A control method of a vienna rectifier under power grid imbalance

Abstract

The application discloses a control method of a Vienna rectifier under power grid imbalance, which comprises the following steps: sampling three-phase input voltage signals V a , b , c of the Vienna rectifier in the power grid, sampling three-phase input current signals I a , b , c and an output voltage signal V dc ; comparing an output voltage reference value V dc‑ref with the output voltage signal V dc to obtain an error value of the output voltage reference value V dc‑ref and the output voltage signal V dc , and inputting the error value into a proportional-integral regulator to form a voltage loop of the Vienna rectifier, wherein the output of the voltage loop is k; respectively converting the three-phase input voltage signals V a , b , c and the three-phase input current signals I a , b , c into corresponding input voltage signals V d , q and input current signals I d , q through a three-phase-two-phase conversion coordinate system. The application solves the problem of unstable output voltage in the prior art, realizes the operation control of the Vienna rectifier under power grid imbalance, speeds up the response speed of the system, and can maintain the unit power factor of the rectifier and the stability of the direct-current voltage.

Description

Technical Field

[0001] This invention relates to the field of power conversion technology, specifically to a control method for a Vienna rectifier under power grid imbalance. Background Technology

[0002] With the development of more-electric and all-electric aircraft technologies, the demand for power capacity from airborne equipment is increasing. Aircraft power systems are increasingly adopting AC variable frequency power supply systems, where the generator directly drives the aircraft engine to produce a three-phase variable frequency AC input with an effective voltage of 115V and a frequency of 360–800Hz. In aviation power supply systems, due to their relative independence and high internal resistance, there are high requirements for the harmonic content of the grid current. Three-phase rectifiers with power factor correction (PFC) functions are particularly important in the power grid. Among them, the three-phase three-level three-switch (Vienna) rectifier has advantages such as high efficiency, low harmonic content, high power density, and low voltage stress, making it very suitable for application in aviation power supply systems.

[0003] As a three-phase active power factor correction device, the input and output performance of the Vienna rectifier is closely related to the grid quality. In practical applications, the grid may experience abnormal operating conditions such as three-phase imbalance and phase deviation, resulting in the grid voltage containing not only positive-sequence components but also negative-sequence and zero-sequence components. Due to the presence of the negative-sequence component, if conventional dual-loop PI control in the dq coordinate system is used, it will cause secondary ripple on the DC side of the rectifier, leading to unstable output voltage. Simultaneously, harmonics will be introduced into the input current, causing current distortion, and in severe cases, leading to abnormal operation of the rectifier or even disconnection from the grid.

[0004] Therefore, a new technological solution is needed. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a control method for a Vienna rectifier under grid imbalance, so as to at least solve the problem of unstable output voltage in the prior art.

[0006] The embodiments of the present invention provide the following technical solutions:

[0007] This invention provides a control method for a Vienna rectifier under power grid imbalance, comprising:

[0008] Sampling the three-phase input voltage signal V of the Vienna rectifier in the power grid a V b V c Three-phase input current signal I a I b I c and output voltage signal V dc ;

[0009] Output voltage reference value V dc-ref With the output voltage signal V dc A comparison is performed to obtain the output voltage reference value V. dc-ref With the output voltage signal V dc The error value is obtained and input into the proportional-integral regulator to form the voltage loop of the Vienna rectifier, whose output is k;

[0010] The three-phase input voltage signal V a V b V c and the three-phase input current signal I a I b I c The corresponding input voltage signal V is obtained by transforming the coordinate system from three-phase to two-phase. d V q and input current signal I d I q ;

[0011] The input voltage signal V d V q and the input current signal I d I q Separate positive and negative sequences to obtain the input current signal. and input voltage signal

[0012] Based on the input voltage signal And output k to obtain the positive and negative sequence current reference values ​​I d-pref I q-pref I d-nref I q-nref ;

[0013] The positive and negative sequence current reference value I d-pref I q-pref I d-nref I q-nref and input current signal The error obtained by comparing the differences is fed into the sliding mode controller to form the current loop of the Vienna rectifier;

[0014] Obtain the control variables of the sliding mode controller, and select an exponential rate sliding mode control function based on the control variables. The exponential rate sliding mode control function is as follows:

[0015]

[0016] Furthermore, the step of obtaining the positive and negative sequence current reference value I d-pref I q-prefI d-nref I q-nref The formula is as follows:

[0017]

[0018]

[0019]

[0020]

[0021] in,

[0022] Furthermore, the control variables of the sliding mode controller are obtained as follows:

[0023]

[0024] in, This is the Vienna rectifier current command in the dq coordinate system.

[0025] Furthermore, the sliding mode control model of the sliding mode controller is as follows:

[0026]

[0027] Where, ε i n i α i k i These are the sliding mode parameters of the current loop sliding mode controller. These are the control voltages in the dq coordinate system, respectively.

[0028] Furthermore, following the current loop constituting the Vienna rectifier, the following is also included:

[0029] The Lyapunov function is defined as follows:

[0030]

[0031] The Lyapunov function is used as the basis for stability judgment to control the stable operation of the Vienna rectifier.

[0032] Furthermore, controlling the stable operation of the Vienna rectifier based on the Lyapunov function as the stability criterion includes:

[0033] To ensure stable operation of the Vienna rectifier When the Vienna rectifier operates stably, it will be stable.

[0034] Furthermore, after obtaining the control variables of the sliding mode controller and selecting the exponentially approaching rate sliding mode control function based on the control variables, the method further includes:

[0035] The output U of the Vienna rectifier current source a U b U c Superimpose the zero-sequence component U o To obtain the three-phase modulated wave U x，o x = a, b, c;

[0036] The three-phase modulation wave U x，o Intersecting with the triangular carrier wave, the conduction time T of the switching transistor is obtained. x，o x = a, b, c;

[0037] Based on the conduction time T x，o The duty cycle signal is obtained and used to drive the switching transistor to turn on and off, thereby controlling the Vienna rectifier.

[0038] Furthermore, the three-phase modulated wave U x，o The calculation formula is as follows:

[0039] U x，o =U x +U o x = a, b, c;

[0040]

[0041] Among them, U o The zero-sequence component is used to increase the modulation ratio of the Vienna rectifier, U max U min For three-phase modulated wave U x，0 The maximum and minimum values ​​are obtained by comparing the amplitude values ​​of the three-phase modulation wave.

[0042] Compared with the prior art, the beneficial effects that the at least one technical solution adopted in the embodiments of the present invention can achieve include at least:

[0043] This invention discloses a control method for a Vienna rectifier under grid imbalance, which involves sampling the three-phase input voltage signal V of the Vienna rectifier in the power grid. a V b V c Three-phase input current signal I a I b I c and output voltage signal V dc ; Output voltage reference value V dc-ref With output voltage signal V dcA comparison is made to obtain the output voltage reference value V. dc-ref With output voltage signal V dc The error value is calculated and input into the proportional-integral regulator to form the voltage loop of the Vienna rectifier, whose output is k; the three-phase input voltage signal V is... a V b V c and three-phase input current signal I a I b I c The corresponding input voltage signal V is obtained by transforming the coordinate system from three-phase to two-phase. d V q and input current signal I d I q ; Input voltage signal V d V q and input current signal I d I q Separate positive and negative sequences to obtain the input current signal. and input voltage signal Based on input voltage signal And output k to obtain the positive and negative sequence current reference values ​​I d-pref I q-pref I d-nref I q-nref ; Set the positive and negative sequence current reference values ​​I d-pref I q-pref I d-nref I q-nref and input current signal The error obtained by comparing the differences is fed into the sliding mode controller to form the current loop of the Vienna rectifier. The control variables of the sliding mode controller are obtained, and the exponential approach rate sliding mode control function is selected based on the control variables. This solves the problem of unstable output voltage in the prior art, realizes the operation control of Vienna rectifier under grid imbalance, speeds up the system response, and can maintain the stability of the rectifier's unity power factor and DC voltage. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 Here is the existing PI control output voltage waveform diagram;

[0046] Figure 2 The output voltage waveform diagram is shown below, illustrating a control method for a Vienna rectifier under grid imbalance according to an embodiment of the present invention.

[0047] Figure 3 The waveforms of the sliding mode control input voltage and input current in an embodiment of the present invention are shown.

[0048] Figure 4 This is a Simulink simulation diagram for sliding mode control. Detailed Implementation

[0049] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0050] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0052] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0053] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0054] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0055] This invention provides a control method for a Vienna rectifier under power grid imbalance, comprising:

[0056] Step S102: Sample the three-phase input voltage signal V of the Vienna rectifier in the power grid. a V b V c Three-phase input current signal I a I b I c and output voltage signal V dc ;

[0057] Step S104: Set the output voltage reference value V dc-ref With the output voltage signal V dc A comparison is performed to obtain the output voltage reference value V. dc-ref With the output voltage signal V dc The error value is obtained and input into the proportional-integral regulator to form the voltage loop of the Vienna rectifier, whose output is k;

[0058] Step S106: Convert the three-phase input voltage signal V a V b V c and the three-phase input current signal I a I b I c The corresponding input voltage signal V is obtained by transforming the coordinate system from three-phase to two-phase. d V q and input current signal I d I q ;

[0059] Step S108: Convert the input voltage signal V d V q and the input current signal I d I q Separate positive and negative sequences to obtain the input current signal. and input voltage signal

[0060] Step S110: Based on the input voltage signal And output k to obtain the positive and negative sequence current reference values ​​Id-pref I q-pref I d-nref I q-nref ;

[0061] Step S112: Set the positive and negative sequence current reference value I d-pref I q-pref I d-nref I q-nref and input current signal The error obtained by comparing the differences is fed into the sliding mode controller to form the current loop of the Vienna rectifier;

[0062] Step S114: Obtain the control variables of the sliding mode controller, and select the exponential rate sliding mode control function based on the control variables. The exponential rate sliding mode control function is:

[0063]

[0064] Furthermore, the step of obtaining the positive and negative sequence current reference value I d-pref I q-pref I d-nref I q-nref The formula is as follows:

[0065]

[0066]

[0067]

[0068]

[0069] in,

[0070] Furthermore, the control variables of the sliding mode controller are obtained as follows:

[0071]

[0072] in, This is the Vienna rectifier current command in the dq coordinate system.

[0073] Furthermore, the sliding mode control model of the sliding mode controller is as follows:

[0074]

[0075] Where, ε i n i α i k i These are the sliding mode parameters of the current loop sliding mode controller. These are the control voltages in the dq coordinate system, respectively.

[0076] Furthermore, following the current loop constituting the Vienna rectifier, the following is also included:

[0077] The Lyapunov function is defined as follows:

[0078]

[0079] The Lyapunov function is used as the basis for stability judgment to control the stable operation of the Vienna rectifier.

[0080] Furthermore, controlling the stable operation of the Vienna rectifier based on the Lyapunov function as the stability criterion includes:

[0081] To ensure stable operation of the Vienna rectifier When the Vienna rectifier operates stably, it will be stable.

[0082] Furthermore, after obtaining the control variables of the sliding mode controller and selecting the exponentially approaching rate sliding mode control function based on the control variables, the method further includes:

[0083] The output U of the Vienna rectifier current source a U b U c Superimpose the zero-sequence component U o To obtain the three-phase modulated wave U x，o x = a, b, c;

[0084] The three-phase modulation wave U x，o Intersecting with the triangular carrier wave, the conduction time T of the switching transistor is obtained. x，o x = a, b, c;

[0085] Based on the conduction time T x，o The duty cycle signal is obtained and used to drive the switching transistor to turn on and off, thereby controlling the Vienna rectifier.

[0086] The intersection method between the modulating wave and the carrier wave needs to be determined based on the sign of the modulating wave.

[0087] The three-phase duty cycle signals Da, Db, and Dc can be obtained based on the conduction time of the switching transistors, and then sent to the PWM module of the digital controller to output three-phase drive signals to realize the control of the rectifier.

[0088] Furthermore, the three-phase modulated wave U x，o The calculation formula is as follows:

[0089] U x，o =U x +U o x = a, b, c;

[0090]

[0091] Among them, U o The zero-sequence component is used to increase the modulation ratio of the Vienna rectifier, U max U min For three-phase modulated wave U x，0 The maximum and minimum values ​​are obtained by comparing the amplitude values ​​of the three-phase modulation wave.

[0092] The technical solutions of the present invention are not limited to the above embodiments. All technical solutions obtained by equivalent substitution fall within the scope of protection claimed by the present invention.

[0093] To verify the superiority and feasibility of this invention, a simulation model and experimental prototype were built to conduct simulation and experimental verification of the Vienna rectifier control method under power grid imbalance proposed in this invention.

[0094] Simulation example:

[0095] like Figures 1-4 As shown, using the Vienna rectifier control method under grid imbalance in this embodiment, a simulation model is built on Simulink simulation software to simulate the Vienna rectifier in the application scenario. The steps are as follows:

[0096] The effective values ​​of the input voltages are set as follows: Phase A 200V, Phase B 220V, Phase C 240V. There is a 20V imbalance in the three-phase voltage. The input voltage frequency is 50Hz, the output voltage is 700V, the output power is 4.9kW, the switching frequency is 50kHz, the sampling frequency is 100kHz, the input inductance is 3mH, and the output capacitance is 660μF.

[0097] Simulation results show that the control method proposed in this invention can suppress the input current harmonics and output voltage second ripple of the Vienna rectifier under three-phase unbalanced input. It can also maintain the control effect when the grid frequency changes, and the response speed is faster than that of traditional PI control.

[0098] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the product embodiments described later, since they correspond to the methods, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions in the system embodiments.

[0099] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for a Vienna rectifier under power grid imbalance, characterized in that, include: Sampling the three-phase input voltage signal V of the Vienna rectifier in the power grid a V b V c Three-phase input current signal I a I b I c and output voltage signal V dc ; Output voltage reference value V dc-ref With the output voltage signal V dc A comparison is performed to obtain the output voltage reference value V. dc-ref With the output voltage signal V dc The error value is obtained and input into the proportional-integral regulator to form the voltage loop of the Vienna rectifier, whose output is k; The three-phase input voltage signal V a V b V c and the three-phase input current signal I a I b I c The corresponding input voltage signal V is obtained by transforming the coordinate system from three-phase to two-phase. d V q and input current signal I d I q ; The input voltage signal V d V q and the input current signal I d I q Separate positive and negative sequences to obtain the input current signal. , , , and input voltage signal , , , ; Based on the input voltage signal , , , And output k to obtain the positive and negative sequence current reference values ​​I d-pref I q-pref I d-nref I q-nref The step of obtaining the positive and negative sequence current reference value I d-pref I q-pref I d-nref I q-nref The formula is as follows: ； ； ； ； Where D=( ) 2 +( ) 2 -( ) 2 -( ) 2 , ; The positive and negative sequence current reference value I d-pref I q-pref I d-nref I q-nref and input current signal , , , The error obtained by comparing the differences is fed into the sliding mode controller to form the current loop of the Vienna rectifier; Obtain the control variables of the sliding mode controller, and select an exponential rate sliding mode control function based on the control variables. The exponential rate sliding mode control function is as follows: ； in, , , , These are the sliding mode parameters of the current loop sliding mode controller; The output U of the Vienna rectifier current source a U b U c Superimpose the zero-sequence component U o To obtain the three-phase modulated wave U x，o x = a, b, c; The three-phase modulation wave U x，o Intersecting with the triangular carrier wave, the conduction time T of the switching transistor is obtained. x，o x = a, b, c; Based on the conduction time T x，o The duty cycle signal is obtained and the switching transistor is driven to turn on and off, thereby controlling the Vienna rectifier. The three-phase modulation wave U x，o The calculation formula is as follows: U x，o =U x +U o ,x=a,b,c; ； Among them, U o The zero-sequence component is used to increase the modulation ratio of the Vienna rectifier, U max U min For three-phase modulated wave U x，0 The maximum and minimum values ​​are obtained by comparing the amplitude values ​​of the three-phase modulation wave.

2. The control method according to claim 1, characterized in that, The control variables of the sliding mode controller are obtained as follows: in, , , , This is the Vienna rectifier current command in the dq coordinate system.

3. The control method according to claim 1, characterized in that, The sliding mode control model of the sliding mode controller is as follows: ； in, , , , These are the sliding mode parameters of the current loop sliding mode controller. , , , These are the control voltages in the dq coordinate system, respectively.

4. The control method according to claim 2, characterized in that, Following the current loop that constitutes the Vienna rectifier, the following is also included: The Lyapunov function is defined as follows: ； The Lyapunov function is used as the basis for stability judgment to control the stable operation of the Vienna rectifier.

5. The control method according to claim 4, characterized in that, Using the Lyapunov function as the stability criterion, controlling the stable operation of the Vienna rectifier includes: To ensure stable operation of the Vienna rectifier , , , When the Vienna rectifier operates stably, it will be stable.

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