A method for coordinated operation control of double-end converters in long-distance power distribution lines

Abstract

The application provides a long-distance power distribution line double-end converter coordinated operation control method, and relates to the technical field of power electronic conversion and power distribution network operation control. A first converter, a power communication module and a second converter are sequentially connected with each other, so that periodic electrical parameter transmission is performed; the first converter is driven to operate in a rectification mode based on the transmitted electrical parameters; fuzzy droop control is performed based on the transmitted electrical parameters, and the second converter is driven to operate in an inversion mode based on the control result; when the power direction in the electrical parameters is reversed, the operation modes of the first converter and the second converter are rapidly converted, so that the coordinated operation control of the rectification end and the inversion end is realized. The method stabilizes the output DC voltage, AC voltage and power, simultaneously considers the fast dynamic response of mutual aid power and the high steady-state precision regulation of the terminal voltage, and realizes the coordinated operation control of the rectification end and the inversion end.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronic conversion and distribution network operation control, and more particularly to a long-distance distribution line double-end converter coordinated operation control method. BACKGROUND

[0002] In the existing low-voltage distribution network structure, the energy mutual assistance between different transformer areas mainly relies on three-phase alternating current long-distance distribution lines. However, with the increase of line length and the uneven distribution of load, the voltage drop and transmission loss of the alternating current line become increasingly prominent, resulting in a significant decrease in the terminal voltage of the distribution line, which affects the quality of power supply to users and the stability of terminal equipment operation. If new energy power supply equipment is built at the remote terminal user, the problem of voltage over-limit is likely to occur. To improve the terminal voltage problem, the traditional scheme usually adds voltage regulators or reactive power compensation devices in the middle of the line, such as installing on-load voltage regulators, static var generators or capacitor compensation units, but such methods have poor layout flexibility due to installation conditions and cost limitations. At the same time, the adjustment response of such devices depends on mechanical structure or fixed control parameters, and it is difficult to quickly respond to dynamic fluctuations of load. In addition, the traditional voltage regulating device can only adjust the voltage amplitude and cannot realize the coordinated control of active and reactive power, which may still cause terminal voltage deviation under rapid disturbance. On the other hand, the active power transmission capacity of long-distance alternating current distribution lines is limited by line impedance, and the decrease of power factor leads to a decrease in transmission efficiency, further aggravating the voltage quality problem of low-voltage distribution systems.

[0003] With the development of power electronic technology, AC-DC hybrid power supply structure gradually becomes an important direction to improve the power supply quality and operation efficiency of low-voltage distribution systems. By introducing a DC interconnection line between transformer areas, line loss can be effectively reduced, voltage stability can be improved, and flexible power exchange between distributed energy and load can be realized. However, in the DC interconnection system with bidirectional power flow, the coordinated operation control of the rectifier end and the inverter end becomes a core difficulty. The rectifier end needs to maintain the stability of the DC bus voltage, while its output is affected by load fluctuations and line impedance. The inverter end needs to realize dynamic matching of power and voltage with the AC end transformer area grid. Both need to reasonably allocate active and reactive power, and ensure the stability of output voltage and frequency. The traditional fixed droop control strategy is difficult to balance the fast dynamic response of interconnection power and the high steady-state accuracy regulation of terminal voltage due to constant control coefficients, and the control effect is likely to deteriorate due to performance degradation under light or heavy load conditions. SUMMARY

[0004] In order to solve the problem that the prior art cannot simultaneously consider the fast dynamic response of mutual assistance power and the high steady-state accuracy adjustment of terminal voltage, the application provides a long-distance power distribution line double-ended converter coordinated operation control method, which considers the dynamic distribution of mutual assistance power and the steady-state maintenance of terminal voltage, and avoids the deterioration of control effect caused by performance degradation.

[0005] In order to achieve the above technical effects, the technical scheme of the application is as follows:

[0006] In the first aspect, the application provides a long-distance power distribution line double-ended converter coordinated operation control method, the double-ended converter comprising a first converter and a second converter, one end of the first converter being connected to a first alternating current side of a power distribution line, the other end being connected to one end of the second converter through a power communication module, the other end of the second converter being connected to a second alternating current side of the power distribution line, the power communication module being used to establish a data link for the first converter and the second converter to perform periodic electrical parameter exchange transmission between the first converter and the second converter, and comprising the following steps:

[0007] S1. Based on the terminal direct current voltage transmitted by the second converter and the reference voltage, performing double-loop control of the direct current voltage outer loop and the current inner loop on the first converter to drive the first converter to operate in a rectification operation mode;

[0008] S2. Based on the voltage signal and the current signal of the second alternating current side, using a pre-set fuzzy droop controller to perform fuzzy droop control, and correcting the droop coefficient of the fuzzy droop controller in the fuzzy droop control process;

[0009] S3. Outputting the droop coefficient correction amount, and based on the droop coefficient and the droop coefficient correction amount, performing double-loop control of the direct current voltage and the current inner loop on the second converter to drive the second converter to operate in an inversion operation mode;

[0010] S4. Based on the direct current terminal current of the power distribution line, judging the power direction on the power distribution line, and when the power direction is reversed, converting the operation modes of the first converter and the second converter.

[0011] In the technical solution, the first converter, the power communication module and the second converter are sequentially connected with each other to form an organic whole, so that periodic electrical parameter transmission is performed between the first converter and the second converter; the first converter is driven to operate in a rectification mode based on the transmitted electrical parameters; fuzzy droop control is performed based on the transmitted electrical parameters, and double closed loop control of a direct current voltage and current inner loop is performed on the second converter based on a control result to drive the second converter to operate in an inversion mode; when the power direction in the electrical parameters is reversed, the operation mode of the first converter and the second converter is converted, and coordinated operation control of the rectification end and the inversion end is realized. The method provided in the application stabilizes the direct current voltage, alternating current voltage and power of the double-end converter used on the long-distance distribution line, and simultaneously takes into account the fast dynamic response of the mutual power of the double converters and the high steady-state precision adjustment of the terminal voltage, and realizes the coordinated operation control of the rectification end and the inversion end.

[0012] Preferably, the electrical parameters include: a direct current voltage at the terminal of the long-distance distribution line, a direct current at the terminal of the long-distance distribution line, active power at the second alternating current side, reactive power at the second alternating current side, a converter operation state and a converter operation warning symbol.

[0013] Preferably, the process of performing double closed loop control of the direct current voltage outer loop and the current inner loop on the first converter is:

[0014] based on an actual value of the direct current voltage at the terminal of the long-distance distribution line and a direct current voltage reference value at the terminal of the long-distance distribution line , a voltage difference value is calculated, and the expression is:

[0015]

[0016] The voltage difference value is input into a preset first voltage outer loop controller , and a d-axis direct current reference value is output through PI control. The d-axis direct current reference value output by the first voltage outer loop controller and the actual d-axis direct current are input into a preset first current inner loop controller , and a q-axis direct current reference value and a deviation of the actual d-axis direct current are input into the preset first current inner loop controller , so that double closed loop control of the direct current voltage outer loop and the current inner loop is completed, and a PWM driving signal is output to drive the first converter to operate in a rectification mode; the first voltage outer loop controller and the first current inner loop controller respectively satisfy the expressions:

[0017]

[0018]

[0019] wherein, represents a first voltage loop proportional coefficient, represents a first voltage loop integral coefficient, represents a first current loop proportional coefficient, represents a first current loop integral coefficient, represents a complex frequency variable in Laplace transform.

[0020] Preferably, before the fuzzy droop control is performed, the method further comprises: pre-processing the voltage signal and the current signal on the second AC side, the process being:

[0021] based on the voltage signal and the current signal on the second AC side, calculating active power , reactive power , active power change rate and reactive power change rate , and eliminating high-frequency noise in the active power change rate and the reactive power change rate .

[0022] normalizing and fuzzifying the active power , the reactive power , the active power change rate and the reactive power change rate .

[0023] Preferably, the process of outputting the droop coefficient correction amount is:

[0024] based on the calculated active power , reactive power , active power change rate and reactive power change rate , setting a fuzzy rule triggering strength, the expression being:

[0025]

[0026] wherein, represents the strength of the th fuzzy rule being triggered at the current input, represents the membership function value of the active power to the active power fuzzy set, represents the membership function value of the active power change rate to the active power change rate fuzzy set, The membership function value represents the fuzzy set of the rate of change of reactive power with respect to active power. The membership function value of the rate of change of reactive power to the fuzzy set of the rate of change of reactive power;

[0027] Based on pre-set fuzzy rules and their trigger strength, output fuzzy sets. Clipping the fuzzy set to the activation intensity The expression below is:

[0028]

[0029] in, Indicates the first The fuzzy set output by each rule Indicates the output variable. Represents the fuzzy set after clipping;

[0030] All cropped fuzzy sets are aggregated to form a comprehensive output fuzzy set. The comprehensive output fuzzy set Perform defuzzing and calculate the active power droop coefficient correction amount. and reactive power droop factor correction amount The expression is:

[0031]

[0032]

[0033] in, This represents the correction amount for the fuzzy active power droop coefficient. This represents the correction amount for the fuzzy reactive power droop factor. Indicates the number of fuzzy rules. , Indicates the first i The output center value of each rule.

[0034] Preferably, the process of performing dual closed-loop control of the DC voltage and current inner loop on the second converter is as follows:

[0035] Calculate the reference output frequency based on the droop correction and droop coefficient. With reference output voltage The expression is:

[0036]

[0037]

[0038] in, This represents the initial active power droop coefficient. an initial reactive droop coefficient, an initial frequency, an initial voltage, an active power reference value, a reactive power reference value;

[0039] a reference output frequency and a reference output voltage are input to a second voltage outer loop controller and a second current inner loop controller for double closed-loop control, and output control quantities drive the second converter to operate in inverter mode; the expression is:

[0040]

[0041]

[0042] wherein, the second voltage loop proportional coefficient is denoted as Kp2, the second voltage loop integral coefficient is denoted as Ki2, the second current loop proportional coefficient is denoted as Kp4, the second current loop integral coefficient is denoted as Ki4.

[0043] Preferably, a protection module is further configured for the first voltage outer loop controller , the first current inner loop controller , the second voltage outer loop controller and the second current inner loop controller .

[0044] Preferably, the step S4 judges the power direction on the power distribution line based on the DC terminal current of the power distribution line, and when the power direction is reversed, the operating mode of the first converter and the second converter is converted, and the process is:

[0045] The power direction on the power distribution line is judged based on the pre-acquired DC current of the first converter and the DC current of the second converter , the pre-defined positive threshold , the negative threshold and the delay threshold :

[0046] If , and the duration is greater than the delay threshold , the first converter is driven to operate in rectifier mode and the second converter is driven to operate in inverter mode; if , and the duration is greater than the delay threshold drive the first converter to operate in a rectification mode and the second converter to operate in an inversion mode;

[0047] Otherwise, the original operation mode of the first converter and the second converter is maintained.

[0048] In a second aspect, the present application further provides a computer device, which comprises:

[0049] a memory, a processor and a computer program stored in the memory and executable by the processor, wherein the processor executes the computer program to implement the method for coordinated operation control of double-ended converters in long-distance power distribution lines.

[0050] In a third aspect, the present application further provides a computer storage medium having a computer program stored thereon, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer is caused to execute the method for coordinated operation control of double-ended converters in long-distance power distribution lines.

[0051] Compared with the prior art, the present application has the following beneficial effects:

[0052] The present application provides a method for coordinated operation control of double-ended converters in long-distance power distribution lines, which connects a first converter, a power communication module and a second converter in sequence to form an organic whole, so that periodic transmission of electrical parameters between the first converter and the second converter is realized; the first converter is driven to operate in a rectification mode based on the transmitted electrical parameters; fuzzy droop control is performed based on the transmitted electrical parameters, and double-loop control of a direct-current voltage and current inner loop is performed on the second converter based on the control result to drive the second converter to operate in an inversion mode; when the power direction in the electrical parameters is reversed, the operation modes of the first converter and the second converter are switched, thereby realizing coordinated operation control of the rectification end and the inversion end. The method provided by the present application stabilizes the direct-current voltage, alternating-current voltage and power of the double-ended converters in long-distance power distribution lines, and simultaneously takes into account the fast dynamic response of mutual-aid power of the double converters and the high steady-state accuracy regulation of the terminal voltage, thereby realizing coordinated operation control of the rectification end and the inversion end. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 a flowchart showing a method for coordinated operation control of double-ended converters in long-distance power distribution lines according to an embodiment of the present application;

[0054] Figure 2 a schematic diagram showing an equivalent circuit structure of a long-distance power distribution line equipped with double-ended converters according to an embodiment of the present application;

[0055] Figure 3Fig. 2 is a schematic diagram of a process of performing double closed-loop control of a direct-current voltage outer loop and a current inner loop on the first converter according to the embodiment 2 of the present application;

[0056] Figure 4 Fig. 3 is a schematic diagram of a process of performing fuzzy droop control according to the embodiment 2 of the present application;

[0057] Figure 5 Fig. 4 is a schematic diagram of a process of performing double closed-loop control of a direct-current voltage outer loop and a current inner loop on the second converter according to the embodiment 2 of the present application;

[0058] Figure 6 Fig. 5 is a schematic diagram of a waveform of a line-end direct-current bus voltage according to the embodiment 3 of the present application;

[0059] Figure 7 Fig. 6 is a schematic diagram of a waveform of a system power change amount according to the embodiment 3 of the present application;

[0060] Figure 8 Fig. 7 is a schematic diagram of waveforms of active power and reactive power of the first converter and the second converter according to the embodiment 3 of the present application;

[0061] Figure 9 Fig. 8 is a schematic diagram of waveforms of three-phase alternating-current voltage and current of the first converter and the second converter according to the embodiment 3 of the present application;

[0062] Figure 10 Fig. 9 is a schematic diagram of a structure of a computer device according to the embodiment 4 of the present application. DETAILED DESCRIPTION

[0063] The accompanying drawings are only used for illustrative description and cannot be understood as a limitation to the present application;

[0064] In order to better illustrate the present embodiment, some parts of the drawings are omitted, enlarged or reduced, and do not represent the actual size;

[0065] For those skilled in the art, it is understandable that some well-known descriptions in the drawings can be omitted.

[0066] The technical solutions of the present application will be further described below in combination with the drawings and embodiments.

[0067] The positional relationship described in the drawings is only used for illustrative description and cannot be understood as a limitation to the present application;

[0068] Embodiment 1

[0069] The present embodiment proposes a long-distance power distribution line double-end converter coordinated operation control method, and a schematic diagram of a flow of the method is shown in Fig. 1. Figure 1The double-ended converter comprises a first converter and a second converter, one end of the first converter is connected to a first alternating current side of a power distribution line, the other end of the first converter is connected to one end of the second converter through a power communication module, the other end of the second converter is connected to a second alternating current side of the power distribution line, and the power communication module is used to establish a data link for the first converter and the second converter to perform periodic electrical parameter exchange transmission between the first converter and the second converter. Figure 2 As shown in Figure 2 , one end of the first converter 1 is connected to a first alternating current side of a power distribution line, the first alternating current side of the power distribution line comprises alternating current power supplies , , , capacitors , resistors and inductors , the other end of the first converter is connected to one end of the second converter 2 through a power communication module 3, and the direct current ports of the first converter 1 and the second converter 2 are interconnected through line impedance and two distributed capacitors , to form a direct current channel for bidirectional power transmission; the other end of the second converter 2 is connected to a second alternating current side of the power distribution line, and the second alternating current side of the power distribution line comprises alternating current power supplies , , , capacitors , resistors and inductors .

[0070] As shown in Figure 1 , the method comprises the following steps:

[0071] S1. Based on the terminal direct current voltage transmitted by the second converter and a reference voltage, performing double closed-loop control of a direct current voltage outer loop and a current inner loop on the first converter to drive the first converter to operate in a rectification operation mode;

[0072] S2. Based on a voltage signal and a current signal of the second alternating current side, performing fuzzy droop control by using a pre-set fuzzy droop controller, and correcting a droop coefficient of the fuzzy droop controller in the fuzzy droop control process;

[0073] S3. Outputting a droop coefficient correction amount, and based on the droop coefficient and the droop coefficient correction amount, performing double closed-loop control of a direct current voltage and a current inner loop on the second converter to drive the second converter to operate in an inversion operation mode;

[0074] S4. Based on the DC end current of the distribution line, determine the power direction on the distribution line. When the power direction reverses, switch the operating modes of the first converter and the second converter.

[0075] In this embodiment, the first converter, the power communication module, and the second converter are sequentially interconnected to form an organic whole, enabling periodic transmission of electrical parameters between the first and second converters. Based on the transmitted electrical parameters, the first converter is driven to operate in rectification mode. Fuzzy droop control is performed based on the transmitted electrical parameters, and based on the control results, dual closed-loop control of DC voltage and current inner loops is executed on the second converter, driving it to operate in inverter mode. When the power direction in the electrical parameters reverses, the operating modes of the first and second converters are switched, achieving coordinated operation control of the rectifier and inverter ends. The method proposed in this application stabilizes the DC voltage, AC voltage, and power of dual-ended converters on long-distance distribution lines, while also considering the rapid dynamic response of the mutual power assistance between the two converters and the high steady-state accuracy adjustment of the terminal voltage, achieving coordinated operation control of the rectifier and inverter ends. Example 2

[0076] In this embodiment, the electrical parameters include: DC voltage at the end of the long-distance power distribution line, DC current at the end of the long-distance power distribution line, active power on the second AC side, reactive power on the second AC side, converter operating status, and converter operating warning signs.

[0077] Specifically, when the first converter is in rectification mode, the three-phase AC input is converted into DC power by the rectifier bridge, and the output filter branch... , Composition, capacitor Smoothing bus voltage fluctuations; the second converter receives energy from the DC line, converts it into three-phase AC output via an inverter bridge, and supplies power to the distribution area load or local power grid; the filter branch... , Composition, capacitor Stable output bus voltage.

[0078] Specifically, the communication frame for electrical parameter communication includes a frame header, version number, sequence number, timestamp, load data area, and cyclic redundancy check field. When packet loss or check errors occur in electrical parameter communication, the system executes a degradation strategy of maintaining the previous valid value and linear interpolation to prevent sudden changes in control signals. After communication is restored, the system gradually restores normal control quantities through a smooth recovery algorithm to ensure a stable and shock-free switching process. The electrical communication module also has a clock synchronization function, employing a timestamp comparison and correction mechanism to ensure timing consistency between the two ends.

[0079] In this embodiment, the process of performing dual closed-loop control of the first converter, consisting of an outer loop for DC voltage and an inner loop for current, is as follows:

[0080] Based on the actual DC voltage value at the end of long-distance power distribution lines Reference value of DC voltage at the end of long-distance power distribution lines Calculate the voltage difference The calculation expression is:

[0081]

[0082] voltage difference Input to the preset first voltage outer loop controller In the middle, the d-axis DC current reference value is output via PI control. The first voltage outer loop controller Output d-axis DC current reference value With actual d-axis DC current deviation q-axis DC current reference value With actual d-axis DC current deviation Input to the preset first current inner loop controller In the process, a dual closed-loop control of the DC voltage outer loop and the current inner loop is completed, and a PWM drive signal is output to drive the first converter to operate in rectification mode; the first voltage outer loop controller and the first current inner loop controller They satisfy the following expressions respectively:

[0083]

[0084]

[0085] in, This represents the proportional coefficient of the first voltage loop. Indicates the integral coefficient of the first voltage loop. This represents the proportionality coefficient of the first current loop. Indicates the integral coefficient of the first current loop. This represents the complex frequency variable in the Laplace transform.

[0086] Specifically, the flowchart for the dual closed-loop control of the DC voltage outer loop and current inner loop for the first converter is shown below. Figure 3 , Figure 3 In the middle, the first voltage outer loop controller The DC voltage at the inverter end is obtained by sampling. With reference voltage deviation The input is sent to the preset first voltage outer loop controller. In the middle, the d-axis current reference value is output. Then, the d-axis DC current reference value... With actual d-axis DC current deviation q-axis DC current reference value With actual d-axis DC current deviation The inputs are respectively fed into the preset first current inner loop controller. In the middle, the first current inner loop controller by Compared with the measured current deviation as well as Compared with the measured current deviation The input is used as input, and the output results are output and driven by the rectifier bridge power devices after being modulated by PWM, thereby realizing constant voltage control of the voltage at the end of the long-distance power distribution line.

[0087] In this embodiment, before performing fuzzy droop control, the method further includes: preprocessing the voltage and current signals on the second AC side, the process of which is as follows:

[0088] Calculate the active power based on the voltage and current signals from the second AC side. reactive power Active power change rate and reactive power change rate and the rate of change of active power and reactive power change rate High-frequency noise elimination;

[0089] Active power reactive power Active power change rate and reactive power change rate Normalization and fuzzification processing.

[0090] Specifically, before the normalization and fuzzification processes, the active power is also analyzed. reactive power Active power change rate and reactive power change rate According to rated capacity With sampling period Standardization is performed to reduce the impact of scale differences on reasoning;

[0091] Specifically, the normalization includes normalization of active power. reactive power Active power change rate and reactive power change rate Perform normalization to map it to or Domain of discourse.

[0092] The fuzzification process includes classifying active power according to pre-set hierarchical rules. reactive power Active power change rate and reactive power change rate It is divided into three levels: high, medium, and low; the preset grading rules include defined triangular or trapezoidal membership functions. For example, in On the unified domain, respectively active power reactive power Active power change rate and reactive power change rate A triangular membership function is defined for three segments, with three levels: LOW, MED, and HIGH. The level range is defined proportionally during the setting process; for example, in this embodiment, it is set as follows: 0.3 is considered low. 0.7 is High; 0.7 is for Med;

[0093] Each membership function is defined in a piecewise linear form, with the following expressions:

[0094]

[0095]

[0096]

[0097] in, These are the inflection points set according to the typical operating power range. Rate of change A similar approach is used to classify the levels into SLOW / FAST and provide the corresponding triangular membership functions. This results in... These respectively represent "the degree to which the current active power belongs to the i-th power level" and "the degree to which the current active power change rate belongs to the i-th change level".

[0098] In this embodiment, the process of outputting the droop coefficient correction amount is as follows:

[0099] Based on the calculated active power reactive power Active power change rate and reactive power change rate Set the trigger strength for the fuzzy rule using the following expression:

[0100]

[0101] wherein, represents the strength of the th fuzzy rule being triggered under the current input, represents the membership function value of active power to the active power fuzzy set, represents the membership function value of active power change rate to the active power change rate fuzzy set, represents the membership function value of reactive power to the active power change rate fuzzy set, represents the membership function value of reactive power change rate to the reactive power change rate fuzzy set;

[0102] Based on the pre-set fuzzy rules and the fuzzy rule triggering strength, the fuzzy set is outputted.

[0103]

[0104] wherein, represents the th rule output fuzzy set, represents the output variable, represents the fuzzy set after clipping;

[0105] All the fuzzy sets after clipping are aggregated to form a comprehensive output fuzzy set , and the comprehensive output fuzzy set is de-fuzzied to calculate the active power droop coefficient correction amount and the reactive power droop coefficient correction amount , the expression being:

[0106]

[0107]

[0108] wherein, represents the fuzzy active power droop coefficient correction amount, represents the fuzzy reactive power droop coefficient correction amount, represents the number of fuzzy rules, , represents the output center value of the i th rule.

[0109] Specifically, the output center value and can be calibrated through offline simulation or test; the running period can be grouped and configured according to seasons, load types, or periodically fine-tuned according to running indexes.

[0110] Specifically, , and The values ​​are all limited to The activation intensity. The derivation is performed using the Mamdani-type reasoning method. Since Mamdani-type reasoning uses the "AND" operation, it means that the rule is only strongly activated when all conditions are met, so the minimum value needs to be taken.

[0111] Specifically, all the cropped fuzzy sets are aggregated to form a comprehensive output fuzzy set. The expression is:

[0112]

[0113] Among them, all the cropped fuzzy sets Aggregates into a single fuzzy output set based on the maximum value. Since the rules are parallel, the maximum value should be taken as the current output membership degree.

[0114] Specifically, the fuzzy active power droop factor correction amount And the correction amount of fuzzy reactive power droop coefficient It includes five levels of correction arranged from smallest to largest: NB, NM, ZO, PM, and PB. PB corresponds to the largest positive correction, NM to a small negative correction, ZO to no correction, PM to a small positive correction, and NB to the largest negative correction. The correction amount for the fuzzy active power droop coefficient is also included. With active power and its rate of change as the primary inputs, the fuzzy reactive power droop coefficient correction is... With reactive power and its rate of change as the primary inputs, under high load and rapid power increase conditions, the command is given... The "stiffening" rule is used to suppress frequency or voltage fluctuations, providing a constraint under light load or power reduction conditions. The "stiffness reduction" rule aims to reduce steady-state deviation. For example, "the currently sampled..." Larger The rate of change is relatively fast, if ,but For HIGH; if ,but For FAST; if ,but For HIGH; if ,but For FAST; at this time, the activation intensity The highest membership degree of the corresponding output fuzzy set is limited to 0.6 instead of the original 1, indicating that the rule supports the conclusion "ΔKp is PB" with a confidence level of 0.6 under the current working condition. The specific ΔKp value is then obtained by aggregating the outputs of all rules and defuzzifying the centroids. The activation strength of the i-th rule under the current input is... Given the minimum value of the four input membership functions, then using this... For output fuzzy sets The process involves cropping and aggregation, followed by deblurring using the centroid method to obtain the final numerical output. Therefore, the input fuzzy set is only used to calculate the activation degree of each rule, and the output fuzzy set is used to describe the "range of values ​​of the droop correction when the i-th rule takes effect". The two are logically mapped through the rule base, rather than being a simple numerical function relationship.

[0115] In addition, under special circumstances, a small number of crossover rules between active and reactive power may be used to suppress coupled oscillations, but the activation region and the amplitude of the center value should be limited to avoid subsynchronous oscillations caused by excessive coupling.

[0116] Specifically, this also includes setting amplitude limits and dead zone constraints during correction, and applying inverse integral saturation processing to the deblurring result to suppress oscillations and improve stability margin, setting its correction amplitude to satisfy:

[0117]

[0118] in, To correct the upper limit of the droop coefficient, it is generally taken as 0.5 to 1.0 times the initial droop coefficient to prevent excessive stiffness from causing system oscillation;

[0119] When the correction reaches the limit boundary, the integral separation or integral recharge mechanism is activated for anti-saturation control to prevent the continuous accumulation of the integral term in the fuzzy controller; the expression for anti-saturation process control is:

[0120]

[0121] in, The inverse saturation coefficient, This is the saturation value;

[0122] If the absolute value of the correction is less than the dead zone threshold If the output is zero, the output is set to zero to eliminate frequent corrections caused by small power disturbances. The expression is:

[0123]

[0124] Among them, the dead zone threshold Typically, 1%–5% of the output universe of discourse is taken.

[0125] In the embodiment, the process of performing double closed-loop control of DC voltage and current inner loop on the second converter is:

[0126] Based on the droop correction amount and the droop coefficient, the reference output frequency is calculated and the reference output voltage , the expression is:

[0127]

[0128]

[0129] wherein, represents the initial active droop coefficient, represents the initial reactive droop coefficient, represents the initial frequency, represents the initial voltage, represents the active power reference value, represents the reactive power reference value.

[0130] The reference output frequency and the reference output voltage are input to the second voltage outer loop controller and the second current inner loop controller respectively to perform double closed-loop control, and output control quantity to drive the second converter to operate in inverter operation mode; the expression is:

[0131]

[0132]

[0133] wherein, represents the second voltage loop proportional coefficient, represents the second voltage loop integral coefficient, represents the second current loop proportional coefficient, represents the second current loop integral coefficient.

[0134] Specifically, the flow chart of the fuzzy droop control is shown in Figure 4 , Figure 4 First, the deviation is calculated, which includes the active deviation between the reference active power and the actual active power and the reactive deviation between the reference reactive power and the actual reactive power ; the active deviation is combined with the active droop coefficient , the active droop coefficient correction amount and the basic output frequency , the reference output frequency is calculated , the reference output frequency is calculated , the angle is integrated to obtain ; in another aspect, the reactive power deviation is combined with the reactive power droop coefficient , the reactive power droop coefficient correction amount and the reference output voltage , the reference output voltage is calculated ; then based on the angle and the voltage reference , the three-phase voltage reference value is synthesized , , the expression is:

[0135]

[0136]

[0137]

[0138] Based on the three-phase voltage reference value , , the d-axis voltage reference value and the q-axis voltage reference value are calculated, the expression is:

[0139]

[0140] Finally, based on the obtained d-axis voltage reference value and the q-axis voltage reference value , the double closed-loop control of the direct current voltage and current inner loop is performed on the second converter;

[0141] The flow chart of the double closed-loop control of the direct current voltage and current inner loop performed on the second converter is shown in Figure 5 , Figure 5 , the second voltage outer loop controller respectively takes two deviations as input, the deviations include the d-axis deviation and the q-axis deviation , the d-axis deviation is the deviation between the d-axis voltage reference value and the d-axis voltage actual value , and the q-axis deviation is the deviation between the q-axis voltage reference value and the q-axis voltage actual value ; the second voltage outer loop controller outputs the d-axis current reference value and the q-axis current reference value Then the d-axis direct current reference value is input into a preset second current inner loop controller together with the deviation of the actual d-axis direct current , the q-axis direct current reference value is input into a preset second current inner loop controller together with the deviation of the actual q-axis direct current , and the output results are respectively output to drive the inverter bridge power devices after PWM modulation, so that stable alternating voltage and power are output, and power is smoothly sent out.

[0142] In the embodiment, a protection module is further configured for the first voltage outer loop controller , the first current inner loop controller , the second voltage outer loop controller and the second current inner loop controller .

[0143] In the embodiment, the power direction on the power distribution line is judged based on the direct current at the end of the power distribution line, and when the power direction is reversed, the operation mode of the first converter and the second converter is converted, and the process is as follows:

[0144] The power direction on the power distribution line is judged based on the direct current of the first converter and the direct current of the second converter , the pre-defined positive threshold , the negative threshold and the delay threshold .

[0145] If , and the duration is greater than the delay threshold , the first converter is driven to operate in the rectification operation mode, and the second converter is driven to operate in the inversion operation mode; if , and the duration is greater than the delay threshold , the first converter is driven to operate in the inversion operation mode, and the second converter is driven to operate in the rectification operation mode.

[0146] Otherwise, the original operation mode of the first converter and the second converter is maintained.

[0147] Specifically, a soft switching process is performed in the converter operation mode switching process, the voltage and power instructions are gradually adjusted to prevent current spikes; the minimum dwell time and the hysteresis angle are set during switching to prevent frequent switching at critical power points; in the case of overcurrent, overvoltage or communication out-of-step, the switching is aborted and rolled back to the working condition before switching, and at the same time, an alarm is sent and the event is recorded.

[0148] Example 3

[0149] This embodiment proposes a specific implementation of the coordinated operation control method for dual-ended converters in long-distance power distribution lines. The operating conditions are set as follows: the first converter operates in rectification mode, and the second converter operates in inverter mode. Some electrical parameters are as follows: the AC bus voltage of both the first and second converters is 311V, and the DC side voltage is stabilized at 750V. Under this condition, the active power of both the first and second converters is set to 20kW. At that time, 20kW was put into the inverter terminal to simulate the power fluctuations that may occur in actual operation.

[0150] A waveform diagram of the DC bus voltage at the end of the line is shown below. Figure 6 As shown, in Figure 6 In the process, the DC bus voltage stabilizes at 750V after a 0.1s transition period; the waveform diagram of the system power change is shown below. Figure 7 As shown, Figure 7 In the above scenario, the system power change stabilizes at 0kW after adjustment, indicating that the power at each port achieves complementary absorption. The active and reactive power waveforms of the first and second converters are shown in the diagram below. Figure 8 As shown, Figure 8 In the diagram, the first waveform represents the active and reactive power waveforms of the first converter, and the second waveform represents the active and reactive power waveforms of the second converter. Purple lines represent active power, and green lines represent reactive power. When the inverter is switched on at 20kW, the DC bus voltage and power of the system respond immediately, with only a small fluctuation. After a transition of 0.05s, the system can reach steady-state operation, verifying the rapid suppression capability of the method disclosed in this embodiment for power disturbances and the good stability of the system.

[0151] The schematic diagram of the three-phase AC voltage and current waveforms of the first and second converters is shown below. Figure 9 As shown, by Figure 9 It can be seen that within the time period of 0.17~0.25s, the first waveform diagram represents the voltage waveform of the first converter, the second waveform diagram represents the current waveform of the first converter, the second waveform diagram represents the voltage waveform of the second converter, and the second waveform diagram represents the current waveform of the second converter. The AC voltages of both the first and second converters can be stabilized at 311V, and the output current and output voltage remain in phase, indicating that the system achieves unity power factor operation. When the inverter is connected to 20kW, the output current increases accordingly with the load connection, further verifying the effectiveness of the method disclosed in this embodiment in maintaining voltage and current stability.

[0152] Embodiment 4

[0153] The embodiment provides a computer device, in the embodiment, the computer device comprises a memory 101, a processor 102 and a computer program stored on the memory 101 and capable of being run on the processor, and the processor 102 executes the computer program to realize the long-distance power distribution line double-end converter coordinated operation control method, and a structural schematic diagram of the device is shown in FIG. 1. Figure 10

[0154] The embodiment further provides a computer storage medium, and the computer storage medium stores a computer program, and the computer program comprises program instructions, and the program instructions are executed by a computer to enable the computer to execute the long-distance power distribution line double-end converter coordinated operation control method.

[0155] Obviously, the above embodiment of the present application is only an example for clearly illustrating the present application, and is not a limitation on the implementation manner of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the implementation manners are not required or can not be exhausted. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.​

Claims

1. A method for coordinated operation control of dual-ended converters in long-distance power distribution lines, characterized in that, The dual-ended converter includes a first converter and a second converter. One end of the first converter is connected to the first AC side of the power distribution line, and the other end is connected to one end of the second converter via a power communication module. The other end of the second converter is connected to the second AC side of the power distribution line. The power communication module is used to establish a data link between the first converter and the second converter to perform periodic electrical parameter exchange and transmission between them. The process includes the following steps: S1. Based on the terminal DC voltage and reference voltage transmitted by the second converter, perform dual closed-loop control of the DC voltage outer loop and the current inner loop on the first converter to drive the first converter to operate in rectification mode. S2. Based on the voltage and current signals of the second AC side, fuzzy droop control is performed using a pre-set fuzzy droop controller. During the fuzzy droop control process, the droop coefficient of the fuzzy droop controller is corrected. S3. Output droop coefficient correction amount. Based on the droop coefficient and the droop correction amount, perform dual closed-loop control of DC voltage and current inner loop on the second converter to drive the second converter to operate in inverter mode. S4. Based on the DC end current of the distribution line, determine the power direction on the distribution line. When the power direction reverses, switch the operating modes of the first converter and the second converter.

2. The coordinated operation control method for double-ended converters in long-distance power distribution lines according to claim 1, characterized in that, The electrical parameters include: DC voltage at the end of the long-distance power distribution line, DC current at the end of the long-distance power distribution line, active power on the second AC side, reactive power on the second AC side, converter operating status, and converter operating warning signs.

3. The coordinated operation control method for double-ended converters in long-distance power distribution lines according to claim 2, characterized in that, The process of performing dual closed-loop control of the first converter, consisting of an outer loop for DC voltage and an inner loop for current, is as follows: Based on the actual DC voltage value at the end of long-distance power distribution lines Reference value of DC voltage at the end of long-distance power distribution lines Calculate the voltage difference The calculation expression is: voltage difference Input to the preset first voltage outer loop controller In the middle, the d-axis DC current reference value is output via PI control. The first voltage outer loop controller Output d-axis DC current reference value With actual d-axis DC current deviation q-axis DC current reference value With actual d-axis DC current deviation Input to the preset first current inner loop controller In the process, a dual closed-loop control of the DC voltage outer loop and the current inner loop is completed, and a PWM drive signal is output to drive the first converter to operate in rectification mode; the first voltage outer loop controller and the first current inner loop controller They satisfy the following expressions respectively: in, This represents the proportional coefficient of the first voltage loop. Indicates the integral coefficient of the first voltage loop. This represents the proportionality coefficient of the first current loop. Indicates the integral coefficient of the first current loop. This represents the complex frequency variable in the Laplace transform.

4. The coordinated operation control method for double-ended converters in long-distance power distribution lines according to claim 3, characterized in that, Before performing fuzzy droop control, the method further includes: preprocessing the voltage and current signals on the second AC side, the process of which is as follows: Calculate the active power based on the voltage and current signals from the second AC side. reactive power Active power change rate and reactive power change rate and the rate of change of active power and reactive power change rate High-frequency noise elimination; Active power reactive power Active power change rate and reactive power change rate Normalization and fuzzification processing.

5. The coordinated operation control method for double-ended converters in long-distance power distribution lines according to claim 4, characterized in that, The process of correcting the output droop coefficient is as follows: Based on the calculated active power reactive power Active power change rate and reactive power change rate Set the trigger strength for the fuzzy rule using the following expression: in, Indicates the first The intensity at which a fuzzy rule is triggered under the current input. This represents the membership function value of active power to the active power fuzzy set. The membership function value of the rate of change of active power to the fuzzy set of the rate of change of active power. The membership function value represents the fuzzy set of the rate of change of reactive power with respect to active power. The membership function value of the rate of change of reactive power to the fuzzy set of the rate of change of reactive power; Based on pre-set fuzzy rules and their trigger strength, output fuzzy sets. Clipping the fuzzy set to the activation intensity The expression below is: in, Indicates the first The fuzzy set output by each rule Indicates the output variable. Represents the fuzzy set after clipping; All cropped fuzzy sets are aggregated to form a comprehensive output fuzzy set. The comprehensive output fuzzy set Perform defuzzing and calculate the active power droop coefficient correction amount. and reactive power droop factor correction amount The expression is: in, This represents the correction amount for the fuzzy active power droop coefficient. This represents the correction amount for the fuzzy reactive power droop factor. Indicates the number of fuzzy rules. , Indicates the first i The output center value of each rule.

6. The coordinated operation control method for double-ended converters in long-distance power distribution lines according to claim 5, characterized in that, The process of performing dual closed-loop control of the DC voltage and current inner loop on the second converter is as follows: Calculate the reference output frequency based on the droop correction and droop coefficient. With reference output voltage The expression is: in, This represents the initial active power droop coefficient. Describe the initial reactive power droop coefficient. Indicates the initial frequency. Indicates the initial voltage. This represents the reference value for active power. This indicates the reference value for reactive power. The reference output frequency is respectively With reference output voltage Input to the second voltage outer loop controller Second current inner loop controller Dual closed-loop control is implemented, and the output control quantity drives the second converter to operate in inverter mode; the expression is: in, This represents the proportionality coefficient of the second voltage loop. This represents the integral coefficient of the second voltage loop. This represents the proportionality coefficient of the second current loop. This represents the integral coefficient of the second current loop.

7. The coordinated operation control method for double-ended converters in long-distance power distribution lines according to claim 6, characterized in that, It also includes a first voltage outer loop controller. First current inner loop controller Second voltage outer loop controller Second current inner loop controller Configure the protection module.

8. The method for coordinated operation control of double-ended converters in long-distance power distribution lines according to claim 7, characterized in that, Step S4 describes determining the power direction on the power distribution line based on the DC end current. When the power direction reverses, the operating modes of the first and second converters are switched. The process is as follows: Based on the pre-collected DC current of the first converter With the DC current of the second converter Predefined positive threshold Negative threshold and delay threshold Determine the direction of power on the power distribution line: like , And the duration is greater than the delay threshold. The first converter is driven to operate in rectification mode, and the second converter is driven to operate in inverter mode; if , And its duration is greater than the delay threshold. The first converter is driven to operate in inverter mode, and the second converter is driven to operate in rectifier mode. Otherwise, the original operating modes of the first and second converters will be maintained.

9. A computer device, characterized in that, The computer device includes a memory, a processor, and a computer program stored in the memory that can be run on the processor, wherein the processor executes the computer program to implement the method according to any one of claims 1 to 8.

10. A computer storage medium, characterized in that, It stores a computer program, which includes program instructions that, when executed by a computer, cause the computer to perform the method described in any one of claims 1 to 8.

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