阅读说明：本技术 一种单相pwm整流器的直接电流控制方法 (direct current control method of single-phase PWM rectifier ) 是由 吴宁 肖静 韩帅 陈卫东 孙乐平 冯玉斌 吴宛潞 郭小璇 于 2019-09-11 设计创作，主要内容包括：本发明公开了一种单相PWM整流器的直接电流控制方法,根据有功电流指令、无功电流指令和电网同步旋转角数据计算出虚拟电流信号,将三相PWM整流器中广泛应用的基于PI控制器的直接电流控制方法成功运用于单相PWM整流器场合。本发明不仅能够实现对电流的无静差跟踪,同时允许有功电流和无功电流的独立控制。与常规基于延迟法构造电流信号相比,该方法无需引入延时模块,电流响应速度大幅提高。同时虚拟电流信号计算不依赖系统参数,系统具有很强的稳定性和抗干扰能力。(The invention discloses a direct current control method of a single-phase PWM rectifier, which calculates a virtual current signal according to an active current instruction, a reactive current instruction and power grid synchronous rotation angle data and successfully applies the direct current control method based on a PI controller widely applied to the three-phase PWM rectifier to the single-phase PWM rectifier occasion. The invention can realize the non-static tracking of the current and simultaneously allow the independent control of the active current and the reactive current. Compared with the conventional method for constructing the current signal based on the delay method, the method does not need to introduce a delay module, and the current response speed is greatly improved. Meanwhile, the virtual current signal calculation does not depend on system parameters, and the system has strong stability and anti-interference capability.)

1. A direct current control method of a single-phase PWM rectifier is characterized by comprising the following steps:

Step S1, adopting the method of delaying the signal by 60 degrees to make the single-phase voltage u on the network side_sLag 60 DEG to obtain u₆₀(ii) a And make u_sIs equal to u_a，-u₆₀Is equal to u_cWherein u is_aFor ac voltage signals of grid a, u_cIs a power grid c alternating voltage signal;

Step S2, according to the grid a alternating voltage signal u obtained in the step S1_aAc voltage signal u of power grid_cAccording to the three-phase power grid voltage symmetry principle, a power grid b-phase voltage signal u is calculated by using a formula (1)_b：

u_b＝-u_a-u_c (1)；

Step S3, according to the grid a alternating voltage signal u obtained in the step S1_aAc voltage signal u of power grid_cAnd a grid b-phase voltage signal u obtained by S2_bObtaining a voltage signal u under a two-phase static coordinate system by using CLACK conversion, namely formula (2)_α、u_β：

Step S4, obtaining the voltage signal u under the two-phase static coordinate system according to the step S3_α、u_βCalculating the synchronous rotation angles sin theta and cos theta of the power grid according to the formula (3):

Step S5, collecting the voltage u on the DC side by a voltage sensor_dcReference voltage value u on the DC side_dc ^*Directly setting the voltage u on the DC side obtained by collection_dcand a DC side reference voltage u_dc ^*Performing difference comparison, inputting the result after difference comparison into a PI controller to obtain an active current instruction i_d ^*Instruction of reactive current i_q ^*Directly giving;

Step S6, the grid synchronous rotation angles sin θ and cos θ obtained in step S4 and the active current command value i obtained in step S5 are used_d ^*Directly specified reactive current command value i_q ^*Inputting a virtual current construction module to calculate a virtual orthogonal current signal i_m；

Step S7, collecting actual current i by using a current sensor_sAccording to the grid synchronous rotation angles sin theta and cos theta obtained in step S4, the actual current i is converted into the actual current i according to the formula (4)_sAnd the virtual orthogonal current signal i obtained in step S6_mConverting to a synchronous rotating coordinate system to obtain an active current component i_dAnd a reactive current component i_q：

Step S8, the active current component i obtained in step S7_dAnd a reactive current component i_qRespectively with the active current command i obtained in step S5_d ^*Reactive current command i_q ^*After difference comparison, inputting the result of difference comparison into a PI current controller, and outputting by the PI current controller to obtain a d-axis voltage command signal u_d ^*And q-axis voltage command signal u_q ^*；

Step S9, according to the grid synchronous rotation angles sin θ and cos θ obtained in step S4 and the d-axis voltage command signal u obtained in step S8_d ^*And q-axis voltage command signal u_q ^*According to the formula (5), the conversion from the rotating coordinate system to the static coordinate system is carried out to obtain the modulation wave signal u under the static coordinate system_α ^*and u_β ^*：

Step S10, according to the modulation wave signal u in the static coordinate system obtained in the step S9_α ^*Modulating by using a sinusoidal pulse width modulation technology as a final modulation signal to generate a switching signal to drive a single-phase PWM rectifier to work, wherein a modulation wave signal u under a static coordinate system_β ^*Are discarded.

2. The direct current control method of the single-phase PWM rectifier according to claim 1, wherein said step S6 calculates the virtual quadrature current signal i_mthe method comprises the following specific steps:

step S61, the active current command i obtained by the calculation of the step S5_d ^*And a reactive current command i_q ^*Respectively squaring and adding, and taking the root of the square sum result as a virtual axis current amplitude A;

Step S62, the reactive current command i given directly in step S5_q ^*Divided by the active current command i_d ^*And performing arc tangent trigonometric function operation on the result to obtain a virtualInitial phase of shaft current

Step S63, calculating the grid synchronous rotation angles sin theta and cos theta according to the step S4, and obtaining the virtual axis current amplitude A and the initial phase position obtained in the steps S61 and S62Calculating a virtual orthogonal current signal i orthogonal to the actual grid signal according to equation (8)_m：

Technical Field

the invention relates to the field of single-phase PWM converter control systems in the technical field of power electronics, in particular to a direct current control method of a single-phase PWM rectifier.

Background

With the continuous improvement of the performance of power electronic devices, the single-phase PWM rectifier has the advantages of simple principle structure, bidirectional energy flow, controllable direct-current side voltage, unit power factor and the like, and is widely applied to the fields of railway locomotive traction, photovoltaic grid connection, power electronic transformers, static var generators and the like. Because of this, the single-phase PWM rectifier and its control technology are becoming the research hot spots in the scientific research institutions and the industrial field.

The existing single-phase PWM rectifier control method is mainly divided into two categories, namely Proportional Resonance (PR) control based on a static coordinate system and Proportional Integral (PI) control based on a synchronous rotating coordinate system. Although Proportional Resonance (PR) control can achieve quiet control of the sinusoidal current, PR controllers are sensitive to grid frequency variations and have poor stability. PI control based on a synchronous rotating coordinate system has been widely used in three-phase PWM rectifiers. According to the method, through coordinate transformation, alternating current in a static coordinate system is transformed into direct current in a synchronous rotating coordinate system, and independent control over active current and reactive current is achieved. Compared with a three-phase PWM rectifier, the single-phase PWM rectifier needs to construct a virtual AC flow orthogonal to the AC flow of an actual system to realize the coordinate rotation transformation of the AC flow so as to meet the design requirement. The conventional scheme adopts a time delay-based method to construct two-phase orthogonal signals, and the method constructs a virtual orthogonal component by delaying an actual physical quantity for 1/4 grid cycles. Although the delay method is simple, if any form of sudden change occurs in the actual physical quantity, such as sudden change in the current command, the sudden change is reflected in the virtual component after 1/4 grid cycles, so that the dynamic response of the system is deteriorated, the system is slowed down, and even oscillation is caused, and the dynamic performance of the system is seriously affected. The current novel method is to use a single-phase PWM rectifier system model to construct a virtual circuit to obtain orthogonal current components, i.e. a virtual circuit method. Although the method improves the current response speed, the method depends on system parameters, and once the circuit parameters (such as connection inductance parameters) of an actual circuit are different from those of a virtual circuit, the current can be distorted, and the stability and the anti-interference capability of the system are seriously influenced.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a direct current control method of a single-phase PWM rectifier, which adopts an active current instruction, a reactive current instruction and power grid synchronous rotation angle data to reconstruct two-phase orthogonal current signals, realizes the decomposition of an active current component and a reactive current component under a synchronous rotation coordinate system, and further realizes the independent control of the active current and the reactive current; the method calculates the virtual current signal in real time, greatly improves the current response speed, does not depend on system parameters, and further enhances the anti-interference capability of the system stability.

A direct current control method of a single-phase PWM rectifier comprises the following steps:

Step S1, adopting the method of delaying the signal by 60 degrees to make the single-phase voltage u on the network side_sLag 60 DEG to obtain u₆₀(ii) a And make u_sIs equal to u_a，-u₆₀Is equal to u_cWherein u is_aFor ac voltage signals of grid a, u_cIs a power grid c alternating voltage signal;

Step S2, according to the grid a alternating voltage signal u obtained in the step S1_aAc voltage signal u of power grid_cAccording to the three-phase power grid voltage symmetry principle, a power grid b-phase voltage signal u is calculated by using a formula (1)_b：

u_b＝-u_a-u_c (1)；

Step S3, obtaining the result according to the step S1A AC voltage signal u of power grid_aAc voltage signal u of power grid_cAnd a grid b-phase voltage signal u obtained by S2_bObtaining a voltage signal u under a two-phase static coordinate system by using CLACK conversion, namely formula (2)_α、u_β：

step S4, obtaining the voltage signal u under the two-phase static coordinate system according to the step S3_α、u_βCalculating the synchronous rotation angles sin theta and cos theta of the power grid according to the formula (3):

Step S5, collecting the voltage u on the DC side by a voltage sensor_dcReference voltage value u on the DC side_dc ^*Directly setting the voltage u on the DC side obtained by collection_dcAnd a DC side reference voltage u_dc ^*Performing difference comparison, inputting the result after difference comparison into a PI controller to obtain an active current instruction i_d ^*Instruction of reactive current i_q ^*Directly giving;

step S6, the grid synchronous rotation angles sin θ and cos θ obtained in step S4 and the active current command value i obtained in step S5 are used_d ^*Directly specified reactive current command value i_q ^*Inputting a virtual current construction module to calculate a virtual orthogonal current signal i_m；

Step S7, collecting actual current i by using a current sensor_sAccording to the grid synchronous rotation angles sin theta and cos theta obtained in step S4, the actual current i is converted into the actual current i according to the formula (4)_sAnd the virtual orthogonal current signal i obtained in step S6_mConverting to a synchronous rotating coordinate system to obtain an active current component i_dAnd a reactive current component i_q：

Step S8, the active current component i obtained in step S7_dAnd a reactive current component i_qRespectively with the active current command i obtained in step S5_d ^*Reactive current command i_q ^*After difference comparison, inputting the result of difference comparison into a PI current controller, and outputting by the PI current controller to obtain a d-axis voltage command signal u_d ^*And q-axis voltage command signal u_q ^*；

step S9, according to the grid synchronous rotation angles sin θ and cos θ obtained in step S4 and the d-axis voltage command signal u obtained in step S8_d ^*And q-axis voltage command signal u_q ^*According to the formula (5), the conversion from the rotating coordinate system to the static coordinate system is carried out to obtain the modulation wave signal u under the static coordinate system_α ^*And u_β ^*：

Step S10, according to the modulation wave signal u in the static coordinate system obtained in the step S9_α ^*Modulating by using a sinusoidal pulse width modulation technology as a final modulation signal to generate a switching signal to drive a single-phase PWM rectifier to work, wherein a modulation wave signal u under a static coordinate system_β ^*Are discarded.

Further, the step S6 calculates a virtual orthogonal current signal i_mThe method comprises the following specific steps:

Step S61, the active current command i obtained by the calculation of the step S5_d ^*and a reactive current command i_q ^*Respectively squaring and adding, and taking the root of the square sum result as a virtual axis current amplitude A;

Step S62, the reactive current command i given directly in step S5_q ^*Divided by the active current command i_d ^*And performing arc tangent trigonometric function operation on the result to obtain the initial phase of the virtual axis current

Step S63, calculating the grid synchronous rotation angles sin theta and cos theta according to the step S4, and obtaining the virtual axis current amplitude A and the initial phase position obtained in the steps S61 and S62Calculating a virtual orthogonal current signal i orthogonal to the actual grid signal according to equation (8)_m：

The invention has the beneficial effects that:

1. the invention introduces the direct current control method of the three-phase PWM rectifier into the single-phase PWM rectifier system, realizes the independent control of the active current and the reactive current of the system by using the PI controller, can realize the non-differential tracking of the current signal and has high control performance.

2. Compared with the existing method for constructing the two-phase orthogonal signal based on the time delay method, the method disclosed by the invention has the advantages that the virtual axis current signal is calculated through the current instruction signal and the power grid phase angle data, the algorithm calculation is simple, and the dynamic response speed of the current is high.

3. Compared with the existing virtual circuit method, the method has the advantages that the virtual circuit is constructed to obtain the orthogonal current without depending on system parameters, and the system stability and the anti-interference capability are enhanced.

Drawings

Fig. 1 is a single phase PWM rectifier topology.

Fig. 2 is an overall block diagram of direct current control of a single-phase PWM rectifier based on a virtual current configuration module.

fig. 3 is a schematic diagram of the inside of a virtual current configuration module.

Fig. 4 is a schematic diagram of the principle of the pulse width modulation technique.

Fig. 5 is a current response experimental diagram of the time delay method in a dq rotation coordinate system.

Fig. 6 is a current response experimental diagram of a virtual circuit method in a dq rotation coordinate system.

FIG. 7 is a current response experimental diagram under dq rotation coordinate system.

Fig. 8 is a stability test experimental diagram of a virtual circuit method in a dq rotation coordinate system.

FIG. 9 is a graph of the stability test experiment under dq rotation coordinate system.

Detailed Description

The foregoing embodiments and description have been presented only to illustrate the principles and preferred embodiments of the invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention as hereinafter claimed.

The invention is described in further detail below with reference to the figures and the specific embodiments.

Aiming at the characteristic that a single-phase PWM rectifier has less freedom degree, the invention utilizes an active current instruction, a reactive current instruction and power grid synchronous rotation angle data to calculate a virtual current component orthogonal to an actual single-phase current signal, then converts an alternating orthogonal current signal into an equivalent direct current signal through coordinate transformation under a two-phase static coordinate system, and uses a PI controller to realize independent control of the active current and the reactive current. Particularly, the virtual current component is calculated by an active current instruction, a reactive current instruction and a power grid phase angle and does not depend on system parameters. Therefore, the stability and the anti-interference capability of the system are further enhanced, and the dynamic response of the system is quicker.

FIG. 1 shows a single-phase PWM rectifier topology of the present invention, u_sFor the mains voltage, i_sFor the grid current, L is the filter inductance, R_LThe equivalent resistance of the filter inductor is R is the equivalent load of the direct current side; u. of_dcIs a DC side voltage u_cFor the voltage at the alternating current side, the mathematical equation at the alternating current side of the single-phase PWM rectifier system is as follows:

Because the main circuit of the single-phase system lacks of freedom degree, a mirror image circuit is constructed to obtain a virtual orthogonal voltage signal u_mvirtual quadrature current signal i_mThen, an alternating-current side mathematical equation under a two-phase system is obtained:

In equation (II), i_sFor grid current, i_mFor virtual quadrature current signals, u_sIs the grid voltage u_smFor virtual circuits under a stationary coordinate system, u_cFor the actual circuit rectifier inverter side voltage u_cmThe voltage on the inverting side of the rectifier is a virtual circuit.

And obtaining a mathematical equation of the single-phase PWM rectifier under a d-q rotating coordinate system by using stationary-to-rotating coordinate transformation, wherein the mathematical equation is as follows:

In equation (III), i_dAs active current component, i_qIs a reactive current component, u_dIs the active voltage component of the AC voltage source u_qIs a reactive voltage component of the AC voltage source, u_cdIs the active voltage component of the inverter side of the rectifier u_cqThe frequency is a reactive voltage component on the inversion side of the rectifier, R is an equivalent load on the direct current side, L is a filter inductor, and omega is the angular frequency of the power grid.

From equation (iii), the mathematical equation of the single-phase PWM rectifier in the dq rotation coordinate system is consistent with the mathematical equation of the three-phase PWM rectifier in the d-q rotation coordinate system, so that the active current and the reactive current are independently controlled by using the direct current control method of the three-phase PWM rectifier.

As shown in fig. 2, which is a control block diagram of the control method of the present invention, a direct current control method of a single-phase PWM rectifier includes the following steps:

Step S1, adopting the method of delaying the signal by 60 degrees to make the single-phase voltage u on the network side_sLag 60 DEG to obtain u₆₀(ii) a And make u_sIs equal to u_a，-u₆₀Is equal to u_cWherein u is_aFor ac voltage signals of grid a, u_cIs a grid c-phase alternating voltage signal.

Step S2, according to the grid a alternating voltage signal u obtained in the step S1_aAc voltage signal u of power grid_cAccording to the three-phase power grid voltage symmetry principle, a power grid b-phase voltage signal u is calculated by using a formula (1)_b：

u_b＝-u_a-u_c (1)。

Step S3, according to the grid a alternating voltage signal u obtained in the step S1_aAc voltage signal u of power grid_cAnd a grid b-phase voltage signal u obtained by S2_bObtaining a voltage signal u under a two-phase static coordinate system by using CLACK conversion, namely formula (2)_α、u_β：

Step S4, obtaining the voltage signal u under the two-phase static coordinate system according to the step S3_α、u_βCalculating the synchronous rotation angles sin theta and cos theta of the power grid according to the formula (3):

Step S5, collecting the voltage u on the DC side by a voltage sensor_dcReference voltage value u on the DC side_dc ^*Directly setting the voltage u on the DC side obtained by collection_dcAnd a DC side reference voltage u_dc ^*Making difference comparison, inputting the result after difference comparisonEntering a PI controller to obtain an active current instruction i_d ^*Instruction of reactive current i_q ^*Is directly given.

Step S6, the grid synchronous rotation angles sin θ and cos θ obtained in step S4 and the active current command value i obtained in step S5 are used_d ^*Directly specified reactive current command value i_q ^*Inputting a virtual current construction module to calculate a virtual orthogonal current signal i_mAs shown in fig. 3, the specific steps are as follows:

step S61, the active current command i obtained by the calculation of the step S5_d ^*And a reactive current command i_q ^*Respectively squaring and adding, and taking the root of the square sum as the virtual shaft current amplitude A:

Step S62, the reactive current command i given directly in step S5_q ^*Divided by the active current command i_d ^*And performing arc tangent trigonometric function operation on the result to obtain the initial phase of the virtual axis current

Step S63, calculating the grid synchronous rotation angles sin theta and cos theta according to the step S4, and obtaining the virtual axis current amplitude A and the initial phase position obtained in the steps S61 and S62Calculating a virtual orthogonal current signal i orthogonal to the actual grid signal according to equation (6)_m：

Step S7, collecting actual current i by using a current sensor_sAccording to the grid synchronous rotation angles sin theta and cos theta obtained in step S4, the actual current i is converted into the actual current i according to the formula (7)_sAnd the virtual orthogonal current signal i obtained in step S6_mConverting to a synchronous rotating coordinate system to obtain an active current component i_dAnd a reactive current component i_q：

step S8, the active current component i obtained in step S7_dAnd a reactive current component i_qRespectively with the active current command i obtained in step S5_d ^*reactive current command i_q ^*After difference comparison, inputting the result of difference comparison into a PI current controller, and outputting by the PI current controller to obtain a d-axis voltage command signal u_d ^*And q-axis voltage command signal u_q ^*。

Step S9, according to the grid synchronous rotation angles sin θ and cos θ obtained in step S4 and the d-axis voltage command signal u obtained in step S8_d ^*And q-axis voltage command signal u_q ^*according to the formula (8), the conversion from the rotating coordinate system to the static coordinate system is carried out to obtain the modulation wave signal u under the static coordinate system_α ^*And u_β ^*：

Step S10, according to the modulation wave signal u in the static coordinate system obtained in the step S9_α ^*The final modulation signal is modulated by a sinusoidal pulse width modulation technique, and a schematic diagram of the modulation technique is shown in fig. 4, in which a triangular carrier C and a modulation wave u are combined_α ^*Sending the synthesized PWM signal to a power device, generating a switching signal to drive a single-phase PWM rectifier to work, and generating a modulation wave signal u under a static coordinate system_β ^*Are discarded.

FIGS. 5-7 show a given current fingerCurrent response experiment in real time. In order to realize response to a current command, the direct current side connecting resistor of the PWM rectifier is changed to be connected with a direct current power supply, the direct current power supply is 400V, a reactive current command value of 20A is given at 0.15s, an active current command value of 10A is given at 0.18s, the alternating current side connecting grid voltage is 220V, the inductance value of the connecting reactor is 10mH, and the resistance value of the connecting reactor is 0.01 omega. As shown in fig. 5, with the time delay method, since 1/4 grid cycles are required to construct the virtual axis current, the actual active current component i in the dynamic process_dAnd a reactive current component i_qThe current distortion phenomenon occurs in the response process, the response time exceeds 5ms, and the instruction value cannot be tracked in real time; as shown in fig. 6, the command current is tracked in real time by using a virtual circuit method, and the actual active current component i_dAnd a reactive current component i_qThe distortion phenomenon is avoided, the response time of the current signal is about 1ms, and the response speed of the current signal is greatly improved; as shown in FIG. 7, the method of the present invention is adopted to track the command current in real time, and the actual active current component i_dAnd a reactive current component i_qThe distortion phenomenon is avoided, the response time of the current signal is about 1ms, and the response speed of the current signal is greatly improved.

In an actual system, as the power level of the system is increased or the operation time is increased, the connection inductance parameter in the actual circuit is changed, which causes inconsistency with the connection inductance parameter of the virtual circuit in the virtual circuit method. In order to further compare the test effect of the virtual circuit method and the method of the invention on the circuit parameter sensitivity, a stability test experiment is carried out. At the moment, the parameter of the connection inductance of the actual circuit is 12mH, the direct current side connection resistance of the PWM rectifier is changed into connection with a direct current power supply, the direct current power supply is 400V, a reactive current instruction value of 20A is given at 0.15s, an active current instruction value of 10A is given at 0.18s, the voltage of the alternating current side connection power grid is 220V, and the resistance value of the connection reactance is 0.01 omega. When the virtual circuit method is adopted, the virtual circuit connection inductance parameter is changed into 24mH, as shown in FIG. 8, and the experimental result shows that the active current component i_dand a reactive current component i_qno distortion phenomenon occurs in the response process, namely the transient process, the response time of the current signal is about 1ms, and the current response speedFaster, but the real circuit inductance parameter is not consistent with the virtual circuit inductance parameter, the active current component i_dAnd a reactive current component i_qDistortion phenomena (steady state processes) occur and the system stability is poor. As shown in fig. 9, by adopting the method of the present invention, since the method does not depend on system parameters, the current response speed is fast, the current signal response time is about 1ms, no distortion phenomenon occurs in the current in the transient state and steady state processes, and the system stability and the anti-interference performance are stronger.

The present invention is not limited to the above-described embodiments, which are merely preferred embodiments of the present invention, and the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.