CN102638044B - Control method for predicating switching signal of three-phase four-wire active filter - Google Patents

Abstract

Translated fromChinese

本发明公开了一种三相四线有源滤波器开关信号预测控制方法，包括以下步骤：步骤1：采集信号，并计算参考电流信号I_ref：参考电流信号的计算公式为I_ref＝I_pref*sinωt+I_dc-pref/3+I_h；步骤2：计算下一时刻的开关时间T_K+1；或采用下式计算：步骤3：根据T_K+1控制三电平逆变桥中的每相的开关器件。该三相四线有源滤波器开关信号预测控制方法根据有源滤波器的单相状态预测下一控制周期的开关状态，易于实施，响应速度快。

The invention discloses a three-phase four-wire active filter switching signal predictive control method, comprising the following steps: Step 1: collecting signals, and calculating a reference current signal I_ref : the calculation formula of the reference current signal is I_ref =I_pref *sinωt+I_dc-pref /3+I_h ; Step 2: Calculate the switching time T_K+1 at the next moment; Or use the following formula to calculate: Step 3: Control the switching devices of each phase in the three-level inverter bridge according to T_K+1 . The switch signal predictive control method of the three-phase four-wire active filter predicts the switch state of the next control cycle according to the single-phase state of the active filter, is easy to implement, and has fast response speed.

Description

Translated fromChinese

三相四线有源滤波器开关信号预测控制方法Three-phase four-wire active filter switching signal predictive control method

技术领域technical field

本发明属于有源滤波技术，涉及一种三相四线有源滤波器开关信号预测控制方法。The invention belongs to the active filter technology, and relates to a three-phase four-wire active filter switch signal predictive control method.

背景技术Background technique

随着家用电子设备的普及，配电网电能质量受到严重的影响，特别是家用电器设备广泛使用整流器变流供电，对配电网带来了大量的谐波污染，必须予以治理。对谐波的治理主要有无源滤波器、有源滤波器和混合型滤波器。并联无源滤波器是最简单的谐波治理方法，但只能对特定次谐波有较好的滤波效果，滤波频带很窄。无源滤波器是一种电力电子装置，能补偿任意频率和大小的谐波，补偿特性不受电网阻抗和频率变化的影响，是一种理想的谐波补偿装置，但受限于电力电子器件容量的影响，很难直接应用到高压系统中。混合型滤波器兼顾了无源滤波器和有源滤波器的优点，利用无源部分滤除大部分谐波，而有源部分主要用来改善无源部分的滤波性能。With the popularization of household electronic equipment, the power quality of distribution network is seriously affected. In particular, household electrical equipment widely uses rectifiers for power supply, which brings a lot of harmonic pollution to distribution network and must be treated. The treatment of harmonics mainly includes passive filters, active filters and hybrid filters. Parallel passive filter is the simplest harmonic control method, but it can only have a good filtering effect on specific harmonics, and the filtering frequency band is very narrow. Passive filter is a power electronic device that can compensate harmonics of any frequency and size. The compensation characteristics are not affected by grid impedance and frequency changes. It is an ideal harmonic compensation device, but it is limited by power electronic devices. The effect of capacity is difficult to be directly applied to high-voltage systems. The hybrid filter takes into account the advantages of the passive filter and the active filter, and uses the passive part to filter out most of the harmonics, while the active part is mainly used to improve the filtering performance of the passive part.

在配电网中，电压等级低、电流小，更加适合于直接采用有源电力滤波器，这是由于无源滤波器的价格正逐步上升，而小容量的电力电子器件价格却在稳步下降，直接使用有源电力滤波器在成本上更有优势，同时又具有更好的滤波性能。In the distribution network, the voltage level is low and the current is small, which is more suitable for the direct use of active power filters. This is because the price of passive filters is gradually increasing, while the price of small-capacity power electronic devices is steadily decreasing. Direct use of active power filters has more advantages in cost, and at the same time has better filtering performance.

对于配电网三相四线有源电力滤波器，由于需要治理的谐波频带很宽(一般要求从2次谐波到50次谐波)，必须保证控制器在宽频范围了都有较大的增益，传统的PI控制很难满足。为此，必须将2到50次谐波分别检出，然后针对每次谐波单独设计控制器，这使得控制器将会变得非常复杂，难以保证系统的响应速度，如果还要进行不平衡补偿，则必须三相分别控制，更加加重了控制器的负担。For the three-phase four-wire active power filter of the distribution network, since the harmonic frequency band to be controlled is very wide (generally from the 2nd harmonic to the 50th harmonic), it must be ensured that the controller has a large frequency range in the wide frequency range. Gain, the traditional PI control is difficult to meet. For this reason, the 2nd to 50th harmonics must be detected separately, and then a controller is designed for each harmonic separately, which makes the controller very complicated and it is difficult to guarantee the response speed of the system. compensation, the three phases must be controlled separately, which further increases the burden on the controller.

发明内容Contents of the invention

本发明所要解决的技术问题是提供一种三相四线有源滤波器开关信号预测控制方法，该三相四线有源滤波器开关信号预测控制方法根据有源滤波器的单相状态预测下一控制周期的开关状态，易于实施，响应速度快。The technical problem to be solved by the present invention is to provide a three-phase four-wire active filter switching signal predictive control method. The switching state of a control cycle is easy to implement and has a fast response speed.

发明的技术解决方案如下：The technical solution of the invention is as follows:

一种三相四线有源滤波器开关信号预测控制方法，所述的三相四线有源滤波器由双电容、三电平逆变桥和两级LC输出滤波器组成；双电容为第一电容和第二电容组成的串联支路；第一电容与第二电容的连接点接三相四线电网的中线；双电容与三电平逆变桥的三个桥臂并联，三电平逆变桥的输出端经两级LC输出滤波器与电网连接；两级LC输出滤波器为前级LC输出滤波器和后级LC输出滤波器；A three-phase four-wire active filter switching signal predictive control method, the three-phase four-wire active filter is composed of a double capacitor, a three-level inverter bridge and a two-stage LC output filter; the double capacitor is the first A series branch composed of a capacitor and a second capacitor; the connection point of the first capacitor and the second capacitor is connected to the neutral line of the three-phase four-wire grid; the two capacitors are connected in parallel with the three bridge arms of the three-level inverter bridge, and the three-level The output end of the inverter bridge is connected to the power grid through a two-stage LC output filter; the two-stage LC output filter is a pre-stage LC output filter and a post-stage LC output filter;

对A、B、C三相采用分相控制，包括以下步骤：Phase separation control is adopted for the three phases A, B, and C, including the following steps:

步骤1：采集信号，并计算参考电流信号I_ref：Step 1: Collect the signal and calculate the reference current signal I_ref :

所采集的信号包括三电平逆变桥的输出电压U_inv，电网电压U_S，前级输出滤波器中电感上的电流I_inv、前级输出滤波器中电感上的电流I_L、前级输出滤波器中电容输出的电流I_C1、后级输出滤波器中电容输出的电流I_C2，第一电容电压U_CD1和第二电容电压U_CD2；The collected signals include the output voltage U_inv of the three-level inverter bridge, the grid voltage U_S , the current I_inv of the inductance in the pre-stage output filter, the current I_L of the inductance in the pre-stage output filter, the pre-stage The current I_C1 output by the capacitor in the output filter, the current I_C2 output by the capacitor in the subsequent output filter, the first capacitor voltage U_CD1 and the second capacitor voltage U_CD2 ;

参考电流信号的计算公式为I_ref＝I_pref*sinωt+I_dc-pref/3+I_h；The calculation formula of the reference current signal is I_ref =I_pref *sinωt+I_dc-pref /3+I_h ;

其中：in:

I_h为负载谐波电流，通过对负载电流进行同步变换得到；I_pref为U_CD1+U_CD2-U_DCref经第一PI控制器后的输出量；其中U_DCref为电容电压参考值【U_DCref取700-800之间的一个值，可设置为800V，设为700也可以，只是影响调制系数】I_h is the load harmonic current, which is obtained by synchronously transforming the load current; I_pref is the output of U_CD1 + U_CD2 -_{U DCref} after passing through the first PI controller; where U_DCref is the capacitor voltage reference value [U_DCref Take a value between 700-800, it can be set to 800V, and it can also be set to 700, but it only affects the modulation coefficient]

ω为电网电压基波频率；ω is the fundamental frequency of grid voltage;

I_dc-pref为用于稳定电容电压的有功电流，I_dc-pref为U_CD1-U_CD2经第二PI控制器的输出量；I_dc-pref is the active current used to stabilize the capacitor voltage, and I_dc-pref is the output of U_CD1 -U_CD2 through the second PI controller;

步骤2：计算下一控制周期的开关时间T_K+1；Step 2: Calculate the switching time T_K+1 of the next control cycle;

$T_{K+1}=(U_s+L_1\frac{I_{\mathrm{ref}}-I_{\mathrm{inv}}-I_{C1}-I_{C2}}{T}+L_2\frac{I_{\mathrm{ref}}-I_L-I_{C1}}{T})/U_{\mathrm{DC}1};$其中T为控制周期【T取10^-4，即开关频率设为10kHz】；L₁、L₂分别为滤波器的第一级、第二级的电感值，【分别取值1.5mH，0.5fmH】。$T_{K+1}=(u_{\mathrm{the\; s}}+L_1\frac{I_{\mathrm{ref}}-I_{\mathrm{inv}}-I_{C1}-I_{C2}}{T}+L_2\frac{I_{\mathrm{ref}}-I_L-I_{C1}}{T})/{\mathrm{<figure-callout\; label="u\; DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">u</figure-callout>}}_{\mathrm{DC}};$ Among them, T is the control cycle [take 10^-4 for T, that is, the switching frequency is set to 10kHz]; L₁ and L₂ are the inductance values of the first stage and the second stage of the filter respectively, [the values are 1.5mH and 0.5fmH respectively 】.

判断T_K+1＜0是否成立，如果成立，按下式更新T_K+1，否则保持T_K+1不变：Determine whether T_K+1 < 0 is true, if true, update T_K+1 according to the formula, otherwise keep T_K+1 unchanged:

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>K</span>K</span>}<span><span>+</span>+</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span><span><span>-</span>-</span><span><span>(</span>(</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>inv</span>inv</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>L</span>L</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>)</span>)</span><span><span>/</span>/</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>DC</span>DC</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>;</span>;</span>$

步骤3：根据T_K+1控制三电平逆变桥中的每相的开关器件。Step 3: Control the switching devices of each phase in the three-level inverter bridge according to T_K+1 .

对于最终得到的T_K+1，如果T_K+1＞0，表示下一个周期内，应控制逆变器输出正电平T_K+1时间，输出0电平T-T_K+1时间；For the final T_K+1 , if T_K+1 >0, it means that in the next cycle, the inverter should be controlled to output positive level for T_K+1 time, and output 0 level for TT_K+1 time;

如果T_K+1＝0，则表示下一个控制周期内，逆变器的输出全为0；If T_K+1 = 0, it means that in the next control cycle, the output of the inverter is all 0;

如果T_K+1＜0，则表示下一个控制周期内，逆变器的输出负电平T_K+1时间，输出0电平T-T_K+1时间。If T_K+1 <0, it means that in the next control cycle, the inverter outputs negative level for T_K+1 time, and outputs 0 level for TT_K+1 time.

第一PI控制器参数为：比例系数取0.01，积分系数取1，第二PI控制的参数为：比例系数取0.1，积分系数取100。The parameters of the first PI controller are: the proportional coefficient is 0.01, and the integral coefficient is 1; the parameters of the second PI controller are: the proportional coefficient is 0.1, and the integral coefficient is 100.

假设一个控制周期T内，三电平逆变器输出正电平时间为T_on，输出负电平时间为T_off，输出0电平时间为T₀(T₀＝T-T_on-T_off)，占空比可以表示为T₀/T。Assuming that within a control period T, the three-level inverter outputs positive level time for T_on , outputs negative level time for T_off , and outputs 0 level time for T₀ (T₀ =TT_on -T_off ), accounting for The duty ratio can be expressed as T₀ /T.

则，逆变器输出电压为：Then, the inverter output voltage is:

U_inv＝T_onU_DC1-T_offU_DC2U_inv ＝T_on U_DC1 -T_off U_DC2

考虑输出滤波器的状态方程，有：Considering the state equation of the output filter, there are:

${\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>inv</span>inv</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>S</span>S</span>}}<span><span>=</span>=</span>{\mathrm{<span><span>L</span><figure-callout\; label="L"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{{\mathrm{<span><span>dI</span>iGO</span>}}_{\mathrm{<span><span>inv</span>inv</span>}}}{\mathrm{<span><span>dt</span>dt</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{{\mathrm{<span><span>dI</span>iGO</span>}}_{\mathrm{<span><span>L</span>L</span>}}}{\mathrm{<span><span>dt</span>dt</span>}}$

I_L＝I_inv+I_C1I_L =I_inv +I_C1

I_Z＝I_L+I_C2I_Z =I_L +I_C2

其中L₁是两级输出滤波器第一级电感，L₂是第二级电感。最后整理得到三相四线有源滤波器的模型为：Among them,_L1 is the first-stage inductance of the two-stage output filter, and_L2 is the second-stage inductance. Finally, the model of the three-phase four-wire active filter is obtained as follows:

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>on</span>on</span>}}{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>DC</span>DC</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>off</span>off</span>}}{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>DC</span>DC</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>=</span>=</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{\mathrm{<span><span>d</span>d</span>}<span><span>(</span>(</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>z</span>z</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>)</span>)</span>}{\mathrm{<span><span>dt</span>dt</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{\mathrm{<span><span>d</span>d</span>}<span><span>(</span>(</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>z</span>z</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>)</span>)</span>}{\mathrm{<span><span>dt</span>dt</span>}}$

为了降低逆变器开关频率，在一个控制周期内，逆变器的输出电压不应该同时出现正电平，0，负电平的情况，为此可以先假设逆变器在下一周期只输出正电平和0电平，此时，T_off＝0，则：In order to reduce the switching frequency of the inverter, in one control cycle, the output voltage of the inverter should not appear in positive level, 0, and negative level at the same time. For this reason, it can be assumed that the inverter only outputs positive voltage in the next cycle. Level and 0 level, at this time, T_off =0, then:

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>on</span>on</span>}}<span><span>=</span>=</span><span><span>(</span>(</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{\mathrm{<span><span>d</span>d</span>}<span><span>(</span>(</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>z</span>z</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>)</span>)</span>}{\mathrm{<span><span>dt</span>dt</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{\mathrm{<span><span>d</span>d</span>}<span><span>(</span>(</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>z</span>z</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>)</span>)</span>}{\mathrm{<span><span>dt</span>dt</span>}}<span><span>)</span>)</span><span><span>/</span>/</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>DC</span><figure-callout\; label="DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">DC</figure-callout></span>}\mathrm{<span><span>1</span>1</span>}}$

为了保证下一周期注入到电网的电流跟踪到参考电流I_ref，即：In order to ensure that the current injected into the grid in the next cycle tracks to the reference current I_ref , that is:

I_Z＝I_refI_Z = I_ref

同时，由于输出滤波器电容主要包含开关频率谐波，可以假定下一周期电容上的电流和电网电压变化不大，并利用差分形式表示微分，可得：At the same time, since the output filter capacitor mainly contains switching frequency harmonics, it can be assumed that the current on the capacitor in the next cycle and the grid voltage will not change much, and the differential can be represented by the differential form, which can be obtained as follows:

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>on</span>on</span>}}<span><span>=</span>=</span><span><span>(</span>(</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{<span><span>(</span>(</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>)</span>)</span><span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>inv</span>inv</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{<span><span>(</span>(</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>)</span>)</span><span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>L</span>L</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>)</span>)</span><span><span>/</span>/</span>{\mathrm{<span><span>U</span><figure-callout\; label="u\; DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; label="u\; DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}"></figure-callout>}}_{\mathrm{<span><span></span></span>}}$

其中，I_ref是参考电流信号，由负载谐波，稳定双电容电压的有功电流和调节电容电压平衡的直流电流组成。Among them, I_ref is the reference current signal, which is composed of load harmonics, active current for stabilizing the double capacitor voltage and DC current for adjusting the balance of capacitor voltage.

如果T_on＞0，则表示下一个控制周期内，逆变器的输出一部分时间在正电平，一部分时间在0；If T_on >0, it means that in the next control cycle, the output of the inverter is at a positive level for a part of the time, and is at 0 for a part of the time;

如果T_on＝0，则表示下一个控制周期内，逆变器的输出全为0；If T_on =0, it means that in the next control cycle, the output of the inverter is all 0;

如果T_on＜0，则表示下一个控制周期内，逆变器的输出有一部分时间在负电平，为此，令滤波器模型中的T_on＝0，保留T_off，重新以上计算步骤。If T_on <0, it means that in the next control cycle, the output of the inverter is at a negative level for a part of the time. Therefore, set T_on =0 in the filter model, keep T_off , and repeat the above calculation steps.

根据占空比，总共有3中分配方法，以T_on＞0为例，According to the duty cycle, there are a total of 3 distribution methods, taking T_on > 0 as an example,

1)在控制周期起始时间内输出T_on时间的正电平，然后输出T-T_on时间的0电平；1) Output the positive level of the T_on time within the initial time of the control cycle, and then output the 0 level of the TT_on time;

2)在控制周期起始时间内输出

的0电平，然后输出T_on的正电平，最后再输出

的0电平；2) Output within the start time of thecontrol cycle

0 level, then output the positive level of T_on , and finallyoutput

0 level;

3)在控制周期起始时间内输出T-T_on时间的0电平，然后输出T_on时间的正电平。3) Output a 0 level for the TT_on time within the start time of the control cycle, and then output a positive level for the T_on time.

为了降低开关谐波，分配策略为：根据前一周期最后时刻的开关状态选择合适的分配方法，保证前后2次控制周期中出现的开关变化次数最少，即：In order to reduce the switching harmonics, the allocation strategy is: select an appropriate allocation method according to the switch state at the last moment of the previous cycle, and ensure that the number of switch changes in the two control cycles before and after is the least, that is:

1)如果上一周期最后时刻出现的是正电平，则选择分配方法1)；1) If a positive level appeared at the last moment of the previous cycle, select distribution method 1);

2)如果上一周期最后时刻出现的是0电平，则选择分配方法3)；2) If the 0 level appeared at the last moment of the previous cycle, select the allocation method 3);

3)如果上一周期最后时刻出现的是负电平，则选择分配方法2)。3) If a negative level appeared at the last moment of the previous cycle, select distribution method 2).

有益效果：Beneficial effect:

本发明的三相四线有源滤波器开关信号预测控制方法，根据有源滤波器的单相状态模型，直接计算出下一周期为了保证注入电网的电流跟踪电流参考信号应采用多大的占空比，然后采用开关次数最少变化策略，确定下一开关周期中正电平、0电平和负电平的出现顺序，最后对逆变桥开关按照设定的控制模式进行通断操作，不仅提高了滤波器的响应速度，同时保证了在极宽频范围内都有足够的增益，特别在补偿三相不平衡谐波电流时，性能突出。According to the three-phase four-wire active filter switching signal prediction control method of the present invention, according to the single-phase state model of the active filter, directly calculate how much duty should be used in the next cycle to ensure that the current injected into the grid tracks the current reference signal Then adopt the least switching strategy to determine the sequence of positive level, 0 level and negative level in the next switching cycle, and finally perform the on-off operation of the inverter bridge switch according to the set control mode, which not only improves the efficiency of the filter Excellent response speed, while ensuring sufficient gain in a very wide frequency range, especially when compensating three-phase unbalanced harmonic current, the performance is outstanding.

本发明的有益效果是：1)本发明的开关信号预测控制可以分相进行，能补偿三相不平衡谐波；2)本发明的控制对象是注入电网的电流，而不是逆变器输出电流，抑制了两级输出滤波器与电网之间可能发生的谐振；3)本发明直接通过有源电力滤波器模型计算出开关器件在下一周期的占空比，在很宽的频带范围了都有较大的增益，提高了系统的控制精度，针对于常见的带阻容性整流桥负荷，采用本发明后，THD(总谐波失真，即电网电流畸变率)由50％多下降到4％以下；4)预测算法简单，不需要复杂的计算就可以直接控制逆变器开关，提高了系统响应速度，当谐波负荷发生变化时，只需2个周波就可以达到新的稳定状态；5)开关周期固定，利于设计输出滤波器。The beneficial effects of the present invention are: 1) the switching signal predictive control of the present invention can be carried out in phases, and can compensate the unbalanced harmonics of the three phases; 2) the control object of the present invention is the current injected into the power grid, rather than the output current of the inverter , which suppresses the resonance that may occur between the two-stage output filter and the grid; 3) The present invention directly calculates the duty cycle of the switching device in the next cycle through the active power filter model, which has a wide frequency range Larger gain improves the control accuracy of the system. For common loads with resistive-capacitive rectifier bridges, after adopting the present invention, THD (total harmonic distortion, that is, grid current distortion rate) is reduced from more than 50% to 4%. The following; 4) The prediction algorithm is simple, and the inverter switch can be directly controlled without complicated calculations, which improves the system response speed. When the harmonic load changes, it only takes 2 cycles to reach a new stable state; 5 ) The switching period is fixed, which is conducive to the design of the output filter.

附图说明Description of drawings

图1是本发明所述的三电平三相四线有源电力滤波器结构图；Fig. 1 is a structural diagram of a three-level three-phase four-wire active power filter of the present invention;

图2是本发明所述参考电流信号检测原理图；Fig. 2 is a schematic diagram of the reference current signal detection of the present invention;

图3是本发明所述的预测控制流程图；Fig. 3 is the predictive control flowchart of the present invention;

图4为三电平逆变桥的拓扑结构图；Fig. 4 is a topological structure diagram of a three-level inverter bridge;

图5为稳态效果图；其中图a为应用本发明之前的网侧电流；图b为采用本发明后的网侧电流；Fig. 5 is a steady-state effect diagram; wherein Fig. a is the grid-side current before applying the present invention; Fig. b is the grid-side current after adopting the present invention;

图6为动态效果图。其中图a为应用本发明之前的网侧电流；图b为采用本发明后的网侧电流波形。Figure 6 is a dynamic effect diagram. Among them, figure a is the grid-side current before applying the present invention; figure b is the grid-side current waveform after adopting the present invention.

具体实施方式Detailed ways

以下将结合附图和具体实施例对本发明做进一步详细说明：The present invention will be described in further detail below in conjunction with accompanying drawing and specific embodiment:

实施例1：Example 1:

图1是三电平三相四线有源电力滤波器结构图，由双电容，三电平逆变桥，两级LC输出滤波器组成。其工作原理是，根据参考电流信号I_ref，计算出三电平逆变桥的控制开关状态，使得注入电网的电流I_z能跟踪I_ref的变化，达到谐波滤波的目的。Figure 1 is a structural diagram of a three-level three-phase four-wire active power filter, which consists of dual capacitors, a three-level inverter bridge, and a two-stage LC output filter. Its working principle is to calculate the control switch state of the three-level inverter bridge according to the reference current signal I_ref , so that the current I_z injected into the grid can track the change of I_ref to achieve the purpose of harmonic filtering.

图2是参考电流信号I_ref检测原理图，I_ref由3个部分组成：负载谐波电流，用于稳定电容电压的有功电流，和用于维持两电容电压平衡的直流电流。负载谐波用瞬时无功功率理论检出；有功电流用两电容上的电压之和，与参考值U_DCref比较，然后进行PI调节，最后乘以与电压同步变化的sinωt检出；Figure 2 is a schematic diagram of the reference current signal I_ref detection. I_ref consists of three parts: load harmonic current, active current used to stabilize the capacitor voltage, and DC current used to maintain the balance of the two capacitor voltages. The load harmonic is detected by the instantaneous reactive power theory; the active current is detected by the sum of the voltages on the two capacitors, compared with the reference value U_DCref , then PI adjustment, and finally multiplied by sinωt that changes synchronously with the voltage;

第一PI控制的参数为：比例系数取0.01，积分系数取1，第二PI控制的参数为：比例系数取0.1，积分系数取100。The parameters of the first PI control are: the proportional coefficient is 0.01, and the integral coefficient is 1; the parameters of the second PI control are: the proportional coefficient is 0.1, and the integral coefficient is 100.

直流电流用上下两电容上的电压差，然后进行PI调节，最后平均分配到三相检出。The DC current uses the voltage difference between the upper and lower capacitors, and then performs PI adjustment, and finally distributes it to the three-phase detection on average.

图3是预测控制流程图。首先读取逆变器输出电压U_inv，电网电压U_S，输出滤波器上的电流I_inv、I_L、I_C1、I_C2，逆变器直流侧两电容电压U_CD1、U_CD2，和参考电流信号I_ref。本发明采用分相控制，如果上述信号(除了U_CD1、U_CD2以外)均取自于A相，则控制输出针对于A相，如果取自于B相或者C相，则控制输出也相应针对于B向或者C相。Figure 3 is a flow chart of predictive control. First read the inverter output voltage U_inv , the grid voltage U_S , the currents I_inv , I_L , I_C1 , I_C2 on the output filter, the voltages U_CD1 , U_CD2 of the two capacitors on the DC side of the inverter, and the reference current signal I_ref . The present invention adopts phase-splitting control. If the above-mentioned signals (except U_CD1 and U_CD2 ) are taken from phase A, the control output is aimed at phase A. If it is taken from phase B or phase C, the control output is also aimed at In B direction or C phase.

然后计算出下一时刻的开关时间，Then calculate the switching time at the next moment,

$T_{K+1}=(U_s+L_1\frac{I_{\mathrm{ref}}-I_{\mathrm{inv}}-I_{C1}-I_{C2}}{T}+L_2\frac{I_{\mathrm{ref}}-I_L-I_{C1}}{T})/U_{\mathrm{DC}1},$实际中T取0.0001s。$T_{K+1}=(u_{\mathrm{the\; s}}+L_1\frac{I_{\mathrm{ref}}-I_{\mathrm{inv}}-I_{C1}-I_{C2}}{T}+L_2\frac{I_{\mathrm{ref}}-I_L-I_{C1}}{T})/{\mathrm{<figure-callout\; label="u\; DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">u</figure-callout>}}_{\mathrm{DC}},$ In practice, T takes 0.0001s.

如果T_K+1＜0，则换一个模型计算，If T_K+1 <0, then change to another model for calculation,

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>K</span>K</span>}<span><span>+</span>+</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span><span><span>-</span>-</span><span><span>(</span>(</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>inv</span>inv</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>L</span>L</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>)</span>)</span><span><span>/</span>/</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>DC</span>DC</span>}\mathrm{<span><span>2</span>2</span>}}$

得到的T_K+1值表示下一周期，逆变器需要输出相应电平的时间：The obtained T_K+1 value indicates the time for the inverter to output the corresponding level in the next cycle:

T_K+1＞0，表示下一个周期内，应控制逆变器输出正电平T_K+1时间，输出0电平T-T_K+1时间；T_K+1 > 0, which means that in the next cycle, the inverter should be controlled to output positive level for T_K+1 time, andoutput 0 level for TT_K+1 time;

如果T_K+1＝0，则表示下一个控制周期内，逆变器的输出全为0；If T_K+1 = 0, it means that in the next control cycle, the output of the inverter is all 0;

如果T_K+1＜0，则表示下一个控制周期内，逆变器的输出负电平T_K+1时间，输出0电平T-T_K+1时间。If T_K+1 <0, it means that in the next control cycle, the inverter outputs negative level for T_K+1 time, andoutputs 0 level for TT_K+1 time.

最后根据电平分配策略控制开关器件通断。Finally, the on-off of the switching device is controlled according to the level distribution strategy.

以图4中的A相为例，首先检测A相的逆变器输出电压U_{inv_A}，电网电压U_{S_A}，输出滤波器上的电流I_{inv_A}、I_{L_A}、I_{C1_A}、I_{C2_A}，逆变器直流侧两电容电压U_CD1、U_CD2，和参考电流信号I_{ref_A}。设逆变器开关频率为10kHz，则在下一个控制周期，Taking phase A in Figure 4 as an example, first detect the inverter output voltage U_{inv_A} of phase A, the grid voltage U_{S_A} , the currents I_{inv_A} , I_{L_A} , I_{C1_A} , and I_{C2_A} on the output filter, and the inverter DC Two side capacitor voltages U_CD1 , U_CD2 , and a reference current signal I_{ref_A} . Assuming that the switching frequency of the inverter is 10kHz, then in the next control cycle,

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>K</span>K</span>}<span><span>+</span>+</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span><span><span>(</span>(</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>S</span>S</span>}<span><span>\_</span>\_</span>\mathrm{<span><span>A</span>A</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}<span><span>\_</span>\_</span>\mathrm{<span><span>A</span>A</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>inv</span>inv</span>}<span><span>\_</span>\_</span>\mathrm{<span><span>A</span>A</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span><figure-callout\; label="I\; C"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">I</figure-callout></span><figure-callout\; label="I\; C"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}"></figure-callout>}}_{\mathrm{<span><span></span></span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}<span><span>\_</span>\_</span>\mathrm{<span><span>A</span>A</span>}}}{{\mathrm{<span><span>10</span>10</span>}}^{<span><span>-</span>-</span>\mathrm{<span><span>4</span>4</span>}}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}<span><span>\_</span>\_</span>\mathrm{<span><span>A</span>A</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>L</span>L</span>}<span><span>\_</span>\_</span>\mathrm{<span><span>A</span>A</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span><figure-callout\; label="I\; C"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">I</figure-callout></span><figure-callout\; label="I\; C"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}"></figure-callout>}}_{\mathrm{<span><span></span></span>}}}{{\mathrm{<span><span>10</span>10</span>}}^{<span><span>-</span>-</span>\mathrm{<span><span>4</span>4</span>}}}<span><span>)</span>)</span><span><span>/</span>/</span>{\mathrm{<span><span>U</span><figure-callout\; label="u\; DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; label="u\; DC"\; filenames="HDA0000154163810000021.png"\; state="\{\{state\}\}"></figure-callout>}}_{\mathrm{<span><span></span></span>}}$

假设通过计算后，T_K+1＞0，并且在上一时刻结束的时候，A相输出正电平，则触发VT1、VT2导通T_K+1时间，然后关断VT1并触发VT2、VT3导通(0.0001-T_K+1)时间。(从VT1、VT2导通变化到VT2、VT3导通，可以使得逆变器输出电平由Udc1变化到0，如果是VT3、VT4导通则是由Udc1变化到-Udc2，电压变化大，会引起较大的du/dt)。Assuming that after the calculation, T_K+1 > 0, and at the end of the previous moment, the A-phase outputs a positive level, then trigger VT1, VT2 to conduct for T_K+1 time, then turn off VT1 and trigger VT2, VT3 Turn-on (0.0001-T_K+1 ) time. (The change from VT1, VT2 conduction to VT2, VT3 conduction can make the output level of the inverter change from Udc1 to 0. If VT3 and VT4 are conduction, it will change from Udc1 to -Udc2. If the voltage changes greatly, it will cause a larger du/dt).

假设通过计算后，T_K+1＝0，并且上一时刻结束的时候，A项输出正电平，则关断VT1、VT4，并触发VT2、VT3导通0.0001s的时间。Assuming that after the calculation, T_K+1 = 0, and at the end of the last moment, item A outputs a positive level, then turn off VT1 and VT4, and trigger VT2 and VT3 to turn on for 0.0001s.

B相和C相的情况类似。The situation of phase B and phase C is similar.

然后转入下一个控制周期的计算。Then turn to the calculation of the next control cycle.

直流侧两电容分别取值1000μF。第一级LC滤波器取电感1.8mH，电容5.2uF，第二级LC滤波器取电感0.5mH，电容2.2uF。The values of the two capacitors on the DC side are 1000μF respectively. The first-stage LC filter takes an inductor of 1.8mH and a capacitor of 5.2uF, and the second-stage LC filter takes an inductor of 0.5mH and a capacitor of 2.2uF.

图5为本发明的稳态仿真效果图，在稳态时，电网电流畸变率从57.02％下降到3.84％。图6为本发明的动态仿真效果图，0.3s时，负荷电流突然增大，经过大约2个周波，在0.34s时，系统达到新的稳定状态，响应速度很快。Fig. 5 is a steady-state simulation effect diagram of the present invention. In a steady state, the grid current distortion rate drops from 57.02% to 3.84%. Fig. 6 is a dynamic simulation effect diagram of the present invention. At 0.3s, the load current increases suddenly. After about 2 cycles, at 0.34s, the system reaches a new stable state, and the response speed is very fast.

Claims (3)

Translated fromChinese

1.一种三相四线有源滤波器开关信号预测控制方法，所述的三相四线有源滤波器由双电容、三电平逆变桥和两级LC输出滤波器组成；双电容为第一电容和第二电容组成的串联支路；第一电容与第二电容的连接点接三相四线电网的中线；双电容与三电平逆变桥的三个桥臂并联，三电平逆变桥的输出端经两级LC输出滤波器与电网连接；两级LC输出滤波器为前级LC输出滤波器和后级LC输出滤波器；1. A three-phase four-wire active filter switching signal predictive control method, the three-phase four-wire active filter is made up of a double capacitor, a three-level inverter bridge and a two-stage LC output filter; the double capacitor It is a series branch composed of the first capacitor and the second capacitor; the connection point of the first capacitor and the second capacitor is connected to the neutral line of the three-phase four-wire grid; the double capacitor is connected in parallel with the three bridge arms of the three-level inverter bridge, and the three The output end of the level inverter bridge is connected to the power grid through a two-stage LC output filter; the two-stage LC output filter is a pre-stage LC output filter and a post-stage LC output filter;其特征在于，对A、B、C三相采用分相控制，包括以下步骤：It is characterized in that phase separation control is adopted for the three phases A, B and C, including the following steps:步骤1：采集信号，并计算参考电流信号I_ref：Step 1: Collect the signal and calculate the reference current signal I_ref :所采集的信号包括三电平逆变桥的输出电压U_inv，电网电压U_S，前级LC输出滤波器中电感上的电流I_inv、后级LC输出滤波器中电感上的电流I_L、前级LC输出滤波器中电容输出的电流I_C1、后级LC输出滤波器中电容输出的电流I_C2，第一电容电压U_CD1和第二电容电压U_CD2；The collected signals include the output voltage U_inv of the three-level inverter bridge, the grid voltage U_S , the current I_inv of the inductor in the pre-stage LC output filter, the current I_L of the inductor in the post-stage LC output filter, The current I_C1 output by the capacitor in the pre-stage LC output filter, the current I_C2 output by the capacitor in the post-stage LC output filter, the first capacitor voltage U_CD1 and the second capacitor voltage U_CD2 ;参考电流信号的计算公式为I_ref=I_pref*sinωt+I_dc-pref/3+I_h；The calculation formula of the reference current signal is I_ref =I_pref *sinωt+I_dc-pref /3+I_h ;其中：in:I_h为负载谐波电流，通过对负载电流进行同步变换得到；I_pref为U_CD1+U_CD2-U_DCref经第一PI控制器后的输出量；其中U_DCref为电容电压参考值；I_h is the load harmonic current, which is obtained by synchronously transforming the load current; I_pref is the output of U_CD1 + U_CD2 -_{U DCref} after passing through the first PI controller; where U_DCref is the capacitor voltage reference value;ω为电网电压基波频率；ω is the fundamental frequency of grid voltage;I_dc-pref为用于稳定电容电压的有功电流，I_dc-pref为U_CD1-U_CD2经第二PI控制器的输出量；I_dc-pref is the active current used to stabilize the capacitor voltage, and I_dc-pref is the output of U_CD1 -U_CD2 through the second PI controller;步骤2：计算下一控制周期的开关时间T_K+1；Step 2: Calculate the switching time T_K+1 of the next control cycle;$T_{K+1}=(U_s+L_1\frac{I_{\mathrm{ref}}-I_{\mathrm{inv}}-I_{C1}-I_{C2}}{T}+L_2\frac{I_{\mathrm{ref}}-I_L-I_{C1}}{T})/U_{\mathrm{CD}1};$其中T为控制周期；L₁、L₂分别为滤波器的前级、后级的电感值；$T_{K+1}=(u_{\mathrm{the\; s}}+L_1\frac{I_{\mathrm{ref}}-I_{\mathrm{inv}}-I_{C1}-I_{C2}}{T}+L_2\frac{I_{\mathrm{ref}}-I_L-I_{C1}}{T})/u_{\mathrm{cd}1};$ Where T is the control cycle; L₁ and L₂ are the inductance values of the front and rear stages of the filter respectively;判断T_K+1<0是否成立，如果成立，按下式更新T_K+1，否则保持T_K+1不变：Determine whether T_K+1 <0 is true, if true, update T_K+1 according to the formula, otherwise keep T_K+1 unchanged:${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>K</span>K</span>}<span><span>+</span>+</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span><span><span>(</span>(</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>1</span>1</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>inv</span>inv</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>2</span>2</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>+</span>+</span>{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>2</span>2</span>}}\frac{{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>ref</span>ref</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>L</span>L</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>C</span>C</span>}\mathrm{<span><span>1</span>1</span>}}}{\mathrm{<span><span>T</span>T</span>}}<span><span>)</span>)</span><span><span>/</span>/</span>{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>CD</span>cd</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>;</span>;</span>$步骤3：根据T_K+1控制三电平逆变桥中的每相的开关器件。Step 3: Control the switching devices of each phase in the three-level inverter bridge according to T_K+1 .2.根据权利要求1所述的三相四线有源滤波器开关信号预测控制方法，其特征在于，对于最终得到的T_K+1，如果T_K+1>0，表示下一个周期内，应控制逆变器输出正电平T_K+1时间，输出0电平T-T_K+1时间；2. The three-phase four-wire active filter switching signal predictive control method according to claim 1 is characterized in that, for the finally obtained T_K+1 , if T_K+1 >0, it means that in the next cycle, The inverter should be controlled to output positive level for T_K+1 time, and output 0 level for TT_K+1 time;如果T_K+1=0，则表示下一个控制周期内，逆变器的输出全为0；If T_K+1 =0, it means that in the next control cycle, the output of the inverter is all 0;如果T_K+1<0，则表示下一个控制周期内，逆变器的输出负电平T_K+1时间，输出0电平T-T_K+1时间。If T_K+1 <0, it means that in the next control cycle, the inverter will output negative level for T_K+1 time, and output 0 level for TT_K+1 time.3.根据权利要求1所述的三相四线有源滤波器开关信号预测控制方法，其特征在于，第一PI控制器参数为：比例系数取0.01，积分系数取1，第二PI控制的参数为：比例系数取0.1，积分系数取100。3. three-phase four-wire active filter switching signal predictive control method according to claim 1, is characterized in that, the first PI controller parameter is: proportional coefficient gets 0.01, integral coefficient gets 1, the second PI control The parameters are: the proportional coefficient is 0.1, and the integral coefficient is 100.

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