阅读说明：本技术 一种三相逆变器分区间调制模式下调制方法 (Modulation method of three-phase inverter in interval modulation mode ) 是由 游江 王芳瑞 张春雷 周玮 于 2020-11-02 设计创作，主要内容包括：本发明公开了一种三相逆变器分区间调制模式下调制方法,通过指针的方式给定输出三相电压相位,给定输出电压与实际输出电压经过坐标变换得到的偏差经过电压控制器得到i_(ref),i_(ref)与实际输出电流经过坐标变换得到偏差经过电流控制器得到i_(dr),将i_(dr)用作坐标逆变换d轴分量。强制令i_(qr)＝0作为坐标逆变换q轴分量,使得调制波与输出电压波形同相位,将坐标逆变换得到的分量,利用电压相位分区后进行单周期控制得到开关管的控制信号。本发明通过减少每一时刻同时进行高频斩波的开关管数量来降低开关损耗,强制令i_(qr)＝0作为坐标逆变换的q轴分量,使得调制波与输出电压波形同相位,减小在区间转换处的电压畸变。(The invention discloses a modulation method of a three-phase inverter in a partitioned modulation mode, which is characterized in that three-phase voltage phases are given and output in a pointer mode, and the deviation obtained by coordinate transformation of given output voltage and actual output voltage is obtained by a voltage controller to obtain i ref ，i ref Obtaining a deviation from the actual output current through coordinate transformation and obtaining i through a current controller dr I is to dr Used as the coordinate inverse transform d-axis component. Compel order i qr And (3) taking the coordinate as a q-axis component of coordinate inverse transformation, enabling the modulated wave to be in phase with the output voltage waveform, carrying out component obtained by coordinate inverse transformation, and carrying out single-cycle control after voltage phase division to obtain a control signal of the switching tube. The invention reduces the switching loss by reducing the number of switching tubes which simultaneously carry out high-frequency chopping at each moment, and forcibly makes i qr 0 as the q-axis component of the inverse coordinate transform, so that the modulated wave is in phase with the output voltage waveform, reducing voltage distortion at the interval transition.)

1. A modulation method of a three-phase inverter in a partitioned modulation mode is characterized by comprising the following steps:

step 1: given output three-phase voltage phase theta_a,b,c；

Step 2: averagely dividing one power frequency period of any phase of the three-phase output voltage into 6 sectors according to the phase information;

and step 3: the three-phase voltage v under the abc coordinate system_a、v_bAnd v_cConverted into a two-phase voltage v in a synchronously rotating dq coordinate system_d、v_qThe current; the three-phase inductive current i under the abc coordinate system_La、i_LbAnd i_LcConverted into a two-phase current i under a synchronously rotating dq coordinate system_Ld、i_Lq；

And 4, step 4: output voltage reference signal and v_dComparing to obtain an error, and outputting the error as a current inner loop reference signal i after passing through a PI (proportional integral) controller_ref；

And 5: current inner loop reference signal i_refAnd i_LdComparing to obtain an error, wherein the error is given as a d-axis component of dq inverse transformation through a current inner loop PI controller, and the output of the current inner loop PI controller is given as a q-axis component i of the dq inverse transformation_qrCarrying out dq inverse transformation when the value is zero;

step 6: performing single-cycle control on components of the abc channel obtained by dq inverse transformation in different sectors obtained in the step 2, and outputting a three-phase modulation signal;

and 7: and comparing the modulation signal with the three-phase carrier signal to obtain a switching pulse signal of the switching tube.

2. The modulation method of claim 1 in the three-phase inverter split-zone modulation mode, characterized in that: step 6, performing single-cycle control on components of the abc channel obtained by dq inverse transformation in different sectors obtained in step 2 specifically comprises: in any sector, only two switching tubes carry out high-frequency chopping at the same time, and the other switching tubes are kept to be connected or disconnected, so that the three-phase inverter works in a Buck circuit mode.

Technical Field

The invention relates to a modulation method of a three-phase inverter in an interval modulation mode, in particular to a modulation method for reducing output voltage distortion in the interval modulation mode of the three-phase inverter, belonging to the control technology of a DC/AC electric energy conversion device in the technical field of power electronics.

Background

With the wide application of power electronic technology, people pay more and more attention to reducing power loss of power semiconductor devices in electric energy conversion and improving the overall efficiency of switching power converters. Particularly, in the power converters with a large number of power semiconductor devices, the inverter with high power factor and low harmonic content and the energy-saving control strategy thereof are the hot problems of the current research. As a common DC/AC conversion device, a conventional control method causes a large loss of power semiconductor devices of the inverter, so it is necessary to develop an energy-saving inversion control technology.

Disclosure of Invention

Aiming at the prior art, the technical problem to be solved by the invention is to provide a modulation method of a three-phase inverter in an inter-zone modulation mode, which reduces the switching loss of a power semiconductor device to the maximum extent and reduces the distortion of output voltage by a zone modulation algorithm.

In order to solve the technical problem, the invention provides a modulation method of a three-phase inverter in an interval modulation mode, which comprises the following steps:

step 1: given output three-phase voltage phase theta_a,b,c；

Step 2: averagely dividing one power frequency period of any phase of the three-phase output voltage into 6 sectors according to the phase information;

and step 3: the three-phase voltage v under the abc coordinate system_a、v_bAnd v_cConverted into a two-phase voltage v in a synchronously rotating dq coordinate system_d、v_qThe current; the three-phase inductive current i under the abc coordinate system_La、i_LbAnd i_LcConverted into a two-phase current i under a synchronously rotating dq coordinate system_Ld、i_Lq；

And 4, step 4: output voltage reference signal and v_dComparing to obtain an error, and outputting the error as a current inner loop reference signal i after passing through a PI (proportional integral) controller_ref；

And 5: current inner loop reference signal i_refAnd i_LdComparing to obtain an error, wherein the error is obtained through a current inner loop PI controller, and the output of the current inner loop PI controller is used as dq inverse transformationd-axis component given while inverting dq-axis component i_qrCarrying out dq inverse transformation when the value is zero;

step 6: performing single-cycle control on components of the abc channel obtained by dq inverse transformation in different sectors obtained in the step 2, and outputting a three-phase modulation signal;

and 7: and comparing the modulation signal with the three-phase carrier signal to obtain a switching pulse signal of the switching tube.

The invention also includes:

in step 6, performing single-cycle control on components of the abc channel obtained by dq inverse transformation in different sectors obtained in step 2 specifically comprises: in any sector, only two switching tubes carry out high-frequency chopping at the same time, and the other switching tubes are kept to be connected or disconnected, so that the three-phase inverter works in a Buck circuit mode.

The invention has the beneficial effects that: a method for reducing the switching loss of a power semiconductor device through a software control algorithm is provided, and meanwhile, the problem of distortion of the final output voltage of an inverter is reduced. The method can averagely divide any phase of the three-phase output voltage into 6 intervals by taking the phase of any phase as a reference, and the angle of each interval is 60 degrees, so that the partitioned modulation is realized. In each interval, only two switching tubes are chopped at high frequency at each moment, and the other switching tubes are kept on or off. The switching loss is reduced by reducing the number of switching tubes that simultaneously perform high frequency chopping at each instant. I obtained by simultaneously outputting current inner loop controller_drD-axis component used as an inverse dq transformation, forcing i_qr0 as the q-axis component of the inverse coordinate transform, so that the modulated wave is in phase with the output voltage waveform, reducing voltage distortion at the interval transition.

Drawings

FIG. 1(a) is a schematic diagram of a three-phase inverter topology;

FIG. 1(b) is a control diagram of inter-division modulation and reduction of voltage distortion;

fig. 1(c) is a schematic diagram of interval division.

FIG. 2(a) is a block 1Buck equivalent circuit diagram;

FIG. 2(b) is a block 2Buck equivalent circuit diagram;

FIG. 2(c) is a block 3Buck equivalent circuit diagram;

FIG. 2(d) is a block 4Buck equivalent circuit diagram;

FIG. 2(e) is a block 5Buck equivalent circuit diagram;

FIG. 2(f) is a block 6Buck equivalent circuit diagram;

FIG. 3 is an inter-partition modulation drive signal;

FIG. 4 is a conventional inverter control algorithm drive signal;

FIG. 5 is a waveform of an output voltage current before the q-axis component is zeroed;

FIG. 6 is a waveform of the output voltage current after the q-axis component is made zero;

fig. 7 is a flow chart of the method of the present invention.

The main symbols and meanings in the drawings are described below.

θ_a,b,cFor the internal setting of the output voltage phase, v, by means of a pointer_a、v_bAnd v_cFor the inverter output phase voltage i_La、i_LbAnd i_LcIs a three-phase inductive current, L_a、L_bAnd L_cFor outputting the filter inductance, S₁、S₂、S₃、S₄、S₅And S₆Is a switching tube, v_dcIs a DC power supply, C_dIs an input filter capacitor, C₁、C₂And C₃To output filter capacitors, R_a、R_bAnd R_cIs a load resistance, v_refTo output a voltage reference signal, i_refFor outputting the output signal of the voltage controller, v_d、v_qTo output a signal of voltage in dq coordinate system, i_Ld、i_LqFor outputting signals of the inductor current in dq coordinate system, i_drFor the output signal via a PI controller, i_qrCurrent reference signal for q-axis component in dq coordinate system, i_ar、i_brAnd i_crIs i_qrAnd (5) inversely transforming the output signal under the abc coordinate system through dq.

Detailed Description

The following further describes the embodiments of the present invention with reference to the drawings.

The method is improved on the basis of the traditional single-period control, and the traditional three-phase single-period bipolar control has low voltage utilization rate and large switching loss. The control method of digital single-period interval modulation can reduce switching loss to the maximum extent, improve system efficiency, and simultaneously can reduce output voltage distortion of the inverter. The main circuit topology adopts a three-phase inverter as shown in figure 1(a), an improved control algorithm is shown in figure 1(b), and the phase theta of the output three-phase voltage is given and output in a pointer mode in the program_a,b,cGiven an output voltage v_refV obtained by coordinate transformation with actual output voltage_dIs passed through a voltage controller to obtain i_ref，i_refI obtained by coordinate transformation of actual output current_LdIs passed through a current controller to obtain i_drI is to_drUsed as the d-axis component of the coordinate inverse transform. Compel order i_qr0 as the q-axis component of the inverse coordinate transform, so that the modulated wave is in phase with the output voltage waveform to reduce voltage distortion at the interval transition. I obtained by inverse transformation of coordinates_ar、i_br、i_crComponents, using them and the voltage phase theta_a,b,cAnd after partitioning, performing single-cycle control to obtain a control signal of the switching tube.

The control method provided by the invention introduces the zone control on the basis of the digital single-cycle control, can realize that only two switching tubes carry out high-frequency chopping at the same time in a certain zone, and reduces the loss by reducing the number of the switching tubes working at the same time. The distortion of the output voltage of the inverter is reduced by making the q-axis component of the inverse conversion of dq to abc zero and making the modulation wave in phase with the output voltage.

With reference to fig. 7, the embodiment of the present invention is:

(1) the invention analyzes the phase a of the load connected with the midpoint of the first bridge arm, in the figure 1(b), the d axis and the q axis under the dq coordinate system are simultaneously corrected by using a PI controller in the traditional inverter control, the PI controller is only adopted in the d axis, and the q axis component is directlyAnd (4) zero. In the conventional inverter using dq conversion control, the d-axis component and the q-axis component are simultaneously regulated by a PI controller. Due to sampling delay, the output result of the q-axis component after passing through the PI regulator is larger than 0, the d-axis component and the q-axis component are subjected to dq-abc coordinate system inverse transformation after passing through the PI controller, and the phase of the obtained modulation wave leads the phase of the voltage. Just as the three-phase inverter shown in fig. 2(a) to 2(f) is essentially a modification of the Buck converter, the waveform will be distorted when the phase of the modulation wave is ahead of the phase of the output voltage at any one interval transition. In the equivalent circuits shown in fig. 2(c) and 2(d), the dc power supply in the section 3 is respectively connected to S₁、D₂、L_a、L_cAnd S₃、D₄、L_b、L_cAnd when the Buck circuit works, the upper tube of the A-phase B-phase bridge arm is chopped, the lower tube of the C-phase is kept on, and the other A, B, C-phase switching tubes are switched off. The DC power supply in interval 4 is respectively connected with S₂、D₅、L_a、L_bAnd S₆、D₁、L_c、L_bAnd when the Buck circuit works, the lower tube of the A-phase C-phase bridge arm chops, the B-phase upper tube keeps on, and the A, B, C three-phase other switching tubes are switched off. Analyzing the commutation situation of the interval 3 switched to the interval 4, if the q-axis component is greater than zero at the interval switching position in the split-interval modulation mode, the modulated wave obtained by inverse transformation will be ahead of the voltage phase, that is, the control mode of the interval 4 is already entered in the control, but the actual current still works according to the circuit corresponding to the interval 3 and the graph 2(c), so that the current in the inductor is directly reduced to zero, and the waveform is distorted at the zero-crossing point. And after the q-axis component is forced to be zero, the same phase of the modulation wave and the voltage can be ensured, the condition is avoided, and the distortion of the output voltage is reduced.

After the partition control algorithm is introduced, only two switching tubes are used for high-frequency chopping at the same time in each interval, and compared with the traditional algorithm that six switching tubes work in each 1/6 period, the switching loss is reduced, and the switching loss is reduced. The partitioning principle of the partition modulation is shown in table 1 below and fig. 1 (c):

TABLE 1 principle of modulation mode partitioning between partitions

(2) Using theta given by means of pointers inside the program_a,b,cAngular division and transformation of the stationary abc coordinate system to the synchronously rotating dq coordinate system for three-phase ac voltages and currents are performed. And converting the three-phase alternating current electric quantity under the stationary abc coordinate system into the direct current electric quantity under the synchronous rotation dq coordinate system.

(3) Referring to fig. 1(b), three-phase output voltage v is converted by conversion from a stationary abc coordinate system to a synchronously rotating dq coordinate system_a、v_bAnd v_cIs transformed into v_d、v_qThe three-phase inductive current i_La、i_LbAnd i_LcIs transformed into i_Ld、i_Lq. Comparing the reference voltage signal with v_dAnd comparing to obtain an error, and outputting the error as a reference signal of the current inner loop after the error passes through the PI controller. Reference current signal and i_LdThe difference is passed through a PI controller of the current inner loop, whose output is given by the d-axis component of the inverse dq transformation. Q-axis component i of dq inverse transformation_qrAnd carrying out dq inverse transformation, and carrying out single-cycle control in the inter-partition mode by combining the output result of the dq inverse transformation with different partitioned partitions in the graph (b) in the graph 1. When the phase a as a reference is in the interval 1, chopping is carried out on the upper tubes of the first bridge arm and the third bridge arm, and the lower tube of the second bridge arm is kept open; when the current is positioned in the interval 2, chopping is carried out on the lower tubes of the second bridge arm and the third bridge arm, and the upper tube of the first bridge arm is kept open; when the bridge arm is positioned in the section 3, chopping is carried out on the upper tubes of the first bridge arm and the second bridge arm, and the lower tube of the third bridge arm is kept open; when the bridge arm is positioned in the section 4, chopping is carried out on the lower tubes of the first bridge arm and the third bridge arm, and the upper tube of the second bridge arm is kept open; when the current is positioned in the interval 5, chopping is carried out on the upper tubes of the second bridge arm and the third bridge arm, and the lower tube of the second bridge arm is kept open; when the bridge arm is positioned in the section 6, the lower tubes of the first bridge arm and the second bridge arm are chopped, and the upper tube of the third bridge arm is kept open.

The specific zone control duty ratios are shown in the table below.

TABLE 2 Duty ratio equation of switching tube in interval mode

Comparing the driving signals in fig. 3 and fig. 4, it can be seen that only two switching tubes perform high-frequency chopping at the same time in each interval after the partition control algorithm is adopted, and compared with the conventional algorithm in which six switching tubes operate in each 1/6 cycles, switching loss is reduced. Comparing the output voltage current waveforms of fig. 5 and 6, it can be seen that the output voltage current waveform after making the q-axis zero is significantly better than the waveform before making the q-axis zero. Thus, the method of the present invention is accurate and efficient.