Novel virtual space vector modulation method and system for bidirectional charging pile based on power factor self-adaption
Through the virtual space vector modulation method based on power factor adaptation, the problem of difficult balance of midpoint potential and high switching losses of bidirectional charging piles is solved, and the midpoint balance and efficiency improvement are achieved.
Patent Information
- Application Number
- CN202411904696.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-05-02
AI Technical Summary
In the prior art, the midpoint potential of the bidirectional charging pile is difficult to balance, the switching loss is high, and the converter efficiency is low.
A new virtual space vector modulation method based on power factor adaptation is adopted to generate modulation waves through space vector synthesis, generate driving signals of the switch tubes, control each phase bridge arm switch to achieve midpoint balance, and reduce switching losses through virtual space vector synthesis.
Effectively suppress midpoint potential fluctuations, achieve midpoint balance within the full power factor range, reduce switching losses, and improve converter efficiency.
Smart Images
Figure CN119921590A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of power electronic conversion technology, and in particular to a novel virtual space vector modulation method and system for a bidirectional charging pile based on power factor adaptation. Background Art
[0002] With the rapid development of electric vehicles and charging piles, their control and modulation technologies have also been developed accordingly. Charging piles are generally two-stage converters, in which the front-stage AC / DC converter adopts a midpoint clamped three-level converter. Its modulation strategies can be divided into three types: sinusoidal pulse width modulation (SPWM), space vector pulse width modulation (SVPWM) and virtual space vector pulse width modulation (VSVPWM). Among them, SPWM is simple to implement, but the DC utilization rate is low; SVPWM and VSVPWM can be equivalent to carriers, and both can achieve high DC utilization rates. However, SVPWM exhibits poor midpoint balance characteristics at low power factors, and there is a three-fold midpoint potential fluctuation. VSVPWM can solve the above problems by combining different vectors, but it has high switching losses, which reduces the converter efficiency. It can be seen that in the prior art, there are problems such as the difficulty in balancing the midpoint potential of the bidirectional charging pile, high switching losses, and low converter efficiency. Summary of the invention
[0003] The present invention provides a novel virtual space vector modulation method and system for a bidirectional charging pile based on power factor adaptation to solve the problems existing in the prior art.
[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:
[0005] In a first aspect, the present invention provides a novel virtual space vector modulation method for a bidirectional charging pile based on power factor adaptation, comprising the following steps:
[0006] S1: Generate modulation wave based on space vector synthesis method;
[0007] S2: generating a driving signal for a switch tube based on the modulation wave;
[0008] S3: Based on the driving signal, each switch tube of each phase bridge arm is controlled to be turned on and off to achieve output of +U per phase dc / 2, 0, -U dc / 2 three levels, among which U dcThe high-frequency voltage signal is filtered out by the LCL filter to generate a three-phase sinusoidal signal.
[0009] In a second aspect, the present application provides a new virtual space vector modulation system for a bidirectional charging pile based on power factor adaptation, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method described in the first aspect when executing the computer program.
[0010] Beneficial effects:
[0011] The novel virtual space vector modulation method of a bidirectional charging pile based on power factor adaptation provided by the present invention is simple to implement; can effectively suppress midpoint potential fluctuations and achieve midpoint balance within the full power factor range; reduce switching losses and improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 A hardware topology diagram of a midpoint clamped three-level converter according to a preferred embodiment of the present invention;
[0013] Figure 2 A control block diagram of a midpoint clamped three-level converter according to a preferred embodiment of the present invention;
[0014] Figure 3 A three-level converter SVPWM space vector diagram of a preferred embodiment of the present invention;
[0015] Figure 4 A schematic diagram of generating a switch tube driving signal according to a preferred embodiment of the present invention;
[0016] Figure 5 A three-level converter VSVPWM space vector diagram of a preferred embodiment of the present invention;
[0017] Figure 6 Schematic diagram of the switch sequence of the preferred embodiment of the present invention; (a) is the improved strategy switch sequence; (b) is the traditional strategy switch sequence;
[0018] Figure 7 This is a schematic diagram of the dual modulation wave carrier equivalent of a preferred embodiment of the present invention;
[0019] Figure 8 It is an overall schematic diagram of a novel virtual space vector modulation method for a bidirectional charging pile based on power factor adaptation according to a preferred embodiment of the present invention. DETAILED DESCRIPTION
[0020] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only a 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0021] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate quantity restrictions, but indicate the existence of at least one. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.
[0022] The present application provides a novel virtual space vector modulation method for a bidirectional charging pile based on power factor adaptation, comprising the following steps:
[0023] S1: Generate modulation wave based on space vector synthesis method;
[0024] S2: generating a driving signal for a switch tube based on the modulation wave;
[0025] S3: Based on the driving signal, each switch tube of each phase bridge arm is controlled to be turned on and off to achieve output of +U per phase dc / 2, 0, -U dc / 2 three levels, among which U dc The high-frequency voltage signal is filtered out by the LCL filter to generate a three-phase sinusoidal signal.
[0026] The above-mentioned novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation is simple to implement; it can effectively suppress the midpoint potential fluctuation and achieve midpoint balance within the full power factor range; it can reduce switching losses and improve efficiency.
[0027] It should be understood that the present invention proposes a novel virtual space vector modulation method for a bidirectional charging pile based on power factor adaptation. The bidirectional charging pile adopts a two-stage topology. The present invention analyzes the front-stage AC / DC converter. The AC / DC converter adopts a mid-point clamped three-level converter. The circuit topology and specific control block diagram are shown in FIG. Figure 1 and Figure 2As shown in the figure, the main circuit and the control block diagram are included. The circuit topology consists of a type I three-level converter, an LCL filter and a power grid. The control loop is divided into two parts: control and modulation. The control part uses PQ control to achieve closed-loop control of the generator-side current.
[0028] Below, a complete example is used to describe the detailed implementation of the novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation as follows:
[0029] The constant power control block diagram of type I three-level converter is as follows: Figure 2 , Figure 8 As shown. The goal of constant power control is for the converter to achieve zero-error tracking of active and reactive commands, so the output active and reactive power are used as the input of the closed-loop control system. The d-axis and q-axis current set values are obtained through the instantaneous power calculation formula. The dq-axis components of the grid-connected current are obtained through Park transformation as feedback. The difference between the two is output as a modulation voltage after the PI controller. For the modulation link, the modulation voltage is compared with the triangular carrier to obtain the drive signal of the switch tube. Each phase bridge arm of the I-type three-level converter is composed of four power switch tubes with anti-parallel freewheeling diodes. The DC side forms three circuit terminals of P, O, and N through two capacitors in series, so that the converter can output three levels. The above drive signal will control the opening and closing of the four switch tubes in each phase bridge arm, which can realize the output of +U in this phase. dc / 2, 0, -U dc / 2 Three levels. The high-frequency harmonic components contained in the output voltage of the three-level bridge arm are filtered out by the LCL filter to ensure the quality of grid-connected power.
[0030] Specifically, for the modulation link, the output of the current inner loop is used as the reference signal of the modulation wave. Different from the traditional method, the present invention proposes to add power factor identification in the modulation link. The real-time power factor is detected. When the power factor is higher than the set value (set to 0.5 in the present invention), the SVPWM modulation strategy of zero-sequence component injection is adopted. At this time, the modulation wave is expressed as shown in formula (1), and the vector synthesis is as follows: Figure 3 As shown. Among them, v a ** ,v b ** and v c ** is the generated modulation wave, v a * ,v b * and v c * is the reference voltage output by the controller, v 0sv It is the zero-sequence voltage component generated at this time.
[0031]
[0032] Then, the expression of the zero-sequence component is:
[0033]
[0034] According to the above modulation wave, the switch tube T is generated. a1-4 , T b1-4 , T c1-4 The driving signal is Figure 4 shown.
[0035] When the charging pile works in the inverter mode and detects that the power factor is lower than the set value, it is in the condition of emitting capacitive reactive power. At this time, the SVPWM strategy has insufficient ability to adjust the balance of the midpoint potential, and the midpoint potential is prone to fluctuations, while the traditional VSVPWM modulation has the problem of large switching losses. Taking the first sector as an example, the present invention proposes a new virtual space vector synthesis method, as shown in formula (3). Among them, the maximum phase and minimum phase of the virtual mid-vector are clamped at the P level and the N level respectively, so different clamping areas can be selected according to the position of the reference vector to achieve a reduction in switching losses.
[0036]
[0037] Where V VS1 , V VS2 Respectively represent two virtual small vectors in the virtual space vector, V VM1 represents the virtual mean vector, V ONN , V POO Represents a small vector in the space vector, V PON Represents the mean vector in the space vector, V PPN , V PNN represents a large vector in the space vector. It is worth pointing out that if Figure 3 As shown, the length of the line segment in the figure can represent the size of the vector. The length of vector ONN and vector POO is smaller than that of vector PON, and smaller than that of vector PPN and PNN.
[0038] For example, when the reference vector is located in the 3rd and 5th small areas, such as Figure 5 As shown in FIG. 1 , the switching sequence of synthesizing the reference vector is: ONN-PNN-PON-PPN-PON-PNN-ONN. At this time, the minimum phase is clamped at the N level and there is no switching action. When the reference voltage vector is located in the third small area, the switching sequence of the traditional VSVPWM modulation strategy is: ONN-PNN-PON-POO-PPO-PNN-PON-PNN-ONN. The comparison of the modulation strategy proposed by the present invention and the output sequence of the traditional VSVPWM modulation strategy is shown in FIG. Figure 6Compared with the traditional VSVPWM method, the improved strategy reduces two switching actions per switching cycle and reduces switching losses.
[0039] according to Figure 6 The switching sequence in (a) is compared with the carrier wave by using the three-phase modulation voltage. The generated switching sequences are superimposed to obtain the PWM sequence of the modulation strategy proposed by the present invention. Since three levels appear in the middle phase, it is necessary to use a dual modulation wave and a carrier wave for comparison, such as Figure 7 As shown, according to the theory of similar triangles, the amplitude of the modulated wave can be obtained.
[0040]
[0041] In the formula, and They are the upper and lower modulation waves of maximum phase, middle phase and minimum phase respectively. The maximum phase, middle phase and minimum phase of the controller input reference voltage, t PON Represents the vector PON action time, t PPN represents the vector PPN action time, t PNN Represents the vector PNN action time.
[0042] The action time of different vectors is obtained according to the volt-second balance principle, as shown in formula (5).
[0043]
[0044] Where, t ONN is the ONN action time of the vector, t PNN is the vector PNN action time, Input the maximum phase, minimum phase and middle phase of the reference voltage to the controller.
[0045] The above analysis is about the dual modulation wave carrier equivalent process when the reference voltage vector is located in the third and fifth small areas of the first sector. Similarly, the expressions for other areas can be obtained. The overall dual modulation wave equivalent relationship of the modulation strategy proposed by the present invention is shown in formula (6):
[0046]
[0047] In the formula, and They are the upper and lower modulation waves of maximum phase, middle phase and minimum phase respectively. Enter the maximum phase, middle phase, and minimum phase of the reference voltage for the controller.
[0048] It can be seen from the above working process that the new virtual space vector modulation method for bidirectional charging pile based on power factor adaptation proposed in the present invention is simple to implement by introducing direct identification of power factor; it can effectively suppress midpoint fluctuation and achieve midpoint balance under the full power factor range; compared with traditional methods, the switching loss is reduced and the efficiency is improved.
[0049] The present application also provides a new virtual space vector modulation system for a bidirectional charging pile based on power factor self-adaptation, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program. The new virtual space vector modulation system for a bidirectional charging pile based on power factor self-adaptation can implement various embodiments of the above-mentioned microgrid regional protection method based on characteristic signals, and can achieve the same beneficial effects, which will not be described in detail here.
[0050] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.
Claims
1. A novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation, characterized in that: The following steps are involved: S1: Generate modulation wave based on space vector synthesis method; S2: generating a driving signal for a switch tube based on the modulation wave; S3: Based on the driving signal, each switch tube of each phase bridge arm is controlled to be turned on and off to achieve output of +U per phase dc / 2, 0, -U dc / 2 three levels, among which U dc The high-frequency voltage signal is filtered out by the LCL filter to generate a three-phase sinusoidal signal.
2. According to claim 1, the novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation is characterized in that: The S1 includes: The power factor is detected in real time in the modulation link, and when the power factor is higher than the set value, the space vector pulse width modulation strategy of zero-sequence component injection is adopted to obtain the modulation wave and vector switching sequence at this time.
3. The novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation according to claim 1 is characterized in that: The modulation wave satisfies the following relationship: In the formula, v a ** ,v b ** and v c ** is the generated modulation wave, v a * ,v b * and v c * is the reference voltage output by the controller, v 0sv is the zero-sequence voltage component generated at this time; The zero-sequence component satisfies the following relationship:
4. The novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation according to claim 2 is characterized in that: When the power factor is lower than the set value, the modulation wave and vector switching order at this time are obtained based on the set virtual space vector synthesis method, wherein the maximum phase and the minimum phase of the virtual vector are clamped at the P level and the N level respectively, and different clamping areas are selected according to the position of the reference vector.
5. The novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation according to claim 4 is characterized in that: The virtual space vector synthesis method set above satisfies the following relationship: Where V VS1 , V VS2 Respectively represent two virtual small vectors in the virtual space vector, V VM1 represents the virtual mean vector, V ONN , V POO Represents a small vector in the space vector, V PON Represents the mean vector in the space vector, V PPN , V PNN Represents a large vector in the space vector.
6. The novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation according to claim 4 is characterized in that: The equivalent process of the dual modulation wave carrier when the reference voltage vector is located in the third and fifth small areas of the first sector is as follows: The switching sequence of the synthetic reference vector is: ONN-PNN-PON-PPN-PON-PNN-ONN. At this time, the minimum phase is clamped at the N level and there is no switching action. When the reference voltage vector is located in the third small area of the first sector, the three-phase modulation voltage is used to compare with the carrier respectively according to the switching sequence, and the generated switching sequence is superimposed to obtain a PWM sequence of the modulation strategy; Since three levels appear in the middle phase, it is necessary to use dual modulation waves and carrier waves for comparison. According to the similar triangle theory, the amplitude of the modulation wave is obtained as follows: In the formula, and They are the upper and lower modulation waves of maximum phase, middle phase and minimum phase respectively. The maximum phase, middle phase and minimum phase of the controller input reference voltage, t PON Represents the vector PON action time, t PPN represents the vector PPN action time, t PNN represents the action time of vector PNN; Among them, the action time of different vectors is obtained according to the volt-second balance principle and satisfies the following relationship: Where, t ONN is the ONN action time of the vector, t PNN is the vector PNN action time, Input the maximum phase, minimum phase and middle phase of the reference voltage to the controller.
7. The novel virtual space vector modulation method for bidirectional charging pile based on power factor adaptation according to claim 4 is characterized in that: The dual modulation wave decomposition corresponding to the proposed modulation strategy satisfies the following relationship:
8. A novel virtual space vector modulation system for bidirectional charging piles based on power factor adaptation, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method described in any one of claims 1 to 7 are implemented.