Voltage control method, device and storage medium based on DC power distribution mode

Abstract

The present invention discloses a voltage control method, device, and storage medium based on a DC distribution mode, applicable to a low-voltage, two-terminal AC / DC power distribution system. The method comprises: transforming the three-phase unbalanced voltage in the low-voltage, two-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system using positive-sequence rotating coordinates and negative-sequence rotating coordinates; transforming the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system into a DC voltage; and transforming the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage into a second harmonic voltage; filtering out several subharmonic voltages in the two-phase coordinate system to obtain positive-sequence fundamental output voltage components and negative-sequence fundamental output voltage components; and regulating the positive-sequence fundamental output voltage components and the negative-sequence fundamental output voltage components based on classical theory to eliminate voltage distortion in a receiving-end converter in the low-voltage, two-terminal AC / DC power distribution system under unbalanced load. Embodiments of the present invention can effectively improve voltage control effectiveness.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a voltage control method, device and storage medium based on a direct current distribution mode. Background Art

[0002] Taking the Guangdong power grid as an example, users in the mountainous areas of western and northern Guangdong are scattered. This dispersed load creates a significant challenge in ensuring voltage compliance at end users. The existing 400V three-phase AC power supply method, if the power supply radius is large (over 2.5km), can result in significant line voltage drops under heavy loads, easily causing low voltage (below 160V) at end users, impacting the normal operation of electrical equipment and leading to low voltage complaints.

[0003] The existing voltage control method mainly increases the voltage at the end of the line by installing reactive power compensation and voltage regulating devices. However, the existing voltage control method is difficult to increase the voltage at the end of the line to a voltage value that meets the requirements, resulting in poor voltage control effect. Summary of the Invention

[0004] The present invention provides a voltage control method, device and storage medium based on the DC power distribution mode to solve the technical problem that the existing voltage control method is difficult to increase the voltage at the end of the line to a voltage value that meets the requirements, resulting in poor voltage control effect.

[0005] An embodiment of the present invention provides a voltage control method based on a DC power distribution mode, applicable to a low-voltage two-terminal AC / DC power distribution system, comprising:

[0006] The three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system is transformed into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system are transformed into DC voltage, and the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage are transformed into second harmonic voltage;

[0007] In the two-phase coordinate system, several harmonic voltages are filtered out to obtain the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave;

[0008] Based on the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave described in classical theory, the voltage distortion of the receiving-end converter in the low-voltage double-terminal AC / DC power distribution system under unbalanced load is eliminated.

[0009] Furthermore, filtering out several harmonic voltages in the two-phase coordinate system to obtain the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave includes:

[0010] The harmonic voltage in the two-phase coordinate system is filtered out by integrating over one power frequency cycle to obtain an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave.

[0011] Furthermore, before transforming the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, the method further includes:

[0012] The electrical quantities in the three-phase stationary coordinate system are transformed into the negative-sequence rotating coordinate system to obtain the negative-sequence rotating transformation matrix;

[0013] Perform negative sequence rotation transformation on the voltage quantity in the stationary coordinate system.

[0014] Furthermore, the low-voltage double-terminal AC / DC power distribution system includes:

[0015] A sending-end converter, a receiving-end converter and several switching circuit breakers;

[0016] The three terminals of the sending-end converter are respectively connected to the three phases of the distribution line;

[0017] The three terminals of the receiving-end converter are respectively connected to the three phases of the distribution line;

[0018] A switching circuit breaker is provided at both ends of the sending-end converter, a switching circuit breaker is provided at both ends of the receiving-end converter, a switching circuit breaker is provided on the distribution line between the two ends of the sending-end converter, and a switching circuit breaker is provided on the distribution line between the two ends of the receiving-end converter.

[0019] Furthermore, the voltage control method further includes:

[0020] The three-phase symmetrical stationary coordinate system is transformed into a coordinate system that rotates synchronously with the fundamental frequency of the AC side through coordinate transformation;

[0021] The fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronous rotating coordinate system.

[0022] An embodiment of the present invention provides a voltage control device based on a DC power distribution mode, comprising:

[0023] a voltage conversion module, configured to convert the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, convert the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system into a DC voltage, and convert the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage into a second harmonic voltage;

[0024] A voltage filtering module is used to filter out several harmonic voltages in a two-phase coordinate system to obtain an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave;

[0025] The voltage control module is used to control the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave based on the classical theory, so as to eliminate the voltage distortion of the receiving-end converter in the low-voltage double-terminal AC / DC power distribution system under unbalanced load.

[0026] Furthermore, the voltage filtering module is specifically used to:

[0027] The harmonic voltage in the two-phase coordinate system is filtered out by integrating over one power frequency cycle to obtain an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave.

[0028] Furthermore, the voltage control device further includes a rotation conversion module, which is used to:

[0029] The electrical quantities in the three-phase stationary coordinate system are transformed into the negative-sequence rotating coordinate system to obtain the negative-sequence rotating transformation matrix;

[0030] Perform negative sequence rotation transformation on the voltage quantity in the stationary coordinate system.

[0031] Furthermore, the voltage control device further includes a coordinate conversion module, which is used to:

[0032] The three-phase symmetrical stationary coordinate system is transformed into a coordinate system that rotates synchronously with the fundamental frequency of the AC side through coordinate transformation;

[0033] The fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronous rotating coordinate system.

[0034] An embodiment of the present invention provides a computer storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the voltage control method in the DC power distribution mode are implemented as described above.

[0035] In the embodiment of the present invention, the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system is transformed into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system are transformed into DC voltage, and the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage are transformed into second-harmonic voltage. Several harmonic voltages are filtered out in the two-phase coordinate system to obtain the output voltage component of the positive-sequence fundamental and the output voltage component of the negative-sequence fundamental. The output voltage component of the positive-sequence fundamental and the output voltage component of the negative-sequence fundamental are regulated based on the classical theory to eliminate the voltage distortion of the receiving-end converter in the low-voltage double-terminal AC / DC power distribution system under unbalanced load, effectively suppress the output voltage distortion caused by the negative-sequence component, and maintain the three-phase symmetrical voltage output under unbalanced load conditions, so that the voltage at the end of the line meets the requirements, thereby effectively improving the voltage control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 1 is a flow chart of a voltage control method under a DC power distribution mode provided by an embodiment of the present invention;

[0037] Figure 2 This is a block diagram of the positive sequence separation control under the DC distribution state provided by the embodiment of the present invention

[0038] Figure 3 This is a comparison diagram of simulation waveforms of traditional dual-loop control and improved dual-loop control of a three-phase receiving-end converter under unbalanced load conditions provided by an embodiment of the present invention;

[0039] Figure 4 This is a control diagram of a receiving-end converter in a DC power distribution state provided by an embodiment of the present invention;

[0040] Figure 5 is a load terminal voltage and current waveform diagram provided by an embodiment of the present invention;

[0041] Figure 6 1 is a schematic structural diagram of a low-voltage DC power distribution system provided by an embodiment of the present invention;

[0042] Figure 7 This is a load-side voltage waveform diagram without negative sequence compensation in the DC distribution mode provided by an embodiment of the present invention;

[0043] Figure 8 This is a load-side voltage waveform diagram with negative sequence compensation in the DC power distribution mode provided by an embodiment of the present invention;

[0044] Figure 9 It is a structural diagram of a voltage control device in a DC power distribution mode provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0046] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0047] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0048] See also Figure 1 The embodiment of the present invention provides a voltage control method based on a DC power distribution mode, which is applicable to a low-voltage two-terminal AC / DC power distribution system, including:

[0049] S1, by transforming the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, transforming the positive-sequence fundamental AC voltage and negative-sequence fundamental AC voltage in the three-phase stationary coordinate system into DC voltage, and transforming the positive-sequence fundamental AC voltage and negative-sequence fundamental AC voltage into second harmonic voltage;

[0050] In an embodiment of the present invention, before transforming the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, the method further includes:

[0051] The electrical quantities in the three-phase stationary coordinate system are transformed into the negative-sequence rotating coordinate system to obtain the negative-sequence rotating transformation matrix;

[0052] In the embodiment of the present invention, the three-phase stationary abc coordinate system can be synchronized to the two-phase positive sequence rotating dq coordinate system, and can also be synchronized to the two-phase negative sequence rotating dq coordinate system. The formula for transforming the electrical quantity in the abc stationary coordinate system to the negative sequence rotating coordinate system is:

[0053]

[0054] Among them, T n is the negative order rotation transformation matrix.

[0055] Perform negative sequence rotation transformation on the voltage quantity in the stationary coordinate system.

[0056]

[0057] S2. Filter out several harmonic voltages in a two-phase coordinate system to obtain a positive-sequence fundamental output voltage component and a negative-sequence fundamental output voltage component;

[0058] In the embodiment of the present invention, the harmonic voltage in the two-phase coordinate system is filtered out by integrating over one power frequency cycle to obtain the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave.

[0059] S3. Based on the classical theory, the output voltage components of the positive sequence fundamental wave and the negative sequence fundamental wave are regulated to eliminate the voltage distortion of the receiving-end converter under unbalanced load in the low-voltage double-terminal AC / DC distribution system.

[0060] In the embodiment of the present invention, classical control theory shows that, in a synchronously rotating coordinate system, the integral action of the closed-loop feedback PI controller can force the positive and negative sequence output voltages to track the reference value without static error, effectively suppressing the fundamental wave disturbance of the output voltage of the receiving converter. Based on this conclusion, the traditional dual-loop control strategy can be used to regulate and control the positive and negative sequence components of the output voltage separately. The overall control block diagram is shown as follows: Figure 2 shown.

[0061] See also Figure 3 , which is a comparison diagram of simulation waveforms of traditional dual-loop control and improved dual-loop control of a three-phase receiving-end converter under unbalanced load conditions according to an embodiment of the present invention.

[0062] Please continue reading Figure 3 It can be seen that under the condition of unbalanced load, the traditional dual-loop control has a large imbalance of 1.89% in the output three-phase voltage, and the waveform has a certain distortion. However, the improved dual-loop control provided by the embodiment of the present invention has a small imbalance of 0.61% in the output three-phase voltage, with small waveform distortion and good symmetry. That is, the embodiment of the present invention can effectively suppress the output voltage distortion caused by the negative sequence component and can still maintain the three-phase symmetrical output voltage under the condition of unbalanced load.

[0063] See also Figure 6 In one embodiment, a low-voltage double-terminal AC / DC power distribution system includes:

[0064] A sending-end converter, a receiving-end converter and several switching circuit breakers;

[0065] The three terminals of the sending-end converter are connected to the three phases of the distribution line respectively;

[0066] The three terminals of the receiving-end converter are respectively connected to the three phases of the distribution line;

[0067] A switching circuit breaker is provided at both ends of the sending-end converter, a switching circuit breaker is provided at both ends of the receiving-end converter, a switching circuit breaker is provided on the distribution line between the two ends of the sending-end converter, and a switching circuit breaker is provided on the distribution line between the two ends of the receiving-end converter.

[0068] In this embodiment of the present invention, both the sending-end converter and the receiving-end converter employ a diode-clamped three-level topology. The sending-end converter's terminals (ABC) are connected to phases A, B, and C of the existing distribution line, respectively. The positive terminal of the sending-end converter is connected to phase A of the existing line, the negative terminal is connected to phase C of the existing line, and the N terminal is connected to the N line of the existing three-phase, four-wire line. Correspondingly, the receiving-end converter's terminals (ABC) are connected to the load's three-phase lines (A, B, and C). The positive terminal of the receiving-end converter is connected to phase A, the negative terminal is connected to phase C, and the N terminal is connected to the N line. It should be noted that the specific structure of the low-voltage, two-terminal AC / DC power distribution system described above is only one embodiment. In practice, due to the influence of the line phase sequence, the positive and negative terminals of the sending-end converter and the receiving-end converter can be connected to any two non-adjacent phases of the existing three-phase line, and are not necessarily required to be phases A and C.

[0069] In one embodiment, the voltage control method further includes:

[0070] The three-phase symmetrical stationary coordinate system is transformed into a coordinate system that rotates synchronously with the fundamental frequency of the AC side through coordinate transformation;

[0071] In an embodiment of the present invention, the receiving-end converter acts as a voltage source in the DC power distribution state to provide voltage support for the load, that is, to control the three-phase AC voltage output. In the mathematical model of the three-phase stationary coordinate system, the AC side is all time-varying AC quantities, which is not conducive to control system design. In an embodiment of the present invention, a coordinate transformation is used to convert the three-phase symmetrical stationary coordinate system into a coordinate system that rotates synchronously with the fundamental frequency of the AC side. After the coordinate rotation transformation, the fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronously rotating coordinate system, thereby simplifying the control system design.

[0072] The fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronous rotating coordinate system.

[0073] In the embodiment of the present invention, specifically:

[0074] After Park transformation, the grid-side low-frequency mathematical model in the two-phase (dq) rotating coordinate system is obtained:

[0075]

[0076] Where: i sd 、i sq ——d-axis and q-axis components of the current vector on the AC side of the converter; w——grid fundamental angular frequency; u sd 、u sq ——d-axis and q-axis components of the load-end voltage vector; u dn 、u qn ——d and q axis components of the converter output voltage vector.

[0077] After coordinate transformation, the three-phase state equation in the three-phase coordinate system becomes a two-phase state equation. This reduces the order of the state equation, facilitating controller design. However, in the two-phase rotating coordinate system, coupling occurs between the state equations. This means that changes in current along any one axis will cause changes in the current along the other axis. To achieve ideal control effects and reduce the difficulty of controller design, the present invention compensates for the coupling between the two-phase currents using the detected actual current, thereby eliminating the mutual influence between the currents and achieving decoupled current control.

[0078] In the embodiment of the present invention, when a PI controller is used, the following equation can be obtained:

[0079]

[0080] Where: k Pi 、k Ii ——Proportional and integral coefficients of the current loop controller.

[0081] Inner current loop command value is the output of the voltage outer loop controller, which also uses a PI controller:

[0082]

[0083] Where: k Pu 、k Iu ——Proportional and integral coefficients of the current loop controller.

[0084] According to formulas (3)-(5), the embodiment of the present invention obtains Figure 4 The control diagram of the receiving-end converter in the DC distribution state is shown in FIG. On this basis, by introducing current feedback and voltage feedforward, the influence of current coupling and load disturbance voltage can be effectively eliminated. Figure 4 The corresponding simulation waveform is as follows Figure 5 shown.

[0085] See also Figure 5 At t = 1s, the load on the receiving-end converter increases, but the AC side voltage remains stable near the specified value. Spectral analysis shows that the output voltage fundamental value is 311.01V, and the THD is 1.11%, meeting the requirements. This embodiment of the present invention can output a specified voltage signal with minimal voltage error, thereby effectively improving voltage control effectiveness.

[0086] In one embodiment, in order to verify the effectiveness of the embodiment of the present invention, a physical prototype was built for experimental verification. The load is a three-phase unbalanced load, the load resistance of phases A and C is about 13Ω, and the load of phase B is disconnected. The low-voltage two-terminal AC / DC power distribution system is in DC distribution mode. Figure 7 is the three-phase voltage waveform on the load side without negative sequence compensation in DC distribution mode, Figure 8 It is the three-phase voltage waveform on the load side with negative sequence compensation in DC distribution mode. Figure 7-8 It can be seen that after adding negative-sequence compensation, the three-phase voltage imbalance on the load side is reduced, waveform distortion is reduced, and symmetry is improved. In other words, the control strategy of adding negative-sequence compensation to the receiving-end converter under DC power distribution conditions in this embodiment of the present invention can effectively suppress output voltage distortion caused by negative-sequence components, maintain three-phase symmetrical output voltages under unbalanced load conditions, and effectively improve voltage control effectiveness.

[0087] The implementation of the present invention has the following beneficial effects:

[0088] The embodiment of the present invention transforms the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, transforms the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system into DC voltage, transforms the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage into second-harmonic voltage, filters out several sub-harmonic voltages in the two-phase coordinate system, obtains the output voltage component of the positive-sequence fundamental and the output voltage component of the negative-sequence fundamental, and controls the output voltage component of the positive-sequence fundamental and the output voltage component of the negative-sequence fundamental based on classical theory, eliminates the voltage distortion of the receiving-end converter under unbalanced load in the low-voltage double-terminal AC / DC power distribution system, effectively suppresses the output voltage distortion caused by the negative-sequence component, maintains three-phase symmetrical voltage output under unbalanced load conditions, makes the voltage at the end of the line meet the requirements, and thus effectively improves the voltage control effect.

[0089] See also Figure 9 Based on the same inventive concept as the above embodiment, an embodiment of the present invention provides a voltage control device based on a DC power distribution mode, comprising:

[0090] The voltage conversion module 10 is used to convert the three-phase unbalanced voltage in the low-voltage two-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, convert the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system into a DC voltage, and convert the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage into a second harmonic voltage;

[0091] The voltage filtering module 20 is used to filter out several harmonic voltages in a two-phase coordinate system to obtain an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave;

[0092] The voltage control module 30 is used to control the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave based on classical theory, so as to eliminate the voltage distortion of the receiving-end converter under unbalanced load in the low-voltage double-terminal AC / DC power distribution system.

[0093] In one embodiment, the voltage filtering module 20 is specifically configured to:

[0094] The harmonic voltage in the two-phase coordinate system is filtered out by integrating over one power frequency cycle to obtain the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave.

[0095] In one embodiment, the voltage control device further includes a rotation conversion module, configured to:

[0096] The electrical quantities in the three-phase stationary coordinate system are transformed into the negative-sequence rotating coordinate system to obtain the negative-sequence rotating transformation matrix;

[0097] Perform negative sequence rotation transformation on the voltage quantity in the stationary coordinate system.

[0098] In one embodiment, the voltage control device further includes a coordinate conversion module for:

[0099] The three-phase symmetrical stationary coordinate system is transformed into a coordinate system that rotates synchronously with the fundamental frequency of the AC side through coordinate transformation;

[0100] The fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronous rotating coordinate system.

[0101] An embodiment of the present invention provides a computer storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the voltage control method in the DC power distribution mode are implemented.

[0102] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A voltage control method based on DC distribution mode, applicable to low-voltage double-terminal AC / DC distribution system, characterized in that: include: The three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system is transformed into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage in the three-phase stationary coordinate system are transformed into DC voltage, and the positive-sequence fundamental AC voltage and the negative-sequence fundamental AC voltage are transformed into second harmonic voltage; In the two-phase coordinate system, several harmonic voltages are filtered out to obtain the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave; Based on the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave described in classical theory, voltage distortion of the receiving-end converter in the low-voltage double-terminal AC / DC power distribution system under unbalanced load is eliminated; The filtering of several harmonic voltages in the two-phase coordinate system to obtain the output voltage component of the positive sequence fundamental wave and the output voltage component of the negative sequence fundamental wave includes: By integrating over one power frequency cycle and filtering out the harmonic voltage in the two-phase coordinate system, an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave are obtained; The low-voltage double-terminal AC / DC power distribution system comprises: A sending-end converter, a receiving-end converter and several switching circuit breakers; The three terminals of the sending-end converter are respectively connected to the three phases of the distribution line; The three terminals of the receiving-end converter are respectively connected to the three phases of the distribution line; A switching circuit breaker is provided at both ends of the sending-end converter, a switching circuit breaker is provided at both ends of the receiving-end converter, a switching circuit breaker is provided on the distribution line between the two ends of the sending-end converter, and a switching circuit breaker is provided on the distribution line between the two ends of the receiving-end converter.

2. The voltage control method based on the DC power distribution mode according to claim 1, characterized in that: Before transforming the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, the method further includes: The electrical quantities in the three-phase stationary coordinate system are transformed into the negative-sequence rotating coordinate system to obtain the negative-sequence rotating transformation matrix; Perform negative sequence rotation transformation on the voltage quantity in the stationary coordinate system.

3. The voltage control method based on the DC power distribution mode according to claim 1, characterized in that: Also includes: The three-phase symmetrical stationary coordinate system is transformed into a coordinate system that rotates synchronously with the fundamental frequency of the AC side through coordinate transformation; The fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronous rotating coordinate system.

4. A voltage control device based on DC power distribution mode, characterized in that: include: A voltage conversion module is used to convert the three-phase unbalanced voltage in the low-voltage double-terminal AC / DC power distribution system into a two-phase synchronous rotating coordinate system through positive-sequence rotating coordinates and negative-sequence rotating coordinates, convert the positive-sequence fundamental AC voltage and negative-sequence fundamental AC voltage in the three-phase stationary coordinate system into DC voltage, and convert the positive-sequence fundamental AC voltage and negative-sequence fundamental AC voltage into second harmonic voltage; A voltage filtering module is used to filter out several harmonic voltages in a two-phase coordinate system to obtain an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave; A voltage control module, configured to control the output voltage component of the positive-sequence fundamental and the output voltage component of the negative-sequence fundamental according to classical theory, thereby eliminating voltage distortion of the receiving-end converter in the low-voltage double-terminal AC / DC power distribution system under unbalanced load; The voltage filtering module is specifically used for: By integrating over one power frequency cycle and filtering out the harmonic voltage in the two-phase coordinate system, an output voltage component of a positive sequence fundamental wave and an output voltage component of a negative sequence fundamental wave are obtained; The low-voltage double-terminal AC / DC power distribution system comprises: A sending-end converter, a receiving-end converter and several switching circuit breakers; The three terminals of the sending-end converter are respectively connected to the three phases of the distribution line; The three terminals of the receiving-end converter are respectively connected to the three phases of the distribution line; A switching circuit breaker is provided at both ends of the sending-end converter, a switching circuit breaker is provided at both ends of the receiving-end converter, a switching circuit breaker is provided on the distribution line between the two ends of the sending-end converter, and a switching circuit breaker is provided on the distribution line between the two ends of the receiving-end converter.

5. The voltage control device in the DC power distribution mode according to claim 4, characterized in that: Also includes a rotation transformation module for: The electrical quantities in the three-phase stationary coordinate system are transformed into the negative-sequence rotating coordinate system to obtain the negative-sequence rotating transformation matrix; Perform negative sequence rotation transformation on the voltage quantity in the stationary coordinate system.

6. The voltage control device in the DC power distribution mode according to claim 4, characterized in that: Also includes coordinate transformation modules for: The three-phase symmetrical stationary coordinate system is transformed into a coordinate system that rotates synchronously with the fundamental frequency of the AC side through coordinate transformation; The fundamental sinusoidal quantity in the three-phase symmetrical stationary coordinate system is converted into a DC variable in the synchronous rotating coordinate system.

7. A computer storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the voltage control method in the DC power distribution mode are implemented according to any one of claims 1 to 3.

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