CN103701130A

CN103701130A - Hysteresis control method of three-phase four-switch-type active filter

Info

Publication number: CN103701130A
Application number: CN201410024721.6A
Authority: CN
Inventors: 梅军; 郑建勇; 张宸宇; 郭邵卿; 周福举; 胡洛瑄
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2014-01-20
Filing date: 2014-01-20
Publication date: 2014-04-02
Anticipated expiration: 2034-01-20
Also published as: CN103701130B

Abstract

The invention discloses a current hysteresis control method suitable for a three-phase four-switch active filter. The hysteresis control algorithm of the three-phase four-switch active filter includes the following steps: ① Firstly, the three-phase reference command current of the active filter and the actual output three-phase compensation current value are transformed into α-β two-phase positive current by Park transformation. ②The error signal between the reference current transformed by Park and the actual output current is passed through the hysteresis comparator to obtain output signals d _α and d _β ; ③According to the three-phase four-switch active filter The corresponding switch state table is obtained from the topology structure, and the switching action function of the two bridge arms is obtained by combining the hysteresis comparison result and the switch state table to realize the hysteresis control of the three-phase four-switch active filter. The invention is simple and reliable, has good dynamic performance, and has good economic significance and market prospect.

Description

Hysteresis control method of three-phase four-switch active filter

技术领域technical field

本发明涉及一种有源滤波器，特别涉及一种三相四开关型有源滤波器的滞环控制方法。The invention relates to an active filter, in particular to a hysteresis control method of a three-phase four-switch active filter.

背景技术Background technique

随着电力电子装置的应用愈加广泛，分布式电源大量接入电网，电力系统的电能质量问题日趋严重，作为动态并联补偿装置，有源电力滤波器(activepowerfilter,APF)由于可以实时补偿系统谐波及无功，得到了广泛的研究及应用。APF发展至今，出现了多种不同形式的拓扑结构，比如单独型、多变流器混合型、有源滤波与无源滤波的混合型以及本发明所涉及的新型三相四开关混合型有源滤波器。With the increasingly widespread application of power electronic devices, a large number of distributed power sources are connected to the power grid, and the power quality problem of the power system is becoming more and more serious. As a dynamic parallel compensation device, the active power filter (APF) can compensate system harmonics in real time. And reactive power, has been extensively researched and applied. Since the development of APF, many different forms of topologies have appeared, such as single type, multi-converter hybrid type, active filter and passive filter hybrid type, and the new three-phase four-switch hybrid active filter.

由于APF长期在恶劣的工业现场运行，功率开关器件IGBT一直处于大功率高频率高温现场环境，所以功率开关器件可靠运行是保证APF稳定性的必要因素。一旦有IGBT发生过压或者过流击穿，目前一般处理情况是将APF设备退网等待检修。而随着三相四开关APF(three-phasefour-switchshuntAPF,TFSSAPF)的出现，当设备中有单相功率器件出现故障时，APF仍可通过改变其拓扑结构继续有效可靠地工作，这使得APF具有了一定的自愈能力，为APF有效工作增长了时间，也为APF故障后维修赢得了更多的时间。Since the APF has been operating in harsh industrial sites for a long time, and the power switching device IGBT has been in a high-power, high-frequency and high-temperature field environment, the reliable operation of the power switching device is a necessary factor to ensure the stability of the APF. Once there is an IGBT overvoltage or overcurrent breakdown, the current general processing situation is to withdraw the APF equipment from the network and wait for maintenance. With the emergence of three-phase four-switch APF (three-phase four-switch shuntAPF, TFSSAPF), when a single-phase power device in the equipment fails, the APF can continue to work effectively and reliably by changing its topology, which makes the APF have It has a certain self-healing ability, which increases the time for APF to work effectively, and also wins more time for APF maintenance after failure.

自从上世纪80年代以来，国内外学者对于常规的三相六开关APF进行了大量的研究，其调制控制算法已趋于完善，但是作为其容错拓扑三相四开关APF的调制控制策略却并没有得到深入的研究。所谓三相四开关APF是传统三相六开关APF故障重构后的容错电路拓扑形式，由于开关器件的减少，四开关APF具有降低成本和运行维护费用少的潜力，因此具有很重要的研究价值。Since the 1980s, scholars at home and abroad have done a lot of research on the conventional three-phase six-switch APF, and its modulation control algorithm has tended to be perfected, but the modulation control strategy for its fault-tolerant topology three-phase four-switch APF has not. be studied in depth. The so-called three-phase four-switch APF is a fault-tolerant circuit topology after the fault reconstruction of the traditional three-phase six-switch APF. Due to the reduction of switching devices, the four-switch APF has the potential to reduce costs and operation and maintenance costs, so it has very important research value .

作为有源滤波器的核心部分，电流控制直接影响着有源滤波器的补偿性能，为了实现电流的快速控制，传统的三相六开关有源滤波器目前常用的电流控制方案主要有滞环电流控制、脉宽调制（PWM）和空间矢量调制(SVM)。当APF发生单相断路故障，通过自身故障诊断自动切除已损的相，拓扑结构切为三相四开关。由于拓扑的变化，其电流控制方案也不再同于传统的三相六开关拓扑结构。本发明提出一种基于容错型有源滤波器的滞环控制新方法。该方法可有效地解决三相四开关APF直接连接电容中点一相输出不可直接控制的问题，适应能力强，系统动态响应优异，能较好地治理电网中的谐波。As the core part of the active filter, the current control directly affects the compensation performance of the active filter. In order to realize the rapid control of the current, the current control scheme commonly used in the traditional three-phase six-switch active filter mainly includes hysteresis current Control, Pulse Width Modulation (PWM) and Space Vector Modulation (SVM). When a single-phase open circuit fault occurs in the APF, the damaged phase is automatically removed through its own fault diagnosis, and the topology is cut into three-phase four-switch. Due to the change of topology, its current control scheme is no longer the same as the traditional three-phase six-switch topology. The invention proposes a new hysteresis control method based on fault-tolerant active filter. This method can effectively solve the problem that the three-phase four-switch APF is directly connected to the midpoint of the capacitor and the one-phase output cannot be directly controlled. It has strong adaptability, excellent system dynamic response, and can better control the harmonics in the power grid.

发明内容Contents of the invention

当APF发生单相断路故障时，通过自身故障诊断自动切除故障相，其拓扑切为三相四开关结构。由于拓扑结构的变化，其电流控制方法也不同于传统的三相六开关控制方法。本发明提出一种基于三相四开关容错型APF拓扑结构的新型电流滞环控制方法，在静止两相坐标系下分别对α-β轴进行滞环控制，从而实现了对abc三相电流的整体控制。When a single-phase open circuit fault occurs in the APF, the faulty phase is automatically cut off through its own fault diagnosis, and its topology is cut into a three-phase four-switch structure. Due to the change of topology, its current control method is also different from the traditional three-phase six-switch control method. The present invention proposes a new type of current hysteresis control method based on the three-phase four-switch fault-tolerant APF topological structure, and respectively performs hysteresis control on the α-β axis in the static two-phase coordinate system, thereby realizing the control of the abc three-phase current overall control.

本发明解决其技术问题所采用的技术方案包括以下步骤：The technical solution adopted by the present invention to solve its technical problems comprises the following steps:

首先将滤波器三相参考指令电流i^* _ca、i^* _cb、i^* _cc和实际输出的三相补偿电流i_ca、i_cb、i_cc通过Park变换，变换到α-β两相正交的坐标系上，得到i^* _cα、i^* _cβ和i_cα、i_cβ；First, the filter three-phase reference command current i ^* _ca , i ^* _cb , i ^* _cc and the actual output three-phase compensation current i _ca , i _cb , i _cc are transformed into α-β two-phase quadrature through Park transformation In the coordinate system, i ^* _cα , i ^* _cβ and i _cα , i _cβ are obtained;

将通过Park变换后的参考电流i^* _cα、i^* _cβ与实际输出电流i_cα、i_cβ之间的误差信号经过滞环比较器得到输出信号d_α和d_β；The error signal between the reference current i ^* _cα , i ^* _cβ after Park transformation and the actual output current i _cα , i _cβ passes through the hysteresis comparator to obtain output signals d _α and d _β ;

根据三相四开关型有源滤波器的拓扑结构得到其对应的开关状态表，结合滞环比较结果和开关状态表得到两个桥臂的开关动作函数，实现三相四开关有源滤波器的滞环控制。According to the topology structure of the three-phase four-switch active filter, the corresponding switch state table is obtained, and the switching action function of the two bridge arms is obtained by combining the hysteresis loop comparison result and the switch state table, so as to realize the three-phase four-switch active filter. hysteresis control.

下面结合附图对本发明进行进一步的解释说明：Below in conjunction with accompanying drawing, the present invention is further explained:

如图1所示，假设发现三相六开关有源滤波器出现c相IGBT开路故障，硬件电路产生驱动信号驱动交流接触器将故障相切除，并将故障相的输出端直接接到直流侧电容中点,即系统拓扑电路（如图2）切换到三相四开关状态（如图3）。当直流侧电压控制稳定且电容均压，即u_c1=u_c2=u_dc/2时，由于C相桥臂直接接在了直流侧电容的中点，所以能够直接控制的输出线电压只有u_ao、u_bo。每个开关状态如附图4所示，忽略了死区效应，假设每个桥臂上管和下管互补开通和关断，上管导通时开关函数值为1，下管导通时开关函数值为0。图4中S_a、S_b的开和关分别认为是1和0，根据TFSSAPF的四个开关状态可以写出As shown in Figure 1, assuming that the c-phase IGBT open circuit fault of the three-phase six-switch active filter is found, the hardware circuit generates a driving signal to drive the AC contactor to cut off the faulty phase, and the output terminal of the faulty phase is directly connected to the DC side capacitor The midpoint, that is, the system topology circuit (as shown in Figure 2) switches to the three-phase four-switch state (as shown in Figure 3). When the DC side voltage is controlled stably and the capacitors are balanced, that is, u _c1 = u _c2 = u _dc /2, since the C-phase bridge arm is directly connected to the midpoint of the DC side capacitor, the output line voltage that can be directly controlled is only u _ao , u _bo . The state of each switch is shown in Figure 4, ignoring the dead zone effect, assuming that the upper and lower switches of each bridge arm are complementary on and off, the switching function value is 1 when the upper switch is turned on, and the switch is switched on when the lower switch is turned on. The function value is 0. In Figure 4, the on and off of S _a and S _b are considered to be 1 and 0 respectively. According to the four switch states of TFSSAPF, it can be written

$[\begin{matrix} {u u}_{ao ao} \\ {u u}_{bo the bo} \end{matrix}] = = \frac{{u u}_{dc dc}}{22} [\begin{matrix} 22 {S S}_{a a} - - 11 \\ 22 {S S}_{b b} - - 11 \end{matrix}] - - - - - - ((11))$

将静止三相坐标系投影到α-β坐标下有Projecting the static three-phase coordinate system to α-β coordinates has

$U u = = {u u}_{α α} + + j j {u u}_{β β} = = \sqrt{\frac{22}{33}} (({u u}_{a a} + + {u u}_{b b} {e e}^{j j \frac{22}{33} π π} + + {u u}_{c c} {e e}^{j j \frac{22}{33} π π})) - - - - - - ((22))$

将式（2）写成矩阵形式Write formula (2) in matrix form

$[\begin{matrix} {u u}_{α α} \\ {u u}_{β β} \end{matrix}] = = {C C}_{abc abc - - αβ αβ} [\begin{matrix} {u u}_{ao ao} \\ {u u}_{bo the bo} \\ {u u}_{co co} \end{matrix}] - - - - - - ((33))$

式（3）中In formula (3)

${C C}_{abc abc - - αβ αβ} = = \sqrt{\frac{22}{33}} [\begin{matrix} 11 & - - 11 / / 22 & - - 11 / / 22 \\ 00 & \sqrt{33} / / 22 & - - \sqrt{33} / / 22 \end{matrix}] - - - - - - ((44))$

由于u_co输出一直为0，结合式(1)、式(3)有Since the output of u _co is always 0, combined with formula (1) and formula (3), we have

$[\begin{matrix} {u u}_{α α} \\ {u u}_{β β} \end{matrix}] = = \frac{{u u}_{dc dc}}{\sqrt{66}} [\begin{matrix} 11 & - - 11 / / 22 \\ 00 & \sqrt{33} / / 22 \end{matrix}] [\begin{matrix} 22 {S S}_{a a} - - 11 \\ 22 {S S}_{b b} - - 11 \end{matrix}] - - - - - - ((55))$

根据式(5)得到α-β坐标系下开关信号与电压空间矢量之间的对应关系，如下：According to formula (5), the corresponding relationship between the switch signal and the voltage space vector in the α-β coordinate system is obtained as follows:

由于新的APF拓扑结构不能单独控制c相输出电流，所以不能再使用独立的三个滞环比较器去分别控制三相电流。本发明提出一种三相四线制α-β坐标下的滞环控制方法，在两相正交坐标系下分别对α-β轴进行滞环控制，从而实现了对abc三相电流的整体控制，基本流程如图5所示。Since the new APF topology cannot control the c-phase output current alone, it is no longer possible to use three independent hysteresis comparators to control the three-phase current respectively. The present invention proposes a hysteresis control method under the α-β coordinates of the three-phase four-wire system, and performs hysteresis control on the α-β axes respectively under the two-phase orthogonal coordinate system, thereby realizing the overall control of the abc three-phase current Control, the basic process is shown in Figure 5.

结合上表和图5，以α轴来说明，当实际输出电流大于(小于)指令值时，d_α为-1(+1)，所以需要α轴输出一个负(正)电压去减小(增大)实际输出电流。所以结合开关信号与电压空间矢量之间的对应关系以及α-β坐标下的滞环输出状态d_α和d_β可以得到当前时刻的开关状态U_k，如下表所示：Combining the above table and Figure 5, using the α axis to illustrate, when the actual output current is greater (less than) the command value, d _α is -1 (+1), so the α axis needs to output a negative (positive) voltage to reduce ( increase) the actual output current. Therefore, combining the corresponding relationship between the switch signal and the voltage space vector and the hysteresis output states d _α and d _β under the α-β coordinates, the switch state U _k at the current moment can be obtained, as shown in the following table:

d_α d _α d_β d _β U_k _k S_a S _a S_b S _b -1-1 -1-1 U₀ U ₀ 00 00 -1-1 +1+1 U₁ U ₁ 00 11 +1+1 -1-1 U₂ U ₂ 11 00 +1+1 +1+1 U₃ U ₃ 11 11

基于α-β坐标下的滞环控制有效解决了三相四开关容错型APF拓扑结构直接连接电容中点一相输出不可直接控制的问题，使得APF具有一定的自愈能力，方法简单可靠，系统动态响应优异，使得为APF有效工作延长了时间，也为APF故障后的维修赢得了更多的时间，具有很好的经济意义和市场前景。The hysteresis control based on the α-β coordinates effectively solves the problem that the three-phase four-switch fault-tolerant APF topology directly connects the midpoint of the capacitor and the one-phase output cannot be directly controlled, so that the APF has a certain self-healing ability, the method is simple and reliable, and the system The excellent dynamic response prolongs the effective working time of the APF and wins more time for the maintenance of the APF after failure, which has good economic significance and market prospects.

附图说明Description of drawings

图1为容错型APF拓扑结构；Figure 1 is a fault-tolerant APF topology;

图2为APF正常状态拓扑结构；Figure 2 is the topology structure of APF in normal state;

图3为三相四开关型APF拓扑结构；Figure 3 is a three-phase four-switch APF topology;

图4为三相四开关型APF的开关状态；Fig. 4 is the switching state of the three-phase four-switch APF;

图5为α-β坐标下的滞环控制框图；Fig. 5 is the hysteresis control block diagram under α-β coordinate;

图6为接入三相四开关型APF的系统基本结构图；Figure 6 is a basic structural diagram of a system connected to a three-phase four-switch APF;

图7为采用α-β坐标下的滞环控制方法补偿后网侧电流波形。Fig. 7 is the grid-side current waveform after compensation using the hysteresis control method under α-β coordinates.

具体实施方式Detailed ways

图6是接入三相四开关有源滤波器的系统图，该系统包括两部分：APF主电路和测控电路。APF主电路通过串联电感与电网相连，功能是产生实际所需要的补偿电流，以补偿电网中的谐波和无功电流。测控电路的功能是检测电网侧的电压电流、负载侧的电流、APF补偿电流、直流侧电容电压、各个接触器的开关状态，完成对电路的保护，产生主电路IGBT的驱动信号。APF主电路中：QF1、QF2为空气开关；KM1、KM2、KM3和KM4为交流接触器；R1、R2、R3为缓冲电阻；R4、R5为放电电阻；C1、C2为直流母线电容；L为交流侧连接电感。测控电路部分主要有五部分组成：以DSP芯片为核心的主控电路、模拟量采集/AD转换电路、过零比较电路、过电压及过电流检测电路以及开关量输入/输出电路。Figure 6 is a system diagram for accessing a three-phase four-switch active filter. The system includes two parts: APF main circuit and measurement and control circuit. The APF main circuit is connected to the power grid through a series inductor, and its function is to generate the actual required compensation current to compensate the harmonic and reactive current in the power grid. The function of the measurement and control circuit is to detect the voltage and current on the grid side, the current on the load side, the APF compensation current, the capacitor voltage on the DC side, and the switching status of each contactor, complete the protection of the circuit, and generate the driving signal of the main circuit IGBT. In the APF main circuit: QF1 and QF2 are air switches; KM1, KM2, KM3 and KM4 are AC contactors; R1, R2 and R3 are buffer resistors; R4 and R5 are discharge resistors; C1 and C2 are DC bus capacitors; Connect the inductor to the AC side. The measurement and control circuit part mainly consists of five parts: main control circuit with DSP chip as the core, analog quantity acquisition/AD conversion circuit, zero-crossing comparison circuit, overvoltage and overcurrent detection circuit, and switching input/output circuit.

如图1，当有源滤波器出现某相IGBT开路故障，硬件电路产生驱动信号驱动交流接触器将故障相切除，并将故障相的输出端直接接到直流侧电容中点，由于新的APF拓扑结构不能单独控制故障相输出电流，所以不能再使用独立的三个滞环比较器去分别控制三相电流，控制算法也应从原来的适用于三相六开关有源滤波器的滞环控制算法切换为适用于三相四开关的新型滞环控制，算法包括以下步骤：As shown in Figure 1, when an IGBT open circuit fault occurs in a certain phase of the active filter, the hardware circuit generates a driving signal to drive the AC contactor to cut off the faulty phase, and the output terminal of the faulty phase is directly connected to the midpoint of the DC side capacitor. Due to the new APF The topology structure cannot control the output current of the fault phase alone, so three independent hysteresis comparators can no longer be used to control the three-phase currents respectively, and the control algorithm should also be changed from the original hysteresis control algorithm suitable for three-phase six-switch active filters Switching to a new type of hysteresis control suitable for three-phase four-switches, the algorithm includes the following steps:

1)首先将有源滤波器三相参考指令电流i^* _ca、i^* _cb、i^* _cc通过Park变换，变换到α-β两相正交的坐标系上，得到i^* _cα、i^* _cβ：1) First, the three-phase reference command current i ^* _ca , i ^* _cb , and i ^* _cc of the active filter are transformed into the α-β two-phase orthogonal coordinate system through Park transformation, and i ^* _cα , i ^* _cβ are obtained :

$[\begin{matrix} {i i}_{cα cα} \\ {i i}_{cβ cβ} \end{matrix}] = = {C C}_{3232} [\begin{matrix} {i i}_{ca ca} \\ {i i}_{cb cb} \\ {i i}_{cc cc} \end{matrix}]$

其中： $C_{32} = \sqrt{2 / 3} [\begin{matrix} 1 & - 1 / 2 & - 1 / 2 \\ 0 & \sqrt{3} / 2 & - \sqrt{3} / 2 \end{matrix}]$ in: $C_{32} = \sqrt{2 / 3} [\begin{matrix} 1 & - 1 / 2 & - 1 / 2 \\ 0 & \sqrt{3} / 2 & - \sqrt{3} / 2 \end{matrix}]$

2）同理将有源滤波器中实际输出的三相补偿电流i_ca、i_cb、i_cc也通过Park变换转换到α-β坐标系下，得到i_cα、i_cβ：2) Similarly, the three-phase compensation currents i _ca , i _cb , and i _cc actually output in the active filter are also transformed into the α-β coordinate system through Park transformation, and i _cα , i _cβ are obtained:

$[\begin{matrix} {i i}_{cα cα}^{* *} \\ {i i}_{cβ cβ}^{* *} \end{matrix}] = = {C C}_{3232} [\begin{matrix} {i i}_{ca ca}^{* *} \\ {i i}_{cb cb}^{* *} \\ {i i}_{cc cc}^{* *} \end{matrix}]$

3）变流器实际输出电流与参考电流之间的误差信号经过滞环比较器得到输出信号d_α和d_β。3) The error signal between the actual output current of the converter and the reference current passes through the hysteresis comparator to obtain output signals d _α and d _β .

如果α轴电流误差i*_cα-i_cα大于（小于）设定的正（负）环宽时，意味着变流器实际输出的补偿电流过小（过大），应通过调整使得变流器输出电流加大（减小）。此时应选择一个正（负）的电压矢量u_α；如果_α轴电流误差i*_cα-i_cα在设定的环宽之内，滞环比较输出器输出信号d_α=0。此时变流器开关动作维持原有状态不变，从而可以使得α轴输出电流能够跟踪参考指令电流，也就实现了电流在α-β坐标系下的跟踪控制，进而实现了电流在abc坐标系下的跟踪控制。If the α-axis current error i* _cα -i _cα is greater (less than) the set positive (negative) ring width, it means that the actual output compensation current of the converter is too small (too large), and the converter should be adjusted so that The output current increases (decreases). At this time, a positive (negative) voltage vector u _α should be selected; if _{the α-} axis current error i* _cα -i _cα is within the set loop width, the output signal d _α =0 of the hysteresis comparison output device. At this time, the switching action of the converter maintains the original state, so that the α-axis output current can track the reference command current, and the tracking control of the current in the α-β coordinate system is realized, and the current in the abc coordinate Tracking control under the system.

4）APF各相输出电压取决于三桥臂的状态S_abc，三个桥臂的开关函数S_i(i=a,b,c)都可以独立的取0和1，由于三相四开关型APF处于一个桥臂故障（假设c相），三相四开关共有四种开关状态。将四种开关函数组合代入：4) The output voltage of each phase of the APF depends on the state S _abc of the three bridge arms, and the switching functions S _i (i=a,b,c) of the three bridge arms can independently take 0 and 1, because the three-phase four-switch type The APF is in a bridge arm fault (assuming phase c), and there are four switching states for three-phase four-switches. Substitute the four switch function combinations into:

$[\begin{matrix} {u u}_{ao ao} \\ {u u}_{bo the bo} \end{matrix}] = = \frac{{u u}_{dc dc}}{22} [\begin{matrix} 22 {S S}_{a a} - - 11 \\ 22 {S S}_{b b} - - 11 \end{matrix}]$

可以得到相应的APF输出相电压值，并将桥臂相电压u_a、u_b和u_c变换至α-β坐标系下，可得到各个开关状态下相应的u_α和u_β，下表给出了4个开关状态和各个相应的电压值(电压以U_dc为基准)：The corresponding APF output phase voltage value can be obtained, and the bridge arm phase voltage u _a , u _b and u _c can be transformed into the α-β coordinate system, and the corresponding u _α and u _β in each switch state can be obtained. The following table gives There are 4 switch states and each corresponding voltage value (the voltage is based on U _dc ):

根据滞环比较结果选择电压矢量及开关动作状态，选择过程如下所示：Select the voltage vector and switch action state according to the hysteresis comparison result, the selection process is as follows:

最终根据滞环比较结果dα和dβ对比开关状态表得到两个桥臂的开关动作状态，实现三相四开关有源滤波器的滞环控制。Finally, according to the hysteresis loop comparison results dα and dβ compared with the switching state table, the switching action states of the two bridge arms are obtained, and the hysteresis control of the three-phase four-switch active filter is realized.

为了验证本发明提出方法的可行性和正确性，基于Matlab/Simulink建立了TFSSAPF的系统模型，假设c相断路故障，故障处理结果将c相桥臂直接连接在直流侧电容中性点上。仿真系统参数为：380V工频三相交流电源，系统阻抗忽略不计；非线性负载为三相不控整流桥，R_L=23Ω，APF直流侧采用6800μF电解容，直流侧设定电压约为三相六开关直流侧电压设定值的两倍，本发明中设定为1400V；输出滤波器为L滤波器，L=1mH。In order to verify the feasibility and correctness of the method proposed by the present invention, a system model of TFSSAPF was established based on Matlab/Simulink, assuming a c-phase open circuit fault, and the fault processing result directly connects the c-phase bridge arm to the neutral point of the DC side capacitor. The simulation system parameters are: 380V power frequency three-phase AC power supply, the system impedance is negligible; the nonlinear load is a three-phase uncontrolled rectifier bridge, R _L =23Ω, the APF DC side uses a 6800μF electrolytic capacitor, and the DC side set voltage is about three Twice the set value of the DC side voltage of the six-phase switch is set to 1400V in the present invention; the output filter is an L filter, L=1mH.

图7为采用本文提出的α-β坐标下的滞环控制方法的TFSSAPF补偿后稳态时网测电流波形图。通过图7可以看出，采用本发明提出的α-β坐标下的滞环控制方法能够有效的控制TFSSAPF，并且有较好的补偿效果，对于三相四开关型有源滤波器具有普适性，得APF具有一定的自愈能力，方法简单可靠，动态性能好，使得为APF有效工作延长了时间，也为APF故障后的维修赢得了更多的时间，具有很好的经济意义和市场前景。Fig. 7 is the network measured current waveform in the steady state after TFSSAPF compensation using the hysteresis control method under the α-β coordinates proposed in this paper. It can be seen from Figure 7 that the hysteresis control method under the α-β coordinates proposed by the present invention can effectively control TFSSAPF, and has a better compensation effect, and is universal for three-phase four-switch active filters , the APF has a certain self-healing ability, the method is simple and reliable, and the dynamic performance is good, which prolongs the time for the effective work of the APF and wins more time for the maintenance of the APF after failure, which has good economic significance and market prospects .

Claims

1. A current hysteresis control method based on a three-phase four-switch type active filter topological circuit is characterized by comprising the following steps:

when a certain phase IGBT open circuit fault occurs in the three-phase six-switch active filter, the hardware circuit generates a driving signal to drive the alternating current contactor to cut off the fault phase, the output end of the fault phase is directly connected to the middle point of the direct current side capacitor, the topology circuit changes, and the control process also changes, and the method comprises the following steps:

1) firstly, three-phase reference command current i of a filter^* _ca、i^* _cb、i^* _ccAnd the actually output three-phase compensation current i_ca、i_cbAnd converting the ic into an alpha-beta two-phase orthogonal coordinate system through Park transformation to obtain i^* _cα、i^*c_βAnd i_cα、i_cβ；

2) Reference current i converted by Park^* _cα、i^* _cβAnd the actual output current i_cα、i_cβThe error signal between the two signals passes through a hysteresis comparator to obtain an output signal d_αAnd d_β；

3) And obtaining a corresponding switch state table according to the topological structure of the three-phase four-switch active filter, and obtaining the switching action functions of the two bridge arms by combining the hysteresis comparison result and the switch state table to realize the hysteresis control of the three-phase four-switch active filter.

2. The method for controlling current hysteresis based on three-phase four-switch type active filter topological structure according to claim 1, wherein in the step 2), the reference command current i in the three-phase static coordinate system is obtained^* _ca、i^* _cb、i^* _ccAnd a compensation current i_ca、i_cb、i_ccConverting the reference command current i into a reference command current i under a two-phase orthogonal coordinate system through Park^* _cα、i^* _cβAnd the actual compensation current i_cα、i_cβThe transformation formula is as follows:

wherein,

3. the current hysteresis control method based on the three-phase four-switch type active filter topological structure according to claim 1, wherein the detailed method of the step 3) is as follows:

comparing the command reference current and the actual compensation current under the two-phase orthogonal system by difference:

wherein,

when the actual output current i is illustrated by the alpha axis_cαGreater than instruction value

When d is reached_αAt-1, the α axis is required to output a negative voltage to reduce the actual output current; when the actual output current i_cαLess than instruction value

When d is reached_αAt +1, an alpha axis is required to output a positive voltage to increase the actual output current;

an error signal between the instruction reference current and the actual compensation current under the two-phase orthogonal system passes through a hysteresis comparator to obtain an output signal d_αAnd d_β；

Obtaining a switching state equation based on a three-phase static coordinate system of a, b and c according to the topological structure of the three-phase four-switch type active filter:

[\begin{matrix} u_{ao} \\ u_{bo} \\ u_{co} \end{matrix}] = \frac{u_{dc}}{2} [\begin{matrix} 2 S_{a} - 1 \\ 2 S_{b} - 1 \\ 0 \end{matrix}]

and transforming the switch state function under the three-phase static coordinate to an alpha-beta two-phase orthogonal coordinate system, wherein the formula is as follows:

wherein:

the switching state function of the three-phase four-switch type active filter under an alpha-beta two-phase orthogonal coordinate system can be obtained:

the corresponding relation between the switching signal and the voltage space vector can be listed according to the switching state function of the three-phase four-switch type active filter under an alpha-beta two-phase orthogonal coordinate system, and is shown in the following table:

combining the corresponding relation between the switch signal and the elegant space vector and the hysteresis output state d under the alpha-beta coordinate_αAnd d_βWherein if d_α=-1，d_β=1, then:

when d is_α=1, the α axis needs to output a negative voltage to reduce the actual output current;

when d is_βThe =1, β axis requires a negative voltage output to reduce the actual output current;

from the above table, it can be seenAt this time U_k=U₀，S_a=0，S_b=0；

Since the three-phase four-switch type APF is in one bridge arm fault, the assumption is that_cThe phase failure, three-phase four-switch have four switch states, and the other three conditions can be obtained in the same way, and the obtained switch state table is summarized as follows:

d_α d_β U_k S_a S_b -1 -1 U₀ 0 0 -1 +1 U₁ 0 1 +1 -1 U₂ 1 0 +1 +1 U₃ 1 1

finally according to the hysteresis comparison result d_α、d_βAnd comparing the switch state tables to obtain the switch action states of the two bridge arms, and realizing hysteresis control of the three-phase four-switch active filter.