阅读说明：本技术 一种pwm整流器控制方法及装置 (PWM rectifier control method and device ) 是由 尚敬 张少云 佘岳 徐凤星 盛建科 谭宇 戴茜茜 黄禹文 彭韬 江海啸 于 2018-05-29 设计创作，主要内容包括：本发明公开了一种PWM整流器控制方法及装置,包括如下步骤：S1.通过预测获取预设个数的控制矢量预测值；S2.对所述控制矢量预测值进行排列组合,得到不同的矢量序列；S3.从所述矢量序列中选择开关次数最少的矢量序列作为PWM整流器的控制序列。具有能够在保证预测周期不变的情况下有效限制系统的开关频率,并能保证系统的动态性能,简单、响应速度快,处理系统约束灵活等优点。(The invention discloses a PWM rectifier control method and a device, comprising the following steps: s1, obtaining control vector predicted values of a preset number through prediction; s2, arranging and combining the control vector predicted values to obtain different vector sequences; and S3, selecting the vector sequence with the least switching times from the vector sequences as a control sequence of the PWM rectifier. The method has the advantages of effectively limiting the switching frequency of the system under the condition of ensuring that the prediction period is not changed, ensuring the dynamic performance of the system, along with simplicity, high response speed, flexible constraint of the processing system and the like.)

1. a PWM rectifier control method is characterized in that: the method comprises the following steps:

s1, obtaining control vector predicted values of a preset number through prediction;

S2, arranging and combining the control vector predicted values to obtain different vector sequences;

and S3, selecting the vector sequence with the least switching times from the vector sequences as a control sequence of the PWM rectifier.

2. the PWM rectifier control method according to claim 1, characterized in that: the specific steps of step S1 include:

S1.1, calculating to obtain the output of the current action period according to the output of the previous action period and the control vector predicted value of the current action period through a preset prediction model;

S1.2, predicting a control vector possible value of a next action cycle according to the control vector predicted value of the current action cycle and the output of the current action cycle through the preset prediction model;

and S1.3, selecting a value closest to a preset reference value from the possible values of the control vector as a predicted value of the control vector of the next action period.

3. The PWM rectifier control method according to claim 1 or 2, characterized in that: in step S2, the control vector prediction values are arranged and combined to satisfy a preset constraint condition; the constraint includes at least any one of:

A. in any control period, the number of the changed switches is less than or equal to a first preset value;

B. in any action period, the number of the changed switches is less than or equal to a second preset value;

C. The last switching state of the previous active period is the first switching state of the next active period.

4. The PWM rectifier control method according to claim 3, characterized in that: the constraint further comprises:

D. And the zero vector in the vector sequence is the starting position or the ending position in the vector sequence.

5. The PWM rectifier control method according to claim 4, characterized in that: the constraint further comprises:

E. For each phase, the arrangement is based on the principle of first conducting and then switching off.

6. The PWM rectifier control method according to claim 4, characterized in that: the constraint further comprises:

F. For each phase, switching is only once.

7. the PWM rectifier control method according to claim 3, characterized in that: the first preset value is 1, and the second preset value is 3.

8. A PWM rectifier control device, characterized in that: the system comprises a processor and a memory, wherein the processor is used for executing a control program stored on the memory; the memory stores a control program which, when executed, implements the control method of any one of claims 1 to 7.

9. A PWM rectifier control device, characterized in that: the device comprises a prediction module, a sorting module and a selection module;

the prediction module is used for obtaining the control vector prediction values of a preset number through prediction;

The sorting module is used for carrying out permutation and combination on the control vector predicted values to obtain different vector sequences;

the selection module is used for selecting the vector sequence with the least switching times from the vector sequences as the control sequence of the PWM rectifier.

10. The PWM rectifier control apparatus according to claim 9, wherein: the prediction module is specifically configured to: calculating to obtain the output of the current action period according to the output of the previous action period and the control vector predicted value of the current action period through a preset prediction model; predicting a control vector possible value of a next action cycle according to the control vector predicted value of the current action cycle and the output of the current action cycle through the preset prediction model; and selecting a value closest to a preset reference value from the control vector possible values as a control vector predicted value of the next action period.

11. The PWM rectifier control apparatus according to claim 9 or 10, characterized in that: the sorting module is used for carrying out permutation and combination on the control vector predicted values to meet a preset constraint condition; the constraint includes at least any one of:

A. In any control period, the number of the changed switches is less than or equal to a first preset value;

B. In any action period, the number of the changed switches is less than or equal to a second preset value;

C. the last switching state of the previous active period is the first switching state of the next active period.

12. The PWM rectifier control apparatus according to claim 11, wherein: the constraint further comprises:

D. And the zero vector in the vector sequence is the starting position or the ending position in the vector sequence.

13. the PWM rectifier control apparatus according to claim 12, wherein: the constraint further comprises:

E. For each phase, the arrangement is based on the principle of first conducting and then switching off.

14. The PWM rectifier control apparatus according to claim 12, wherein: the constraint further comprises:

F. For each phase, switching is only once.

15. the PWM rectifier control apparatus according to claim 11, wherein: the first preset value is 1, and the second preset value is 3.

Technical Field

The invention relates to the technical field of PWM rectifier control, in particular to a PWM rectifier control method and device.

background

the voltage of the direct current side is controlled, the voltage of the direct current bus is kept constant, the output of the direct current side is used as an alternating current (or power) instruction of an alternating current (or power) inner ring, the current of the alternating current side is quickly and timely adjusted by the alternating current (or power) inner ring, the influence of load disturbance is restrained, the actual alternating current can quickly track the alternating current instruction, and the unit power factor control is realized. In dual loop control, the voltage outer loop must be matched in speed with the current (or power) inner loop, the outer loop being much slower than the inner loop. Such controls include primarily voltage-directed vector control (VOC) and Direct Power Control (DPC).

VOC is one of control strategies widely applied in PWM rectifier control at present, the static performance of a system is good, but the dynamic performance is limited by a PI regulator, and the dynamic performance cannot reach a high index.

The traditional DPC does not need current inner ring setting, so that the dynamic response is quick, the robustness is better, and the control structure is simple. And the DPC directly selects a proper vector to implement bang-bang control on active power and reactive power through a correlation vector table. DPC control effect relies on the accurate degree of vector table, and switching frequency is unset, and system steady state performance is poor, and the ripple is great during the steady state, needs very high sampling frequency just can obtain better steady state performance, and is higher to the hardware requirement, and the current waveform is also not enough sinusoidal simultaneously, has more high-frequency harmonic component.

Model Predictive Control (MPC) was first proposed by scholars richlet and Cutler in 1978. After more than 30 years of development, great success is achieved in the field of complex industrial process control, and the obvious advantage of processing a complex constraint optimization control problem is shown. In the 21 st century, with the development of DSP and FPGA technologies and the increasing requirements of people for system control targets and constraints, MPC is gradually applied to the fields of power electronics and motion control.

in 2007, the Jose Rodriguez of chile scholars utilizes the inherent characteristics of the existence of a power electronic converter containing limited switch states, proposes a finite control set model predictive control (FCS-MPC) scheme of the converter, introduces the complete MPC scheme into the converter control, and the control system comprises two parts of model prediction and rolling optimization. In the scheme, the prediction and optimization mode is used for correcting the optimal control, and the modeling is convenient; by adopting a rolling optimization strategy, uncertainty caused by model mismatch, distortion, interference and the like is timely compensated, and the interference resistance and the adaptability are improved; but because of no fixed switching frequency and high switching frequency, the high-power PWM rectifier is difficult to be applied in engineering.

Patent application No. 201610983876.1 entitled "a flux linkage vector-based torque control strategy for a permanent magnet synchronous motor" is a background document of the present application, which implements a flux linkage vector-based torque control strategy by calculating and using an optimal duty cycle of each candidate voltage vector when another cost function is minimized in order to reduce switching frequency loss, but since the switching combination is updated every prediction period, the reduction of the switching frequency is very limited by using this method.

Disclosure of Invention

the technical problem to be solved by the invention is as follows: aiming at the technical problems in the prior art, the invention provides the PWM rectifier control method and the device which can effectively limit the switching frequency of the system under the condition of ensuring that the prediction period is not changed, can ensure the dynamic performance of the system, are simple, have high response speed and are flexible in processing system constraint.

In order to solve the technical problems, the technical scheme provided by the invention is as follows: a PWM rectifier control method comprises the following steps:

s1, obtaining control vector predicted values of a preset number through prediction;

s2, arranging and combining the control vector predicted values to obtain different vector sequences;

And S3, selecting the vector sequence with the least switching times from the vector sequences as a control sequence of the PWM rectifier.

Further, the specific step of step S1 includes:

S1.1, calculating to obtain the output of the current action period according to the output of the previous action period and the control vector predicted value of the current action period through a preset prediction model;

s1.2, predicting a control vector possible value of a next action cycle according to the control vector predicted value of the current action cycle and the output of the current action cycle through the preset prediction model;

And S1.3, selecting a value closest to a preset reference value from the possible values of the control vector as a predicted value of the control vector of the next action period.

further, in step S2, the predicted values of the control vectors are arranged and combined to satisfy a preset constraint condition; the constraint includes at least any one of:

A. In any control period, the number of the changed switches is less than or equal to a first preset value;

B. in any action period, the number of the changed switches is less than or equal to a second preset value;

C. The last switching state of the previous active period is the first switching state of the next active period.

Further, the constraint condition further includes:

D. And the zero vector in the vector sequence is the starting position or the ending position in the vector sequence.

Further, the constraint condition further includes:

E. For each phase, the arrangement is based on the principle of first conducting and then switching off.

Further, the constraint condition further includes:

F. For each phase, switching is only once.

further, the first preset value is 1, and the second preset value is 3.

A PWM rectifier control apparatus comprising a processor and a memory, the processor for executing a control program stored on the memory; the memory stores a control program which, when executed, implements a control method as defined in any one of the above.

A PWM rectifier control device comprises a prediction module, a sorting module and a selection module;

The prediction module is used for obtaining the control vector prediction values of a preset number through prediction;

The sorting module is used for carrying out permutation and combination on the control vector predicted values to obtain different vector sequences;

the selection module is used for selecting the vector sequence with the least switching times from the vector sequences as the control sequence of the PWM rectifier.

further, the prediction module is specifically configured to: calculating to obtain the output of the current action period according to the output of the previous action period and the control vector predicted value of the current action period through a preset prediction model; predicting a control vector possible value of a next action cycle according to the control vector predicted value of the current action cycle and the output of the current action cycle through the preset prediction model; and selecting a value closest to a preset reference value from the control vector possible values as a control vector predicted value of the next action period.

further, the sorting module performs permutation and combination on the control vector predicted values to meet a preset constraint condition; the constraint includes at least any one of:

A. In any control period, the number of the changed switches is less than or equal to a first preset value;

B. in any action period, the number of the changed switches is less than or equal to a second preset value;

C. The last switching state of the previous active period is the first switching state of the next active period.

Further, the constraint condition further includes:

D. And the zero vector in the vector sequence is the starting position or the ending position in the vector sequence.

Further, the constraint condition further includes:

E. For each phase, the arrangement is based on the principle of first conducting and then switching off.

Further, the constraint condition further includes:

F. For each phase, switching is only once.

Further, the first preset value is 1, and the second preset value is 3.

Compared with the prior art, the invention has the advantages that:

1. The invention obtains the control vector predicted value through the calculation of the preset prediction model, rearranges and combines the control vector predicted values to obtain a new vector sequence, and selects the vector sequence with the least switching times from the vector sequence to control the PWM rectifier, thereby effectively reducing the switching frequency of the PWM rectifier system.

2. In the invention, in an action period, under the condition that the conduction time of each phase of switching tube is determined, the conduction time of the switching tube is different, and the average output voltage is not influenced, so that the method can effectively ensure the dynamic performance of the system under the condition of effectively reducing the switching frequency of the PWM rectifier system.

3. the control algorithm of the invention is simple, the response speed is fast, and the constraint mode of the processing system is flexible.

Drawings

FIG. 1 is a schematic flow chart of an embodiment of the present invention.

fig. 2 is a schematic diagram of the prediction principle of the control vector predictor according to the embodiment of the present invention.

fig. 3 is a schematic diagram of an arrangement and combination of control vector predictors according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of different pulse arrangements under the same average output voltage according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of a vector predictor sequence obtained by prediction according to an embodiment of the present invention.

fig. 6 is a schematic diagram illustrating rearrangement and combination of vector predictor sequences according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of 4 kinds of characteristic voltage vector sequences after sequence rearrangement according to the embodiment of the present invention.

Detailed Description

the invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.

As shown in fig. 1, the PWM rectifier control method of the present embodiment includes the following steps: s1, obtaining control vector predicted values of a preset number through prediction; s2, arranging and combining the control vector predicted values to obtain different vector sequences; and S3, selecting the vector sequence with the least switching times from the vector sequences as a control sequence of the PWM rectifier.

in this embodiment, the specific step of step S1 includes: s1.1, calculating to obtain the output of the current action period according to the output of the previous action period and the control vector predicted value of the current action period through a preset prediction model; s1.2, predicting a control vector possible value of a next action period according to a control vector predicted value of the current action period and the output of the current action period through a preset prediction model; and S1.3, selecting a value closest to a preset reference value from the possible values of the control vector as a predicted value of the control vector of the next action period.

In this embodiment, a multi-step prediction is performed to obtain a preset number of control vector prediction values. As shown in fig. 2, there are n prediction periods per active period, and in fig. 2, each vertical line is used to divide the control period, wherein tk0, tk1, tk2 are also used to divide the active periods. At the time tk0, the output of a rectifier of the previous action period (previous action period of tk0) at the current time can be directly obtained through detection, and predicted values of control vectors { S (tk0), S (tk0+1), …, S (tk0+ n-1) } of the current action period (action period of tk0 to tk1) can be obtained through previous prediction, and the output { x (tk0+1), x (tk 63 0+2), …, x (tk0+ n-1), x (tk1) }ofthe rectifier of the current action period can be obtained through calculation by a preset prediction model through the two parameters, wherein x (tk0+1), x (tk0+2), …, x (tk0+ n-1) are intermediate process quantities for obtaining x (tk 1); next, according to the calculated output x (tk1) of the rectifier in the current action period, calculating, through a preset prediction model, control vector possible values of each control period in the next action period (action period of tk1 to tk 2) under different combinations of control vector predicted values { S (tk0), S (tk0+1), …, S (tk0+ n-1) }, such as at time tk1+1 in fig. 2, control vector possible values are S1, S2, …, Sn; similarly, for the rest of control periods tk1+2 tk1+ n-1, the corresponding control vector possible values S1, S2, … and Sn can be obtained through the prediction model; next, the control vector possible values S1, S2, …, and Sn of each control cycle may be screened by a preset reference value, and one value closest to the preset reference value is selected from the control vector possible values S1, S2, …, and Sn as the control vector predicted value of the corresponding control cycle. In this embodiment, the controller needs to calculate the switching function combination sequence { S (tk1), S (tk1+1), …, S (tk1+ n-1) } in the next active period before time tk 1.

in this embodiment, the control vector prediction values are arranged and combined in step S2 to satisfy the preset constraint condition; the constraint includes at least any one of: A. in any control period, the number of the changed switches is less than or equal to a first preset value; B. in any action period, the number of the changed switches is less than or equal to a second preset value; C. the last switching state of the previous active period is the first switching state of the next active period. The first preset value is 1 and the second preset value is 3. Through the constraint conditions, the switching device of the PWM rectifier can work according to a certain rule, and the switching frequency is controlled. Constraints a and B define the number of state changes and the number of changes of the switching device within each action period (sampling period), and constraint C avoids the state change at the beginning or end of the action period. Both of these constraints reduce switching losses and extend rectifier life. As shown in fig. 3, the control vector prediction value u is respectively (100), (110) and a zero vector in one action period T, and the zero vector includes (000) and (111). The possible voltage vector application sequences in sector I include the four possible scenarios shown in fig. 3, and the control of which rectifier is specifically selected may be determined according to constraint C. Each control vector predictor includes three bits, each representing three phases, where 1 represents the phase on and 0 represents the phase off.

In this embodiment, the constraint condition further includes: the final effective voltage of the zero vectors (000) and (111) is the same, and the average output voltage of the period is the same under various vector arrangements in an action period. Therefore, in the vector control, SPWM, SVPWM, and various DPWM can be used as the modulation method. In an action period, under the condition that the conduction time of each phase of switch tube is determined, the average output voltage is not influenced by the different conduction time of the switch tube (although the effective vector of the output possibly changes). As shown in fig. 4 (1) a and (1) b, although the action vectors are different, the average output voltage of the period is the same because the on-time corresponding to each phase is the same; similarly, (2) a and (2) b in fig. 4 have the same characteristics.

In this embodiment, the constraint condition for permutation and combination of the control vector prediction values further includes: D. the zero vector in the vector sequence is the starting position or the ending position in the vector sequence. And/or E, for each phase, arranging according to the principle of switching on first and then switching off. And/or, f. only switching once for each phase. In fig. 3, the zero vector (111) is arranged at the start position in fig. 1, the zero vector (111) is arranged at the end position in fig. 2, the zero vector (000) is arranged at the start position in fig. 3, and the zero vector (000) is arranged at the end position in fig. 4.

In this embodiment, if the constraint condition C cannot be satisfied, that is, it cannot be guaranteed that the last switching state of the previous active cycle is the first switching state of the next active cycle, the vector sequence is selected as the control sequence of the PWM rectifier according to the principle that the number of switching operations is the minimum.

In the present embodiment, for better explanation of the control process, a case of 6-step prediction, that is, one action period (sampling period) including 6 prediction periods is taken as an example for explanation. Setting the predicted values of the 6 control vectors obtained by calculation of the prediction module as { u1, u2, u1, u2, u0 and u3}, wherein the values of the prediction vectors are as follows: u0(000), u1(100), u2(110), u3 (010). The pulse sequence is shown in fig. 5. The on-time of each phase in the period is counted and arranged according to the sequence of 1 (on) and 0 (off), so that the sequence shown in fig. 6 can be obtained. It can be seen that the original pulse sequence has a large number of switching times and contains 3 effective vectors u1, u2 and u3, and the rearranged effective vectors only contain 2 effective vectors and 1 zero vector. Then, the zero vector is 000 or 111, the zero vector is located at the initial position or the end position, and the total of 4 features are arranged, and the obtained sequence is shown as 4 sub-graphs in fig. 7. And finally, selecting the pulse arrangement sequence with the least switching times according to the last switching state of the previous period, and taking the pulse arrangement sequence as a control sequence of the PWM rectifier, namely the final effective pulse.

In this embodiment, as can be seen from fig. 7, each sampling period has only two switching actions, and the average sampling frequency is 3 times of the switching frequency due to the three-phase circuit. Therefore, after the switching frequency is determined according to the system performance and the heat dissipation capacity, the sampling period of the system can be determined, and then the prediction period and the prediction period number in each sampling period can be determined.

The PWM rectifier control device of the embodiment comprises a processor and a memory, wherein the processor is used for executing a control program stored in the memory; the memory stores a control program that, when executed, implements the control method as described above.

the PWM rectifier control device comprises a prediction module, a sequencing module and a selection module; the prediction module is used for obtaining the control vector prediction values of a preset number through prediction; the sorting module is used for carrying out permutation and combination on the control vector predicted values to obtain different vector sequences; the selection module is used for selecting the vector sequence with the least switching times from the vector sequences as the control sequence of the PWM rectifier.

in this embodiment, the prediction module is specifically configured to: calculating to obtain the output of the current action period according to the output of the previous action period and the control vector predicted value of the current action period through a preset prediction model; predicting a control vector possible value of a next action period according to a control vector predicted value of the current action period and the output of the current action period through a preset prediction model; and selecting the value closest to the preset reference value from the possible values of the control vector as the predicted value of the control vector of the next action period.

In this embodiment, the sorting module performs permutation and combination on the control vector predicted values to meet a preset constraint condition; the constraint includes at least any one of: A. in any control period, the number of the changed switches is less than or equal to a first preset value; B. in any action period, the number of the changed switches is less than or equal to a second preset value; C. the last switching state of the previous active period is the first switching state of the next active period. The constraints further include: D. the zero vector in the vector sequence is the starting position or the ending position in the vector sequence. The constraints further include: E. for each phase, the arrangement is based on the principle of first conducting and then switching off. The constraints further include: F. for each phase, switching is only once. In the present embodiment, the above-mentioned constraint condition may be selected as needed. In the present embodiment, the first preset value is 1, and the second preset value is 3.

the foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.