CN102611109B

CN102611109B - Method for controlling LC (inductance and capacitance) hybrid active power filter with two switch arms

Info

Publication number: CN102611109B
Application number: CN2012100669524A
Authority: CN
Inventors: 罗安; 马伏军; 孙运宾; 何志兴; 刘雷
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2012-03-14
Filing date: 2012-03-14
Publication date: 2013-11-06
Anticipated expiration: 2032-03-14
Also published as: CN102611109A

Abstract

The invention discloses a method for controlling an LC (inductance and capacitance) hybrid active power filter with two switch arms. By the aid of the method, voltage of a direct-current side is stabilized by means of PI (proportion integration), a deadbeat control method based on an inverter mathematical switch module is adopted for an inner current loop control, quick deadbeat tracking of harmonic current can be carried out, and dynamic balance of capacitance voltage is maintained by a voltage-sharing control method in order to keep the balance of the balance of the capacitance voltage on the direct-current side. Compared with a common indirect control method, the method for controlling the LC hybrid active power filter with the two switch arms has the advantages of high control precision and fine dynamic performance, and a compensation performance of a system is greatly improved.

Description

A control method of LC type hybrid active power filter with two switching arms

技术领域 technical field

本发明涉及适用于中高压系统的混合有源电力滤波器，特别是一种转二开关臂的LC式混合有源电力滤波器的控制方法。The invention relates to a hybrid active power filter suitable for medium and high voltage systems, in particular to a control method for an LC type hybrid active power filter with two switching arms.

背景技术 Background technique

在工业应用领域，在某些中压应用场合，如风机、电磁搅拌等容量达到数百千瓦的交流传动系统，并不需要快速的动态响应和回馈制动，一般直接使用三相不控整流做前级电路，其在效率上和实用性上比PWM整流器更具优势。然而三相不控整流器会对电网注入大量的谐波，给电力系统中的发电、输电和变电设备的运行带来严重危害，严重影响电力系统的安全可靠运行。In the field of industrial applications, in some medium-voltage applications, such as fans, electromagnetic stirring and other AC drive systems with a capacity of hundreds of kilowatts, fast dynamic response and regenerative braking are not required. Generally, three-phase uncontrolled rectification is used directly. The pre-stage circuit has more advantages than the PWM rectifier in terms of efficiency and practicability. However, the three-phase uncontrolled rectifier will inject a large number of harmonics into the power grid, which will bring serious harm to the operation of power generation, transmission and transformation equipment in the power system, and seriously affect the safe and reliable operation of the power system.

针对上述的交流传动负荷产生的谐波等问题，常用的方法就是安装LC无源滤波器(passive power filter，PPF)，进行某些特定次谐波的补偿，并补偿一定的无功。随着电力电子技术的发展，有源滤波器(active power filter，APF)被用来对负载谐波进行动态治理。但是在中高压场合，APF采用多重化技术、变流器多电平技术，装置复杂，成本高，可靠性不高。为此，有学者提出混合型有源滤波器(hybrid active power filter，HAPF)的概念，综合无源和有源滤波器的优点，有源滤波器的容量大大降低。典型结构有无源和有源滤波器并联，有源滤波器通过降压变压器并网；有源滤波器通过变压器耦合之后与旁路电感并联，然后与电容或者LC滤波器串联并网；有学者提出在耦合变压器一边并联基波谐振支路，进一步减小有源滤波器容量。前面所述的混合型有源滤波器都有降压变压器，体积庞大，成本优势不明显。为此，日本学者赤木泰文提出了一种LC式混合有源滤波器(LC-HAPF)，三相三电平逆变器通过LC无源滤波器接入电网，有源部分可以向电网注入谐波电流用以补偿负载电流中的谐波分量。由于LC滤波器的电容可以承担大部分的电网基波电压，在不增设降压变压器的情况下，同样可以大大减小有源部分的容量，装置成本大大降低。For the above-mentioned harmonics and other problems generated by the AC drive load, a common method is to install an LC passive power filter (PPF) to compensate certain harmonics and compensate certain reactive power. With the development of power electronics technology, active power filter (APF) is used to dynamically control load harmonics. However, in medium and high voltage applications, APF adopts multiple technology and converter multi-level technology, the device is complicated, the cost is high, and the reliability is not high. For this reason, some scholars have proposed the concept of hybrid active power filter (HAPF), which combines the advantages of passive and active filters, and the capacity of active filters is greatly reduced. The typical structure has passive and active filters connected in parallel, and the active filter is connected to the grid through a step-down transformer; the active filter is connected in parallel with the bypass inductor after being coupled by the transformer, and then connected in series with the capacitor or LC filter; some scholars It is proposed to connect the fundamental resonant branch in parallel with the coupling transformer to further reduce the capacity of the active filter. The hybrid active filters mentioned above all have step-down transformers, which are bulky and have no obvious cost advantage. To this end, Japanese scholar Akagi Taifumi proposed a LC-type hybrid active filter (LC-HAPF). The three-phase three-level inverter is connected to the grid through the LC passive filter, and the active part can inject harmonics into the grid The wave current is used to compensate the harmonic component in the load current. Since the capacitance of the LC filter can bear most of the fundamental wave voltage of the power grid, the capacity of the active part can also be greatly reduced without adding a step-down transformer, and the device cost is greatly reduced.

现有的参考文献显示，LC-HAPF一般采用一种间接控制方法，即将逆变器输出电压控制成u_c＝K*i_Sh或者u_c＝K*i_Lh，由于没有采用逆变器输出电流的闭环控制，其谐波电流补偿能力差，动态跟踪性能不佳。The existing references show that LC-HAPF generally adopts an indirect control method, that is, the inverter output voltage is controlled to u _c =K*i _Sh or u _c =K*i _Lh , since the inverter output current is not used closed-loop control, its harmonic current compensation ability is poor, and its dynamic tracking performance is not good.

发明内容 Contents of the invention

本发明所要解决的技术问题是，针对现有技术不足，提供一种二开关臂的LC式混合有源电力滤波器的控制方法，增强谐波电流补偿能力，改善动态跟踪性能，提高控制精度和系统的补偿性能。The technical problem to be solved by the present invention is to provide a control method for an LC-type hybrid active power filter with two switching arms to enhance the harmonic current compensation capability, improve dynamic tracking performance, and improve control accuracy and Compensation performance of the system.

为解决上述技术问题，本发明所采用的技术方案是：一种二开关臂的LC式混合有源电力滤波器的控制方法，包括基于三相二臂逆变器的LC式混合型有源电力滤波器，基于三相二臂逆变器的LC式混合型有源电力滤波器包括LC无源滤波器、基于三相二臂的三电平逆变器，基于三相二臂的三电平逆变器通过LC无源滤波器并联接入电网和负载之间；基于三相二臂的三电平逆变器包括两个并联的三电平开关臂、一个由至少两个电容串联组成的电容支路，电容支路与三电平开关臂并联，电容支路为基于三相二臂逆变器的LC式混合型有源电力滤波器的直流侧，两个三电平开关臂分别为A、B相，电容支路为C相；三电平开关臂由四个串联的开关管和两个串联的续流二极管组成，两个串联的续流二极管与中间两个开关管并联，该控制方法的具体步骤如下：In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a control method of an LC-type hybrid active power filter with two switching arms, including an LC-type hybrid active power filter based on a three-phase two-arm inverter. Filter, LC type hybrid active power filter based on three-phase two-arm inverter includes LC passive filter, three-level inverter based on three-phase two-arm, three-level inverter based on three-phase two-arm The inverter is connected in parallel between the power grid and the load through an LC passive filter; the three-level inverter based on three-phase two-arm includes two parallel-connected three-level switching arms, and a capacitor composed of at least two capacitors in series The capacitor branch is connected in parallel with the three-level switching arm. The capacitor branch is the DC side of the LC type hybrid active power filter based on the three-phase two-arm inverter. The two three-level switching arms are respectively Phase A and B, the capacitor branch is phase C; the three-level switch arm is composed of four series-connected switch tubes and two series-connected freewheeling diodes, and the two series-connected freewheeling diodes are connected in parallel with the middle two switch tubes. The specific steps of the control method are as follows:

1)电流信号的检测1) Detection of current signal

检测系统的三相负载电流i_La、i_Lb、i_Lc和基于三相二臂的三电平逆变器(以下简称三相逆变器)输出电流i_Ca、i_Cb、i_Cc，通过ip-iq算法的三二坐标变换，可以得到分别代表三相负载电流的无功分量i_q和有功分量i_d，以及代表逆变器三相输出电流的无功分量i_Cq，然后通过低通滤波器滤除交流成分后，可以得到各自分量的直流成分I_q、I_d、I_Cq。这样可以得到无功分量的校正量I_Cq，即为LC无源滤波器产生的无功分量。其中ip-iq算法的三二坐标变换公式为：Detect the three-phase load current i _La , i _Lb , i _Lc of the system and the output current i _Ca , i _Cb , i _Cc of the three-level inverter based on the three-phase two-arm (hereinafter referred to as the three-phase inverter), through ip The three-two coordinate transformation of the -iq algorithm can obtain the reactive component i _q and active component i _d representing the three-phase load current respectively, and the reactive component i _Cq representing the three-phase output current of the inverter, and then through low-pass filtering After filtering out the AC components, the DC components I _q , I _d , and I _Cq of the respective components can be obtained. In this way, the correction value I _Cq of the reactive component can be obtained, which is the reactive component generated by the LC passive filter. The three-two coordinate transformation formula of the ip-iq algorithm is:

${T T}_{abc abc / / dq dq} = = \sqrt{\frac{22}{33}} [\begin{matrix} sin sin wt wt & sin sin ((wt wt - - 22 π π / / 33)) & sin sin ((wt wt + + 22 π π / / 33)) \\ - - cos cos wt wt & - - cos cos ((wt wt - - 22 π π / / 33)) & - - cos cos ((wt wt + + 22 π π / / 33)) \end{matrix}] - - - - - - ((11))$

2)直流侧电压的PI控制2) PI control of DC side voltage

直流侧电压外环采用一个PI控制器，被用来实现直流侧电压外环的闭环调。其中PI控制器的公式为：The outer loop of the DC side voltage adopts a PI controller, which is used to realize the closed-loop regulation of the outer loop of the DC side voltage. The formula for the PI controller is:

${I I}_{out out} = = {K K}_{P P} {Δu Δ u}_{dc dc} + + \frac{{K K}_{P P}}{{T T}_{i i}} &Integral; &Integral; {Δu Δu}_{dc dc} dt dt - - - - - - ((22))$

其中Δu_dc＝U_ref-u_dc，U_ref直流侧电压参考值，u_dc为直流侧电压，u_dc＝V_c1+V_c2，V_C1、V_C2为直流侧两电容电压值，K_P为比例系数，T_i为积分系数，I_out为调节直流侧电压的有功校正量Where Δu _dc ＝U _ref -u _dc , U _ref DC side voltage reference value, u _dc is the DC side voltage, u _dc ＝V _c1 +V _c2 , V _C1 , V _C2 are the voltage values of the two capacitors on the DC side, K _P is Proportional coefficient, T _i is the integral coefficient, I _out is the active power correction amount for adjusting the DC side voltage

3)校正量叠加及其逆变换3) Superposition of correction amount and its inverse transformation

将无功和有功的校正量I_Cq、I_out分别和I_q、I_d叠加，可以得到系统无功和有功分量的参考量

然后ip-iq算法的二三坐标逆变换，可以得到三相逆变器A、B两相的基波电流成分i_af、i_bf，其中包含了调节直流侧电压的有功量和无源滤波器产生的无功量。其中ip-iq算法的二三坐标逆变换公式为：By superimposing the reactive and active correction quantities I _Cq and I _out with I _q and I _d respectively, the reference quantities of reactive and active components of the system can be obtained

Then the two-three coordinates inverse transformation of the ip-iq algorithm can obtain the fundamental current components i _af and i _bf of the two phases of the three-phase inverters A and B, which include the active energy for adjusting the DC side voltage and the passive filter generated reactive power. Among them, the inverse transformation formula of the two and three coordinates of the ip-iq algorithm is:

${T T}_{dq dq / / abc abc} = = \sqrt{\frac{22}{33}} [\begin{matrix} sin sin wt wt & - - cos cos wt wt \\ sin sin ((wt wt - - 22 π π / / 33)) & - - cos cos ((wt wt - - 22 π π / / 33)) \\ sin sin ((wt wt + + 22 π π / / 33)) & - - cos cos ((wt wt + + 22 π π / / 33)) \end{matrix}] - - - - - - ((33))$

4)求取逆变器的电流参考信号4) Obtain the current reference signal of the inverter

将A、B两相负载i_La、i_Lb分别减去i_af、i_bf，就可以得到三相逆变器两三电平开关臂的电流参考信号i_ar、i_br，包含了基波和谐波电流成分。By subtracting i _af and i _bf from the two-phase loads i _La and i _Lb of A and B respectively, the current reference signals i _ar and i _br of the two and three-level switching arms of the three-phase inverter can be obtained, including the fundamental wave and Harmonic current components.

5)直流侧电压的均压控制5) Voltage equalization control of DC side voltage

为了保证直流侧两电容电压的稳定和平衡，采用一种均压控制方法：检测直流侧两电容的电压，并作差可得(V_C1-V_C2)，然后将差值通过PI控制器处理后，可以得到三相逆变器的均压调节指令ΔI_out。In order to ensure the stability and balance of the voltage of the two capacitors on the DC side, a voltage equalization control method is adopted: detect the voltage of the two capacitors on the DC side, and make a difference to get (V _C1 -V _C2 ), and then process the difference through the PI controller After that, the voltage equalization adjustment command ΔI _out of the three-phase inverter can be obtained.

6)求取逆变器的总电流参考信号6) Obtain the total current reference signal of the inverter

将三相逆变器的均压调节指令ΔI_out分别与i_ar、i_br相加，就可以得到三相逆变器的两三电平开关臂的总电流参考信号 The total current reference signal of the two and three level switching arms of the three-phase inverter can be obtained by adding the voltage equalization adjustment command ΔI _out of the three-phase inverter to i _ar and i _br respectively

$\{\begin{matrix} {i i}_{a a}^{* *} = = {i i}_{ar ar} + + {ΔI ΔI}_{out out} \\ {i i}_{b b}^{* *} = = {i i}_{br br} + + {ΔI ΔI}_{out out} \end{matrix} - - - - - - ((44))$

7)电流内环的无差拍控制7) Deadbeat control of the current inner loop

根据图2所示的主电路结构图，有如下电压电流关系：According to the main circuit structure diagram shown in Figure 2, there is the following voltage-current relationship:

$\{\begin{matrix} {v v}_{Sa Sa} - - {v v}_{Sc sc} = = L L \frac{{di di}_{Ca Ca}}{dt dt} + + {u u}_{Ca Ca} + + {v v}_{ac ac} - - L L \frac{{di di}_{Cc Cc}}{dt dt} - - {u u}_{Cc Cc} \\ {v v}_{Sb Sb} - - {v v}_{Sc sc} = = L L \frac{{di di}_{Cb Cb}}{dt dt} + + {u u}_{Cb Cb} + + {v v}_{bc bc} - - L L \frac{{di di}_{Cc Cc}}{dt dt} - - {u u}_{Cc Cc} \end{matrix} - - - - - - ((55))$

其中v_Sa，v_Sb，v_Sc分别是交流电压，C为LC无源滤波器的电容值，v_ac，v_bc为三相逆变器的交流侧输出线电压，i_Ca，i_Cb，i_Cc为三相逆变器的交流侧输出电流，u_Ca，u_Cb，u_Cc为LC无源滤波器中三相电容电压值。假设稳态时，三电平逆变器输出的三相电压是平衡的，且没有中性线，则瞬时的三相电压和线电流之和为零，可以得到：Where v _Sa , v _Sb , v _Sc are the AC voltages respectively, C is the capacitance value of the LC passive filter, v _ac , v _bc are the output line voltages of the AC side of the three-phase inverter, i _Ca , i _Cb , i _Cc is the AC side output current of the three-phase inverter, u _Ca , u _Cb , and u _Cc are the voltage values of the three-phase capacitors in the LC passive filter. Assuming that in the steady state, the three-phase voltage output by the three-level inverter is balanced and there is no neutral line, then the sum of the instantaneous three-phase voltage and the line current is zero, and it can be obtained:

$\{\begin{matrix} {i i}_{Cc Cc} = = - - (({i i}_{Ca Ca} + + {i i}_{Cb Cb})) \\ {u u}_{Cc Cc} = = - - (({u u}_{Ca Ca} + + {u u}_{Cb Cb})) \end{matrix} - - - - - - ((66))$

联合(5)式和(6)式，在稳定状态下，根据平均开关原理，三相逆变器交流端电压的平均值能够表达如下：Combining Equation (5) and Equation (6), in a steady state, according to the average switching principle, the average value of the AC terminal voltage of the three-phase inverter can be expressed as follows:

$[\begin{matrix} {v v}_{ac ac} \\ {v v}_{bc bc} \end{matrix}] = = [\begin{matrix} {d d}_{a a} \frac{{u u}_{dc dc}}{22} \\ {d d}_{b b} \frac{{u u}_{dc dc}}{22} \end{matrix}] = = [\begin{matrix} {v v}_{Sac Sac} - - L L \frac{d d}{dt dt} (({22 i i}_{Ca Ca} + + {i i}_{Cb Cb})) - - (({22 u u}_{Ca Ca} + + {u u}_{Cb Cb})) \\ {V V}_{Sbc Sbc} - - L L \frac{d d}{dt dt} (({i i}_{Ca Ca} + + {22 i i}_{Cb Cb})) - - (({u u}_{Ca Ca} + + {22 u u}_{Cb Cb})) \end{matrix}] - - - - - - ((77))$

其中，d_a和d_b为占空比，且d_a和d_b∈[-1，1]；v_Sac和v_Sbc为电网侧线电压并满足以下表达：Among them, d _a and d _b are duty cycles, and d _a and d _b ∈ [-1, 1]; v _Sac and v _Sbc are grid side-line voltages and satisfy the following expressions:

$\{\begin{matrix} {v v}_{Sac Sac} = = {v v}_{Sa Sa} - - {v v}_{Sc sc} = = \sqrt{33} U u sin sin ((wt wt - - \frac{π π}{66})) \\ {v v}_{Sbc Sbc} = = {v v}_{Sb Sb} - - {v v}_{Sc sc} = = \sqrt{33} U u sin sin ((wt wt - - \frac{π π}{22})) \end{matrix} - - - - - - ((88))$

根据式(7)和式(8)，占空比d_a和d_b可表达如下：According to formula (7) and formula (8), the duty cycle d _a and d _b can be expressed as follows:

$\{\begin{matrix} {d d}_{a a} = = \frac{22}{{u u}_{dc dc}} {v v}_{Sac Sac} - - \frac{44 L L}{{u u}_{dc dc}} \frac{{di di}_{Ca Ca}}{dt dt} - - \frac{22 L L}{{u u}_{dc dc}} \frac{{di di}_{Cb Cb}}{dt dt} - - \frac{22}{{u u}_{dc dc}} (({22 u u}_{Ca Ca} + + {u u}_{Cb Cb})) \\ {d d}_{b b} = = \frac{22}{{u u}_{dc dc}} {v v}_{Sbc Sbc} - - \frac{22 L L}{{u u}_{dc dc}} \frac{{di di}_{Ca Ca}}{dt dt} - - \frac{44 L L}{{u u}_{dc dc}} \frac{{di di}_{Cb Cb}}{dt dt} - - \frac{22}{{u u}_{dc dc}} (({u u}_{Ca Ca} + + 22 {u u}_{Cb Cb})) \end{matrix} - - - - - - ((99))$

将式(9)所示的占空比计算公式进一步离散化形式表示，并将(4)式表示的k时刻的总电流参考信号作为流过电感下一时刻的电流值代入公式，可得无差拍控制公式：The duty ratio calculation formula shown in formula (9) is further expressed in a discretized form, and the total current reference signal at time k represented by formula (4) is substituted into the formula as the current value flowing through the inductor at the next moment, we can get Beat control formula:

$\{\begin{matrix} {d d}_{a a} ((k k)) = = \frac{22}{{u u}_{dc dc}} {v v}_{Sac Sac} ((k k)) - - \frac{44 L L}{{u u}_{dc dc}} \frac{[[{i i}_{a a}^{* *} ((k k)) - - {i i}_{Ca Ca} ((k k))]]}{{T T}_{S S}} - - \frac{22 L L}{{u u}_{dc dc}} \frac{[[{i i}_{b b}^{* *} ((k k)) - - {i i}_{Cb Cb} ((k k))]]}{{T T}_{S S}} - - \frac{44}{{u u}_{dc dc}} {u u}_{Ca Ca} ((k k)) - - \frac{22}{{u u}_{dc dc}} {u u}_{Cb Cb} ((k k)) \\ {d d}_{b b} ((k k)) = = \frac{22}{{u u}_{dc dc}} {v v}_{Sbc Sbc} ((k k)) - - \frac{22 L L}{{u u}_{dc dc}} \frac{[[{i i}_{a a}^{* *} ((k k)) - - {i i}_{Ca Ca} ((k k))]]}{{T T}_{S S}} - - \frac{44 L L}{{u u}_{dc dc}} \frac{[[{i i}_{b b}^{* *} ((k k)) - - {i i}_{Cb Cb} ((k k))]]}{{T T}_{S S}} - - \frac{22}{{u u}_{dc dc}} {u u}_{Ca Ca} ((k k)) - - \frac{44}{{u u}_{dc dc}} {u u}_{Cb Cb} ((k k)) \end{matrix} - - - - - - ((1010))$

上式中，T_S为控制周期。In the above formula, T _S is the control period.

8)根据上面的占空比计算公式，通过采用合适的PWM调制方法，驱动三相逆变器的两个三电平开关管可获得期望的电压电流量。8) According to the calculation formula of the duty ratio above, by adopting a suitable PWM modulation method, the desired voltage and current can be obtained by driving the two three-level switching tubes of the three-phase inverter.

本发明的技术效果在于：本发明采用一种电压电流的双环控制方法，直流侧电压采用PI控制可以进行电压的闭环调节维持直流侧电压的稳定，电流内环采用基于逆变器开关数学模型的无差拍控制方法，可以实现对逆变器输出电流的闭环控制；相对于一般的间接控制方法，本发明的控制方法控制精度高，动态性能好，大大提高了系统的补偿性能。The technical effect of the present invention is that: the present invention adopts a double-loop control method of voltage and current, the DC side voltage adopts PI control to perform closed-loop adjustment of the voltage to maintain the stability of the DC side voltage, and the current inner loop adopts a method based on the mathematical model of the inverter switch. The deadbeat control method can realize the closed-loop control of the inverter output current; compared with the general indirect control method, the control method of the present invention has high control precision and good dynamic performance, and greatly improves the compensation performance of the system.

附图说明 Description of drawings

图1为LC式混合型有源电力滤波器结构图；Figure 1 is a structural diagram of an LC-type hybrid active power filter;

图2为基于三相二臂逆变器的LC式混合型有源电力滤波器结构图；Figure 2 is a structural diagram of an LC-type hybrid active power filter based on a three-phase two-arm inverter;

图3为LC-HAPF的单相基波域和谐波域等效电路图；(a)基波等效电路；(b)谐波等效电路；Figure 3 is the equivalent circuit diagram of the single-phase fundamental wave domain and harmonic domain of LC-HAPF; (a) fundamental wave equivalent circuit; (b) harmonic equivalent circuit;

图4为本发明的控制框图；Fig. 4 is a control block diagram of the present invention;

其中：in:

1：LC无源滤波器；2：三相三电平逆变器；3：基于三相二臂的三电平逆变器。1: LC passive filter; 2: Three-phase three-level inverter; 3: Three-level inverter based on three-phase two-arm.

具体实施方式 Detailed ways

参见图1，图1为一般LC式混合型有源电力滤波器结构图。图中，输出滤波器采用单调谐LC无源滤波器1，一般谐振频率为五次或者七次，以滤除该次谐波电流。在这种结构中，三相三电平逆变器2通过LC无源滤波器接入电网，有源部分可以向电网注入谐波电流用以补偿负载电流中的谐波分量，并且提供基波有功和无功电流以补偿无功和保持直流侧电压的稳定。由于LC滤波器的电容可以承担大部分的电网基波电压，可以大大减小有源部分的容量，而且LC滤波器在开关频率处呈现高阻抗，系统无需设置单独的开关纹波滤波器。该结构能补偿固定的基波无功功率，然后逆变器输出的谐波电流经过LC时会受到不同程度的衰减。总体来说，该种结构利用无源滤波器的低成本优势，来承担大部分的电网基波电压，大大减小逆变器的耐压等级，进而减少系统的容量和成本。该种混合型有源滤波器可以应用于2kV、3kV及6kV等中高压场合。Refer to Fig. 1, Fig. 1 is the structural diagram of general LC type hybrid active power filter. In the figure, the output filter adopts a single-tuned LC passive filter 1, and the general resonant frequency is the fifth or seventh order to filter out the harmonic current of this order. In this structure, the three-phase three-level inverter 2 is connected to the grid through an LC passive filter, and the active part can inject harmonic current into the grid to compensate the harmonic component in the load current and provide fundamental Active and reactive currents are used to compensate reactive power and maintain the stability of the DC side voltage. Because the capacitance of the LC filter can bear most of the fundamental voltage of the power grid, the capacity of the active part can be greatly reduced, and the LC filter presents high impedance at the switching frequency, so the system does not need to set a separate switching ripple filter. This structure can compensate the fixed fundamental reactive power, and then the harmonic current output by the inverter will be attenuated to varying degrees when passing through the LC. Generally speaking, this structure takes advantage of the low-cost advantages of passive filters to bear most of the fundamental voltage of the grid, greatly reducing the withstand voltage level of the inverter, thereby reducing the capacity and cost of the system. This hybrid active filter can be applied to medium and high voltage applications such as 2kV, 3kV and 6kV.

参见图2，图2为基于三相二臂逆变器的LC式混合型有源电力滤波器结构图。Referring to Fig. 2, Fig. 2 is a structural diagram of an LC-type hybrid active power filter based on a three-phase two-arm inverter.

本发明采用的结构为基于三相二臂的三电平逆变器的补偿结构，包括一个基于三相二臂的三电平逆变器3和三个输出LC滤波器1。输出LC无源滤波器1由电感L和电容C构成的三个单调谐滤波器组成。基于三相二臂的三电平逆变器3由A、B、C三相并联组成，A相三电平开关臂由上对开关管T_a1和T_a2，下对开关管T′_a1和T′_a2及两个续流二极管D_a1和D_a2构成；三相逆变器的B相三电平开关臂由上对开关管T_b1和T_b2，下对开关管T′_b1和T′_b2及两个续流二极管D_b1和D_b2构成；三相逆变器的C相臂由电容C₁和C₂组成。基于三相二臂的三电平逆变器3通过三个输出LC无源滤波器1连接到中高压电网。The structure adopted in the present invention is a compensation structure based on a three-phase two-arm three-level inverter, including a three-phase two-arm three-level inverter 3 and three output LC filters 1 . The output LC passive filter 1 consists of three single-tuned filters composed of inductor L and capacitor C. The three-level inverter 3 based on three-phase two-arm is composed of three phases A, B, and C connected in parallel. The three-level switch arm of phase A is composed of the upper pair of switch tubes T _a1 and T _a2 , and the lower pair of switch tubes T′ _a1 and T′ _a2 and two freewheeling diodes D _a1 and D _a2 constitute; the B-phase three-level switching arm of the three-phase inverter consists of the upper pair of switching tubes T _b1 and T _b2 , and the lower pair of switching tubes T′ _b1 and T′ _b2 and two freewheeling diodes D _b1 and D _b2 ; the C-phase arm of the three-phase inverter is composed of capacitors C ₁ and C ₂ . The three-level inverter 3 based on three-phase two-arm is connected to the medium and high voltage grid through three output LC passive filters 1 .

图中，v_Sa，v_Sb，v_Sc分别是交流电源电压，逆变器的交流端输出电流为i_Ca，i_Cb，i_Cc，C为LC无源滤波器中电容值，u_Ca，u_Cb，u_Cc为LC无源滤波器中三相电容电压值。三相交流系统的c相直接连接到两直流电容的中点。在每个桥臂中，三个有效的开关状态可以在交流电压侧产生三种电压。三种开关功能对应得各桥臂输出状态如下：In the figure, v _Sa , v _Sb , and v _Sc are the AC power supply voltage respectively, and the output current of the AC terminal of the inverter is i _Ca , i _Cb , i _Cc , C is the capacitor value in the LC passive filter, u _Ca , u _Cb and u _Cc are the voltage values of the three-phase capacitors in the LC passive filter. Phase C of the three-phase AC system is directly connected to the midpoint of the two DC capacitors. In each bridge arm, three active switching states can generate three voltages on the AC voltage side. The three switch functions correspond to the output status of each bridge arm as follows:

如果假设直流母线的电容电压是相等的，则交流端电压如下：If it is assumed that the capacitor voltages of the DC bus are equal, the AC terminal voltage is as follows:

$\{\begin{matrix} {v v}_{ac ac} = = {v v}_{ao ao} - - {v v}_{co co} = = {g g}_{a a} * * \frac{{u u}_{dc dc}}{22} \\ {v v}_{bc bc} = = {v v}_{bo the bo} - - {v v}_{co co} = = {g g}_{b b} * * \frac{{u u}_{dc dc}}{22} \\ {v v}_{ab ab} = = {v v}_{ao ao} - - {v v}_{bo the bo} = = (({g g}_{a a} - - {g g}_{b b})) * * \frac{{u u}_{dc dc}}{22} \end{matrix} - - - - - - ((1212))$

可见通过采用合适的控制方法来控制两个开关臂的开关管，每个开关臂会输出相应的电压。根据图2所示的主电路，有如下电压电流关系：It can be seen that by using a suitable control method to control the switching tubes of the two switching arms, each switching arm will output a corresponding voltage. According to the main circuit shown in Figure 2, there is the following voltage-current relationship:

$\{\begin{matrix} {v v}_{Sa Sa} - - {v v}_{Sc sc} = = L L \frac{{di di}_{Ca Ca}}{dt dt} + + {u u}_{Ca Ca} + + {v v}_{ac ac} - - L L \frac{{di di}_{Cc Cc}}{dt dt} - - {u u}_{Cc Cc} \\ {v v}_{Sb Sb} - - {v v}_{Sc sc} = = L L \frac{{di di}_{Cb Cb}}{dt dt} + + {u u}_{Cb Cb} + + {v v}_{bc bc} - - L L \frac{{di di}_{Cc Cc}}{dt dt} - - {u u}_{Cc Cc} \end{matrix} - - - - - - ((1313))$

本发明采用的结构只需要两个三电平开关臂和一组串联的电容组成一个逆变器，与普通的三电平逆变器比较，节省了一臂功率开关器件，但具有相同的补偿能力，可以减少器件数量，降低开关损耗。通过LC滤波器的电容可以承担大部分的电网基波电压，可以大大减小有源部分的容量。总的来说，该结构结合了三电平逆变器和LC式混合有源滤波器两者优点，可以实现中高压系统的谐波、无功补偿，并且能大大减少系统的成本和容量。The structure adopted in the present invention only needs two three-level switching arms and a group of capacitors connected in series to form an inverter. Compared with ordinary three-level inverters, it saves one arm of power switching devices, but has the same compensation capability, which can reduce the number of components and reduce switching losses. The capacitance of the LC filter can bear most of the fundamental voltage of the power grid, which can greatly reduce the capacity of the active part. Generally speaking, this structure combines the advantages of three-level inverter and LC type hybrid active filter, which can realize harmonic and reactive power compensation of medium and high voltage systems, and can greatly reduce the cost and capacity of the system.

参见图3，图3所示为LC-HAPF的单相基波和谐波等效电路。将非线性负载等效成一个线性阻抗Z_L和谐波电流源i_Lh，而有源逆变器只补偿谐波，通过闭环控制方法可以等效成一个受控谐波电流源，在基波处的阻抗为零。首先考虑基波等效电路如图3(a)，电网电压直接加在电网阻抗Z_Sf、无源滤波器阻抗Z_Ff和负载上，则由基尔霍夫定律，可得电网基波电流为：See Figure 3, Figure 3 shows the equivalent circuit of the single-phase fundamental and harmonics of LC-HAPF. The nonlinear load is equivalent to a linear impedance Z _L and a harmonic current source i _Lh , while the active inverter only compensates the harmonics, it can be equivalent to a controlled harmonic current source through the closed-loop control method, and the fundamental wave The impedance at is zero. First consider the equivalent circuit of the fundamental wave as shown in Figure 3(a). The grid voltage is directly added to the grid impedance Z _Sf , the passive filter impedance Z _Ff and the load. Then, according to Kirchhoff’s law, the grid fundamental current can be obtained as :

i_Sf＝U_Sf/[Z_Sf+Z_Ff*Z_L/(Z_Ff+Z_L)] (14)i _Sf ＝U _Sf /[Z _Sf +Z _Ff *Z _L /(Z _Ff +Z _L )] (14)

其中，有Z_Ff＝jwL+1/jwC，U_Sf为电网基波电压。由于电网阻抗一般很小，忽略时，则有，Among them, Z _Ff =jwL+1/jwC, U _Sf is the fundamental wave voltage of the grid. Since the grid impedance is generally very small, when neglected, there is,

i_Cf＝U_Sf/Z_Ff＝U_Sf/(jwL+1/jwC) (15)i _Cf ＝U _Sf /Z _Ff ＝U _Sf /(jwL+1/jwC) (15)

基波电流i_Cf全部为容性无功电流，可以根据负载产生的无功电流的大小，对无源滤波器参数进行适当设计来补偿一定的无功。The fundamental wave current i _Cf is all capacitive reactive current, and the passive filter parameters can be properly designed to compensate certain reactive power according to the magnitude of the reactive current generated by the load.

针对系统的单相谐波等效电路，从图3(b)中可知，只要通过采用合适的电流闭环控制方法来控制逆变器，使之输出电流完全补偿负载谐波电流，就可以使电网谐波电流值为0。则有：For the single-phase harmonic equivalent circuit of the system, it can be seen from Fig. 3(b) that as long as the inverter is controlled by a suitable current closed-loop control method so that the output current can fully compensate the load harmonic current, the power grid can be The harmonic current value is 0. Then there are:

i_C＝-i_Lh (16)i _C ＝-i _Lh (16)

参见图4，图4为本发明的控制框图。Referring to Fig. 4, Fig. 4 is a control block diagram of the present invention.

为了实现系统负载谐波电流的补偿，并维持系统安全可靠的运行，本发明提出了一种电压电流的双环控制方法。首先电压外环采用PI控制来进行稳压调节，电流内环采用基于逆变器开关模型的无差拍控制方法来实现两个三电平开关臂的快速调节，以及内环电流的无差、快速跟踪。由于直流侧是由两个电容串联在一起构成，如果控制上不合理或者没有配合好，则两直流侧电压不相等，这样会引起输出电流的偏差，甚至更大的电压不平衡，将会影响装置的补偿效果和安全可靠运行。为了维持两电容电压的平衡，保证补偿系统的正常稳定运行，采用了一种直流侧电压的均压控制方法，实现直流侧电容电压的动态平衡。系统的控制框图如图4所示，具体控制步骤如下：In order to realize the compensation of the system load harmonic current and maintain the safe and reliable operation of the system, the present invention proposes a double-loop control method of voltage and current. Firstly, the voltage outer loop adopts PI control to regulate the voltage, and the current inner loop adopts the deadbeat control method based on the inverter switching model to realize the rapid adjustment of the two three-level switching arms, and the inner loop current has no difference, fast track. Since the DC side is composed of two capacitors connected in series, if the control is unreasonable or not well coordinated, the voltages of the two DC sides will be unequal, which will cause the deviation of the output current, or even a greater voltage imbalance, which will affect the The compensation effect and safe and reliable operation of the device. In order to maintain the balance of the two capacitor voltages and ensure the normal and stable operation of the compensation system, a voltage equalization control method for the DC side voltage is adopted to realize the dynamic balance of the DC side capacitor voltage. The control block diagram of the system is shown in Figure 4, and the specific control steps are as follows:

a.电流信号的检测a. Current signal detection

整个控制系统的检测算法采用通用的ip-iq算法。首先检测系统的三相负载电流和三相逆变器输出电流，通过ip-iq算法的三二坐标变换，可以得到分别代表三相负载电流的无功分量i_q和有功分量i_d，以及代表三相逆变器三相输出电流的无功分量i_Cq，然后通过低通滤波器(lower pass filter，LPF)滤除交流成分后，可以得到各自分量的直流成分I_q、I_d、I_Cq。这样可以得到无功分量的校正量I_Cq，即为LC无源滤波器产生的无功分量。The detection algorithm of the whole control system adopts the common ip-iq algorithm. First, detect the three-phase load current of the system and the output current of the three-phase inverter. Through the three-two coordinate transformation of the ip-iq algorithm, the reactive component i _q and the active component i _d representing the three-phase load current can be obtained, and the representative After the reactive component i _Cq of the three-phase output current of the three-phase inverter is filtered out by a low pass filter (LPF), the DC components I _q , I _d , and I _Cq of the respective components can be obtained . In this way, the correction value I _Cq of the reactive component can be obtained, which is the reactive component generated by the LC passive filter.

b.直流侧电压的PI控制b. PI control of DC side voltage

为了维持直流侧电压的稳定并弥补功率开关管的损失，一个PI控制器被采用来实现直流侧电压外环的闭环调节：In order to maintain the stability of the DC side voltage and compensate for the loss of the power switch tube, a PI controller is adopted to realize the closed-loop regulation of the outer loop of the DC side voltage:

其中Δu_dc＝U_ref-u_dc，U_ref直流侧电压参考值，K_P为比例系数，T_i为积分系数。这样可以得到有功分量的校正量I_out。将I_Cq、I_out分别和I_q、I_d叠加，可以得到逆变器无功和有功分量的参考量

然后通过ip-iq算法的二三坐标逆变换，可以得到三相逆变器A、B两相的基波电流成分i_af、i_bf，其中包含了调节直流侧电压的有功量和无源滤波器产生的无功量。Where Δu _dc = U _ref −u _dc , U _ref is a reference value of the DC side voltage, K _P is a proportional coefficient, and T _i is an integral coefficient. In this way, the correction amount I _out of the active component can be obtained. By superimposing I _Cq , I _out with I _q , I _d respectively, the reference quantities of the reactive and active components of the inverter can be obtained

Then, through the inverse transformation of the two-three coordinates of the ip-iq algorithm, the fundamental current components i _af and i _bf of the two phases of the three-phase inverter A and B can be obtained, which include the active energy for adjusting the DC side voltage and passive filtering The amount of reactive power generated by the device.

c.直流侧电压的均压控制c. Voltage equalization control of DC side voltage

为了保证直流侧两电容电压的稳定和平衡，采用一种均压控制方法。首先检测直流侧两电容的电压，并作差可得差值(V_C1-V_C2)。然后将差值通过PI调节器处理后，可以得到三相逆变器的均压调节指令ΔI_out，之后分别与i_ar、i_br相加，就可以得到三相逆变器的两三电平开关臂的总电流参考信号 In order to ensure the stability and balance of the voltages of the two capacitors on the DC side, a voltage equalization control method is adopted. First, detect the voltages of the two capacitors on the DC side, and make a difference to obtain the difference (V _C1 -V _C2 ). Then, after the difference is processed by the PI regulator, the voltage equalization adjustment command ΔI _{out of} the three-phase inverter can be obtained, and then added to i _ar and i _br respectively to obtain the two and three levels of the three-phase inverter The total current reference signal of the switching arm

d.电流内环的无差拍控制d. Deadbeat control of the current inner loop

假设稳态时，三电平逆变器输出的三相电压是平衡的，且没有中性线，则瞬时的三相电压和线电流之和为零，可以得到：Assuming that in the steady state, the three-phase voltage output by the three-level inverter is balanced and there is no neutral line, the sum of the instantaneous three-phase voltage and the line current is zero, and it can be obtained:

联合(3)式和(9)式，在稳定状态下，根据平均开关原理，交流侧电压的平均值v_ac和v_bc能够表达如下：Combining equations (3) and (9), in a steady state, according to the principle of average switching, the average values of AC side voltage v _ac and v _bc can be expressed as follows:

$[\begin{matrix} {v v}_{ac ac} \\ {v v}_{bc bc} \end{matrix}] = = [\begin{matrix} {d d}_{a a} \frac{{u u}_{dc dc}}{22} \\ {d d}_{b b} {u u}_{} \frac{dc dc}{22} \end{matrix}] = = [\begin{matrix} {v v}_{Sac Sac} - - L L \frac{d d}{dt dt} (({22 i i}_{Ca Ca} + + {i i}_{Cb Cb})) - - (({22 u u}_{Ca Ca} + + {u u}_{Cb Cb})) \\ {V V}_{Sbc Sbc} - - L L \frac{d d}{dt dt} (({i i}_{Ca Ca} + + {22 i i}_{Cb Cb})) - - (({u u}_{Ca Ca} + + {22 u u}_{Cb Cb})) \end{matrix}] - - - - - - ((77))$

根据式(10)和式(11)，占空比d_a和d_b可表达如下：According to formula (10) and formula (11), the duty cycle d _a and d _b can be expressed as follows:

为了实现内环电流的快速无差跟踪，采用无差拍控制方法，将式(12)所示的占空比计算公式进一步离散化形式表示，并将(8)式表示的k时刻的总电流参考信号作为流过电感下一时刻的电流值代入公式。可得：In order to realize the rapid dead-beat tracking of the inner loop current, the dead-beat control method is adopted, and the duty cycle calculation formula shown in formula (12) is further expressed in a discretized form, and the total current at time k expressed in formula (8) is The reference signal is substituted into the formula as the current value flowing through the inductor at the next moment. Available:

上式中，T_S为控制周期。在线电压已定的情况，检测逆变器输出电流和无源滤波器的电容电压，可由式(13)得到占空比d_a和d_b。根据上面的占空比计算公式，通过采用合适的PWM调制方法，驱动三相逆变器的两个三电平开关管可获得期望的电压电流量。In the above formula, T _S is the control period. When the online voltage is fixed, the duty cycle d _a and d _b can be obtained by detecting the output current of the inverter and the capacitor voltage of the passive filter. According to the calculation formula of the duty ratio above, by adopting an appropriate PWM modulation method, the desired voltage and current can be obtained by driving the two three-level switching tubes of the three-phase inverter.

Claims

1. A control method for an LC type hybrid active power filter with two switching arms, including an LC type hybrid active power filter based on a three-phase two-arm inverter, and an LC type based on a three-phase two-arm inverter Type hybrid active power filter includes LC passive filter, three-level inverter based on three-phase two-arm, and three-level inverter based on three-phase two-arm is connected to the power grid in parallel through LC passive filter and the load; the three-level inverter based on three-phase two-arm includes two parallel-connected three-level switching arms, a capacitor branch composed of at least two capacitors connected in series, and the capacitor branch and the three-level switching arm Parallel connection, the capacitor branch is the DC side of the LC hybrid active power filter based on the three-phase two-arm inverter, the two three-level switching arms are A and B phases, and the capacitor branch is C-phase; The level switch arm is composed of four series-connected switch tubes and two series-connected freewheeling diodes, and the two series-connected freewheeling diodes are connected in parallel with the middle two switch tubes, and the method is characterized in that:

1) Detect current signal: detect the three-phase load current i _La , i _Lb , i _Lc and the output current i _Ca , i _Cb , i _Cc of the three-level inverter based on the three-phase two-arm, through the ip-iq algorithm Three-two coordinate transformation, get the reactive component i _q and active component i _d of the three-phase load current, and the reactive component i _Cq of the three-phase output current of the three-level inverter based on the three-phase two-arm, through the low-pass The AC component is filtered out by the filter to obtain the DC components I _q , I _d , and I _Cq of the respective components, so as to obtain the correction value of the reactive component I _Cq , which is the reactive component generated by the LC passive filter;

2) PI control of the DC side voltage: the PI controller is used to realize the closed-loop adjustment of the outer loop of the DC side voltage, and the active power correction value I _{out of} the DC side voltage is obtained;

3) Correction amount superposition and its inverse transformation: superimpose the reactive components I _Cq and I _q , and superimpose the correction quantities I _out and I _d of the active components to obtain the reference quantities of the reactive and active components Through the inverse transformation of the two-three coordinates of the ip-iq algorithm, the fundamental current components i _af and i _bf of the two-phase three-level inverter A and B based on the three-phase two-arm are obtained, which include the active power for adjusting the DC side voltage Quantity and reactive power produced by LC passive filter;

4) Obtain the current reference signal of the three-level inverter based on the three-phase two-arm: subtract i _af and i _bf from the two-phase loads i _La and i _Lb of A and B respectively, and obtain the three-level inverter based on the three-phase two-arm The current reference signals i _ar and i _br of the two and three level switching arms of the level inverter include fundamental and harmonic current components;

5) Voltage equalization control of the DC side voltage: A voltage equalization PI controller is used to process the voltage difference (V _C1 -V _C2 ) between the two capacitors on the DC side through the PI controller to obtain the voltage equalization adjustment command of the three-phase inverter △I _out , V _C1 and V _C2 are the voltage values of the two capacitors on the DC side respectively;

6) Obtain the total current reference signal of the three-level inverter based on the three-phase two-arm: the voltage equalization regulation command △I _out of the three-level inverter based on the three-phase two-arm respectively with i _ar , i _br Add up to get the total current reference signal of the two three-level switching arms of the three-level inverter based on the three-phase two-arm

7) According to the average switching principle, the average value of the AC terminal voltage of the three-level inverter based on the three-phase two-arm is obtained, so as to obtain the expressions of the two-phase duty ratios d _a and d _b of A and B:

\{\begin{matrix} {d d}_{a a} = = \frac{22}{{u u}_{dc dc}} {v v}_{Sac Sac} - - \frac{44 L L}{{u u}_{dc dc}} \frac{{di di}_{Ca Ca}}{dt dt} - - \frac{22 L L}{{u u}_{dc dc}} \frac{{di di}_{Cb Cb}}{dt dt} - - \frac{22}{{u u}_{dc dc}} (({22 u u}_{Ca Ca} + + {u u}_{Cb Cb})) \\ {d d}_{b b} = = \frac{22}{{u u}_{dc dc}} {v v}_{Sbc Sbc} - - \frac{22 L L}{{u u}_{dc dc}} \frac{{di di}_{Ca Ca}}{dt dt} - - \frac{44 L L}{{u u}_{dc dc}} \frac{{di di}_{Cb Cb}}{dt dt} - - \frac{22}{{u u}_{dc dc}} (({u u}_{Ca Ca} + + {22 u u}_{Cb Cb})) \end{matrix}

Among them: v _Sac and v _Sbc are grid side line voltages, d _a , d _b ∈ [-1,1], i _Ca , i _Cb are the AC side output current of the three-level inverter based on three-phase two-arm, u _Ca ,u _Cb is the voltage value of the three-phase capacitor in the LC passive filter, L is the inductance value of the LC passive filter, u _dc is the DC side voltage, u _dc =V _C1 +V _C2 ;

8) Further discretize the expressions of the duty cycle d _a and d _b in step 7), and the total current reference signal in step 6) As the current value flowing through the inductor at the next moment is substituted into the formula, the discrete expressions of the duty cycle d _a and d _b are obtained:

\{\begin{matrix} {d d}_{a a} ((k k)) = = \frac{22}{{u u}_{dc dc}} {v v}_{Sac Sac} ((k k)) - - \frac{44 L L}{{u u}_{dc dc}} \frac{[[{i i}_{a a}^{* *} ((k k)) - - {i i}_{Ca Ca} ((k k))]]}{{T T}_{S S}} - - \frac{22 L L}{{u u}_{dc dc}} \frac{[[{i i}_{b b}^{* *} ((k k)) - - {i i}_{Cb Cb} ((k k))]]}{{T T}_{S S}} - - \frac{44}{{u u}_{dc dc}} {u u}_{Ca Ca} ((k k)) - - \frac{22}{{u u}_{dc dc}} {u u}_{Cb Cb} ((k k)) \\ {d d}_{b b} ((k k)) = = \frac{22}{{u u}_{dc dc}} {v v}_{Sbc Sbc} ((k k)) - - \frac{22 L L}{{u u}_{dc dc}} \frac{[[{i i}_{a a}^{* *} ((k k)) - - {i i}_{Ca Ca} ((k k))]]}{{T T}_{S S}} - - \frac{44 L L}{{u u}_{dc dc}} \frac{[[{i i}_{b b}^{* *} ((k k)) - - {i i}_{Cb Cb} ((k k))]]}{{T T}_{S S}} - - \frac{22}{{u u}_{dc dc}} {u u}_{Ca Ca} ((k k)) - - \frac{44}{{u u}_{dc dc}} {u u}_{Cb Cb} ((k k)) \end{matrix},,

Among them: k represents the kth moment, T _S is the control cycle;

9) According to the discrete expression of the duty cycle in 8), by using the PWM modulation method, drive the two three-level switching tubes of the three-level inverter based on the three-phase two-arm to obtain the desired voltage and current.

2. The control method of the LC-type hybrid active power filter with two switching arms according to claim 1, characterized in that, in the step 1), the three-two coordinate transformation formula of the ip-iq algorithm is:

{T T}_{abc abc / / dq dq} = = \sqrt{\frac{22}{33}} [\begin{matrix} sin sin wt wt & sin sin ((wt wt - - 22 π π / / 33)) & sin sin ((wt wt + + 22 π π / / 33)) \\ - - cos cos wt wt & - - cos cos ((wt wt - - 22 π π / / 33)) & - - cos cos ((wt wt + + 22 π π / / 33)) \end{matrix}] . .

3. The control method of the LC-type hybrid active power filter with two switching arms according to claim 1, characterized in that, in the step 2), the formula of the PI controller is:

{I I}_{out out} = = {K K}_{p p} Δ Δ {u u}_{dc dc} + + \frac{{K K}_{P P}}{{T T}_{i i}} &Integral; &Integral; Δ Δ {u u}_{dc dc} dt dt,,

Among them: △u _dc =U _ref -u _dc , U _ref is the DC side voltage reference value, K _P is the proportional coefficient, T _i is the integral coefficient, and I _out is the active power correction amount for adjusting the DC side voltage.

4. The control method of the LC-type hybrid active power filter with two switching arms according to claim 1, characterized in that, in the step 3), the two-three coordinate inverse transformation formula of the ip-iq algorithm is:

{T T}_{dq dq / / abc abc} = = \sqrt{\frac{22}{33}} [\begin{matrix} sin sin wt wt & - - cos cos wt wt \\ sin sin ((wt wt - - 22 π π / / 33)) & - - cos cos ((wt wt - - 22 π π / / 33)) \\ sin sin ((wt wt + + 22 π π / / 33)) & - - cos cos ((wt wt + + 22 π π / / 33)) \end{matrix}] . .