Three-phase three-wire system PWM rectifier control method and device

Abstract

The invention relates to the field of power electronic technology devices, and discloses a three-phase three-wire PWM rectifier control method and device, which are characterized in that in order to realize high-efficiency energy consumption of a high-frequency switching power supply system, a double-closed-loop control method based on state feedback is adopted, an outer loop adopts a voltage loop, and an inner loop adopts a dead-beat control strategy; quick response and no-error tracking of the system are realized, and the working performance of the inverter is improved; the fast response of the inverter can be realized through a feedforward mode, and the change of load power can be tracked in real time; through a high-frequency PWM modulation mode, high power factor rectification of the system is realized, and voltage and current distortion of the system is reduced. Harmonic waves of preset times are superposed on the basis of the initial modulation waves, so that the utilization rate of the direct-current bus is improved.

Description

Technical Field

[0001] The present invention relates to the field of power electronic technology devices, and in particular to a three-phase three-wire PWM rectifier control method and device. Background Art

[0002] With the increasing emphasis on energy conservation and emission reduction, PWM rectifiers are widely used in energy storage, electrolysis, electroplating and other industries due to their advantages of high power factor, stable DC output voltage, bidirectional energy flow and effective suppression of harmonics. In recent years, experts and scholars in related fields have proposed control technologies for PWM rectifiers, such as direct power control, predictive current control, adaptive control, space vector control, hysteresis switch table control, and deadbeat current control.

[0003] The deadbeat current control method has the advantages of simple control, fast dynamic response, and good tracking performance, but it also has the problems of large switching frequency changes, high calculation difficulty, sensitivity to circuit parameters, and easy influence by AD sampling and digital operation control delay, thus the harmonic suppression effect is not ideal. At the same time, in order to improve the utilization rate of the DC bus, the method of superimposing the third harmonic is usually adopted, but there is a lot of calculation in the modulation wave to superimpose the third harmonic, and the effect is not satisfactory. Summary of the invention

[0004] In view of this, the present invention provides a three-phase three-wire PWM rectifier control method to solve the shortcomings of PWM rectifier control in the above related technologies.

[0005] In the first aspect, the present invention provides a three-phase three-wire PWM rectifier control method, including: constructing a voltage outer loop and obtaining an initial current reference command amplitude output by the voltage outer loop; calculating a feedforward current command amplitude according to the energy balance principle; adjusting the initial current reference command amplitude using the feedforward current command amplitude, and constructing a three-phase current reference signal; on the basis of zero-beat control, based on the three-phase current reference signal, calculating the three-phase duty cycle of the PWM rectifier and constructing an initial modulation wave, and obtaining a saddle-shaped modulation wave after superimposing a preset order harmonic on the basis of the initial modulation wave; based on the saddle-shaped modulation wave, using a PWM modulation method, obtaining a switching sequence of the PWM rectifier.

[0006] In order to achieve efficient energy use of the high-frequency switching power supply system, the present invention adopts a dual closed-loop control method based on state feedback, the outer loop adopts a voltage loop, and the inner loop adopts a deadbeat control strategy to achieve rapid response and deadbeat tracking of the system, thereby improving the working performance of the inverter; the fast response of the inverter can be achieved through a feedforward method, and the change of load power can be tracked in real time; the high-frequency PWM modulation method can be used to achieve high power factor rectification of the system and reduce the voltage and current distortion of the system. Preset harmonics are superimposed on the initial modulation wave, thereby improving the utilization rate of the DC bus.

[0007] In an optional implementation, the process of obtaining the initial current reference command amplitude includes: subtracting the PWM rectifier DC voltage from the DC voltage command to obtain a DC voltage difference; and using a PI controller to convert the DC voltage difference into the initial current reference command amplitude.

[0008] In order to maintain the stability of the DC side voltage and compensate for the energy loss of the power switch tube and the subsequent circuit, the present invention adopts a PI controller to realize the closed-loop control of the DC side voltage outer loop.

[0009] In an optional embodiment, the process of calculating the feedforward current command amplitude includes: calculating the DC side load power based on the energy balance principle using the phase voltage amplitude, phase current amplitude and power factor angle on the three-phase side of the PWM rectifier; considering the expected value of the power factor angle of the PWM rectifier to be 0, and calculating the feedforward current command amplitude using the DC side load power.

[0010] In an optional embodiment, the process of constructing a three-phase current reference signal includes: taking the product of the feedforward current command amplitude and the synchronization signal of each phase as the feedforward current command; taking the product of the initial current reference command amplitude and the synchronization signal of each phase as the voltage regulation command; and superimposing the feedforward current command and the voltage regulation command to obtain a three-phase current reference signal.

[0011] In an optional implementation, the calculation formula for the three-phase duty cycle of the PWM rectifier is as follows:

[0012]

[0013] Where, d a ,d b ,d c is the three-phase duty cycle; u dc is the DC side voltage; u sa 、u sb 、u sc is the three-phase grid voltage; i da 、i db 、i dc is the three-phase current reference signal; i Sa 、i Sb 、i Sc is the three-phase grid current; 0 <k<1。

[0014] In an optional implementation, the process of obtaining a saddle-shaped modulation wave includes: obtaining a minimum value of the initial modulation wave at each moment; and taking a difference between the initial modulation wave of each phase and the minimum value as a three-phase saddle-shaped modulation wave.

[0015] In a second aspect, the present invention provides a three-phase three-wire PWM rectifier control device, comprising: a voltage outer loop module, used to construct a voltage outer loop and obtain an initial current reference command amplitude output by the voltage outer loop; a feedforward module, used to calculate the feedforward current command amplitude according to the energy balance principle; a current loop module, used to construct a three-phase current reference signal after adjusting the initial current reference command amplitude using the feedforward current command amplitude; a duty cycle calculation module, used to calculate the three-phase duty cycle of the PWM rectifier based on the three-phase current reference signal on the basis of zero-beat control, and construct an initial modulation wave, and obtain a saddle-shaped modulation wave after superimposing a preset order harmonic on the basis of the initial modulation wave; a modulation module, used to obtain a switching sequence of the PWM rectifier based on the saddle-shaped modulation wave and using a PWM modulation method.

[0016] In a third aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the three-phase three-wire PWM rectifier control method of the first aspect or any corresponding embodiment thereof by executing the computer instructions.

[0017] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the three-phase three-wire PWM rectifier control method of the above-mentioned first aspect or any corresponding embodiment thereof.

[0018] In a fifth aspect, the present invention provides a computer program product, comprising computer instructions, wherein the computer instructions are used to enable a computer to execute the three-phase three-wire PWM rectifier control method of the above-mentioned first aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a flow chart of a PWM rectifier control method according to an embodiment of the present invention;

[0021] Figure 2 is a topological diagram of a PWM rectifier according to an embodiment of the present invention;

[0022] Figure 3 is a control block diagram of a PWM rectifier according to an embodiment of the present invention;

[0023] Figure 4 is a single-phase equivalent circuit of a PWM rectifier according to an embodiment of the present invention;

[0024] Figure 5 is a waveform diagram of a carrier wave and a modulated wave according to an embodiment of the present invention;

[0025] Figure 6 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0027] According to an embodiment of the present invention, a three-phase three-wire PWM rectifier control method embodiment is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0028] In this embodiment, a three-phase three-wire PWM rectifier control method is provided. Figure 1 As shown, including:

[0029] Step S1: construct a voltage outer loop and obtain an initial current reference command amplitude output by the voltage outer loop.

[0030] Optionally, the three-phase three-wire PWM rectifier topology is as follows Figure 2 As shown, reference Figure 3 The deadbeat control block diagram based on load power feedforward shown in the figure makes a difference between the PWM rectifier DC voltage and the DC voltage command to obtain the DC voltage difference; and uses the PI controller to convert the DC voltage difference into the initial current reference command amplitude.

[0031] Specifically, Figure 3 In the circuit, the voltage outer loop adopts a PI controller to obtain the output signal of the voltage outer loop PI controller, that is, the initial current reference command amplitude I out .

[0032] Step S2: Calculate the feedforward current command amplitude according to the energy balance principle.

[0033] Optionally, refer to Figure 3According to the energy balance principle, the DC side load power is calculated using the phase voltage amplitude, phase current amplitude and power factor angle of the three-phase side of the PWM rectifier; the expected value of the power factor angle of the PWM rectifier is regarded as 0, and the feedforward current command amplitude is calculated using the DC side load power. The feedforward method can achieve a fast response of the inverter and track the changes in load power in real time.

[0034] Specifically, by sampling the three-phase voltage signal, current signal and DC voltage signal on the AC side, the power P of the DC side load is calculated according to the principle of energy balance. D , where the energy balance formula is as follows:

[0035] (3UIcosθ) / 2=P D (1)

[0036] Where U, I and θ are the phase voltage amplitude, phase current amplitude and power factor angle of the three-phase side respectively.

[0037] Ideally, the power factor angle θ of the three-phase three-wire PWM rectifier is expected to be 0, so the expected three-phase grid current amplitude is:

[0038] I S =2P D / 3U (2)

[0039] In the formula, I S is the desired three-phase grid current amplitude, that is, the feedforward current command amplitude.

[0040] Step S3: After adjusting the initial current reference command amplitude using the feedforward current command amplitude, a three-phase current reference signal is constructed.

[0041] Optionally, refer to Figure 3 , the product of the feedforward current command amplitude and the synchronization signal of each phase is used as the feedforward current command; the product of the initial current reference command amplitude and the synchronization signal of each phase is used as the voltage regulation command; the feedforward current command and the voltage regulation command are superimposed to obtain a three-phase current reference signal.

[0042] Specifically, the single-phase equivalent circuit of the three-phase three-wire PWM rectifier is as follows: Figure 4 As shown, based on Figure 4 , the following voltage and current expressions are obtained:

[0043] Ldi C / dt=u S -u N (3)

[0044] in,

[0045] u S =U Ssin(ωt) (4)

[0046]

[0047] In the formula, u s is the grid voltage; u N is the rectifier output voltage; for u s with u N The phase difference; ω is the fundamental angular frequency.

[0048] Specifically, refer to Figure 3 , the feedforward current command is superimposed on the voltage regulation command to obtain the three-phase current reference signal:

[0049]

[0050] In the formula, i da 、i db 、i dc is the three-phase current reference signal.

[0051] Step S4: On the basis of deadbeat control, based on the three-phase current reference signal, the three-phase duty cycle of the PWM rectifier is calculated, and an initial modulation wave is constructed. After superimposing a preset order harmonic on the basis of the initial modulation wave, a saddle-shaped modulation wave is obtained.

[0052] Specifically, in order to achieve fast and error-free tracking of the inner loop current of the three-phase three-wire PWM rectifier, the control method of this embodiment is added based on the analysis of its single-phase equivalent model, which is as follows:

[0053] The three-phase converter is essentially a parallel mode of three half-bridge converters, and the three half-bridge converters share a set of DC side voltages. Since the three-phase currents of the three-phase converter are symmetrical in steady state and the sum is 0, the neutral line is omitted. For each half-bridge converter, there are two output modes: when the upper switch tube is turned on and the lower switch tube is turned off, the converter output voltage is u dc / 2; when the upper switch is turned off and the lower switch is turned on, the converter output voltage is -u dc / 2. According to the voltage-current relationship shown in equation (3), within a unit control cycle:

[0054]

[0055] Where d is the duty cycle of the PWM rectifier output; u dc is the DC bus voltage value; T S is the control period; Δi c is the change of inductor current in a unit control cycle, then the duty cycle is:

[0056]

[0057] In the actual debugging process, generally the following formula is followed to obtain better stability:

[0058]

[0059] Therefore, based on formula (9), the calculation formula of the three-phase duty cycle of the PWM rectifier is as follows:

[0060]

[0061] Where, d a d b d c is the three-phase duty cycle; u dc is the DC side voltage; u sa 、u sb 、u sc is the three-phase grid voltage; i Sa 、i Sb 、i Sc is the three-phase grid current; 0 <k<1。

[0062] Step S5: Based on the saddle-shaped modulation wave, using the PWM modulation method, a switching sequence of the PWM rectifier is obtained.

[0063] Specifically, in order to achieve efficient energy utilization of high-frequency switching power supply systems, a dual closed-loop control method based on state feedback is adopted. The outer loop adopts a voltage loop and the inner loop adopts a zero-beat control strategy to achieve rapid response and zero-difference tracking of the system and improve the working performance of the inverter. Through high-frequency PWM modulation, high power factor rectification of the system is achieved and the voltage and current distortion of the system is reduced.

[0064] Optionally, the process of obtaining the saddle-shaped modulation wave includes: obtaining the minimum value of the initial modulation wave at each moment; and taking the difference between the initial modulation wave of each phase and the minimum value as the three-phase saddle-shaped modulation wave. The preset number of times may be three times.

[0065] Optionally, the third harmonic superposition method is used to improve the voltage utilization of the DC bus, for example: a d b d c For a sine wave with a phase difference of 120°, obtain the corresponding duty cycle values ​​d of A, B, and C at a certain point in time a d b d c , get it at this time point, and use it to get the minimum value of the three at a certain time. min Then use d a -d min d b -d min dc -d min The duty cycle waveform can be changed into a saddle shape.

[0066] Optionally, in the a -d min ,d b -d min ,d c -d min The minimum and maximum values ​​are limited to form a new modulation wave, which is then compared with the DSP's triangular wave. The value of the DSP's timer period register is set to 7500, and the timer of the DSP's EVA module is used as the carrier signal. The frequency of the triangular wave is 10KHz. According to the SPWM modulation method, the comparison register is set to the rising edge signal flip mode. The duty cycle signal calculated by the deadbeat formula for each control cycle transferred by the comparison registers CMPR1, CMPR2, and CMPR3 is compared with the triangular wave to obtain the SPWM signal, such as Figure 5 shown.

[0067] In this embodiment, a three-phase three-wire PWM rectifier control device is also provided, which is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware of a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0068] This embodiment provides a three-phase three-wire PWM rectifier control device, including:

[0069] The voltage outer loop module is used to construct the voltage outer loop and obtain the initial current reference command amplitude output by the voltage outer loop;

[0070] A feedforward module is used to calculate the feedforward current command amplitude according to the energy balance principle;

[0071] A current loop module is used to construct a three-phase current reference signal after adjusting the initial current reference command amplitude using the feedforward current command amplitude;

[0072] A duty cycle calculation module is used to calculate the three-phase duty cycle of the PWM rectifier based on the three-phase current reference signal on the basis of deadbeat control, and to construct an initial modulation wave. After superimposing a preset harmonic order on the initial modulation wave, a saddle-shaped modulation wave is obtained;

[0073] The modulation module is used for obtaining a switching sequence of a PWM rectifier by using a PWM modulation method based on a saddle-shaped modulation wave.

[0074] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0075] The three-phase three-wire PWM rectifier control device in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0076] The embodiment of the present invention also provides a computer device having the above Figure 6 The three-phase three-wire PWM rectifier control device shown.

[0077] See also Figure 6 , Figure 6 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Figure 6 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 6 A processor 10 is taken as an example.

[0078] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0079] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0080] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0081] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0082] The computer device further comprises a communication interface 30 for the computer device to communicate with other devices or a communication network.

[0083] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0084] A part of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the existence of the computer program instruction in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc., and accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium accessible to the computer.

[0085] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A three-phase three-wire PWM rectifier control method, characterized in that: include: Constructing a voltage outer loop and obtaining an initial current reference command amplitude output by the voltage outer loop; According to the energy balance principle, the feedforward current command amplitude is calculated; After adjusting the initial current reference command amplitude by using the feedforward current command amplitude, a three-phase current reference signal is constructed; On the basis of deadbeat control, based on the three-phase current reference signal, the three-phase duty cycle of the PWM rectifier is calculated, and an initial modulation wave is constructed, and a saddle-shaped modulation wave is obtained after a preset order harmonic is superimposed on the initial modulation wave; Based on the saddle-shaped modulation wave, a switching sequence of the PWM rectifier is obtained by using a PWM modulation method.

2. The three-phase three-wire PWM rectifier control method according to claim 1, characterized in that: The process of obtaining the initial current reference command amplitude includes: Subtracting the DC voltage of the PWM rectifier from the DC voltage command to obtain a DC voltage difference; The DC voltage difference is converted into an initial current reference command amplitude by using a PI controller.

3. The three-phase three-wire PWM rectifier control method according to claim 1, characterized in that: The process of calculating the feedforward current command amplitude includes: According to the energy balance principle, the DC side load power is calculated using the phase voltage amplitude, phase current amplitude and power factor angle on the three-phase side of the PWM rectifier; The expected value of the power factor angle of the PWM rectifier is regarded as 0, and the feedforward current command amplitude is calculated using the DC side load power.

4. The three-phase three-wire PWM rectifier control method according to claim 1, characterized in that: The process of constructing a three-phase current reference signal includes: The product of the feedforward current command amplitude and the synchronization signal of each phase is used as the feedforward current command; The product of the initial current reference command amplitude and the synchronization signal of each phase is used as a voltage regulation command; The feedforward current instruction is superimposed on the voltage regulation instruction to obtain the three-phase current reference signal.

5. The three-phase three-wire PWM rectifier control method according to claim 1, characterized in that: The calculation formula of the three-phase duty cycle of the PWM rectifier is as follows: Where, d a d b d c is the three-phase duty cycle; u dc is the DC side voltage; u sa 、u sb 、u sc is the three-phase grid voltage; i da 、i db 、i dc is the three-phase current reference signal; i Sa 、i Sb 、i Sc is the three-phase grid current; 0 <k<1。 6. The three-phase three-wire PWM rectifier control method according to claim 1, characterized in that: The process of obtaining a saddle-shaped modulation wave includes: At each moment, obtain the minimum value of the initial modulation wave; The difference between the initial modulation wave of each phase and the minimum value is taken as the three-phase saddle-shaped modulation wave.

7. A three-phase three-wire PWM rectifier control device, characterized in that: include: The voltage outer loop module is used to construct the voltage outer loop and obtain the initial current reference command amplitude output by the voltage outer loop; A feedforward module is used to calculate the feedforward current command amplitude according to the energy balance principle; A current loop module, used to construct a three-phase current reference signal after adjusting the initial current reference command amplitude by using the feedforward current command amplitude; A duty cycle calculation module, for calculating the three-phase duty cycle of the PWM rectifier based on the three-phase current reference signal on the basis of deadbeat control, and constructing an initial modulation wave, and obtaining a saddle-shaped modulation wave after superimposing a preset harmonic order on the initial modulation wave; The modulation module is used to obtain the switching sequence of the PWM rectifier based on the saddle-shaped modulation wave by using a PWM modulation method.

8. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the three-phase three-wire PWM rectifier control method according to any one of claims 1 to 6 by executing the computer instructions.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the three-phase three-wire PWM rectifier control method according to any one of claims 1 to 6.

10. A computer program product, characterized in that The invention comprises computer instructions, wherein the computer instructions are used to make a computer execute the three-phase three-wire PWM rectifier control method according to any one of claims 1 to 6.

Images