A PWM control method, rectifier and controller

Abstract

The present specification provides a PWM control method, a rectifier and a controller, the method comprising: calculating S d , S q , transforming S d , S q to a two-phase stationary coordinate system to obtain S α , S β in the alpha-beta coordinate system; transforming S α , S β to a three-phase stationary coordinate system to obtain the switching state S a of phase A, the switching state S b of phase B; calculating the switching state S c of phase C according to the following formula: S L =S H +ρ(S L -S a ), and controlling the on-off state of each controllable switch on each bridge arm according to S b , S c . The present scheme can achieve the same effect as the SVPWM modulation algorithm. The present scheme equivalent to the modulation algorithm is to solve the general solution and special solution of linear equations, and according to the constraint condition, the change range of the general solution is obtained. Compared with the SVPWM modulation algorithm, the present scheme does not need to make sector judgment, the flow is simpler, the calculation workload is smaller, and the control real-time performance is higher.

Description

Technical Field

[0001] This application relates to the field of power electronic control technology, and in particular to a PWM control method, rectifier and controller. Background Technology

[0002] Traditional SVPWM (Space Vector Pulse Width Modulation) modulation algorithms based on space vectors require coordinate transformation and sector determination, involve a large number of irrational number operations and trigonometric function operations, and have complex calculation processes, large computational load, complex procedures, and poor real-time control performance. Summary of the Invention

[0003] The purpose of this application is to provide a PWM control method, rectifier, and controller to solve the problems of large computational load, complex process, and poor real-time control of existing SVPWM modulation algorithms.

[0004] To solve the above-mentioned technical problems, the first aspect of this specification provides a PWM control method for a PWM rectifier. The PWM rectifier includes three parallel bridge arms, each corresponding to one phase of a three-phase power supply (A, B, C). Each bridge arm has an upper bridge arm and a lower bridge arm, and each upper and lower bridge arm has a controllable switch. Both ends of the three bridge arms are used to connect to a DC load. A target point on the bridge arm is used to connect to an AC power supply, and the target point is located on the connection line between two controllable switches. The method includes: acquiring the following parameters: the target voltage u of the DC load. dc The proportional gain K of the current PI regulator iP Integral adjustment gain K iI Current expectation Real-time current acquisition value i d i q The equivalent inductance L on the AC side, the angular frequency ω on the AC side, and the d-axis voltage e on the AC side. d ; Calculate S according to the obtained parameters using the following formula d S q : Among them, S d S represents the on / off state of the d-axis in the dq coordinate system. q This represents the on / off state of the q-axis in the dq coordinate system; S d S q Transforming to a two-phase stationary coordinate system, we obtain S in the αβ coordinate system. α S β ;S α S β Transforming to a three-phase stationary coordinate system, we obtain the switching state S of phase A. a The switching state S of phase Bb Calculate the switching state S of phase C using the following formula. c =S L +ρ(S H -S L ), where ρ is the distribution coefficient; and S m Indicates the amplitude of the modulation voltage, then

[0005]

[0006] According to the S a S b S c Control the on / off state of each controllable switch on each bridge arm.

[0007] In some embodiments, the allocation coefficient may take the following values: 0, 0.5, or 1.

[0008] In some embodiments, the modulation voltage amplitude S m The maximum value is the expected output voltage value on the DC side. times.

[0009] This specification provides a PWM rectifier in a second aspect, comprising: three parallel bridge arms, each corresponding to one phase of a three-phase electrical circuit (A, B, C), each bridge arm having an upper bridge arm and a lower bridge arm, and each upper and lower bridge arm having a controllable switch; both ends of the three bridge arms being used to connect to a DC load; a first interface and a second interface on the DC side, the first interface being connected to a first end of each bridge arm, and the second interface being connected to a second end of each bridge arm; the first interface and the second interface being used to connect to a DC load; a first interface, a second interface, and a third interface on the AC side, the first interface being connected to a target point on the corresponding bridge arm (A), the second interface being connected to a target point on the corresponding bridge arm (B), and the third interface being connected to a target point on the corresponding bridge arm (C); the target point being located on the connection line between two controllable switches on the bridge arm; and a controller for executing the PWM control method described in any of the first aspects.

[0010] A third aspect of this specification provides a controller comprising: a memory and a processor, the processor and the memory being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to implement the steps of the method described in any of the first aspects.

[0011] A fourth aspect of this specification provides a computer storage medium storing computer program instructions that, when executed, implement the steps of the method described in any of the first aspects.

[0012] The PWM control method, rectifier, and controller provided in this manual achieve the same effect as the SVPWM modulation algorithm. This scheme equates the modulation algorithm to solving the general and particular solutions of a linear equation, and obtains the range of variation of the general solution based on constraints. Compared to the SVPWM modulation algorithm, this scheme does not require sector determination, has a simpler process, requires less computation, and thus offers higher real-time control performance. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 The circuit model of the PWM rectifier is shown;

[0015] Figure 2 A schematic diagram of the rectifier's control principle is shown;

[0016] Figure 3 S is shown m Waveforms of each variable when = 0.5;

[0017] Figure 4 S is shown m When ΔS = 0.5 HL Waveform diagram;

[0018] Figure 5 The waveform of the duty cycle in the ρ=0.5 mode is shown;

[0019] Figure 6 The waveform of the duty cycle in the ρ=0 mode is shown;

[0020] Figure 7 The waveform of the duty cycle in the ρ=1 mode is shown;

[0021] Figure 8 The three-phase sinusoidal modulation wave U is shown. ra U rb U rc and bipolar triangular wave U t ;

[0022] Figure 9 The voltage u between connection point A and point N of phase A bridge arm is shown. AN The waveform;

[0023] Figure 10 The voltage u between point B and point N of the B-phase bridge arm connection is shown.BN The waveform;

[0024] Figure 11 The voltage u between the connection point C and point N of the C-phase bridge arm is shown. CN The waveform;

[0025] Figure 12 A flowchart of the PWM control method provided in this specification is shown;

[0026] Figure 13 A schematic diagram of the internal structure of the controller provided in this specification is shown. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0028] A rectifier is a device used to convert alternating current (AC) to direct current (DC). A PWM rectifier uses a PWM (Pulse Width Modulation) control algorithm to convert AC to DC.

[0029] The PWM rectifier includes three parallel bridge arms, each corresponding to one of the three phases (A, B, and C). Each bridge arm has an upper arm and a lower arm, and each upper and lower arm has a controllable switch. Both ends of the three bridge arms are used to connect to DC loads. The AC power output is electrically connected to the connection line between the two controllable switches on the bridge arm.

[0030] Figure 1 The circuit model of a PWM rectifier is shown. Q1, Q2, Q3, Q4, Q5, and Q6 are controllable switches, specifically, for example, IGBTs (Insulated Gate Bipolar Transistors). The branch containing Q1 and Q4 is the first bridge arm, the branch containing Q3 and Q6 is the second bridge arm, and the branch containing Q5 and Q2 is the third bridge arm. The first, second, and third bridge arms are connected in parallel.

[0031] The DC side of the PWM rectifier is connected to a DC load. Capacitor C is the equivalent capacitance on the DC side, and R... L i is the equivalent resistance on the DC side. dc i is the total current on the DC side. L The current flowing through the equivalent resistance, udc This is the voltage on the DC side.

[0032] The AC side of the PWM rectifier is connected to a three-phase AC power supply. On the AC side, each phase corresponds to a branch. Inductance L is the equivalent inductance of the AC side branch, and R is the equivalent resistance of the AC side branch. A, B, and C are the connection points between each phase on the AC side and each bridge arm, respectively. a i is the electromotive force of phase A in the AC power supply. a Let u be the phase A current. a The input voltage is the A-phase voltage of the PWM rectifier; e b i is the electromotive force of phase B in the AC power supply. b For phase B current, u b The input voltage of the B-phase PWM rectifier; e c i is the C-phase electromotive force in the AC power supply. c For phase C current, u c This is the C-phase voltage of the input PWM rectifier. N is the connection point of the three-phase branch of the AC power supply. The three-phase AC power supply is connected to the middle of the bridge arm, that is, to the connection line between the two controllable switches.

[0033] PWM rectifiers typically employ a current feedforward control method. Figure 2 A schematic diagram of the rectifier's control principle is shown.

[0034] The following section introduces the theoretical basis of the PWM control method provided in this manual, based on the circuit model of the PWM rectifier and the current feedforward control principle.

[0035] First, using Kirchhoff's voltage and current laws, the differential equations of the rectifier in the three-phase stationary coordinate system (i.e., the coordinate system of the abc three-phase system) are obtained as follows:

[0036]

[0037] Since the three-phase voltages or currents in a three-phase system are not independent, it is necessary to transform the equations in the three-phase stationary coordinate system into a two-phase stationary coordinate system to establish a mathematical model. First, the variables in the three-phase stationary coordinate system are transformed into the αβ coordinate system. In the αβ coordinate system, the angle between the α axis and the β axis is 90°, and one of the α axis and the β axis is in the same position as one of the coordinate axes in the abc three-phase coordinate system.

[0038] There are two types of variable transformation: equal transformation and equal power transformation. This paper uses equal transformation. The equal transformation matrix M... 3 / 2 and inverse transformation matrix M 2 / 3 They are respectively:

[0039]

[0040] M 3 / 2 Used to transform variables in the abc three-phase coordinate system to the αβ coordinate system, M 2 / 3 Used to transform variables in the αβ coordinate system to the abc three-phase coordinate system.

[0041] After equivalent transformation, the mathematical model of the PWM rectifier in the αβ coordinate system is as follows:

[0042]

[0043] Among them, u α =S α u dc u β =S β u dc For modulation voltage, S α S β With S a S b S c The relationship between them can be represented as:

[0044]

[0045] Because S a S b S c S can take the value of either 0 or 1. α S β The value can only take a limited number of states, but in power electronic equipment, the controlled variable is the average value of a PWM cycle, at which point S a S b S c This can be viewed as the duty cycle of the switching transistor. To reduce excessive repetitive variables, the duty cycle of the three-phase bridge arm still uses S. a S b S c express.

[0046] The three-phase voltage and current in the two-phase stationary coordinate system are AC quantities of the same frequency. However, AC quantity control is difficult, and the classic PI regulation in a PWM rectifier cannot achieve a steady-state error of zero for AC quantities. It is usually necessary to transform the variables in the two-phase stationary coordinate system to a synchronously rotating dq coordinate system, thereby converting the AC quantities into DC quantities. Let the symmetrical three-phase power supply voltage be:

[0047]

[0048] Then the transformation matrix M from the αβ coordinate system to the dq coordinate system is... s / r for:

[0049]

[0050] Then the transformation matrix M from the dq coordinate system to the αβ coordinate system is... r / s for:

[0051]

[0052] After equivalent transformation, matrix M 3 / 2 and inverse transformation matrix M 2 / 3 After the transformation, the α-axis component is U m cosωt, the β-axis component is U m sinωt, using M s / r After the transformation matrix undergoes the dq transformation, the mathematical model of the PWM rectifier in the dq coordinate system is as follows:

[0053]

[0054] As can be seen from the above equation, the dq-axis variables of the converter are coupled to each other, which brings certain difficulties to the controller design. Currently, the widely used method is the current feedforward control strategy. Let V... d =e d +ωLi q -S d u dc V q =-ωLi d -S q u dc ,but

[0055] V d V q Treated as a control variable, when the current regulator uses a PI regulator, V d V q It can be represented as The actual control quantity is then obtained as follows:

[0056]

[0057] In the formula K iP K iI These are the proportional and integral adjustment coefficients for the inner current loop, respectively, K. iP K iI Predetermined; For i d and i q Given the current value, S can be solved using this formula. d and S q Find S d and S q Then, S is obtained by inverse dq transformation. α S β .

[0058]

[0059] S a S b S c Let S be the duty cycle of the upper transistors in the three bridge arms a, b, and c. Solving the PWM modulation process involves determining the duty cycle of S. α Solve for S a S b S c The process, and S a S b S c It should satisfy: 0≤S i ≤1, i=a,b,c. Therefore, the essence of modulation is solving equations that satisfy the above constraints. The above equation can be expressed in matrix form as:

[0060]

[0061] Let the coefficient matrix in the formula be A, that is... Its augmented matrix is ​​B, that is:

[0062]

[0063] It's easy to see that regardless of S α S β Given the values ​​of and the rank of matrices B and A being 2, using linear algebra, the system of equations (8) has a solution. Since there are three unknowns in the system of equations, and the rank of matrices B and A is 2, the system of equations has infinitely many solutions, and the dimension of the solution is 1. The general structure of the solution to the system of equations, consisting of a general solution and a particular solution, is as follows:

[0064]

[0065] In the equation, the first term on the right-hand side is the general solution, where c is any number; the second term on the right-hand side is a particular solution. Assume... S c =S c The constraint conditions then become:

[0066]

[0067] so,

[0068]

[0069] definition

[0070]

[0071] Then S L ≤S c≤S H There are infinitely many solutions that satisfy this condition, but the resulting S... α S β They are all equivalent. Let the modulation vector be a circular rotation vector, i.e., S. α S β Represented as:

[0072]

[0073] In the above formula, S m Let S be the amplitude of the modulation voltage, and θ be the phase angle of the modulation voltage. When S... m =0.5 when S α S β S x S y S L S H Waveform diagram, S x S y The amplitude is S α S β 3 times the amplitude, S x The phase lag is S α 30°, S y With S β They are in phase. Therefore, only S needs to be selected. c Satisfying the S L ≤S c ≤S H That's all.

[0074] The following section introduces the maximum modulation output under the unified modulation model. Here, unified modulation refers to the process described earlier where formula calculation replaces the inverse transform solution.

[0075] S L S H The difference between them and S m Related to, with S m As the number of elements increases, the difference between them decreases, and may even decrease to S. L Greater than S H Therefore, it is necessary to study the situation that satisfies equation S. L ≤S c ≤S H Maximum S m Value. Based on the previous equation (13) and The expression can be obtained as follows:

[0076]

[0077] Comparison Figure 3 Divide one period into 6 intervals, S L S H It can be represented as a piecewise function.

[0078]

[0079]

[0080] Figure 3 S is shown m Waveforms of each variable when = 0.5.

[0081] Define function ΔS HL =S H -S L function ΔS HL In S m The curve when = 0.5 is as follows Figure 4 As shown.

[0082] from Figure 4 As can be seen from this, the function ΔS HL There are 6 minimum values ​​within a period. When the minimum value is 0, S... m This is the maximum value that satisfies the above conditions. To find S... m The maximum value of ΔS HL Taking the derivative and setting it to 0, we can find the point where the minimum value occurs. Substituting this into ΔS HL The minimum value can be found by tracing the points where the minimum value occurs. After calculation, the points where the minimum value occurs are located at... At, and ΔS HL The minimum value is Setting it to 0, we get That is, the maximum output phase voltage amplitude is 0.577 times the DC voltage, which is equal to the maximum output value of SVPWM.

[0083] The following section introduces the implementation of SVPWM under the unified modulation model.

[0084] Based on the foregoing analysis, when S m When ≤0.577, S is satisfied. L ≤S H To satisfy S L ≤S c ≤S H S can be defined c =S L +ρ(S H -S L ), 0≤ρ≤1, where ρ is ΔS HL The allocation coefficients. The three most commonly used patterns are: ρ = 0, 0.5, and 1. Figure 5 , Figure 6 , Figure 7 The duty cycle waveforms of phases A, B, and C are shown for three modes: ρ = 0, 0.5, and 1.

[0085] from Figure 5 , Figure 6 , Figure 7 It can be seen that different ΔS HL The waveform under the allocation coefficients is exactly the same as the waveform of the traditional time allocation coefficients with different zero vectors, and the DC voltage rate is also completely consistent with SVPWM. Compared with the traditional SVPWM algorithm, this simplified algorithm does not require coordinate transformation and sector judgment, and does not contain irrational number operations or trigonometric function operations, and has the advantages of simple process and small amount of computation.

[0086] The S generated by this method a S b S c The wave is the modulation wave U of the three phases A, B, and C. ra U rb U rc The modulating wave is then compared with the carrier wave. When the modulating wave and the carrier wave intersect, the turn-on time of the switching transistor is determined by the intersection point, thus obtaining a pulse sequence with equal amplitude and a width that varies according to a sine law. This pulse sequence is the pulse sequence required for PWM modulation. By inputting this pulse sequence into the switching transistors of each bridge arm, the switching transistors of each bridge arm can be turned on and off as needed.

[0087] Figure 8 The three-phase sinusoidal modulation wave U is shown. ra U rb U rc and bipolar triangular wave U t (i.e., carrier wave), these variables are all normalized dimensionless parameters. Figure 9 The voltage u between connection point A and point N of phase A bridge arm is shown. AN waveform, Figure 10 The voltage u between point B and point N of the B-phase bridge arm connection is shown. BN waveform, Figure 11 The voltage u between the connection point C and point N of the C-phase bridge arm is shown. CN The waveform.

[0088] Based on the above theoretical derivation, this specification provides a PWM control method that can be used in a PWM rectifier. The PWM rectifier includes three parallel bridge arms, each corresponding to one phase of a three-phase power supply (A, B, C). Each bridge arm has an upper bridge arm and a lower bridge arm, and each upper and lower bridge arm has a controllable switch. Both ends of the three bridge arms are used to connect to a DC load. The target point on the bridge arm is used to connect to an AC power supply, and the target point is located on the connection line between two controllable switches. The PWM rectifier can be used as follows: Figure 1 As shown.

[0089] like Figure 12 As shown, the PWM control method provided in this manual includes the following steps:

[0090] S10: Obtain the following parameter: the target voltage u of the DC load dc The proportional gain K of the current PI regulator iP Integral adjustment gain K iI Current expectation Real-time current acquisition value i d i q The equivalent inductance L on the AC side, the angular frequency ω on the AC side, and the d-axis voltage e on the AC side. d .

[0091] S20: Calculate S according to the obtained parameters using the following formula. d S q : Among them, S d S represents the on / off state of the d-axis in the dq coordinate system. q This represents the on / off state of the q-axis in the dq coordinate system.

[0092] S30: S d S q Transforming to a two-phase stationary coordinate system, we obtain S in the αβ coordinate system. α S β .

[0093] S40: [S] α S β Transforming to a three-phase stationary coordinate system, we obtain the switching state S of phase A. a The switching state S of phase B b .

[0094] S50: Calculate the switching state S of phase C according to the following formula. c =S L +ρ(S H -S L ), where ρ is the distribution coefficient; and S m Indicates the amplitude of the modulation voltage, then

[0095]

[0096] S60: According to the S a S b S c Control the on / off state of each controllable switch on each bridge arm.

[0097] As can be seen from the theoretical derivation above, the PWM control method described in steps S10 to S60 can achieve the same effect as SVPWM. This scheme equates the modulation algorithm to solving the general and particular solutions of a linear equation, and obtains the range of variation of the general solution based on the constraints. Compared to the SVPWM modulation algorithm, this scheme does not require sector judgment, has a simpler process, and requires less computation, thus resulting in higher real-time control performance.

[0098] The allocation coefficient can range from [0, 1]. In some embodiments, for ease of calculation, the allocation coefficient can be one of the following: 0, 0.5, or 1.

[0099] Modulation voltage amplitude S m The maximum value is the DC-side output voltage. Based on this, the modulation voltage amplitude S can be determined using the known expected DC-side output voltage value. m S m The range of values ​​is

[0100] This specification also provides a PWM rectifier, including three parallel bridge arms, a DC side interface, an AC side interface, and a controller.

[0101] Each bridge arm corresponds to one of the three phases A, B, and C. Each bridge arm is equipped with an upper bridge arm and a lower bridge arm, and each upper bridge arm and lower bridge arm is equipped with a controllable switch. The two ends of the three bridge arms are used to connect DC loads.

[0102] The DC side has a first interface and a second interface. The first interface on the DC side is connected to the first end of each bridge arm, and the second interface on the DC side is connected to the second end of each bridge arm. The first interface and the second interface are used to connect a DC load.

[0103] The first interface on the AC side is connected to the target point on the corresponding bridge arm A, the second interface on the AC side is connected to the target point on the corresponding bridge arm B, and the third interface on the AC side is connected to the target point on the corresponding bridge arm C; the target point is located on the connecting line between two controllable switches on the bridge arm.

[0104] The controller is used to execute the PWM control method provided in this specification.

[0105] This invention also provides a controller, such as... Figure 13 As shown, the controller may include a processor 1301 and a memory 1302, wherein the processor 1301 and the memory 1302 can be connected via a bus or other means. Figure 13 Taking the example of a connection between China and Israel via a bus.

[0106] Processor 1301 may be a central processing unit (CPU). Processor 1301 may also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations thereof.

[0107] The memory 1302, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the PWM control method in the embodiments of the present invention. The processor 1301 executes various functional applications and data processing of the processor by running the non-transitory software programs, instructions, and modules stored in the memory 1302, thereby implementing the PWM control method in the above method embodiments.

[0108] The memory 1302 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created by the processor 1301, etc. Furthermore, the memory 1302 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 1302 may optionally include memory remotely located relative to the processor 1301, and these remote memories may be connected to the processor 1301 via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0109] The one or more modules are stored in the memory 1302, and when executed by the processor 1301, the above-described PWM control method is performed.

[0110] The specific details of the controller described above can be understood by referring to the relevant descriptions and effects in the method embodiments, and will not be repeated here.

[0111] This specification also provides a computer storage medium storing computer program instructions that, when executed, implement the steps of the above-described PWM control method.

[0112] This specification also provides a computer program product comprising a computer program that, when executed by a processor, implements the steps of the above-described PWM control method.

[0113] For details regarding the controller, please refer to the relevant descriptions and effects in the above method embodiments; they will not be repeated here.

[0114] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium can also include combinations of the above types of memory.

[0115] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. The focus of each embodiment is to describe the differences from other embodiments.

[0116] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute certain parts of the methods of various embodiments of this application.

[0117] Those skilled in the art will also know that, besides implementing the controller using purely computer-readable program code, the same functions can be achieved by logically programming the method steps, making the controller function as logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers (PLCs), and embedded microcontrollers. Therefore, such a controller can be considered a hardware component, and the devices within it used to implement various functions can also be considered structures within that hardware component. Alternatively, the devices used to implement various functions can be considered as both software modules implementing the method and structures within a hardware component.

[0118] Those skilled in the art will understand that the embodiments of this specification can be provided as methods, systems, or computer program products. Therefore, the embodiments of this specification can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, the embodiments of this specification can take the form of computer program products implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0119] The above description is merely an embodiment of the present specification and is not intended to limit the embodiments of the present specification. For those skilled in the art, various modifications and variations can be made to the embodiments of the present specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the embodiments of the present specification should be included within the scope of the claims of the embodiments of the present specification.

Claims

1. A PWM control method, characterized in that, For a PWM rectifier, the PWM rectifier includes three parallel bridge arms, each corresponding to one phase of a three-phase power supply (A, B, C). Each bridge arm has an upper bridge arm and a lower bridge arm, and each upper and lower bridge arm has a controllable switch. Both ends of the three bridge arms are used to connect to a DC load. A target point on the bridge arm is used to connect to an AC power supply, and the target point is located on the connection line between two controllable switches. The rectifier includes: Obtain the following parameters: the target voltage u of the DC load. dc The proportional gain K of the current PI regulator iP Integral adjustment gain K iI Current expectation Real-time current acquisition value i d i q The equivalent inductance L on the AC side, the angular frequency ω on the AC side, and the d-axis voltage e on the AC side. d ; Calculate S according to the obtained parameters using the following formula. d S q : Among them, S d S represents the on / off state of the d-axis in the dq coordinate system. q This represents the on / off state of the q-axis in the dq coordinate system. S d S q Transforming to a two-phase stationary coordinate system, we obtain S in the αβ coordinate system. α S β ; S α S β Transforming to a three-phase stationary coordinate system, we obtain the switching state S of phase A. a The switching state S of phase B b ; Calculate the switching state S of phase C using the following formula. c =S L +ρ(S H -S L ), where ρ is the distribution coefficient; and S m Indicates the amplitude of the modulation voltage, then According to the S a S b S c Control the on / off state of each controllable switch on each bridge arm.

2. The method according to claim 1, characterized in that, The allocation coefficient can take one of the following values: 0, 0.5, or 1.

3. The method according to claim 1, characterized in that, The modulation voltage amplitude S m The maximum value is the expected output voltage value on the DC side. times.

4. A PWM rectifier, characterized in that, include: The bridge arm is arranged in parallel, each corresponding to one of the three phases A, B, and C. Each bridge arm is provided with an upper bridge arm and a lower bridge arm, and each upper bridge arm and lower bridge arm is provided with a controllable switch; the two ends of the three bridge arms are used to connect DC loads. The DC side has a first interface and a second interface. The first interface is connected to the first end of each bridge arm, and the second interface is connected to the second end of each bridge arm. The first interface and the second interface are used to connect a DC load. The AC side has a first interface, a second interface, and a third interface. The first interface is connected to the target point on the corresponding bridge arm A, the second interface is connected to the target point on the corresponding bridge arm B, and the third interface is connected to the target point on the corresponding bridge arm C. The target point is located on the connecting line between two controllable switches on the bridge arm. A controller for performing the PWM control method according to any one of claims 1 to 3.

5. A controller, characterized in that, include: A memory and a processor, the processor and the memory being communicatively connected to each other, the memory storing computer instructions, the processor executing the computer instructions to implement the steps of the method according to any one of claims 1 to 3.

6. A computer storage medium, characterized in that, The computer storage medium stores computer program instructions, which, when executed, implement the steps of the method according to any one of claims 1 to 3.

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