave current is far larger than the impedance to the fundamental wave current and also far larger than the impedance of the parallel resonance passive filter to the nth harmonic wave current, so that the harmonic wave current is forced to flow into the passive filter branch circuit and not flow into the power grid side, and a good harmonic wave isolation effect is achieved. The series active power filter mainly has the functions of compensating harmonic voltage in a nonlinear load and power grid background harmonic voltage, isolating load side harmonic current and improving the performance of the passive filter, and can effectively inhibit the generation of series and parallel resonance of a power grid due to high impedance of the series active power filter to harmonic waves. The parallel PPF is a group of parallel resonance band elimination filters, the resonance is at fundamental wave frequency, the parallel resonance is at the load side, the impedance to higher harmonic is very small, the impedance to low-order characteristic harmonic is relatively small, a harmonic current channel is mainly provided for the load, when the harmonic voltage distortion exists at the load side, the low-order harmonic current flowing through the PPF can be effectively limited, meanwhile, the filtering effect is not influenced, the defect that harmonic waves in the PPF of the traditional SHAPF are easy to overflow is overcome, the broadband domain multi-type harmonic comprehensive treatment system can be used for comprehensively compensating different types of harmonic sources, and certain reactive power can be compensated by adjusting the resonance frequency. The series hybrid active power filter in fig. 1 is a wide-band multi-type harmonic comprehensive treatment system.

As shown in fig. 2, the series active power filter of the present invention uses a control method based on the fundamental flux compensation principle of the transformer, only the fundamental current output by the voltage-type inverter needs to be controlled, the frequency of the controlled object is single, and the control is simple and easy to implement. The invention adopts current non-static-error PI control, changes the fundamental current error signal into a direct current signal through coordinate transformation, and then performs PI control on the direct current signal, thereby eliminating the steady-state error of the system.

In order to reduce the number of coordinate transformations, the network current i is first detected_sI.e. the primary current of the series transformer, this current is multiplied by a coefficient-k to obtain the equivalent current value of the secondary side of the transformer, and then the detected output current i of the inverter is subtracted_cThe resulting current i₁Including harmonic currents, a fundamental compensation current reference and error signals of the actual compensation current. In order to extract fundamental wave compensation current error signals, i is carried out on the obtained three-phase current signals according to the instantaneous reactive power theory_p、i_qTransformation, C in the figure_FTAnd C_ITRespectively as positive transform matrix and inverse transform matrix, and low-pass filtering to obtain instantaneous active component of fundamental waveAnd amount of reactive powerThen calculating the amplitude I of the error amount of the fundamental current₁Angle of sumOnly the amplitude of the error current signal is then controlled by proportional-integral, thereby avoiding integration of the frequency and phase angle of the error signal. And the controlled signal is direct current quantity, so that the inverter output current can track the fundamental wave compensation current signal without static error. In addition, an adjustment angle can be superimposed in the phase angle of the signalThe phase delay caused by the links of signal detection and output filtering is compensated, or the phase of the output fundamental current tracks the phase of the voltage of the power grid through phase angle adjustment, so as to achieve the purpose of reactive power compensation. Can be used forThe general PI controller is used for realizing the advantages of the generalized integrator, the number of coordinate transformation and PI controllers is reduced, and the control algorithm is simple and easy to realize.

Wherein, the forward transformation matrix C_FTAnd inverse transform matrix C_ITThe expression of (a) is as follows:

<math> <mrow> <msub> <mi>C</mi> <mi>FT</mi> </msub> <mo>=</mo> <mfrac> <mn>2</mn> <mn>3</mn> </mfrac> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mi>sin</mi> <mi></mi> <mi>&omega;</mi> <mi>t</mi> <mi>sin</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>-</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> <mtd> <mi>sin</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>+</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mi>cos</mi> <mi></mi> <mi>&omega;</mi> <mi>t</mi> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>-</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> <mtd> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>+</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </math>

<math> <mrow> <msub> <mi>C</mi> <mi>IT</mi> </msub> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mi>sin</mi> <mi>&omega;t</mi> </mtd> <mtd> <mi>cos</mi> <mi>&omega;t</mi> </mtd> </mtr> <mtr> <mtd> <mi>sin</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>-</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> <mtd> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>-</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mi>sin</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>+</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> <mtd> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>+</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> </math>

setting:where ω is the fundamental angular frequency. Then it is possible to obtain:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C_{\mathrm{FT}}\left[\begin{array}{c}{i}_{1a}\\ i_{1b}\\ i_{1c}\end{array}\right]---\left(3\right)$

active current component i_pAnd a reactive current component i_qAfter passing through the low-pass filter, the DC components are obtainedAndthe following can be obtained by calculation:

the amplitude and phase information of the fundamental compensation current error signal is included in the formula (4), and the amplitude and phase can be calculated as follows according to the formula:

the amplitude and phase angle of the fundamental wave modulation control signal after PI controller and phase adjustment are assumed to be I respectively^*Andthe instantaneous active component of the output fundamental current modulation control signal can be obtained by simple calculationAnd a reactive componentAs shown in the following formula:

the three-phase alternating current modulation control signal i output by the inverter can be obtained through inverse transformation of the formula^*As follows:

$i^{*}=\left[\begin{array}{c}{i}_a^{*}\\ i_b^{*}\\ i_c^{*}\end{array}\right]=C_{\mathrm{IT}}\left[\begin{array}{c}{i}_p^{*}\\ i_q^{*}\end{array}\right]---\left(7\right)$

Claims (6)

1. A control method of a wide frequency domain multi-type harmonic comprehensive treatment system comprises a series hybrid type active power filter, wherein the series hybrid type active power filter comprises a series active power filter and a parallel passive power filter, the series active power filter comprises an inverter, a filter circuit and a series transformer, the inverter is connected to the secondary side of the series transformer through the filter circuit, the primary side of the transformer is connected in a power grid line in series, the parallel passive power filter is connected to the load side of the series active power filter in parallel, and the parallel passive filter is a fundamental wave parallel resonance passive filter band-stop composed of an inductor and a capacitor; the method is characterized by comprising the following steps:

1) detecting three-phase current i of power grid_sa、i_sb、i_scMultiplying the three-phase current of the power grid by the original secondary side transformation ratio K of the transformer and inverting the phase, namely multiplying the three-phase current by-K to obtain a current containing a secondary side fundamental wave compensation current signal;

2) subtracting the output current i of the inverter from the current signal obtained in the step 1)_ca、i_cb、i_ccObtaining a fundamental wave compensation current error signal;

3) the fundamental wave compensation current error signal is subjected to ip-iq forward conversion, and active components of the error signal are extracted through a low-pass filterAnd a reactive component

4) Calculating amplitude I of fundamental wave compensation current error signal₁Angle of sumPI regulation is carried out on the amplitude, delay compensation is carried out on the phase angle, and amplitude reference quantity is obtainedAnd phase angle reference

5) Calculating current modulation reference active component according to amplitude reference quantity and phase angle reference quantityAnd a reactive component

6) Carrying out ip-iq inverse transformation to obtain a three-phase current modulation control signal i^*And controlling the voltage type inverter to output fundamental wave compensation current.

2. The method of claim 1, wherein the inverter is a three-phase voltage inverter.

3. The method of claim 1, wherein the filter circuit is an LC output filter circuit.

4. The method of claim 1, wherein the primary-secondary side transformation ratio of the series active power filter is k: 1.

5. The method as claimed in claim 1, wherein in step 5), the reference active component is modulated by currentAnd a reactive componentThe calculation formula of (a) is as follows:

wherein,

6. the wide frequency domain multi-type harmonic of claim 1 or 5The control method of the comprehensive treatment system is characterized in that in the step 6), the three-phase current modulates the control signal i^*The calculation formula of (a) is as follows:

$i^{*}=\left[\begin{array}{c}{i}_a^{*}\\ i_b^{*}\\ i_c^{*}\end{array}\right]=C_{\mathrm{IT}}\left[\begin{array}{c}{i}_p^{*}\\ i_q^{*}\end{array}\right],$

wherein, <math> <mrow> <msub> <mi>C</mi> <mi>IT</mi> </msub> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mi>sin</mi> <mi>&omega;t</mi> </mtd> <mtd> <mi>cos</mi> <mi>&omega;t</mi> </mtd> </mtr> <mtr> <mtd> <mi>sin</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>-</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> <mtd> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>-</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mi>sin</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>+</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> <mtd> <mi>cos</mi> <mrow> <mo>(</mo> <mi>&omega;t</mi> <mo>+</mo> <mn>2</mn> <mi>&pi;</mi> <mo>/</mo> <mn>3</mn> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math> where ω is the fundamental angular frequency.