Interconnected power distribution network fault continuous power supply and electric energy control method, system and device

Abstract

The embodiment of the invention discloses an interconnected power distribution network fault continuous power supply and electric energy control method, the method is used for a power distribution network flexible interconnection system, the power distribution network flexible interconnection system comprises N flexible interconnection units and N + 1 power distribution networks, and the Nth flexible interconnection unit is connected with the first power distribution network and the N + 1 power distribution network; the Nth flexible interconnection unit comprises a first flexible interconnection module and a second flexible interconnection module which are reversely connected and are respectively connected with the first power distribution network and the (N + 1) th power distribution network; the method comprises the steps that when it is detected that an ith power distribution network has a single-phase earth fault, the single-phase earth fault phase is determined to be a K phase, and i is smaller than or equal to N; determining a control mode of two converters in the plurality of flexible interconnection units connected with the i-th power distribution network according to a scheduling instruction of the i-th power distribution network; determining a total reference current output by a converter in a plurality of flexible interconnection modules connected with the ith power distribution network according to the control mode; and determining a comprehensive control signal of each bridge arm of the converter in the plurality of flexible interconnection modules according to the total reference current.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power distribution network control, and in particular to a method, system, device and medium for continuous power supply and energy control of interconnected power distribution networks. BACKGROUND

[0002] In modern power systems, the interconnection of multiple power distribution networks has become an important means to improve system reliability and flexibility. With the increasing access of distributed energy, power distribution networks access a variety of sources and loads. The access of these complex devices will inevitably lead to various problems in the operating environment of power distribution networks, especially the frequent single-phase grounding fault problem in power distribution networks. Single-phase grounding fault may cause voltage instability, power grid imbalance and other problems, and may even escalate to arc grounding fault, causing the entire power system to be in a large-scale power outage state, thereby causing widespread power outages, and having a serious impact on life, production and industry in various fields. Traditional protection and control strategies are difficult to meet these needs.

[0003] Therefore, it is of great significance to develop a method and system for continuous power supply and energy control of interconnected power distribution networks with grounding fault ride-through capability. Through the multi-flexible interconnected device of the power distribution network with grounding fault ride-through capability, without additional arc extinguishing device, coordinated operation between multiple power distribution networks can be realized, as well as rapid response and recovery to single-phase grounding fault in the system. SUMMARY

[0004] Therefore, it is of great significance to develop a method and system for continuous power supply and energy control of interconnected power distribution networks with grounding fault ride-through capability. Through the multi-flexible interconnected device of the power distribution network with grounding fault ride-through capability, without additional arc extinguishing device, coordinated operation between multiple power distribution networks can be realized, as well as rapid response and recovery to single-phase grounding fault in the system.

[0005] A method for continuous power supply and energy control of interconnected power distribution networks, the method comprising:

[0006] When a single-phase grounding fault is detected in the ith power distribution network, determine the single-phase grounding fault phase as K phase, where i≤N;

[0007] According to the dispatching instruction of the ith power distribution network, determine the control mode of the two converters in the several flexible interconnection units connected thereto;

[0008] According to the control mode, determine the total reference current output by the converter in the several flexible interconnection modules connected to the ith power distribution network;

[0009] According to the total reference current, determine the comprehensive control signal of each bridge arm of the converter in the several flexible interconnection modules.

[0010] In the above scheme, according to the dispatching instruction of the ith power distribution network, the control mode of the several flexible interconnection

[0011] The control methods for the two converters in the unit specifically include:

[0012] When a single-phase ground fault is detected in the i-th distribution network, several flexible interconnection units are identified that are connected to...

[0013] The converter in the flexible interconnection module connected to the i-th distribution network is a constant power control converter, while the converter in another flexible interconnection module among several flexible interconnection units is a constant voltage control converter.

[0014] In the above scheme, the constant power control specifically includes:

[0015] The first component i of the three-phase current reference value output by the converter in the flexible interconnection module connected to the i-th distribution network is obtained based on instantaneous power theory and dq / abc transformation. i_ref1 Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1 i bi_ref1 i ci_ref1 ;

[0016] The load three-phase harmonic current i of the i-th distribution network ai_ref2 i bi_ref2 i ci_ref2 and three-phase negative sequence current i ai_ref3 i bi_ref3 i ci_ref3 The summation results in the second component i, which serves as the reference value for the three-phase current output of the current converter. i_ref2 ;

[0017] The fault ride-through reference current i of the i-th distribution network is determined according to the following expression. i-ref3 :

[0018] i i-ref3 =U ni Y zi / 3+U ni Y 0i

[0019] In the formula, U ni Y is the neutral-to-ground voltage of the i-th distribution network; 0i Y represents the power supply and ground admittance of the i-th distribution network. zi Let the admittance of the arc suppression coil of the i-th distribution network be denoted as .

[0020] According to the formula: i refi_R =i Ni -i i_ref1 Determine the remaining capacity i of the current converter refi_R In the formula, i Ni i i_ref1 These are the rated current value and the first component of the current converter, respectively;

[0021] According to the formula: Determine the ratio of the remaining capacity of the flexible interconnect module corresponding to the current converter to the remaining capacity of other flexible interconnect modules connected to the i-th distribution network;

[0022] According to the formula: i refi_quanlity =K i* i i_ref2 Determine the command current for power quality control of the flexible interconnect module corresponding to the current converter, where i i_ref2 This is the second component of the current three-phase current reference value output by the converter.

[0023] According to the formula: i refi_short =K i* i i-ref3 Determine the command current for ground fault ride-through of the flexible interconnect module corresponding to the current converter, where i i-ref3 Let be the fault ride-through reference current for the i-th distribution network;

[0024] According to the formula: i i_ref =i i_ref1 +i refi_quanlity +i refi_short Determine the total reference current i of the flexible interconnect module corresponding to the current converter. i_ref ;

[0025] The overall control signal for each bridge arm of the current converter is determined based on the total reference current.

[0026] In the above scheme, the first component i of the reference value of the three-phase current output of the current converter is obtained based on instantaneous power theory and dq / abc transformation. i_ref1 Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1 i bi_ref1 i ci_ref1 Specifically, it includes:

[0027] The reference value i for the d-axis current of the current converter is determined according to the following expression. drefi and q-axis current reference value i qrefi ;

[0028]

[0029]

[0030] In the formula, p refi and q refi These represent the active and reactive power that the current transformer's corresponding i-th distribution network needs to absorb from the (i+1)-th distribution network, respectively. di and u qiThese are the d-axis and q-axis components of the voltage at the connection point of the current transformer connected to the i-th distribution network, respectively.

[0031] The initial phase angle of the i-th distribution network is collected.

[0032] Using the initial phase angle The reference value i for the d-axis current of the current converter drefi and q-axis current reference value i qrefi Perform dq / abc transformation to obtain the first component i of the current converter output three-phase current reference value. i_ref1 Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1 i bi_ref1 i ci_ref1 .

[0033] In the above scheme, the constant voltage control specifically includes:

[0034] Collect the upper arm capacitor voltage v of the DC section of the converter in several flexible interconnection units and flexible interconnection modules that are not connected to the i-th distribution network. dcupi Lower bridge arm capacitor voltage v dcdni Reference value of total capacitor voltage v dcrefi ;

[0035] The upper bridge arm capacitor voltage v dcupi Lower bridge arm capacitor voltage v dcdni Reference value of total capacitor voltage v dcrefi Subtract the values ​​and feed the difference into the first-stage PI controller to obtain the current d-axis current reference value i of the converter. drefi‘ ;

[0036] The initial phase angle of the i-th distribution network is collected.

[0037] The current q-axis current reference value i of the current converter qrefi′ The default value is 0;

[0038] Using the initial phase angle The reference value i for the d-axis current of the current converter drefi‘ and q-axis current reference value i qrefi′ Performing a dq / abc transformation yields the first component i of the current converter output three-phase current reference value. i_ref1′

[0039] Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1’ i bi_ref1‘ i ci_ref1’ ;

[0040] The voltage v of the upper bridge arm capacitor of the DC section of the current converter. dcupi and the voltage v of the lower bridge arm capacitor dcdni Subtracting the two values ​​and substituting the difference into the second-stage PI controller yields the current reference value i for the converter capacitor voltage regulation control current. crefi ;

[0041] Collect the three-phase harmonic current i of the load in the i-th distribution network. ai_ref2‘ i bi_ref2’ i ci_ref2‘ Three-phase negative sequence current i ai_ref3’ i bi_ref3‘ i ci_ref3’ The two components are then added together to form the second component i of the current converter output three-phase current reference value. i_ref2′ ;

[0042] According to the second component i i_ref2′ and the current converter capacitor voltage regulation control current reference value i crefi Determine the total reference current i of the current converter output. i_ref' ;

[0043] The overall control signal for each bridge arm of the current converter is determined based on the total reference current.

[0044] In the above scheme, according to the formula: i drefi‘ =(v dcupi +v dcdni -v dcrefi )×(K p1 +K i1 The reference value of the d-axis current of the current converter is obtained by multiplying (1 / s) by (i) / (1 / s). drefi‘ ;

[0045] According to formula i crefi =(v dcupi -v dcdni )×(K p2 +K i2 ×(1 / s)) yields the current converter capacitor voltage regulation control current reference value i crefi Among them, K p1 and K i1 K represents the proportional and integral coefficients of the first-stage PI controller. p2 and K i2 For the proportional and integral coefficients of the second-stage PI controller, v dcupi v dcdni and v dcrefi′ These are the reference values ​​for the upper bridge arm capacitor voltage, the lower bridge arm capacitor voltage, and the total capacitor voltage, respectively, with s being the integration factor.

[0046] In the above scheme, the proportional coefficient K of the first-stage PI controller p1 The integral coefficient K of the first-stage PI controller is preset to 4.5. i1 The default value is 250, and the proportional coefficient K of the second-stage PI controller is... p2 The default value is 3.2, and the integral coefficient K of the second-stage PI controller is... i2 The default value is 600.

[0047] This application also proposes a continuous power supply and energy control system for interconnected distribution network faults, the system comprising:

[0048] N flexible interconnection units, N+1 distribution network;

[0049] The Nth flexible interconnection unit connects the first distribution network and the N+1th distribution network, where N≥1.

[0050] In the above scheme, the flexible interconnection unit includes:

[0051] Two reverse-connected first flexible interconnect modules and second flexible interconnect modules and a DC bus, wherein either the first flexible interconnect module or the second flexible interconnect module is connected to the first distribution network, and the other is connected to the N+1th distribution network;

[0052] The flexible interconnection module includes a circuit breaker, a three-phase transformer, a reactor, a converter, and two DC floating capacitors.

[0053] This application also proposes a device for continuous power supply and power control during faults in interconnected distribution networks, characterized in that the device comprises:

[0054] The fault detection module is used to detect a single-phase grounding fault in the i-th distribution network and determine that the single-phase grounding fault phase is phase K, where i≤N;

[0055] The converter control mode determination module is used to determine the control mode of two converters among several flexible interconnection units connected to the i-th distribution network according to the dispatching instructions of the i-th distribution network.

[0056] The total reference current acquisition module is used to determine the total reference current output by the converter in several flexible interconnection modules connected to the i-th distribution network according to the control method.

[0057] The signal output module is used to determine the comprehensive control signal of each bridge arm of the converter in several flexible interconnect modules based on the total reference current.

[0058] This application also proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the following steps:

[0059] When a single-phase ground fault is detected in the i-th distribution network, the faulty phase is determined to be phase K, where i≤N;

[0060] Based on the dispatch instructions of the i-th distribution network, determine the control mode of two converters among the several flexible interconnection units connected to it;

[0061] The total reference current output by the converter in several flexible interconnection modules connected to the i-th distribution network is determined according to the control method described above.

[0062] The comprehensive control signals for each bridge arm of the converter in several flexible interconnect modules are determined based on the total reference current.

[0063] This application also proposes a computer device, including a memory and a processor, wherein the memory stores a computer program, and the computer program is executed by the processor in the following steps:

[0064] When a single-phase ground fault is detected in the i-th distribution network, the faulty phase is determined to be phase K, where i≤N;

[0065] Based on the dispatch instructions of the i-th distribution network, determine the control mode of two converters among the several flexible interconnection units connected to it;

[0066] The total reference current output by the converter in several flexible interconnection modules connected to the i-th distribution network is determined according to the control method described above.

[0067] The comprehensive control signals for each bridge arm of the converter in several flexible interconnect modules are determined based on the total reference current.

[0068] The embodiments of the present invention have the following beneficial effects:

[0069] The aforementioned methods, systems, devices, equipment, and media for continuous power supply and power control during interconnected distribution network faults can achieve energy mutual assistance between distribution networks under normal operating conditions, optimize energy distribution, and ensure the reliability of power supply to each distribution network. Simultaneously, they can manage power quality, ensuring the quality of power distribution. When a single-phase ground fault occurs in a distribution network, multiple flexible interconnected modules connected to it can work collaboratively, flexibly injecting specific currents into the distribution network according to the rated current that each flexible interconnected module can inject, preventing the re-formation of the arc, extinguishing the arc, and solving the problem of single-phase ground fault generation. Attached Figure Description

[0070] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0071] in:

[0072] Figure 1 This is a flowchart of a method for continuous power supply and power control during faults in an interconnected distribution network, as shown in one embodiment.

[0073] Figure 2 This is a schematic diagram of the first component of the three-phase current reference value output by the converter 1 in the flexible interconnect module 1 under constant power control.

[0074] Figure 3 This is a schematic diagram of the second component of the three-phase current reference value output by converter 1 in flexible interconnect module 1 under constant power control.

[0075] Figure 4 This is a schematic diagram of the integrated control of each bridge arm by the converter 1 in the flexible interconnect module 1 under constant power control.

[0076] Figure 5 This is a schematic diagram of the integrated control of each bridge arm by the converter 2 in the flexible interconnect module 2 under constant voltage control.

[0077] Figure 6 Here is a waveform diagram of the voltage relative to ground in the first distribution network in one embodiment;

[0078] Figure 7 Here is a waveform diagram of the power supply current of the first distribution network in one embodiment;

[0079] Figure 8 The diagram shows the current waveform output from the first flexible interconnect device to the first distribution network in one embodiment.

[0080] Figure 9 This is a waveform diagram of the current output from the second flexible interconnection device to the first distribution network in one embodiment;

[0081] Figure 10 This is a waveform diagram of the load current of the first distribution network in one embodiment;

[0082] Figure 11 This is a structural diagram of a fault-tolerant power supply and power control system in an interconnected distribution network according to one embodiment.

[0083] Figure 12 for Figure 11 A schematic diagram of the internal structure of the flexible interconnect module 1. Detailed Implementation

[0084] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0085] like Figure 1 As shown, in one embodiment, a method for continuous power supply and power control during faults in an interconnected distribution network is provided. This method can be applied to terminals or to a flexible interconnected distribution network system installed on servers or other devices. The system includes N flexible interconnection units and N+1 distribution networks. The Nth flexible interconnection unit connects the first distribution network and the N+1th distribution network, where N ≥ 1. The Nth flexible interconnection unit includes two reverse-connected first flexible interconnection modules and a second flexible interconnection module. Either the first or second flexible interconnection module is connected to the first distribution network, and the other is connected to the N+1th distribution network. Both the first and second flexible interconnection modules include a circuit breaker, a three-phase transformer, a reactor, a converter, and two DC floating capacitors.

[0086] The above-mentioned methods for continuous power supply and power control during faults in interconnected distribution networks are detailed below:

[0087] S101. When a single-phase ground fault is detected in the i-th distribution network, the phase with the single-phase ground fault is determined to be phase K, where i≤N;

[0088] Specifically, the single-phase ground fault phase is any one of the three phases on the load side of the distribution network and the flexible interconnection device connection point, including phase A1, phase B1, and phase C1.

[0089] In some embodiments, the single-phase ground fault phase of the faulty distribution network can be determined by detecting the current of the faulty distribution network, providing a basic condition for fault ride-through and making it more convenient to replenish the current of the faulty phase.

[0090] S102. Based on the dispatching instructions of the i-th distribution network, determine the control mode of two converters among the several flexible interconnection units connected to it;

[0091] In some embodiments, based on the dispatching instructions of the i-th distribution network, the control mode of two converters among a plurality of flexible interconnection units connected to it is determined, specifically including:

[0092] When a single-phase ground fault is detected in the i-th distribution network, several flexible interconnection units are identified that are connected to...

[0093] The converter in the flexible interconnection module connected to the i-th distribution network is constant power controlled, while the converter in another flexible interconnection module among several flexible interconnection units is constant voltage controlled; for example... Figure 11 As shown, when a single-phase ground fault occurs in the first distribution network, the converters in the flexible interconnection modules 1, 3, 5, and 2N-1 of the first, second, third, and Nth flexible interconnection units connected to it are set to constant power control, and the converters in the flexible interconnection modules 2, 4, 6, and 2N are set to constant voltage control.

[0094] S103. Determine the total reference current output of the converter in several flexible interconnection modules connected to the i-th distribution network according to the control method.

[0095] S104. Determine the integrated control signal for each bridge arm of the converter in several flexible interconnect modules based on the total reference current.

[0096] Preferably, the above-mentioned constant power control specifically includes:

[0097] (1) Based on instantaneous power theory and dq / abc transformation, obtain the first part of the reference value of the three-phase current output of the converter in the flexible interconnection module connected to the i-th distribution network. i_ref1 Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1 i bi_ref1 i ci_ref1 ;

[0098] (2) The load three-phase harmonic current i of the i-th distribution network ai_ref2 i bi_ref2 i ci_ref2 and three-phase negative sequence current i ai_ref3 i bi_ref3 i ci_ref3 The summation results in the second component i, which serves as the reference value for the three-phase current output of the current converter. i_ref2 ;

[0099] (3) Determine the fault ride-through reference current i of the i-th distribution network according to the following expression. i-ref3 :

[0100] i i-ref3 =U ni Y zi / 3+U ni Y 0i

[0101] In the formula, U ni Y is the neutral-to-ground voltage of the i-th distribution network; 0iY represents the power supply and ground admittance of the i-th distribution network. zi Let the admittance of the arc suppression coil of the i-th distribution network be denoted as .

[0102] (4) According to the formula: i refi_R =i Ni -i i_ref1 Determine the remaining capacity i of the current converter refi_R In the formula, i Ni i i_ref1 These are the rated current value and the first component of the current converter, respectively;

[0103] (5) According to the formula: Determine the ratio of the remaining capacity of the flexible interconnect module corresponding to the current converter to the remaining capacity of other flexible interconnect modules connected to the i-th distribution network;

[0104] (6) According to the formula: i refi_quanlity =K i* i i_ref2 Determine the command current for power quality control of the flexible interconnect module corresponding to the current converter, where i i_ref2 This is the second component of the current three-phase current reference value output by the converter.

[0105] (7) According to the formula: i refi_short =K i* i i-ref3 Determine the command current for ground fault ride-through of the flexible interconnect module corresponding to the current converter, where i i-ref3 Let be the fault ride-through reference current for the i-th distribution network;

[0106] (8) According to the formula: i i_ref =i i_ref1 +i refi_quanlity +i refi_short Determine the total reference current i of the flexible interconnect module corresponding to the current converter. i_ref ;

[0107] (9) Determine the integrated control signal for each bridge arm of the current converter based on the total reference current.

[0108] Furthermore, based on instantaneous power theory and dq / abc transformation, the first component i of the current converter output three-phase current reference value is obtained. i_ref1 Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1 i bi_ref1 i ci_ref1 Specifically, it includes:

[0109] A. Determine the reference value i of the d-axis current of the current converter according to the following expression. drefi and q-axis current reference value iqrefi ;

[0110]

[0111]

[0112] In the formula, p refi and q refi These represent the active and reactive power that the current transformer's corresponding i-th distribution network needs to absorb from the (i+1)-th distribution network, respectively. di and u qi These are the d-axis and q-axis components of the voltage at the connection point of the current transformer connected to the i-th distribution network, respectively.

[0113] B. Acquire the initial phase angle of the i-th distribution network.

[0114] C. Using the initial phase angle The reference value i for the d-axis current of the current converter drefi and q-axis current reference value i qrefi Perform dq / abc transformation to obtain the first component i of the current converter output three-phase current reference value. i_ref1 Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1 i bi_ref1 i ci_ref1 .

[0115] like Figure 2 The diagram shows the first component i of the reference value of the three-phase current output by the converter 1 in the flexible interconnect module 1, under constant power control. ref1 Schematic diagram, such as Figure 3 The diagram shows the second component i of the reference value of the three-phase current output by the converter 1 in the flexible interconnect module 1, under constant power control. ref2 A schematic diagram, such as Figure 4 The diagram shows a comprehensive control scheme for each bridge arm under constant power control of the current converter, taking a single-phase ground fault in the first distribution network as an example.

[0116] The following is about the above. Figure 2 , Figure 3 and Figure 4 Explanation (taking constant power control as an example, when a single-phase ground fault occurs in the first distribution network, converter 1 in several flexible interconnected systems connected to it is used):

[0117] (1) Determine the reference values ​​of the d-axis current and q-axis current i in the constant power control of the converter. dref1 iqref1 It can be calculated using the following formula:

[0118]

[0119] In the formula, p 1ref and q 1ref These represent the active and reactive power that the first distribution network corresponding to converter 1 needs to absorb from the second distribution network, obtained from the dispatch instructions; u d1 and u q1 These are the d-axis and q-axis components of the voltage at the connection point of the flexible interconnection module connected to the first distribution network.

[0120] (2) The initial phase angle of the first distribution network is obtained by using a phase-locked loop. Using the initial phase angle Reference value i of d-axis current for constant power control of converter 1 dref1 and q-axis current reference value i qref1 Performing the dq / abc transformation yields the first component i of the reference value of the three-phase output current of converter 1 in the three-phase stationary coordinate system. ref1 Its three-phase components are represented as: i a1_ref1 i b1_ref1 i c1_ref1 ;

[0121] (3) Detect the three-phase harmonic current i of the first distribution network load a1_ref2 i b1_ref2 i c1_ref2 Three-phase negative sequence current i a1_ref3 i b1_ref3 i c1_ref3 The sum of the two is taken as the second component i of the reference value of the three-phase output current of converter 1. ref2 ;

[0122] (4) Calculate the fault ride-through reference current of the first distribution network:

[0123] Based on its grounding method, the three-phase reference current required for fault ride-through in the first distribution network is i. ref3 :

[0124] i ref3 =U n1 Y z1 / 3+U n1 Y 01

[0125] In the formula, U n1 Y is the neutral point-to-ground voltage of the first distribution network; 01 Y is the power supply and ground admittance of the first distribution network. z1 The admittance of the arc suppression coil in the first distribution network was obtained through measurement.

[0126] (5) Calculate the remaining capacity of converter 1 using the current:

[0127] i ref1_R =i N1 -i ref1

[0128] In the formula, i N1 This is the rated current value of converter 1;

[0129] Preferably, the remaining capacity of the other N-1 flexible interconnected modules connected to the first distribution network is calculated similarly, and expressed in terms of current as: i ref2_R i ref3_R …i refN_R .

[0130] (6) Calculate the ratio of the remaining capacity of the flexible interconnection module to the remaining capacity of all flexible interconnection modules connected to the first distribution network:

[0131]

[0132] The command current for power quality control of flexible interconnect module 1 is calculated as follows:

[0133] i ref1_quanlity =K1*i ref2

[0134] The command current for flexible interconnect module 1 to perform ground fault ride-through is calculated as follows:

[0135] i ref1_short =K1*i ref3 ;

[0136] (7) Calculate the total reference current i of flexible interconnect module 1 ref (Total command current):

[0137] i ref =i ref1 +i ref1_quanlity +i ref1_short

[0138] (8) Use hysteresis control for the total reference current to determine the comprehensive control signal for each bridge arm of the current converter.

[0139] Similarly, when a single-phase ground fault occurs in the first distribution network, the converters in other flexible interconnection systems connected to it are controlled by constant power. Or when a single-phase ground fault occurs in the i-th distribution network, the converters in several flexible interconnection systems connected to it are controlled by constant power. The comprehensive control signal of each bridge arm of the current converter is also determined according to the above steps (1) to (8).

[0140] In some embodiments, constant voltage control specifically includes:

[0141] (1) Collect the upper arm capacitor voltage v of the DC section of the converter in several flexible interconnection units and flexible interconnection modules that are not connected to the i-th distribution network. dcupi Lower bridge arm capacitor voltage v dcdni Reference value of total capacitor voltage v dcrefi ;

[0142] Specifically, distribution network parameter testing instruments such as distribution network voltage testers can be used to collect data.

[0143] (2) The voltage v of the upper bridge arm capacitor dcupi Lower bridge arm capacitor voltage v dcdni Reference value of total capacitor voltage v dcrefi Subtract the values ​​and feed the difference into the first-stage PI controller to obtain the current d-axis current reference value i of the converter. drefi‘ ;

[0144] (3) Acquire the initial phase angle of the i-th distribution network.

[0145] (4) Set the current q-axis current reference value i of the converter qrefi′ The default value is 0;

[0146] (5) Using the initial phase angle The reference value i for the d-axis current of the current converter drefi‘ and q-axis current reference value i qrefi′ Performing a dq / abc transformation yields the first component i of the current converter output three-phase current reference value. i_ref1′ Its A-phase component, B-phase component, and C-phase component are respectively represented as: i ai_ref1’ i bi_ref1’ i ci_ref1’ ;

[0147] (6) The voltage v of the upper bridge arm capacitor of the DC section of the current converter. dcupi and the voltage v of the lower bridge arm capacitor dcdni Subtracting the two values ​​and substituting the difference into the second-stage PI controller yields the current reference value i for the converter capacitor voltage regulation control current. crefi ;

[0148] Specifically, the first-level PI controller and the second-level PI controller mentioned above are linear controllers. The PI controller forms a control deviation based on the given value and the actual output value, and combines the proportional and integral of the deviation to form a control quantity to control the controlled object.

[0149] (7) Collect the load three-phase harmonic current i of the i-th distribution network. ai_ref2‘ i bi_ref2’ ici_ref2‘ Three-phase negative sequence current i ai_ref3’ i bi_ref3‘ i ci_ref3’ The two components are then added together to form the second component i of the current converter output three-phase current reference value. i_ref2′ ;

[0150] (8) Based on the second component i i_ref2′ and the current converter capacitor voltage regulation control current reference value i crefi Determine the total reference current i of the current converter output. i_ref' ;

[0151] (9) Determine the integrated control signal for each bridge arm of the current converter based on the total reference current.

[0152] This invention can realize energy mutual assistance between distribution networks, optimize energy distribution, and ensure the reliability of power supply in each distribution network; at the same time, it can also control power quality to ensure the power quality of distribution.

[0153] Preferred: i drefi‘ =(v dcupi +v dcdni -v dcrefi )×(K p1 +K i1 The reference value of the d-axis current of the current converter is obtained by multiplying (1 / s) by (i) / (1 / s). drefi‘ ;

[0154] According to formula i ctefi =(v dcupi -v dcdni )×(K p2 +K i2 ×(1 / s)) yields the current converter capacitor voltage regulation control current reference value i crefi Among them, K p1 and K i1 K represents the proportional and integral coefficients of the first-stage PI controller. p2 and K i2 For the proportional and integral coefficients of the second-stage PI controller, v dcupi v dcdni and v dcrefi′ These are the reference values ​​for the upper bridge arm capacitor voltage, the lower bridge arm capacitor voltage, and the total capacitor voltage, respectively, with s being the integration factor.

[0155] Preferably, the proportional coefficient K of the first-stage PI controller p1 The integral coefficient K of the first-stage PI controller is preset to 4.5. i1 The default value is 250, and the proportional coefficient K of the second-stage PI controller is... p2 The default value is 3.2, and the integral coefficient K of the second-stage PI controller is...i2 The default value is 600.

[0156] like Figure 5 The diagram shows a comprehensive control scheme for each bridge arm under constant voltage control, using converter 2 in flexible interconnect module 2 as an example.

[0157] The following is about Figure 5 Explanation:

[0158] (1) The upper bridge arm capacitor voltage v of the DC section of converter 2 was measured. dcup2 Lower bridge arm capacitor voltage v dcdn2 The reference value for the total capacitor voltage is V. dcref2 ;

[0159] (2) The voltage v of the upper bridge arm capacitor dcup2 and the voltage v of the lower bridge arm capacitor dcdn2 Reference value of total capacitor voltage v dcref2 Subtracting the two values ​​and substituting the difference into the first-stage PI controller, we obtain the d-axis current reference value i for the constant voltage control of converter 2. dref2 :

[0160] i dref2 =(v dcup2 +v dcdn2 -v dcref2 )×(K p1 +K i1 ×(1 / s))

[0161] In the formula, Kp1 and Ki1 are the proportional coefficient and integral coefficient of the first-stage PI controller, respectively, and s is the integral factor;

[0162] (3) The initial phase angle of the second distribution network is obtained by using a phase-locked loop. Using the initial phase angle Reference value i of d-axis current for constant voltage control of converter 2 dref2 and q-axis current reference value i qref2 =0 Performing a dq / abc transformation, we obtain the first component i of the reference value of the three-phase output current of converter 2 in the three-phase stationary coordinate system. a2_ref1 i b2_ref1 i c2_ref1 ;

[0163] (4) To stabilize the voltage of the upper and lower bridge arm capacitors of the DC section of converter 2, the voltage values ​​of the upper and lower bridge arm capacitors are subtracted, and the difference is fed into the second-stage PI controller to obtain the reference value i of the capacitor voltage stabilization control current of converter 2. cref2 :

[0164] i cref2 =(vdcup2 -v dcdn2 )×(K p2 +K i2 ×(1 / s))

[0165] In the formula, Kp2 and Ki2 are the proportional coefficient and integral coefficient of the second-stage PI controller, respectively, and s is the integral factor;

[0166] (5) Detect the three-phase harmonic current i of the load a2_ref2 i b2_ref2 i c2_ref2 Three-phase negative sequence current i a2_ref3 i b2_ref3 i c2_ref3 This is the second component of the reference value of the three-phase current output by converter 2.

[0167] (6) Based on the second component and the current converter capacitor voltage regulation control current reference value i cref2 Determine the total reference current i of the current converter output. ref2 The control signals for each bridge arm are obtained through hysteresis control.

[0168] Similarly, the converter 1 in the flexible interconnection module 1 or other converters in several flexible interconnection systems that are not connected to the first distribution network also obtain control signals for each bridge arm according to the above steps (1) to (6).

[0169] This invention allows for the flexible configuration of the injectable current rating of the converters in each flexible interconnection module to inject a specific current (i.e., the command current for fault ride-through) into the distribution network, preventing the re-formation of electric arcs, solving the problem of single-phase grounding faults, stabilizing the system using constant power control or constant voltage control, optimizing energy distribution, and providing a certain foundation for fault ride-through.

[0170] like Figures 6 to 10 As shown, in one embodiment, current and voltage variations in a distribution network during fault ride-through and power control are provided.

[0171] For example, the second and third distribution networks are connected to the first distribution network through the first and second flexible interconnection systems, respectively. Power quality control begins at 0.08 seconds; power transmission begins at 0.16 seconds; a ground fault occurs in phase C at 0.24 seconds; and fault ride-through control begins at 0.32 seconds.

[0172] For example, starting at 0.08s, the negative sequence current output by the first flexible interconnection system to the first distribution network is calculated to be 9.12A, and the negative sequence current output by the second flexible interconnection system to the first distribution network is 4.56A, effectively solving the three-phase imbalance problem of the power supply current of the first distribution network; after 0.16s, a portion of the power is transferred from the second distribution network to the first distribution network, thus significantly reducing the power supply current of the first distribution network; after 0.24s, a single-phase ground fault occurs, with the voltage of phase C to ground being approximately 2.67kV, resulting in a large ground current; at 0.32s, the zero sequence current output by the first flexible interconnection system to the first distribution network is calculated to be 4.75A, and the zero sequence current output by the first flexible interconnection system to the first distribution network is 2.37A; the voltage of phase C to ground drops to 0, while the power supply current of the first distribution network still maintains a relatively good balance.

[0173] like Figure 11 As shown in the figure, in one embodiment, a structural diagram of continuous power supply and power control during faults in an interconnected distribution network is provided.

[0174] The system includes:

[0175] N flexible interconnection units, N+1 distribution network;

[0176] The Nth flexible interconnection unit connects the Nth distribution network and the N+1th distribution network, where N≥1.

[0177] For example, when N is 3, the continuous power supply and power control of the interconnected distribution network during faults includes 3 flexible interconnection units and 4 distribution networks. The first flexible interconnection unit connects the first distribution network and the second distribution network, the second flexible interconnection unit connects the second distribution network and the third distribution network, the third flexible interconnection unit connects the third distribution network and the fourth distribution network, and so on. The Nth flexible interconnection unit connects the first distribution network and the N+1th distribution network.

[0178] Furthermore, the aforementioned flexible interconnect unit includes:

[0179] Two reverse-connected flexible interconnect modules and a DC bus;

[0180] The flexible interconnection module includes a circuit breaker, a three-phase transformer, a connecting reactor, a converter, and two DC floating capacitors.

[0181] Preferably, the circuit breaker is an operable three-phase circuit breaker. Taking circuit breaker 1 in the flexible interconnection module 1 as an example, the circuit breaker controller 1 controls the on / off state. When a phase-to-phase short circuit fault occurs in the first distribution network, the circuit breaker controller 1 disconnects the circuit breaker 1.

[0182] Preferably, taking the three-phase transformer 1 in the flexible interconnection module 1 as an example, the primary side ports a1, b1, and c1 of the three-phase transformer are connected to the circuit breaker 1; the neutral point n1 of the primary side of the three-phase transformer 1 is connected to the neutral point of the grounding transformer; and the secondary side ports A1, B1, and C1 of the three-phase transformer 1 are connected to the output port of the converter 1 in the flexible interconnection system.

[0183] like Figure 12 The diagram shows the internal structure of flexible interconnect module 1. Each converter group consists of six IGBTs with anti-parallel diodes. The converters in each flexible interconnect module are named according to the module name. Taking the converter in flexible interconnect module 1 as converter 1 (its six IGBTs are named S1, S2, S3, S4, S5, and S6) as an example, the connection method of the converters in the other flexible interconnect modules is the same as that of converter 1. The collectors of S1, S2, and S3 are connected, and the connection point forms the upper node of converter 1; the emitters of S4, S5, and S6 are connected, and the connection point forms the lower node of converter 1; the emitter of S1, the collector of S4, and the emitter of S5 are connected, and the collector of S6 is connected. Electrodes are connected, and the connection point forms output port Ab1; the emitter of S2 and the collector of S5 are connected, and the connection point forms output port Bb1; the emitter of S3 and the collector of S6 are connected, and the connection point forms output port Cb1; Ab1, Bb1, and Cb are connected to ports A1, B1, and C1 on the secondary side of three-phase transformer 1 respectively through a connecting reactor; the upper node of converter 1, the positive terminal of DC floating capacitor C2, and the positive terminal of DC bus are connected, and the lower node, the negative terminal of DC floating capacitor C1, and the negative terminal of DC bus are connected; the positive terminal of DC floating capacitor C1 and the negative terminal of DC floating capacitor C2 are connected, and the connection point is connected to the neutral point N1 on the secondary side of three-phase transformer 1.

[0184] This application also proposes a device for continuous power supply and power control during faults in interconnected distribution networks, the device comprising:

[0185] The fault detection module is used to detect a single-phase grounding fault in the i-th distribution network and determine that the single-phase grounding fault phase is phase K, where i≤N;

[0186] The converter control mode determination module is used to determine the control mode of two converters among several flexible interconnection units connected to the i-th distribution network according to the dispatching instructions of the i-th distribution network.

[0187] The total reference current acquisition module is used to determine the total reference current output by the converter in several flexible interconnection modules connected to the i-th distribution network according to the control method.

[0188] The signal output module is used to determine the comprehensive control signal for each bridge arm of the converter in several flexible interconnect modules based on the total reference current.

[0189] This application also proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the following steps:

[0190] When a single-phase ground fault is detected in the i-th distribution network, the faulty phase is determined to be phase K, where i≤N;

[0191] Based on the dispatch instructions of the i-th distribution network, determine the control mode of two converters among the several flexible interconnection units connected to it;

[0192] The total reference current output of the converter in several flexible interconnection modules connected to the i-th distribution network is determined according to the control method.

[0193] The integrated control signals for each bridge arm of the converter in several flexible interconnect modules are determined based on the total reference current.

[0194] This application also proposes a computer device, including a memory and a processor, wherein the memory stores a computer program, and the computer program is executed by the processor in the following steps:

[0195] When a single-phase ground fault is detected in the i-th distribution network, the faulty phase is determined to be phase K, where i≤N;

[0196] Based on the dispatch instructions of the i-th distribution network, determine the control mode of two converters among the several flexible interconnection units connected to it;

[0197] The total reference current output of the converter in several flexible interconnection modules connected to the i-th distribution network is determined according to the control method.

[0198] The integrated control signals for each bridge arm of the converter in several flexible interconnect modules are determined based on the total reference current.

[0199] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0200] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0201] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for fault-continuity power supply and power control in an interconnected electric power distribution network, characterized by, The method is used for a flexible interconnection system of a power distribution network, the system comprising N flexible interconnection units, N+1 power distribution networks, an Nth flexible interconnection unit connecting a first power distribution network and an N+1th power distribution network, wherein N≥1; the Nth flexible interconnection unit comprising two reversely connected first and second flexible interconnection modules, wherein any one of the first or second flexible interconnection module is connected with the first power distribution network and the other is connected with the N+1th power distribution network, and each of the first and second flexible interconnection modules comprises a circuit breaker, a three-phase transformer, a reactor, a converter, and two DC floating capacitors. The method comprises: detecting a single-phase ground fault of an ith power distribution network and determining a single-phase ground fault phase as a K phase, wherein i≤N; determining a control mode of two converters in a plurality of flexible interconnection units connected with the ith power distribution network according to a dispatching instruction of the ith power distribution network; determining a total reference current output by the converters in a plurality of flexible interconnection modules connected with the ith power distribution network according to the control mode; determining a comprehensive control signal of each bridge arm of the converters in the plurality of flexible interconnection modules according to the total reference current.

2. The method for continuous supply of power and control of electric energy in the interconnected electric distribution network during faults according to claim 1, characterized in that, The determining of the control mode of the two converters in the plurality of flexible interconnection units connected with the ith power distribution network according to the dispatching instruction of the ith power distribution network specifically comprises: after detecting the single-phase ground fault of the ith power distribution network, determining the converters in a flexible interconnection module of a plurality of flexible interconnection units connected with the ith power distribution network as a constant power control, and the converters in another flexible interconnection module of the plurality of flexible interconnection units as a constant voltage control.

3. The method of claim 2, wherein, The constant power control specifically comprises: According to the instantaneous power theory and the dq / abc transformation, a first partial component i of a three-phase current reference value of an output of a converter in the flexible interconnection module connected to the i power distribution network is obtained i_ref1 , whose A-phase component, B-phase component and C-phase component are respectively represented as: ai_ref1 , bi_ref1 , ci_ref1 ; adding the load three-phase harmonic current i ai_ref2 、 bi_ref2 、 ci_ref2 and the three-phase negative sequence current i ai_ref3 、 bi_ref3 、 ci_ref3 as the second partial component i i_ref2 of the three-phase current reference value of the current converter output The fault ride-through reference current i of the i-th power distribution network is determined according to the following expression i-ref3 : i i-ref3 = U ni Y zi / 3 + U ni Y 0i wherein U ni is the neutral-to-ground voltage of the i-th distribution network; Y 0i is the supply-to-ground admittance of the i-th distribution network, Y zi is the arc suppression coil admittance of the i-th distribution network; According to the formula: i refi_R =i Ni -i i_ref1 Determine the remaining capacity i of the current converter refi_R In the formula, i Ni i i_ref1 These are the rated current value and the first component of the current converter, respectively; According to the formula: determining the ratio of the remaining capacity of the flexible interconnection module corresponding to the current converter to the remaining capacity of other flexible interconnection modules connected to the i-th power distribution network; According to the formula: i refi_auanlity = K i *i i_ref2 determining the instruction current of the flexible interconnection module corresponding to the current converter for power quality control, wherein i i_ref2 is the second partial component of the three-phase current reference value output by the current converter; According to the formula: i refi_short = K i *i i-ref3 The instruction current of the flexible interconnection module corresponding to the current converter for the ground fault ride-through is determined, wherein i i-ref3 is the fault ride-through reference current of the i power distribution network; According to the formula: i i_ref = i i_ref1 + i refi_quanlity + i refi_short Determine the total reference current i i_ref of the flexible interconnection module corresponding to the current converter determining a comprehensive control signal of each bridge arm of the current converters according to the total reference current.

4. The method of claim 3, wherein, The first part component i of the three-phase current reference value of the current converter output is obtained according to the instantaneous power theory and the dq / abc transformation i_ref1 The A-phase component, the B-phase component and the C-phase component are respectively represented as: ai_ref1 The A-phase component, the B-phase component and the C-phase component are respectively represented as: bi_ref1 The A-phase component, the B-phase component and the C-phase component are respectively represented as: ci_ref1 Specifically, the method comprises: The d-axis current reference value i drefi and the q-axis current reference value i qrefi of the current converter are determined according to the following expressions where p refi and q refi are the active power and the reactive power that the i-th power distribution network needs to absorb from the i+1-th power distribution network, respectively, corresponding to the current current sensor; u di and u qi are the d-axis component and the q-axis component of the voltage at the access point of the i-th power distribution network, respectively, corresponding to the current current sensor. collecting an initial phase angle of the i-th power distribution network Utilizing an initial phase angle A d-axis current reference value i drefi and a q-axis current reference value i qrefi Performing a dq / abc transformation to obtain a first partial component i i_ref1 of a three-phase current reference value output by the current transformer, whose A-phase component, B-phase component and C-phase component are respectively represented as: i ai_ref1 , i bi_ref1 , i ci_ref1 .

5. The method for continuous supply of power and control of electric energy of the interconnected electric distribution network according to claim 2, characterized in that, The constant voltage control specifically comprises: collecting a DC part voltage v of the upper bridge arm of the converter in the flexible interconnection module which is not connected to the i-th power distribution network dcupi , a DC part voltage v of the lower bridge arm of the converter in the flexible interconnection module which is not connected to the i-th power distribution network dcdni and a total capacitor voltage reference value v dcrefi ; Subtracting the upper bridge arm capacitor voltage v dcupi , the lower bridge arm capacitor voltage v dcdni and the total capacitor voltage reference value v dcrefi , and bringing the difference into the first stage PI controller to obtain the d-axis current reference value i drefi‘ of the current transformer; collecting an initial phase angle of the i-th power distribution network setting the q-axis current reference value i qrefi′ to 0; Utilizing an initial phase angle a d-axis current reference value i drefi‘ and a q-axis current reference value i qrefi′ performing a dq / abc transformation to obtain a first partial component i i_ref1′ The A-phase component, B-phase component, and C-phase component are respectively expressed as: i ai_ref1’ , i bi_ref1‘ , i ci_ref1’ ; Subtracting the upper bridge arm capacitor voltage v dcupi and the lower bridge arm capacitor voltage v dcdni of the direct current part of the current converter, the difference between the two is brought into the second stage PI controller to obtain the current reference value i crefi of the capacitor voltage steady control of the current converter. harmonic current i of the load of the i-th power distribution network ai_ref2‘ bi_ref2’ ci_ref2‘ three-phase negative sequence current i ai_ref3’ bi_ref3‘ ci_ref3’ and adding them to form the second component i of the three-phase current reference value of the current output of the current transformer i_ref2′ ;​​​​ According to the second part component i i_ref2′ And the current inverter capacitor voltage stabilizing control current reference value i crefi Determine the total reference current i i_ref′ ; determining a comprehensive control signal of each bridge arm of the current converters according to the total reference current.

6. The method of claim 5, wherein, According to the formula: i drefi‘ = (v dcupi + v dcdni - v dcrefi ) x (K p1 + K i1 x (1 / s)) the d-axis current reference value i drefi‘ of the current converter is obtained. According to formula i crefi = (v dcupi - v dcdni ) x (K p2 + K i2 x (1 / s)) to obtain the current current reference value i crefi for the voltage stabilization control of the current converter capacitor wherein K p1 and K i1 are the proportional and integral coefficients of the first stage PI controller, K p2 and K i2 are the proportional and integral coefficients of the second stage PI controller, v dcupi , v dcdni and v dcrefi′ are the upper bridge arm capacitor voltage, the lower bridge arm capacitor voltage and the total capacitor voltage reference value, respectively, and s is the integral factor.

7. The interconnected distribution grid persistent power and energy control method of claim 6, wherein, a proportional coefficient K of the first stage PI controller p1 an integral coefficient K of the first stage PI controller preset as 4.5 i1 a proportional coefficient K of the second stage PI controller preset as 250 p2 an integral coefficient K of the second stage PI controller preset as 3.2 i2 preset as 600.

8. A method for power supply and power control of interconnected distribution network during fault, the method comprising the steps of: - providing a power supply and power control of interconnected distribution network during fault according to any one of claims 1 to 6. The system comprises: N flexible interconnection units, N+1 power distribution networks; the Nth flexible interconnection unit connecting the first power distribution network and the N+1th power distribution network, wherein N≥1.

9. The interconnected distribution grid persistent power and energy control of claim 7, wherein, The flexible interconnection unit comprises: two reversely connected first and second flexible interconnection modules and a DC bus, wherein any one of the first or second flexible interconnection module is connected with the first power distribution network and the other is connected with the N+1th power distribution network; the flexible interconnection module comprising a circuit breaker, a three-phase transformer, a reactor, a converter, and two DC floating capacitors.

10. A device for fault-continuity power supply and power control in interconnected distribution networks, characterized by, The device comprises: a fault detection module for detecting a single-phase ground fault of an ith power distribution network and determining a single-phase ground fault phase as a K phase, wherein i≤N; a converter control mode determination module for determining a control mode of two converters in a plurality of flexible interconnection units connected with the ith power distribution network according to a dispatching instruction of the ith power distribution network; a total reference current acquisition module for determining a total reference current output by the converters in a plurality of flexible interconnection modules connected with the ith power distribution network according to the control mode; a signal output module for determining a comprehensive control signal of each bridge arm of the converters in the plurality of flexible interconnection modules according to the total reference current. 11.A computer readable storage medium storing a computer program, the computer program, when executed by a processor, causing the processor to perform the steps of the method according to any one of claims 1 to 7. 12.A computer device comprising a memory and a processor, the memory storing a computer program, the computer program, when executed by the processor, causing the processor to perform the steps of the method according to any one of claims 1 to 7.

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