A power compensation control method and device for a high-power, multifunctional and efficient charging system

Abstract

The present invention belongs to the technical field of high-efficiency power conversion system control, and provides a power compensation control method and device for a high-power, multifunctional and high-efficiency charging system. The topological structure of the charging system is at least two high-frequency chain matrix converters in parallel, and the power compensation control method includes: calculating the difference between the input voltage phase of the i-th converter and the ideal reference input current phase in a dq two-phase synchronous rotating coordinate system; wherein i is an odd number; according to the above phase difference, calculating the phase angle required for the rotation of the space current vector of the i+1th converter; wherein the required rotation phase angle makes the total instantaneous reactive power on the input side of the i-th converter and the i+1th converter zero; performing a corresponding rotation on the space current vector of the i+1th converter, and determining the sector to which the rotated space current vector belongs; based on the corresponding sector and the modulation ratio, generating a corresponding control pulse signal to act on the i+1th converter to achieve power compensation.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-efficiency power conversion system control, and in particular relates to a power compensation control method and device for a high-power, multifunctional and high-efficiency charging system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The demand for charging of electric vehicles is random and intermittent. In the absence of guidance and regulation, users' charging behavior tends to be concentrated, which will have a serious impact on the power grid, not only affecting the balance of electricity consumption, but also generating harmonic pollution to the power grid, resulting in poor point power quality. Power batteries need to be charged by the power grid, and can also be used as flexible distributed energy storage to provide active and reactive power compensation or support for the power grid. As the core of the interaction between electric vehicles and the power grid, the charging system can have multiple functions, including converting grid energy to charge batteries and converting battery energy to provide active and reactive power support to the power grid, thus becoming a multifunctional charging system for power batteries.

[0004] Most existing charging systems are unidirectional topologies that can only charge batteries and cannot feed battery energy back to the grid. The high-frequency link matrix converter is a single-stage topology with advantages such as high energy density and conversion efficiency, input-output isolation, and bidirectional power flow. However, the inventors found that due to the presence of an LC filter on the AC side of the power conversion topology, there is a phase offset between the AC voltage and current. The magnitude of the offset is related to the selected inductance and capacitance, resulting in the high-frequency link matrix converter being able to only compensate for fixed reactive power, and sometimes even causing over-compensation or under-compensation. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a power compensation control method and device for a high-power, multi-functional and efficient charging system, which can not only expand the system capacity or power level, but also flexibly change the phase of the voltage and current on the grid side of the system to achieve rapid dynamic power compensation for the grid.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a power compensation control method for a high-power, multifunctional and efficient charging system, wherein the topology of the charging system is at least two high-frequency link matrix converters connected in parallel, and the power compensation control method comprises:

[0008] In the dq two-phase synchronous rotating coordinate system, calculate the difference between the input voltage phase of the i-th converter and the ideal reference input current phase; where i is an odd number;

[0009] According to the above phase difference, the phase angle required to rotate the space current vector of the i+1th converter is calculated; wherein the required rotation phase angle makes the total instantaneous reactive power on the input side of the i-th converter and the i+1-th converter zero;

[0010] Rotate the space current vector of the i+1th converter accordingly, and determine the sector to which the rotated space current vector belongs;

[0011] Based on the corresponding sectors and modulation ratios, a corresponding control pulse signal is generated to act on the (i+1)th converter to achieve power compensation.

[0012] As an implementation method, the difference between the input voltage phase of the i-th converter and the ideal reference input current phase is calculated based on the transformation matrix of the abc three-phase stationary coordinate system to the dq two-phase synchronous rotating coordinate system.

[0013] As an implementation mode, the A-phase phase of the input voltage of the i-th converter is the angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system.

[0014] As an implementation mode, the angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system is obtained by phase-locking a phase-locked loop.

[0015] As an implementation mode, a control pulse signal is generated based on a bipolar current space vector modulation method.

[0016] A second aspect of the present invention provides a power compensation control device for a high-power, multifunctional and efficient charging system, wherein the topology of the charging system is at least two high-frequency link matrix converters connected in parallel, and the power compensation control device comprises:

[0017] A phase difference calculation module, which is used to calculate the difference between the input voltage phase of the i-th converter and the ideal reference input current phase in a dq two-phase synchronous rotating coordinate system; wherein i is an odd number;

[0018] A vector rotation module, which is used to calculate the phase angle required to rotate the space current vector of the i+1th converter according to the above phase difference; wherein the required rotation phase angle makes the total instantaneous reactive power on the input side of the i-th converter and the i+1-th converter zero;

[0019] A sector determination module, which is used to perform a corresponding rotation on the space current vector of the (i+1)th converter and determine the sector to which the rotated space current vector belongs;

[0020] The pulse modulation module is used to generate a corresponding control pulse signal based on the corresponding sector and the modulation ratio, so as to act on the (i+1)th converter to realize power compensation.

[0021] As an implementation method, the difference between the input voltage phase of the i-th converter and the ideal reference input current phase is calculated based on the transformation matrix of the abc three-phase stationary coordinate system to the dq two-phase synchronous rotating coordinate system.

[0022] As an implementation mode, the A-phase phase of the input voltage of the i-th converter is the angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system.

[0023] As an implementation mode, the angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system is obtained by phase-locking a phase-locked loop.

[0024] As an implementation manner, in the pulse modulation module, a control pulse signal is generated based on a bipolar current space vector modulation method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The power compensation control method for a high-power, multifunctional and efficient charging system proposed in the present invention can flexibly change the phase difference of the voltage and current on the grid side of the system to quickly make them in phase, thereby achieving dynamic power compensation control and unity power factor.

[0027] (2) The topology applied in the present invention can realize high power output of the whole machine by connecting multiple small and medium power converters in parallel, which expands the system capacity and has good scalability; the series connection on the output side can reduce the current ripple through current phase control and avoid the damage of ripple to the battery. The power control compensation method is cleverly designed and portable, and can be widely promoted and applied to other types of power converters.

[0028] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 is a schematic structural diagram of a charging system according to an embodiment of the present invention;

[0031] Figure 2 It is a topological structure diagram of a modular parallel high-frequency link matrix converter according to an embodiment of the present invention;

[0032] Figure 3 This is a block diagram of the power compensation control principle of a high-power, multifunctional and efficient charging system according to an embodiment of the present invention;

[0033] Figure 4 It is the sector division and current vector diagram of the embodiment of the present invention;

[0034] Figure 5 The following is a diagram of the sector division and current vector diagram after rotation according to an embodiment of the present invention;

[0035] Figure 6 is a diagram showing the relationship between a carrier period and a vector according to an embodiment of the present invention;

[0036] FIG. 7( a ) is a diagram showing the voltage and current of phase A at the input side of the first converter after rotation according to an embodiment of the present invention;

[0037] FIG. 7( b ) is a diagram showing the voltage and current of phase A at the input side of the second converter after rotation according to an embodiment of the present invention;

[0038] Figure 8 1 is the voltage and current waveform of phase A input on the grid side of the system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0042] Embodiment 1

[0043] Reference Figure 1 This embodiment provides a power compensation control method for a high-power, multifunctional and efficient charging system, wherein the topology of the charging system is a parallel high-frequency link matrix converter, such as Figure 1 This enables bidirectional power flow, which can both charge the power battery and compensate for the power grid.

[0044] The topology of the power converter is as follows: Figure 2 The whole system can be composed of multiple medium and small power high frequency link matrix converters. Figure 2The structure of two high-frequency link matrix converters is shown in Figure 1. The two converters share a three-phase AC power supply and load, and their connection method is the same as that of multiple converters: parallel connection on the input side and series connection on the output side. They also include input filters, three-phase / single-phase AC-DC matrix converters, high-frequency transformers, single-phase rectifier bridges, and output filters.

[0045] The three-phase / single-phase AC-DC matrix converter converts three-phase industrial frequency AC power into single-phase high-frequency AC power, whose frequency is the same as the switching frequency of the power switching device MOSFET; when charging the DC side load, the LC low-pass filter on the AC side can filter out the high-order harmonics introduced by the three-phase / single-phase AC-DC matrix converter; the single-phase high-frequency AC power passes through a high-frequency transformer (completes the electrical isolation between the AC side and the DC side), is converted into DC through a single-phase rectifier bridge, and then passes through the DC side LC low-pass filter to filter out the high-frequency harmonics in the DC, and finally forms high-quality DC power to charge the battery.

[0046] In order to filter out the high-order harmonics introduced by the three-phase / single-phase AC-DC matrix converter switch, an LC low-pass filter is added between the three-phase grid and the main circuit of the three-phase / single-phase AC-DC matrix converter to minimize harmonic pollution. However, the introduction of the LC low-pass filter on the input side will increase the capacitive reactive component of the system, causing the grid-side current phase to lead the voltage, resulting in a grid-side power factor that is not 1, and only fixed reactive power compensation can be completed.

[0047] In order to make the AC side power factor reach unity power factor and realize flexible compensation of reactive power, a new compensation control method is invented. By rotating the space vector of an even number of converters, the voltage and current phase of the system grid side is changed to realize flexible compensation of unity power factor. The overall control block diagram is as follows: Figure 3 shown.

[0048] The power compensation control principle is:

[0049] (1) In the dq two-phase synchronous rotating coordinate system, calculate the difference between the input voltage phase of the i-th converter and the ideal reference input current phase; where i is an odd number.

[0050] Specifically, the actual value of the three-phase voltage e abc And the actual value of three-phase current i abc Clark and Park transformations give e d 、e q 、i d 、i q ;

[0051] Establish the mathematical model of high-frequency link matrix converter:

[0052] When the three-phase grid voltage is symmetrical, according to Kirchhoff's law, the grid-side loop equation of the high-frequency link matrix converter is established as follows:

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] where e a 、e b 、e c is the grid voltage, U m is the voltage amplitude of the three-phase grid, ω is the angular velocity of the grid, i a 、i b 、i c is the grid current, i ia 、i ib 、i ic is the input current of the three-phase / single-phase AC-DC matrix converter, v a 、v b 、v c is the midpoint voltage of the three bridge arms of the three-phase / single-phase AC-DC matrix converter, i dc is the diode rectifier bridge output current, u dc is the output voltage of the diode rectifier bridge, m is the modulation ratio of the three-phase / single-phase AC-DC matrix converter in the abc three-phase stationary coordinate system, L is the input filter inductor, C is the input filter capacitor, It is the difference between the input voltage phase and the ideal reference input current phase.

[0059] Among them, according to the transformation matrix of converting the abc three-phase stationary coordinate system to the dq two-phase synchronous rotating coordinate system, the difference between the input voltage phase of the i-th converter and the ideal reference input current phase is calculated.

[0060] The A-phase phase of the input voltage of the i-th converter is the angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system.

[0061] The angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system is obtained by phase-locking the phase-locked loop.

[0062] Specifically, the phase-locked loop PLL calculates the angle θ between the a-axis of the three-phase stationary coordinate system and the d-axis of the two-phase rotating coordinate system;

[0063] The transformation matrix T of the abc three-phase stationary coordinate system is converted to the dq two-phase synchronous rotating coordinate system:

[0064]

[0065] Where θ is the angle between the a-axis of the three-phase stationary coordinate system and the d-axis of the two-phase rotating coordinate system, and its value range is: 0≤θ≤2π; considering that the power does not change before and after the transformation, that is, the equal power transformation matrix is ​​adopted, so

[0066] After using Clark and Park transformation modules, the above equation can be converted to

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] Among them, e d 、e q is the active and reactive components of the grid voltage, i d 、i q is the active and reactive components of the grid current, i id 、i iq are the active and reactive components of the input current of the three-phase / single-phase AC-DC matrix converter, v d 、v q It is the active component and reactive component of the bridge arm midpoint voltage of the three-phase / single-phase AC-DC matrix converter.

[0073] In order to further discuss the influence of θ on various quantities in the system, a DC analysis is performed on each dynamic element in the system, that is, the capacitor element is kept open-circuited and the inductor element is kept short-circuited, and the DC characteristics of the system can be obtained.

[0074] Combining equation (8) and equation (9), we can get

[0075]

[0076] When the grid-side d-axis current change rate Main circuit q-axis voltage change rate When , formula (12) becomes

[0077]

[0078] According to formula (13), the grid-side q-axis current component can be obtained as

[0079]

[0080] Substituting equations (7) and (10) into equation (14), we can obtain the grid-side q-axis current component:

[0081]

[0082] Similarly, when the grid-side q-axis current change rate Main circuit d-axis voltage change rate When , formula (12) becomes

[0083]

[0084] According to formula (16), the grid-side d-axis current component can be obtained as

[0085]

[0086] Substituting equations (7) and (10) into equation (16), we can obtain the grid-side d-axis current component:

[0087]

[0088] According to the instantaneous power theory of three-phase circuit, the active and reactive power on the input side can be expressed as

[0089]

[0090] Among them, P s Indicates active power, Q s Represents reactive power. Substituting equations (7), (15), and (18) into equation (19), we can obtain the instantaneous reactive power Q on the input side of the matrix rectifier: s , as shown in formula (20).

[0091]

[0092] Therefore, the reactive power of the first converter is:

[0093]

[0094] R is the output side load; Q s1 is the reactive power of the first converter.

[0095] (2) Based on the above phase difference, calculate the phase angle required to rotate the space current vector of the i+1th converter; wherein the required rotation phase angle makes the total instantaneous reactive power on the input side of the i-th converter and the i+1-th converter zero.

[0096] It can be seen from formula (20) that reactive power is mainly related to C, Therefore, the space current vector of the second converter can be rotated to change θ, thereby changing Then the phase of the voltage and current on its input side is changed to achieve flexible reactive power compensation and enable the entire system to reach unity power factor.

[0097] The space vector of the first converter in the system is as follows Figure 4 shown.

[0098] Among them, θ1 is the angle between the rotating coordinate system and the α-axis. This angle changes periodically and has the same phase as the A-phase voltage in the three-phase voltage.

[0099] Then the space vector of the second converter is rotated counterclockwise by γ, as Figure 5 shown.

[0100] After rotation, the second converter θ2 leads θ1 by γ, which is equivalent to Based on the above, γ is reduced, so the reactive power of the second converter can be expressed as

[0101]

[0102] Among them, γ is the rotation angle of the second converter space vector; only the rotation angle γ and Q s1 Therefore, the angle of γ can be changed to make Q s =Q s1 +Q s2 , so that the system can flexibly compensate for reactive power; when Q s2 =-Q s1 The parallel system can also achieve unity power factor.

[0103] Since the space vector of the second converter is rotated, the action time of the calculated space current vector is earlier than that of the first converter space current vector, such as Figure 6 As shown, this will cause the bidirectional switches in the three-phase / single-phase AC-DC matrix converter to be turned on and off in advance, causing the voltage and current phase shift on the grid side of the system.

[0104] Therefore, the carrier of the second converter is also delayed to suppress its influence on the voltage and current phase of the grid side.

[0105] (3) The space current vector of the (i+1)th converter is rotated accordingly, and the sector to which the rotated space current vector belongs is determined.

[0106] (4) Based on the corresponding sectors and modulation ratios, a corresponding control pulse signal is generated to act on the (i+1)th converter to achieve power compensation.

[0107] Based on the bipolar current space vector modulation method, a control pulse signal is generated, so as to drive the bidirectional switch of the three-phase / single-phase AC-DC matrix converter. The beneficial effect of this embodiment is verified by software simulation.

[0108] The simulation software used is MATLAB / simulink2020a, and the simulation parameters are shown in Table 1.

[0109] Table 1 Simulation parameters

[0110]

[0111]

[0112] FIG. 7( a ) and FIG. 7( b ) show the A-phase voltage and current at the input side of the first converter after rotation, and the A-phase voltage and current at the input side of the second converter after rotation in this embodiment; Figure 8 The voltage and current waveform of phase A input on the grid side of the system of this embodiment is given. It can be seen from the above simulation results that the power compensation control method of this embodiment can flexibly change the phase difference of the voltage and current on the grid side of the system to make them quickly in phase, thereby completing the dynamic control of power compensation and unity power factor.

[0113] Embodiment 2

[0114] This embodiment provides a power compensation control device for a high-power, multifunctional and efficient charging system. The topology of the charging system is at least two high-frequency link matrix converters connected in parallel. The power compensation control device includes:

[0115] (1) a phase difference calculation module, which is used to calculate the difference between the input voltage phase of the i-th converter and the ideal reference input current phase in a dq two-phase synchronous rotating coordinate system; wherein i is an odd number;

[0116] As an implementation method, the difference between the input voltage phase of the i-th converter and the ideal reference input current phase is calculated based on the transformation matrix of the abc three-phase stationary coordinate system to the dq two-phase synchronous rotating coordinate system. The A-phase phase of the input voltage of the i-th converter is the angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system. The angle between the d-axis of the dq two-phase synchronous rotating coordinate system and the a-axis of the abc three-phase stationary coordinate system is obtained by phase-locked loop.

[0117] (2) a vector rotation module, which is used to calculate the phase angle of the space current vector of the i+1th converter required to rotate according to the above phase difference; wherein the required rotation phase angle makes the total instantaneous reactive power on the input side of the i-th converter and the i+1-th converter zero;

[0118] (3) a sector determination module, which is used to rotate the space current vector of the (i+1)th converter accordingly and determine the sector to which the rotated space current vector belongs;

[0119] (4) A pulse modulation module, which is used to generate a corresponding control pulse signal based on the corresponding sector and the modulation ratio, so as to act on the (i+1)th converter to achieve power compensation.

[0120] In a specific implementation process, in the pulse modulation module, a control pulse signal is generated based on a bipolar current space vector modulation method.

[0121] It should be noted here that each module in this embodiment corresponds to each step in Example 1 one by one, and the specific implementation process is the same, which will not be repeated here.

[0122] The power compensation control method for a high-power, multifunctional and efficient charging system provided by the present invention may be a computer program stored therein. The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products of the embodiments of the present invention. It should be understood that each process and / or box in the flowchart and / or block diagram and the combination of the processes and / or boxes in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power compensation control method for a high-power, multifunctional and efficient charging system, characterized in that: The topological structure of the charging system is at least two high-frequency link matrix converters connected in parallel. The power compensation control method includes: exist dq In the two-phase synchronous rotating coordinate system, calculate the i The difference between the input voltage phase of the converter and the ideal reference input current phase; where, i is an odd number; According to the above phase difference, calculate the i +1 The phase angle of the space current vector of the converter needs to rotate; where the required rotation phase angle makes the first i The converter and i +The total instantaneous reactive power on the input side of 1 converter is zero; For i +1 The space current vector of the converter is rotated accordingly, and the sector to which the rotated space current vector belongs is determined; Based on the corresponding sectors and modulation ratios, corresponding control pulse signals are generated to act on the first i +1 converter to achieve power compensation; according to abc The three-phase stationary coordinate system is converted to dq The transformation matrix of the two-phase synchronous rotating coordinate system is calculated. i The difference between the input voltage phase of the converter and the ideal reference input current phase; No. i The phase of the A phase of the converter input voltage is dq Two-phase synchronous rotating coordinate system d Axis and abc Three-phase stationary coordinate system a The angle of the axis; dq Two-phase synchronous rotating coordinate system d Axis and abc Three-phase stationary coordinate system a The angle of the axis is obtained by phase locking of the phase-locked loop.

2. The power compensation control method for a high-power, multifunctional and efficient charging system according to claim 1, characterized in that: Based on the bipolar current space vector modulation method, a control pulse signal is generated.

3. A high-power, multifunctional and efficient charging system power compensation control device using the high-power, multifunctional and efficient charging system power compensation control method according to any one of claims 1 to 2, characterized in that: The topological structure of the charging system is at least two high-frequency link matrix converters connected in parallel, and the power compensation control device comprises: Phase difference calculation module, which is used to dq In the two-phase synchronous rotating coordinate system, calculate the i The difference between the input voltage phase of the converter and the ideal reference input current phase; where, i is an odd number; The vector rotation module is used to calculate the first i +1 The phase angle of the space current vector of the converter needs to rotate; where the required rotation phase angle makes the first i The converter and i +The total instantaneous reactive power on the input side of 1 converter is zero; Sector judgment module, which is used to i +1 The space current vector of the converter is rotated accordingly, and the sector to which the rotated space current vector belongs is determined; The pulse modulation module is used to generate a corresponding control pulse signal based on the corresponding sector and the modulation ratio to act on the first i +1 converter to achieve power compensation.

4. The power compensation control device for a high-power, multifunctional and efficient charging system as claimed in claim 3, characterized in that: according to abc The three-phase stationary coordinate system is converted to dq The transformation matrix of the two-phase synchronous rotating coordinate system is calculated. i The difference between the input voltage phase of a converter and the ideal reference input current phase.

5. The power compensation control device for a high-power, multifunctional and efficient charging system according to claim 3 or 4, characterized in that: No. i The phase of the A phase of the converter input voltage is dq Two-phase synchronous rotating coordinate system d Axis and abc Three-phase stationary coordinate system a The angle of the axis.

6. The power compensation control device for a high-power, multifunctional and efficient charging system as claimed in claim 5, characterized in that: dq Two-phase synchronous rotating coordinate system d Axis and abc Three-phase stationary coordinate system a The angle of the axis is obtained by phase locking of the phase-locked loop.

7. The power compensation control device for a high-power, multifunctional and efficient charging system as claimed in claim 3, characterized in that: In the pulse modulation module, a control pulse signal is generated based on a bipolar current space vector modulation method.

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