Harmonic suppression control method of flexible interconnection device based on power distribution area

Abstract

The invention relates to the technical field of power grid treatment, and particularly provides a harmonic treatment control method of a flexible interconnection device based on a power distribution area. The method comprises the steps that one voltage source converter in the flexible interconnection device is set to be in a first control mode to serve as a first voltage source converter, and other voltage source converters are set to be in a second control mode to serve as second voltage source converters; under the condition that the flexible interconnection device carries out power mutual assistance on the power distribution area, whether harmonic current exists in an alternating current feeder line of the power distribution area or not is detected through a first voltage source current converter and a second voltage source current converter; calculating an output target current of the voltage source converter according to the harmonic current; and controlling the output power of the voltage source converter according to the output target current so as to carry out harmonic suppression on the power distribution area. Therefore, the problems of high cost and complex control, operation and maintenance caused by the need of an additional device during power grid harmonic suppression in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of power grid control, and in particular to a harmonic control method based on a flexible interconnection device of a distribution station area. Background Art

[0002] With the high-density access of a large number of electric vehicles and power electronic equipment, harmonic pollution in distribution areas has become increasingly serious. The presence of a large amount of harmonic currents has increased line losses in distribution areas, reduced the service life of power equipment, and caused malfunctions of relay protection devices, which seriously affects the power supply quality in distribution areas. Therefore, it is of great research significance to control harmonic pollution in distribution areas.

[0003] The existing methods for harmonic control in distribution stations are mainly implemented using passive and active devices. Passive devices such as passive filters are connected in parallel near the harmonic source and are composed of reactors and harmonic capacitors. Although they can control harmonics and compensate for reactive power, there are problems such as system impedance affecting their filtering effect and easy resonance. Active devices such as active filters and static VAR compensators have fast response speeds, good harmonic compensation effects, and can avoid resonance between system impedance and harmonics, but their operation and maintenance are complex and costly. In summary, the existing harmonic control methods have disadvantages such as high investment costs and single functions.

[0004] When performing grid harmonic control in related technologies, additional devices need to be added, which leads to high costs and complex control and operation and maintenance. No effective solution has been proposed so far. Summary of the invention

[0005] The embodiment of the present invention provides a harmonic control method based on a flexible interconnection device in a distribution station area, which at least solves the problem that when performing power grid harmonic control in the related technology, additional devices need to be added, resulting in high costs and complex control and operation and maintenance.

[0006] One aspect of the present invention provides a harmonic control method based on a flexible interconnection device of a distribution station area, comprising: setting a voltage source converter in the flexible interconnection device to a first control mode as a first voltage source converter, and setting other voltage source converters to a second control mode as a second voltage source converter, wherein the first control mode is used to stabilize the DC bus voltage, and the second control mode is used to control the output power of the second voltage source converter to perform harmonic control; when the flexible interconnection device performs power mutual assistance for the distribution station area, detecting whether there is harmonic current in the AC feeder of the distribution station area through the first voltage source converter and the second voltage source converter; when the harmonic current is detected, calculating the output target current of the voltage source converter according to the harmonic current; and controlling the output power of the voltage source converter according to the output target current to perform harmonic control on the distribution station area.

[0007] As an optional scheme, when a harmonic current is detected, the output target current of the voltage source converter is calculated based on the harmonic current, including: obtaining the positive-sequence component and the negative-sequence component of the harmonic current according to the positive-sequence component calculation method; calculating the total harmonic current of the load and the three-phase current target value of power mutual assistance according to the positive-sequence component and the negative-sequence component of the harmonic current; and obtaining the output target current of the voltage source converter by adding the total harmonic current and the three-phase current target values ​​respectively.

[0008] As an optional scheme, the positive-sequence component and negative-sequence component of the harmonic current are obtained according to the positive-sequence component calculation method, including: obtaining two groups of mutually orthogonal orthogonal signals of the load current of the distribution station area in a two-phase orthogonal coordinate system through a double second-order generalized integrator; processing the orthogonal signals according to the positive-sequence component calculation method to obtain the corresponding positive-sequence component and negative-sequence component of the harmonic current.

[0009] As an optional solution, two groups of mutually orthogonal orthogonal signals of the load current in a two-phase orthogonal coordinate system are obtained by a double second-order generalized integrator, including: performing Clarke transformation on the load current to obtain a load current representation in a two-phase orthogonal coordinate system; performing harmonic decoupling processing on the load current representation to obtain a harmonic current signal; and processing the harmonic current signal by a double second-order generalized integrator to obtain a harmonic current and a corresponding orthogonal signal.

[0010] As an optional scheme, the orthogonal signal is processed according to the positive and negative sequence component calculation method to obtain the corresponding positive sequence component and negative sequence component of the harmonic current, including: using the symmetrical component method to calculate the positive sequence, negative sequence and zero sequence components of the orthogonal signal of the harmonic current; performing Clarke transformation on the positive sequence component and the negative sequence component respectively to obtain the corresponding component representation in the two-phase orthogonal coordinate system; performing Clarke inverse transformation on the component representation corresponding to the positive sequence component and the negative sequence component respectively to obtain the positive sequence component and negative sequence component of the three-phase harmonic current in the three-phase coordinate system.

[0011] As an optional scheme, the total harmonic current of the load and the target value of the three-phase current for power mutual assistance are calculated according to the positive-sequence component and the negative-sequence component of the harmonic current, including: calculating the harmonic component and the zero-sequence component according to the positive-sequence component and the negative-sequence component of the harmonic current; summing the harmonic component and the zero-sequence component according to the negative-sequence component to obtain the total harmonic current of the load; calculating the d-axis component target value and the q-axis component target value of the output current of the voltage source converter; performing an inverse Park transform according to the d-axis component target value and the q-axis component target value to obtain the three-phase current target value for power mutual assistance.

[0012] As an optional scheme, the d-axis component target value and the q-axis component target value of the output current of the voltage source converter are calculated, including: using the first voltage source converter, adopting voltage and current dual closed-loop control, comparing the DC bus voltage target value with the actual value, and determining the voltage error; inputting the voltage error into the regulator to obtain the d-axis component target value of the output current of the first voltage source converter, wherein the q-axis component target value is obtained based on the reactive power target value output by the first voltage source converter and is usually set to 0; calculating the active power target value and reactive power target value of the second voltage source converter through the second voltage source converter; calculating the d-axis component target value and the q-axis component target value of the output current of the second voltage source converter based on the active power target value and the reactive power target value.

[0013] As an optional scheme, the output power of the voltage source converter of the flexible interconnection device is controlled according to the magnitude of the harmonic current to perform harmonic control on the distribution station area, including: determining the switch tube gate signal of each voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current; controlling the active power and reactive power output by the corresponding voltage source converter through the switch tube gate signal; and optimizing the power flow distribution of the distribution station area through the active power and reactive power to perform harmonic control.

[0014] As an optional scheme, determining the first switch gate signal of the first voltage source converter according to the magnitude of the harmonic current includes: after comparing the target value of the DC bus voltage of the first voltage source converter with the actual value, outputting a current correction value through a proportional-integral regulator; adding the current correction value to the active current estimate to obtain the target value of the output current d-axis component of the first voltage source converter; subtracting the output reactive power target value of the first voltage source converter from the actual value, and outputting the current correction value through the proportional-integral regulator; adding the current correction value to the q-axis current estimate to obtain the target value of the output current q-axis component of the first voltage source converter; after subtracting the d-axis and q-axis component target values ​​from the actual values, outputting a voltage modulation signal in a dq coordinate system through the proportional-integral regulator; performing an inverse Park transform on the voltage modulation signal in the dq coordinate system to obtain a voltage modulation signal in an αβ coordinate system; using a space vector pulse width modulation control algorithm to generate a first switch gate signal of the switch of the first voltage source converter according to the voltage modulation signal, wherein the first switch gate signal is used to maintain the stability of the DC bus voltage.

[0015] As an optional solution, determining the gate signal of the second switch tube of the second voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current includes: subtracting the output active power target value of the second voltage source converter from the actual value, and outputting a current correction value through a proportional-integral regulator; adding the current correction value to a preset working point to obtain the output current d-axis component target value of the second voltage source converter; subtracting the output reactive power target value of the second voltage source converter from the actual value, and outputting a current correction value through a proportional-integral regulator; and comparing the current correction value with the q obtained by the inverse model. The estimated values ​​of the axis currents are added to obtain the target value of the q-axis component of the output current of the second voltage source converter; after subtracting the target values ​​of the d-axis and q-axis components from the actual values, a voltage modulation signal in the dq coordinate system is output through a proportional-integral regulator; the voltage modulation signal in the dq coordinate system is subjected to an inverse Park transform to obtain a voltage modulation signal in the αβ coordinate system; and a space vector pulse width modulation control algorithm is used to generate a second switch tube gate signal of the switch tube of the first voltage source converter according to the voltage modulation signal, wherein the second switch tube gate signal is used to control the output active and reactive power to reach the corresponding target values.

[0016] As an optional scheme, the method also includes: in the event that a first voltage source converter operating in a first control mode fails, among the remaining second voltage source converters operating in a second control mode, selecting a second voltage source converter with a maximum capacity regulation margin to switch its second control mode to the first control mode as a new first voltage source converter; wherein the capacity regulation margin is calculated based on the rated capacity and the current output apparent power; and the second voltage source converter that needs to be switched is set through a regulator and a selection switch to convert the second voltage source converter from the second control mode to the first control mode.

[0017] Another aspect of the present invention provides an electronic device, comprising: a processor, and a memory storing a program, wherein the program comprises instructions, and when the instructions are executed by the processor, the processor executes the above method.

[0018] Another aspect of the present invention provides a computer program product, including a computer program / instruction, characterized in that when the computer program / instruction is executed by a processor, the above method is implemented.

[0019] The present invention provides a harmonic control method based on a flexible interconnection device in a distribution station area. When the flexible interconnection device performs power mutual assistance on the distribution station area, the first voltage source converter and the second voltage source converter are used to detect whether there is harmonic current in the AC feeder of the distribution station area; when the harmonic current is detected, the output target current of the voltage source converter is calculated according to the harmonic current; the output power of the voltage source converter is controlled according to the output target current, thereby replacing the active filter of the related technology to control the voltage converter to perform harmonic control on the distribution station area. Thus, it is achieved without adding additional equipment, such as active filters, to control the voltage converter and perform harmonic control. It solves the problem that when performing power grid harmonic control in the related technology, it is necessary to add additional equipment, resulting in high cost and complex control and operation, and achieves the technical effect of reducing the cost of harmonic control and simplifying the control process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a flow chart of a harmonic control method based on a flexible interconnection device in a distribution station area according to an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of a connection circuit between a distribution station area i and VSCi in an embodiment of the present invention.

[0023] Figure 3 is the voltage source converter VSC of the embodiment of the present invention. dc Schematic diagram of -Q and PQ control modes.

[0024] Figure 4 It is a schematic diagram of the positive and negative sequence component calculation PNSC architecture of an embodiment created by the present invention.

[0025] Figure 5 It is a schematic diagram of a dual second-order generalized integrator DSOGI architecture of an embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram of the harmonic current extraction process of an embodiment of the present invention.

[0027] Figure 7 It is a schematic diagram of a FID control architecture with load harmonic current management according to an embodiment of the present invention.

[0028] Figure 8 It is a schematic diagram of the DSOGI-PLL structure of an embodiment of the present invention.

[0029] Fig. 9 It is a schematic diagram of the topological structure of the connection between the two-terminal FID and the distribution station area of ​​the embodiment created by the present invention.

[0030] Fig.10 is the three-phase total harmonic component i of the current of the embodiment created by the present invention ah * 、i bh * and i ch * Schematic diagram of .

[0031] Fig.11 is the AC feeder line 2 current i of the embodiment created by the present invention s2 Schematic diagram of .

[0032] Figure 12-1 is the feeder current i of the embodiment of the invention s2 Schematic diagram of THD before compensation.

[0033] Figure 12-2 is the feeder current i of the embodiment of the invention s2 Schematic diagram of THD after compensation.

[0034] Fig.13 It is a structural schematic diagram of the electronic device created by the present invention. DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0036] The distribution substation is an important part of the power system, which directly affects the local economic development and the daily quality of life of users. At present, most low-voltage substations adopt the form of single transformer and single line power supply, which has low reliability, and the power supply between each substation is independent and lacks unified management and control. The Flexible Interconnection Device (FID) based on power electronic devices is a key device for realizing flexible interconnection between distribution substations. It has the functions of realizing flexible mutual assistance of power flow between multiple distribution substations, fast and flexible load transfer after substation failure, and improving the power supply reliability of distribution substations.

[0037] With the high-density access of a large number of electric vehicles and power electronic equipment, harmonic pollution in distribution areas has become increasingly serious. The presence of a large amount of harmonic currents has increased line losses in distribution areas, reduced the service life of power equipment, and caused malfunctions of relay protection devices, which seriously affects the power supply quality in distribution areas. Therefore, it is of great research significance to control harmonic pollution in distribution areas.

[0038] The current FID technology mainly realizes power mutual assistance between substations and solves the problem of insufficient active power carrying capacity in distribution substations, but it cannot solve power quality problems such as harmonic pollution caused by nonlinear loads in substations. Active filters control the harmonics in distribution substations by controlling voltage source converters (VSCs), and FIDs are also connected to distribution substations using VSCs, so they also have the potential to control harmonics in distribution substations. Therefore, in-depth research can be conducted on the control strategy of harmonic pollution in distribution substations by FIDs, laying the foundation for improving the power quality of distribution substations.

[0039] In summary, in order to solve the problems of insufficient power supply capacity and deterioration of power quality in flexible interconnected distribution substations, it is necessary to propose a harmonic current management control algorithm for distribution substations based on the original power mutual assistance function of FID, so as to effectively improve the power supply reliability and power quality of flexible interconnected distribution substations, and provide a reference for relevant engineering and technical personnel to formulate harmonic management strategies for distribution substations.

[0040] In view of the harmonic pollution problem caused by the high-density access of a large number of power electronic devices to the distribution substation, the present invention proposes a control strategy for the control of harmonic currents in the distribution substation on the basis of the power mutual assistance of the FID to the distribution substation. The harmonic current can be effectively controlled without adding additional devices, which has the advantages of improving the utilization rate of FID equipment and reducing costs. The present invention aims to use an innovative FID control algorithm to enable the FID to mutually assist the power of multiple distribution substations while eliminating the harmonic currents in the feeder, thereby improving the power supply reliability and power quality of the distribution substation, and also providing a reference for relevant engineering and technical personnel to formulate harmonic control strategies for distribution substations.

[0041] In order to solve the above technical problems, an embodiment of the present invention provides a harmonic control method based on a flexible interconnection device in a distribution station area. Figure 1 Flow chart of a harmonic control method based on a flexible interconnection device of a distribution station area according to an embodiment of the present invention. Figure 1 As shown, the method provided by the embodiment of the present invention comprises the following steps:

[0042] Step S101, setting a voltage source converter VSC in the flexible interconnect device FID to a first control mode as a first voltage source converter VSC1, and setting other voltage source converters VSC to a second control mode as a second voltage source converter VSC2, wherein the first control mode is used to stabilize the DC bus voltage, and the second control mode is used to control the output power of the second voltage source converter to perform harmonic control;

[0043] Step S102, when the flexible interconnection device FID performs power mutual assistance on the distribution station area, detecting whether there is harmonic current in the AC feeder of the distribution station area through the first voltage source converter and the second voltage source converter, wherein the first voltage source converter and the second voltage source converter are both arranged between the DC bus and the AC feeder of the distribution station area;

[0044] Step S103, when a harmonic current is detected, calculating an output target current of the voltage source converter according to the magnitude of the harmonic current;

[0045] Step S104, controlling the output power of the voltage source converter of the flexible interconnection device to control harmonics in the distribution station area.

[0046] The above-mentioned harmonic control method based on the flexible interconnection device of the distribution station area provided by the embodiment of the invention is that when the flexible interconnection device performs power mutual assistance for the distribution station area, the first voltage source converter and the second voltage source converter are used to detect whether there is harmonic current in the AC feeder of the distribution station area; when the harmonic current is detected, the output target current of the voltage source converter is calculated according to the harmonic current; the output power of the voltage source converter is controlled according to the output target current, thereby replacing the active filter of the related technology to control the voltage converter to perform harmonic control on the distribution station area. Thereby, it is achieved without adding additional equipment, such as active filters, to control the voltage converter and perform harmonic control. The technical effect of reducing the cost of harmonic control and simplifying the control process is achieved.

[0047] The execution subject of the above steps can be a flexible interconnection device FID of the distribution area. The flexible interconnection device FID of the distribution area is mainly composed of two or more voltage source converters VSC (voltage source converter voltage sourced converter) interconnected on the DC side, wherein a certain VSC is connected to the distribution area. The structure diagram is as shown in FIG. Figure 2 shown. Figure 2 It is a schematic diagram of a connection circuit between a distribution station area i and VSCi in an embodiment of the present invention.

[0048] Figure 2 in u siabc is the three-phase voltage at the AC feeder i in the distribution station area (i=1,2…), u viabc and i viabc are the three-phase voltage and current of VSCi, U dc is the DC bus voltage, R and L are the line equivalent resistance and filter inductance respectively, and C1 and C2 are split capacitors.

[0049] The first control mode can be U dc -Q control mode, the second control mode can be PQ control mode. Figure 3 As shown, Figure 3 is the voltage source converter VSC of the embodiment of the present invention. dc Schematic diagram of -Q and PQ control modes.

[0050] Specifically, U dc When Q and PQ control modes are selected, in order to ensure the reliable operation of the flexible interconnected distribution area, one of the VSCs must be selected to operate in U before the FID is started. dc Q control mode, and the remaining VSCs operate in PQ control mode.

[0051] Assuming that the three-phase grid voltage is balanced, the VSCi mathematical model in the dq coordinate system is obtained by Kirchhoff's voltage law and Park's coordinate transformation formula, and its expression is:

[0052]

[0053] In the formula, u vid and u viq are the d-axis and q-axis components of the AC side voltage of VSCi, respectively. vid and i viq are the d-axis and q-axis components of the AC side output current of VSCi, u sid and u siq are the d-axis and q-axis components of the AC feeder line i voltage, is the fundamental angular frequency. If the voltage vector direction of the AC feeder i in the distribution station area is set as the d-axis, then u vid =u sid =U si Andu viq =0,U si is the phase voltage amplitude of AC feeder i. According to the instantaneous power theory, the steady-state inverse model of VSCi can be obtained as:

[0054]

[0055] Where P vi * and Q vi * are the output active and reactive power target values ​​of VSCi, respectively, obtained by dynamic power flow calculation of the distribution station area; i vid ’ and i viq ’ are the estimated values ​​of active and reactive current output by VSCi respectively. vid ’ and i viq ’ Set as the controller preset working point, then U dc -Q and PQ control mode structures are as follows Figure 3 This control structure can shorten the adjustment time in the control process and also effectively reduce the overshoot.

[0056] Since the flexible interconnection device FID is enabled only when power is mutually supported, when the flexible interconnection device FID performs power mutual support for the substation, it monitors in real time whether there is harmonic current in the AC feeder of the substation. Specifically, after the control mode of the voltage source converter VSC connected to each distribution substation is selected, the flexible interconnection device FID starts to run, and the system monitors in real time whether there is harmonic current in the AC feeder of the substation.

[0057] When harmonic current is detected in the AC feeder of a certain distribution area, the voltage source converter VSC connected to the distribution area activates the harmonic current management control strategy. When harmonic current exists on the feeder side of a distribution area, the voltage source converter VSC connected to the distribution area activates the harmonic current management control strategy to solve the harmonic current problem, improve the power quality of the distribution area, and improve the power supply reliability. The harmonic current management control strategy will be explained later.

[0058] As an optional embodiment, when harmonic current is detected, the output target current of the voltage source converter is calculated based on the harmonic current, including: calculating the load current according to the positive and negative sequence component calculation method to determine the harmonic current in the load current; calculating the total harmonic current of the load and the power mutual three-phase current target value based on the harmonic current; and adding the total harmonic current and the three-phase current target values ​​respectively to obtain the output target current of the voltage source converter.

[0059] The above positive and negative sequence component method can decompose the asymmetric load current into positive sequence, negative sequence and zero sequence components, and can transform the complex asymmetric problem into a relatively simple symmetrical problem for processing, which is convenient for calculating harmonic current and analyzing the impact of faults on the system. Specifically, by analyzing the changes in positive and negative sequence components, it is possible to determine whether there is harmonic current in the equipment and the magnitude of the harmonic current.

[0060] Then, the total harmonic current of the load and the target value of the three-phase current of power mutual assistance are calculated based on the harmonic current, and the output target current of the voltage source converter is obtained by adding the total harmonic current and the three-phase current target values ​​respectively, so as to accurately evaluate the output target current required for harmonic control. This facilitates the subsequent control of the voltage source converter and obtains accurate and timely dynamic harmonic control.

[0061] This embodiment uses DSOGI to extract two sets of orthogonal signals in the αβ coordinate system required for harmonic current. The entire harmonic current extraction step is as follows: Figure 6 As shown, Figure 6 It is a schematic diagram of the harmonic current extraction process of the embodiment created by the present invention. The details are as follows:

[0062] First, the load current i labc The current i in the αβ coordinate system is obtained by Clarke transformation αβ , and then the harmonic current signal i is obtained through the harmonic decoupling network n(αβ) Among them, the harmonic decoupling network is composed of a cross-feedback network, which uses the feedback mechanism to eliminate the other harmonic signals fed back by the system to reduce or eliminate the influence between different harmonics of the input signal and retain the harmonic signals that need to be detected.

[0063] Then, the harmonic current i is obtained by using multi-DSOGI n(αβ)And its orthogonal signal ji n(αβ) , the required angular frequency Depend on To ensure that all DSOGI bandwidths are the same, the gain coefficient k of each DSOGI is inversely proportional to the harmonic order. Finally, the positive and negative sequence components i of the harmonic current in the abc coordinate system are obtained by PNSC. nabc + and i nabc - .

[0064] If the distribution substation is a three-phase four-wire system, the load current may have a zero-sequence component, and the zero-sequence current is:

[0065]

[0066] Finally, add the fundamental negative sequence component, harmonic component and zero sequence component other than the fundamental positive sequence component of the current to obtain the total harmonic current i of the load. ah * 、i bh * and i ch * .

[0067] According to the total harmonic current, based on the FID control method of superimposed load harmonic current, the three-phase current target value is determined; according to the total harmonic current and the three-phase current target value, the output target current of the voltage source converter is obtained. Figure 7 Provide explanation.

[0068] As an optional embodiment, the load current is calculated according to the positive and negative sequence component calculation method to determine the harmonic current in the load current, including: obtaining two sets of mutually orthogonal orthogonal signals of the harmonic current in the load current in a two-phase orthogonal coordinate system by a double second-order generalized integrator DSOGI, wherein the orthogonal signal includes i α with ji α 、i β with ji β ; The orthogonal signal is processed according to the positive and negative sequence component calculation method to obtain the corresponding positive sequence component and negative sequence component of the harmonic current.

[0069] When calculating harmonic current, the orthogonal signal of harmonic current is determined based on the load current. Then the positive component and negative sequence component are determined based on the orthogonal signal.

[0070] First, the harmonic current is obtained from the load current through harmonic decoupling. The dual second-order generalized integrator DSOGI is used to obtain two sets of mutually orthogonal orthogonal signals of the harmonic current in the two-phase orthogonal coordinate system. The orthogonal signal is subjected to an inverse Clarke transform to obtain the positive and negative sequence components of the three-phase harmonic current in the corresponding three-phase coordinate system.

[0071] The above-mentioned dual second-order generalized integrator DSOGI has good filtering performance: it can effectively filter out noise and interference signals, and extract the required specific frequency signals. For example, in a power grid environment with high-order harmonics, it can better extract the fundamental component and harmonic component. It can also perform high-precision phase tracking. In applications such as phase-locked loops, it can accurately track the phase changes of the input signal, achieve high-precision phase synchronization, and provide accurate phase information for grid-connected control in power systems. This allows for better processing of harmonic currents, and better extraction and calculation of harmonic currents.

[0072] Specifically, the symmetrical component method PNSC is first used to obtain the sequence components of the load current. The PNSC structure is as follows: Figure 4 shown. Figure 4 It is a schematic diagram of the positive and negative sequence component calculation PNSC architecture of an embodiment created by the present invention.

[0073] By performing Clarke transformation on the positive and negative sequence components of the load current, the positive and negative sequence components of the harmonic current in the αβ coordinate system can be obtained. By performing Clarke inverse transformation on the positive and negative sequence components of the three-phase harmonic current in the abc coordinate system, the positive and negative sequence components of the three-phase harmonic current can be obtained.

[0074] When the positive sequence component and the negative sequence component of the load current are determined, this embodiment adopts a positive and negative sequence calculation (PNSC) method to obtain the positive and negative sequence components of the load current.

[0075] The positive and negative sequence of the load current is separated, and the load current i abc Expressed as the sum of the sequence components:

[0076]

[0077] In the formula, i abc + 、i abc - and i abc 0 They are the positive sequence, negative sequence and zero sequence components of the load current respectively. The symmetrical component method is used to obtain the sequence components of the load current:

[0078]

[0079]

[0080]

[0081] In the formula, .

[0082] The positive and negative sequence components of the load current can characterize the magnitude of the load current. The positive and negative sequence components of the load current in the above αβ coordinate system can be understood as the data form of the load current required for harmonic decoupling processing, which serves as the basis for subsequent decoupling processing and determining the orthogonal signal of the harmonic signal.

[0083] As an optional embodiment, a double second-order generalized integrator is used to obtain an orthogonal signal of a harmonic current in a load current in a two-phase orthogonal coordinate system, including: performing a Clarke transform on the load current to obtain a load current representation in a two-phase orthogonal coordinate system; performing harmonic decoupling processing on the load current representation to obtain a harmonic current signal; and processing the harmonic current signal through a double second-order generalized integrator to obtain a harmonic current and a corresponding orthogonal signal.

[0084] In the process of calculating the harmonic current orthogonal signal, based on the load current in the above data form, after passing through the harmonic decoupling network, the harmonic current signal can be obtained to characterize the magnitude of the harmonic current. The harmonic decoupling network is composed of a cross-feedback network, which uses the feedback mechanism to eliminate the other harmonic signals fed back by the system to reduce or eliminate the influence between different harmonics of the input signal and retain the harmonic signal that needs to be detected.

[0085] Combination Figure 4 It can be seen that to separate the positive and negative sequence components of the current, two sets of mutually orthogonal signals in the αβ coordinate system must be obtained first. Therefore, this embodiment uses a dual second-order generalized integrator DSOGI to obtain the required two sets of current orthogonal signals i α with ji α 、i β with ji β .

[0086] The biquadric generalized integrator SOGI can not only obtain a set of mutually orthogonal signals, but also filter out high-order harmonics. The biquadric generalized integrator SOGI structure is as follows: Figure 5 As shown, Figure 5 It is a schematic diagram of a dual second-order generalized integrator DSOGI architecture of an embodiment of the present invention.

[0087] in, is the input resonant frequency, k is the gain coefficient, and e is the error between the input signal f and the output signal d. Then the transfer function of SOGI is:

[0088]

[0089] If the SOGI input frequency is If the sinusoidal signal f is a sinusoidal signal, then the SOGI output signals d and q are also sinusoidal signals. Representing f, d and q as vector forms, the amplitude-frequency and phase-frequency characteristics of SOGI can be obtained from the above formula:

[0090]

[0091]

[0092]

[0093] From the above formula, we can see that the output signal q always lags 90° behind d, and is related to k, , The value is irrelevant, that is, the output signals d and q form a set of orthogonal signals. for When , the output signal d tracks the input signal f without static error.

[0094] The harmonic current signal is processed by the dual second-order generalized integrator DSOGI to obtain the harmonic current and the corresponding orthogonal signal.

[0095] As an optional embodiment, the orthogonal signal is processed according to the positive and negative sequence component calculation method to obtain the corresponding positive sequence component and negative sequence component of the harmonic current, including: using the symmetrical component method to calculate the positive sequence, negative sequence and zero sequence components of the orthogonal signal of the harmonic current; performing Clarke transformation on the positive sequence component and the negative sequence component respectively to obtain the corresponding component representation in the two-phase orthogonal coordinate system; performing Clarke inverse transformation on the component representation corresponding to the positive sequence component and the negative sequence component respectively to obtain the positive sequence component and negative sequence component of the three-phase harmonic current in the three-phase coordinate system.

[0096] As above, after obtaining the orthogonal signal of the harmonic current, the positive sequence, negative sequence and zero sequence components of the harmonic current are calculated by the above PNSC. Then, the positive sequence component of the harmonic current can be obtained by performing Clarke transformation on the positive sequence component and the negative sequence component of the harmonic current respectively. , and the negative sequence component :

[0097]

[0098] In the formula, i abc1 + 、i abc1 - They are the positive-sequence component and negative-sequence component of harmonic current respectively.

[0099] Further, the positive and negative sequence components of harmonic current in the αβ coordinate system are obtained:

[0100]

[0101] In the formula, is a phase shift operator with a lag of 90°.

[0102] The positive and negative sequence components of the three-phase current in the abc coordinate system are obtained through Clarke inverse transformation.

[0103] As an optional embodiment, the total harmonic current of the load and the target value of the three-phase current of power mutual assistance are calculated according to the positive sequence component and the negative sequence component of the harmonic current, including:

[0104] Calculate harmonic components and zero-sequence components according to the positive-sequence components and negative-sequence components of harmonic current;

[0105] According to the sum of negative sequence component, harmonic component and zero sequence component, the total harmonic current of the load is obtained;

[0106] Calculating a d-axis component target value and a q-axis component target value of an output current of the voltage source converter, wherein the d-axis and the q-axis are coordinate axes of a Parker coordinate system;

[0107] Park inverse transformation is performed according to the d-axis component target value and the q-axis component target value to obtain the power-compensating three-phase current target value.

[0108] If the distribution station area is a three-phase four-wire system, the load current may have a zero-sequence component, and the zero-sequence current is:

[0109]

[0110] Add the fundamental negative sequence component, harmonic component and zero sequence component other than the fundamental positive sequence component of the current to obtain the total harmonic current i ah * 、i bh * and i ch * .

[0111] When calculating the target value of the three-phase current of the power mutual assistance, the first voltage source converter and the second voltage source converter use different calculation methods.

[0112] As an optional embodiment, calculating the d-axis component target value and the q-axis component target value of the output current of the voltage source converter includes:

[0113] By running on U dc The first voltage source converter in the Q control mode adopts voltage and current dual closed-loop control to compare the DC bus voltage target value with the actual value to determine the voltage error;

[0114] The voltage error is input to the regulator to obtain the d-axis component target value i of the output current of the first voltage source converter.vd * , where the q-axis component target value i vq * Obtained according to the reactive power target value output by the first voltage source converter, usually set to 0;

[0115] By operating the second voltage source converter in the PQ control mode, calculating an active power target value and a reactive power target value of the second voltage source converter;

[0116] According to the active power target value and the reactive power target value, a d-axis component target value and a q-axis component target value of the output current of the second voltage source converter are calculated.

[0117] This embodiment has a FID control strategy with harmonic current control function, and its control block diagram is as follows: Figure 7 As shown, it consists of three parts: power mutual aid current calculation, load harmonic current detection and current closed-loop control. Figure 7 It is a schematic diagram of a FID control architecture with load harmonic current management according to an embodiment of the present invention.

[0118] Runs on U dc The first voltage source converter VSC1 in the first control mode adopts voltage and current double closed-loop control, compares the DC bus voltage target value with the actual value, and inputs the error into the PI controller to obtain the target value i of the d-axis component of the AC side output current of the first voltage source converter VSC1. vd * , q-axis component target value i vq * It is obtained based on its output reactive power target value and is usually set to 0.

[0119] For the second voltage source converter VSC2 operating in the PQ control mode, its active and reactive power target values ​​P are dynamically calculated by the power flow of the distribution area connected to the FID. * and Q * , the target values ​​of the current d-axis and q-axis components i are further obtained through the above VSCi steady-state inverse model vd * and i vq * .

[0120] The above PQ or U dc -Q control mode to obtain the current d-axis and q-axis component target values ​​i vd * and i vq * Perform Park inverse transformation to obtain the three-phase current target value i required for power mutual assistance a1 * 、i b1* and i c1 * ; then i a1 * 、i b1 * and i c1 * The total harmonic current i obtained by using the load harmonic current detection method ah * 、i bh * and i ch * Each phase is added separately to obtain the corresponding VSC output current target value i va * 、i vb * and i vc * .

[0121] Next, i va * 、i vb * and i vc * Clarke transformation is performed to obtain the corresponding VSC output current target value i in the αβ coordinate system vα * and i vβ * ; Then, i vα * and i vβ * The corresponding VSC output current actual value i vα and i vβ The error signal is obtained by difference, and the modulation signal V is output through the PR (proportional resonant) controller. vα * and V vβ * ; Finally, the SVPWM control algorithm is used to generate the corresponding VSC switch gate signal.

[0122] Using the above FID control strategy, the load harmonic current is provided by the corresponding VSC, and the distribution station area only needs to provide the current positive sequence fundamental component to the load, thereby achieving effective control of the feeder harmonic current.

[0123] As an optional embodiment, the output power of the voltage source converter of the flexible interconnection device is controlled according to the magnitude of the harmonic current to perform harmonic control on the distribution station area, including:

[0124] Determine the switch gate signal of each voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current;

[0125] The active power and reactive power output by the corresponding voltage source converter are controlled by the switch gate signal;

[0126] The power flow distribution in the distribution area is optimized by active power and reactive power to control harmonics.

[0127] When performing harmonic control, this embodiment simulates the interconnection operation of two distribution stations in a certain area, and simulates the connection topology structure of the two-terminal FID and the distribution station area, such as Fig. 9 As shown, Fig. 9 Schematic diagram of the topological structure of the connection between the two-terminal FID and the distribution area of ​​the embodiment of the present invention. First, select VSC1 to run at V dc Q control mode, VSC2 operates in PQ control mode, and the operating conditions of the two distribution stations are shown in Table 1.

[0128] Table 1 Operating conditions of two distribution stations

[0129] S2: When FID performs power mutual assistance for the substation, it monitors the substation AC feeder in real time to see if there is harmonic current. According to the operating conditions of the two distribution substations in Table 1, the VSC2 power target value P is obtained by the dynamic power flow calculation of the distribution substation. v2 * is 30kW, then the VSC1 power target value P v1 * At 0.35s, the system detected the presence of harmonic current in distribution station area 2.

[0130] S3: The system detected the presence of harmonic current in the distribution station area at 0.35s, and VSC2 connected to station area 2 began to use the harmonic current management control strategy at 0.4s.

[0131] (1) Based on multi-DSOGI, PNSC is used to extract the total harmonic component i of the three-phase load current ah * 、i bh * and i ch * ,like Fig.10 The three-phase total harmonic components of the detected current are shown. Fig.10 is the three-phase total harmonic component i of the current of the embodiment created by the present invention ah * 、i bh * and i ch * Schematic diagram of .

[0132] (2) The fundamental component target value i is obtained a1 * 、i b1 * and i c1 * Respectively with i ah * 、i bh * and i ch * Add together to get the VSC2 output current target value i va * 、i vb * and i vc * , then, i va * 、i vb * and i vc * Clarke transformation is performed to obtain the VSC2 output current target value i in the αβ coordinate system vα * and i vβ * ; Then i vα * and i vβ * The actual value of VSC2 output current i vα and i vβ After making a difference and obtaining the error signal, the PR controller outputs the modulation signal V vα * and V vβ * .

[0133] Finally, the SVPWM control algorithm is used to generate the gate signal of the VSC2 switch tube, control the VSC2, and output the required compensation current. s2 like Fig.11 As shown, Fig.11 is the AC feeder line 2 current i of the embodiment created by the present invention s2 Schematic diagram of .

[0134] i s2 The total harmonic distortion (THD) of Figure 12-1 and Figure 12-2 shown. Figure 12-1 is the feeder current i of the embodiment of the invention s2 Schematic diagram of THD before compensation. Figure 12-2 is the feeder current i of the embodiment of the invention s2Schematic diagram of THD after compensation.

[0135] It can be seen that VSC2 realizes harmonic current compensation for load 2 from 0.4s, so that feeder 2 only provides it with the fundamental positive sequence component of current, and its THD is reduced from 13.37% to 0.65%, which significantly improves the power quality of the distribution station area.

[0136] As an optional embodiment, determining the switch gate signal of the first voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current includes:

[0137] After comparing the target value of the DC bus voltage of the first voltage source converter with the actual value, the current correction value Δi is output through the PI (Proportional Integral) proportional integral regulator vdu ; The current correction value Δi vdu and active current estimate i vdu ’ Add together to obtain the target value i of the d-axis component of the output current of the first voltage source converter VSC1 vd * ; Set the output reactive power target value Q of the first voltage source converter v * With the actual value Q v Make a difference and output the current correction value Δi through the PI regulator dq ; The current correction value Δi dq and the estimated q-axis current i vq ’ Add together to obtain the target value i of the q-axis component of the output current of the first voltage source converter VSC1 vq * ; Set the d-axis and q-axis component target values ​​i vd * and i vq * With the actual value i vd and i vq After the difference is made, the PI regulator outputs the voltage modulation signal V in the dq coordinate system. vd * and V vq * ; For the voltage modulation signal V in the dq coordinate system vd * and V vq Perform Park inverse transformation to obtain the voltage modulation signal V in the αβ coordinate system: vα * and V vβ * ; Using SVPWM control algorithm, according to the voltage modulation signal V vα * and Vvβ * , generating a first gate signal of a switch tube of a first voltage source converter, wherein the first gate signal is used to maintain a stable DC bus voltage.

[0138] With the above Figure 3 As an example, the structure shown in the figure is operated in the first control mode, that is, U dc The first voltage source converter VSC1 in -Q control mode acts as the master station to maintain the DC bus voltage stability and ensure the smooth operation of the flexible interconnected distribution station area.

[0139] U dc The -Q control mode adopts voltage and current dual closed-loop control, and the DC bus voltage target value is compared with the actual value, and then the PI (Proportional Integral) regulator outputs the current correction value Δi vdu .

[0140] Then, it is compared with the estimated active current i vdu ’ The target value i of the d-axis component of the output current of the first voltage source converter VSC1 is obtained by adding vd * ; q-axis component target value i vq * The reactive power target value Q is output by the first voltage source converter VSC1 v * With the actual value Q v The difference is the output current correction value Δi through the PI regulator dq After that, the estimated value of the q-axis current i vq ’ The reactive power target value is usually set to 0.

[0141] Then the d-axis and q-axis component target values ​​i vd * and i vq * With the actual value i vd and i vq After the difference is made, the PI regulator outputs the voltage modulation signal V in the dq coordinate system. vd * and V vq * ; Then, the voltage modulation signal V in the αβ coordinate system is obtained through Park inverse transformation vα * and V vβ *Finally, the SVPWM control algorithm is used to generate the gate signal of the switch tube of the first voltage source converter VSC1, thereby controlling the master station VSC1 to maintain the DC bus voltage stability. Where θ is the output angle of the Double Second-OrderGeneralized Integrators-Phase Locked Loop (DSOGI-PLL).

[0142] As an optional embodiment, determining the switch gate signal of the second voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current includes: determining the output active power target value P of the second voltage source converter in the PQ control mode v * With the actual value P v Make a difference and output the current correction value Δi through the PI regulator vdp ; The current correction value Δi vdp With the preset working point i vdp ’ Add together to get the target value i of the VSC output current d-axis component vd * ; Set the output reactive power target value Q of the second voltage source converter v * With the actual value Q v Make a difference and output the current correction value Δi through the PI regulator vq ; The current correction value Δi vq The estimated q-axis current i obtained by the inverse model vq ’ Add together to get the target value i of the q-axis component of the VSC output current vq *

[0143] Set the d-axis and q-axis component target values ​​i vd * and i vq * With the actual value i vd and i vq After the difference is made, the PI regulator outputs the voltage modulation signal V in the dq coordinate system. vd * and V vq * ; For the voltage modulation signal V in the dq coordinate system vd * and V vq Perform Park inverse transformation to obtain the voltage modulation signal V in the αβ coordinate system: vα * and V vβ * ; Using SVPWM control algorithm, according to the voltage modulation signal Vvα * and V vβ * , generating a second gate signal for the switch tube of the first voltage source converter, wherein the second gate signal is used to control the output active and reactive power to reach corresponding target values.

[0144] Still with the above Figure 3 Taking the structure shown as an example, the second voltage source converter VSC2 operating in the PQ control mode, that is, the second control mode, acts as a slave station, controlling the second voltage source converter VSC2 to output active and reactive power that is the same as its target value, thereby optimizing the power flow distribution in the distribution station area.

[0145] The control process is to set the second voltage source converter VSC2 to output the active power target value P v * With the actual value P v After making the difference, the current correction value Δi is obtained through the PI regulator vdp .

[0146] Then compare it with the preset working point i vdp ’ The target value i of the d-axis component of the output current of the second voltage source converter VSC2 is obtained by adding vd * ; Reactive power target value Q v * The actual output reactive power Q of the second voltage source converter VSC2 v The PI regulator outputs the current correction value Δi vq Then, the estimated q-axis current i obtained by the inverse model is vq ’ Add together to get the q-axis component target value i vq * , reactive power target value Q v * Usually set to 0.

[0147] Then the d-axis and q-axis component target values ​​i vd * and i vq * With the actual value i vd and i vq After the difference is made, the PI regulator outputs the voltage modulation signal V in the dq coordinate system. vd * and V vq * ; Then, the voltage modulation signal V in the αβ coordinate system is obtained through Park inverse transformation vα * and V vβ * .

[0148] Finally, the SVPWM control algorithm is used to generate the gate signal of the switch tube of the second voltage source converter VSC2, so as to control the output of active and reactive power from the slave station VSC and optimize the power flow distribution in the distribution station area.

[0149] As an optional embodiment, the method further includes: dc In the event of a failure of the first voltage source converter in the -Q control mode, among the remaining second voltage source converters operating in the PQ control mode, the second voltage source converter with the largest capacity regulation margin is selected and the PQ control mode is switched to U dc -Q control mode, as the new first voltage source converter; wherein the capacity adjustment margin is calculated based on the rated capacity and the current output apparent power; the second voltage source converter to be switched is set through the regulator and the selection switch, and the second voltage source converter is converted from the PQ control mode to the U dc -Q control mode.

[0150] When running on U dc When a VSC in the -Q control mode fails, the VSC with the largest capacity adjustment margin among the remaining VSCs operating in the PQ control mode needs to be selected as the new master station to operate in the U dc -Q control mode, the master station selection conditions are:

[0151]

[0152] In the formula, S viy , S viN , S vi and S maxvy They are the capacity adjustment margin, rated capacity, current output apparent power and maximum capacity adjustment margin of VSCi. However, after selection, overshoot and oscillation may occur during mode switching. For example, if VSC operates in PQ mode, U dc If the -Q controller is also running at the same time, the output will reach saturation due to the continuous accumulation of input errors, thus switching from PQ mode to U dc -Q mode, its controller will start to adjust from the saturation state, which will produce transient shocks and oscillations; if the VSC operates in PQ mode, U dc -Q controller is not running, its initial state is zero, when switching U dc The -Q controller will start to establish a response from the zero state, at which time the output will drop and the adjustment time required to complete the switching will be long and the overshoot will be large. dc -Smooth switching between Q mode and PQ mode uses the following method:

[0153] PQ mode and U dc -Q mode switching principle is as follows Figure 3 As shown in the figure, since the outer loop q axis controls reactive power, there is no need to switch, only the outer loop d axis needs to be switched. When the VSC operates in PQ mode, the regulator enable signal Ep=1, Eu=0, at this time the PQ mode PI regulator operates, and U dc -Q mode PI regulator does not run and the output is set to zero, and the selection switch is set to 2, and the current inner loop command value is provided by the PQ controller. dc -Q mode, Ep=0, Eu=1, the selector switch is set to 1, and vice versa. Switch from VSC operation in PQ mode to U dc -Q mode is used as an example for analysis.

[0154] A) Switching moment: The current inner loop reference value is determined by U dc -Q mode PI regulator output Δi vdu and the steady-state inverse model output i vdu ’ When VSC operates in PQ mode, U dc -Q mode PI regulator output is set to zero, then at the switching time Δi vdu =0, and then:

[0155]

[0156] In the formula, i vd0 * is the current inner loop reference value at the switching moment.

[0157] B) After the switching is completed and stabilized, when the VSC completes the mode switching and regains stability, the actual output active current i vd Equal to the current inner loop reference value. Then the actual output active power of VSC is:

[0158]

[0159] In the formula, i vd1 * is the reference value of the current inner loop after stabilization. Ignoring the losses of the port converter and the line, the actual output active power of the VSC after stabilization is equal to U dc -Q mode output active power target value P v * Equal, and then:

[0160]

[0161] From the above formula, we can see that the current inner loop reference value at the switching moment is equal to its steady-state value, that is, when the mode is switched, U dc-Q controller will start to adjust from its steady-state output value, so the controller output will remain the same before and after the mode switch. At the same time, there is no impact or drop in the VSC output during the switching process. Therefore, it can be stabilized and switched after a short adjustment, thus achieving U dc -Smooth switching between Q mode and PQ mode.

[0162] In the above control strategy, the dual second-order generalized integrator phase-locked loop DSOGI-PLL is composed of DSOGI, PNSC and synchronous reference frame phase-locked loop (Synchronous Reference Frame-PLL, SRF-PLL). The structure of DSOGI-PLL is as follows: Figure 8 shown. Figure 8 It is a schematic diagram of the DSOGI-PLL structure of an embodiment of the present invention.

[0163] DSOGI and PNSC can accurately detect the positive sequence fundamental component of the grid voltage in a disturbed and distorted grid; SRF-PLL can accurately track the phase and frequency information of the positive sequence fundamental component of the grid voltage. Therefore, in the case of grid voltage distortion or disturbance, DSOGI-PLL can quickly and accurately obtain voltage synchronization phase information to ensure the accuracy of the phase angle information required by the control system.

[0164] The working process of SRF-PLL is to convert the voltage positive sequence fundamental component u in the αβ coordinate system obtained by DSOGI into α + and u β + Perform Park transformation to obtain the voltage positive sequence fundamental component u in the dq coordinate system d + and u q + ; Then, u q + The instantaneous angular frequency is obtained by subtracting the reference value 0 through the PI regulator. ; Finally, The grid phase angle θ is obtained by integration.

[0165] The embodiments of the present invention also provide a non-transitory machine-readable medium storing a computer program, wherein the computer program, when executed by a processor of a computer, is used to cause the computer to execute the method of the embodiments of the present invention.

[0166] The embodiments of the present invention further provide a computer program product, including a computer program, wherein the computer program, when executed by a processor of a computer, is used to cause the computer to execute the method of the embodiments of the present invention.

[0167] The embodiment of the invention also provides an electronic device, comprising: at least one processor; and a memory connected to the at least one processor in communication. The memory stores a computer program that can be executed by the at least one processor, and the computer program is used to enable the electronic device to perform the method of the embodiment of the invention when executed by the at least one processor.

[0168] refer to Fig.13 , a block diagram of an electronic device that can be used as a server or client of an embodiment of the invention will now be described, which is an example of hardware devices that can be applied to various aspects of the invention. The electronic device is intended to represent various forms of digital electronic computer devices, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the invention described and / or required herein.

[0169] like Fig.13 As shown, the electronic device includes a computing unit 1301, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory ROM 1302 or a computer program loaded from a storage unit 1308 to a random access memory RAM 1303. In RAM 1303, various programs and data required for the operation of the electronic device can also be stored. The computing unit 1301, ROM 1302 and RAM 1303 are connected to each other via a bus 1304. An input / output I / O interface 1305 is also connected to the bus 1304.

[0170] Multiple components in the electronic device are connected to the I / O interface 1305, including: an input unit 1306, an output unit 1307, a storage unit 1308, and a communication unit 1309. The input unit 1306 can be any type of device that can input information to the electronic device, and the input unit 1306 can receive input digital or character information, and generate key signal input related to user settings and / or function control of the electronic device. The output unit 1307 can be any type of device that can present information, and can include but is not limited to a display, a speaker, a video / audio output terminal, a vibrator, and / or a printer. The storage unit 1308 can include but is not limited to a disk, an optical disk. The communication unit 1309 allows the electronic device to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks, and can include but is not limited to a modem, a network card, an infrared communication device, and / or a wireless communication transceiver, such as a Bluetooth device, a WiFi device, a WiMax device, a cellular communication device, and / or the like.

[0171] The computing unit 1301 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 1301 include, but are not limited to, a CPU, a graphics processing unit GPU, various dedicated artificial intelligence AI computing units, various computing units running machine learning model algorithms, a digital signal processor DSP, and any appropriate processor, controller, microcontroller, etc. The computing unit 1301 performs the various methods and processes described above. For example, in some embodiments, the method embodiments created by the present invention may be implemented as a computer program, which is tangibly contained in a machine-readable medium, such as a storage unit 1308. In some embodiments, part or all of the computer program may be loaded and / or installed on an electronic device via a ROM 1302 and / or a communication unit 1309. In some embodiments, the computing unit 1301 may be configured to perform the above method in any other appropriate manner (e.g., by means of firmware).

[0172] The computer program for implementing the method of the present invention can be written in any combination of one or more programming languages. These computer programs can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the computer program, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The computer program can be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.

[0173] In the context of the invention, the machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable signal medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, or infrared systems, devices, or equipment, or any suitable combination of the foregoing. More specific examples of machine-readable storage media may include electrical connections based on one or more lines, portable computer disks, hard disks, random access memory RAM, read-only memory ROM, erasable programmable read-only memory EPROM or flash memory, optical fibers, portable compact disk read-only memory CD-ROM, optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0174] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present invention are illustrative and not restrictive. Those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0175] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of the present invention are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0176] The various steps described in the method implementation methods provided by the embodiments of the present invention can be performed in different orders and / or in parallel. In addition, the method implementation methods may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0177] The term "embodiment" in this specification refers to specific features, structures or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same and similar parts between the various embodiments refer to each other. In particular, for the device, equipment, and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiment.

[0178] The above-described embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A harmonic control method based on a flexible interconnection device in a distribution area, characterized in that: include: Setting one voltage source converter in the flexible interconnection device to a first control mode as a first voltage source converter, and setting the other voltage source converters to a second control mode as a second voltage source converter, wherein the first control mode is used to stabilize the DC bus voltage, and the second control mode is used to control the output power of the second voltage source converter to perform harmonic control; When the flexible interconnection device performs power mutual assistance for the power distribution area, detecting whether there is harmonic current in the AC feeder of the power distribution area through the first voltage source converter and the second voltage source converter; When a harmonic current is detected, calculating an output target current of the voltage source converter according to the harmonic current; The output power of the voltage source converter is controlled according to the output target current to perform harmonic control on the distribution station area.

2. The method according to claim 1, characterized in that When a harmonic current is detected, calculating an output target current of a voltage source converter according to the harmonic current comprises: Calculate the load current according to the positive and negative sequence component calculation method to determine the harmonic current in the load current; Calculate the total harmonic current of the load and the target value of the three-phase current of power mutual assistance based on the harmonic current; The output target current of the voltage source converter is obtained by adding the total harmonic current and the three-phase current target values ​​respectively.

3. The method according to claim 2, characterized in that The load current is calculated according to the positive and negative sequence component calculation method to determine the harmonic current in the load current, including: Obtaining the orthogonal signal of the harmonic current in the load current in a two-phase orthogonal coordinate system by a double second-order generalized integrator; The orthogonal signal is processed according to the positive and negative sequence component calculation method to obtain the corresponding positive sequence component and negative sequence component of the harmonic current.

4. The method according to claim 3, characterized in that The orthogonal signals of the harmonic current in the load current in the two-phase orthogonal coordinate system are obtained by using a double second-order generalized integrator, including: The load current is subjected to Clark transformation to obtain the load current representation in a two-phase orthogonal coordinate system; Performing harmonic decoupling processing on the load current representation to obtain a harmonic current signal; The harmonic current signal is processed by a double second-order generalized integrator to obtain a harmonic current and a corresponding orthogonal signal.

5. The method according to claim 3, characterized in that: The orthogonal signal is processed according to the positive and negative sequence component calculation method to obtain the corresponding positive sequence component and negative sequence component of the harmonic current, including: Calculating the positive sequence, negative sequence and zero sequence components of the orthogonal signal of the harmonic current by using a symmetrical component method; Performing Clarke transformation on the positive sequence component and the negative sequence component respectively to obtain corresponding component representations in a two-phase orthogonal coordinate system; Clarke inverse transformation is performed on the component representations corresponding to the positive sequence component and the negative sequence component respectively, so as to obtain the positive sequence component and the negative sequence component of the three-phase harmonic current in the three-phase coordinate system.

6. The method according to claim 2, characterized in that The total harmonic current of the load and the target value of the three-phase current of power mutual assistance are calculated based on the positive sequence component and negative sequence component of the harmonic current, including: Calculate harmonic components and zero-sequence components according to the positive-sequence components and negative-sequence components of harmonic current; According to the negative sequence component, the harmonic component and the zero sequence component, the total harmonic current of the load is obtained by summing up; calculating a d-axis component target value and a q-axis component target value of an output current of the voltage source converter; An inverse Park transformation is performed according to the d-axis component target value and the q-axis component target value to obtain a power-compensating three-phase current target value.

7. The method according to claim 6, characterized in that Calculating a target value of a d-axis component and a target value of a q-axis component of an output current of the voltage source converter comprises: By using the first voltage source converter, a voltage and current dual closed-loop control is adopted to compare the DC bus voltage target value with the actual value to determine the voltage error; Inputting the voltage error into a regulator to obtain a target value of a d-axis component of an output current of the first voltage source converter, wherein the target value of the q-axis component is obtained according to a target value of reactive power output by the first voltage source converter and is usually set to 0; calculating, by means of the second voltage source converter, an active power target value and a reactive power target value of the second voltage source converter; According to the active power target value and the reactive power target value, a d-axis component target value and a q-axis component target value of the output current of the second voltage source converter are calculated.

8. The method according to claim 1, characterized in that The output power of the voltage source converter of the flexible interconnection device is controlled according to the magnitude of the harmonic current to perform harmonic control on the distribution station area, including: Determining the switch gate signal of each voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current; Controlling the active power and reactive power output by the corresponding voltage source converter through the switch tube gate signal; The power flow distribution in the power distribution area is optimized by the active power and reactive power to perform harmonic control.

9. The method according to claim 8, characterized in that Determining a first switch gate signal of the first voltage source converter according to the magnitude of the harmonic current includes: After comparing the target value of the DC bus voltage of the first voltage source converter with the actual value, a current correction value is output through a proportional-integral regulator; adding the current correction amount to the active current estimate to obtain a target value of the output current d-axis component of the first voltage source converter; Subtracting the output reactive power target value of the first voltage source converter from the actual value, and outputting a current correction value through the proportional-integral regulator; Adding the current correction amount to the estimated value of the q-axis current to obtain a target value of the q-axis component of the output current of the first voltage source converter; After subtracting the target value of the d-axis and q-axis components from the actual value, the proportional-integral regulator outputs a voltage modulation signal in the dq coordinate system; Performing an inverse Park transform on the voltage modulation signal in the dq coordinate system, the voltage modulation signal in the αβ coordinate system is obtained; A space vector pulse width modulation control algorithm is used to generate a first switch tube gate signal of a switch tube of a first voltage source converter according to a voltage modulation signal, wherein the first switch tube gate signal is used to maintain the stability of the DC bus voltage.

10. The method according to claim 8, characterized in that Determining a second switch gate signal of a second voltage source converter of the flexible interconnection device according to the magnitude of the harmonic current includes: Subtracting the target value of the output active power of the second voltage source converter from the actual value, and outputting a current correction value through a proportional-integral regulator; Adding the current correction amount to the preset working point to obtain a target value of the output current d-axis component of the second voltage source converter; Subtract the output reactive power target value of the second voltage source converter from the actual value, and output a current correction value through a proportional-integral regulator; Adding the current correction amount to the estimated value of the q-axis current obtained by the inverse model to obtain a target value of the q-axis component of the output current of the second voltage source converter; After the target value and actual value of the d-axis and q-axis components are subtracted, the voltage modulation signal in the dq coordinate system is output through the proportional-integral regulator; Performing an inverse Park transform on the voltage modulation signal in the dq coordinate system, the voltage modulation signal in the αβ coordinate system is obtained; A space vector pulse width modulation control algorithm is used to generate a second switch tube gate signal of the switch tube of the first voltage source converter according to the voltage modulation signal, wherein the second switch tube gate signal is used to control the output active and reactive power to reach the corresponding target value.

11. The method according to claim 1, characterized in that: The method further comprises: In the event of a failure of a first voltage source converter operating in a first control mode, among the remaining second voltage source converters operating in a second control mode, a second voltage source converter having a maximum capacity regulation margin is selected to switch from the second control mode to the first control mode as a new first voltage source converter; wherein the capacity regulation margin is calculated based on the rated capacity and the current output apparent power; The second voltage source converter that needs to be switched is set through the regulator and the selection switch to convert the second voltage source converter from the second control mode to the first control mode.

12. An electronic device comprising: A processor, and a memory storing a program, wherein the program comprises instructions, which, when executed by the processor, cause the processor to perform the method according to any one of claims 1 to 11.

13. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method according to any one of claims 1 to 11 is implemented.

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