Capacity-adjustable power distribution network interconnection system and power transfer and supply method thereof

Abstract

The capacity-adjustable power distribution network interconnection system comprises the following steps: when a first power distribution network is a fault side power distribution network, a second power distribution network is a non-fault side power distribution network, and the interconnection capacity of a split-phase flexible interconnection device is smaller than the to-be-transferred power of the first power distribution network, switching the first power distribution network to the second power distribution network; the split-phase flexible interconnection device is used for absorbing the maximum transfer power corresponding to the interconnection capacity from the second power distribution network and transmitting the maximum transfer power to the first power distribution network, and the adjustable resistor group is used for absorbing the adjustable transfer current corresponding to the adjustable resistor group value from the second power distribution network and transmitting the adjustable transfer current to the first power distribution network; the adjustable resistor group is introduced, so that when the interconnection capacity of the split-phase flexible interconnection device is not enough to support and transfer all fault side loads, the fault side loads can be transferred without adding extra power electronic devices; and the problems of economic loss and adverse effects caused by incapability of transferring all fault side loads due to insufficient interconnection capacity are effectively solved by utilizing the adjustable resistor group.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality governance, and particularly to a distribution network interconnection system with adjustable capacity and its power transfer method. Background Art

[0002] In recent years, with the continuous development of active distribution networks, the large-scale access of distributed energy has led to inconsistent spatio-temporal characteristics of power sources and loads in the distribution network, exacerbating typical problems such as inherent heavy overload, extreme light load, and three-phase imbalance in the distribution network. To effectively solve these problems, using a split-phase flexible interconnection device to achieve the interconnection between different distribution networks has become an important means. The split-phase flexible interconnection device can not only improve the inconsistent load rates of the distribution network but also effectively manage power quality and enhance the overall operation efficiency of the system.

[0003] In practical applications, when a fault occurs at one end of the distribution network, resulting in the suspension of power supply to the load by this distribution network, the load on the faulty-side distribution network can be powered by the non-faulty-side distribution network through the split-phase flexible interconnection device to ensure continuous power supply to the load. However, the split-phase flexible interconnection device usually has a limited capacity, which to a certain extent restricts its full power transfer ability to the faulty-side load. When the interconnection capacity of the split-phase flexible interconnection device is insufficient to support the transfer of all faulty-side loads, the remaining faulty-side loads need to be cut off, resulting in huge economic losses and affecting the normal operation of citizens' lives and many fields. Summary of the Invention

[0004] Based on this, in view of the above problems, it is necessary to propose a distribution network interconnection system with adjustable capacity and its power transfer method, which can effectively solve the problems of economic losses and adverse effects caused by the inability to transfer all faulty-side loads due to insufficient interconnection capacity by using an adjustable resistor group without adding additional power electronic devices.

[0005] To achieve the above object, in the first aspect of the present invention, a distribution network interconnection system with adjustable capacity is provided. The system includes a split-phase flexible interconnection device and an adjustable resistor group;

[0006] The split-phase flexible interconnection device is connected to the adjustable resistor group and forms two distribution network access ends. The first distribution network access end is used to connect to the three-phase lines of the first distribution network, and the second distribution network access end is used to connect to the three-phase lines of the second distribution network;

[0007] When the first distribution network is the faulty-side distribution network, the second distribution network is the non-faulty-side distribution network, and the interconnection capacity of the split-phase flexible interconnection device is less than the required power transfer of the first distribution network, the split-phase flexible interconnection device is used to absorb the maximum power transfer corresponding to the interconnection capacity from the second distribution network and transmit it to the first distribution network;

[0008] The adjustable resistor bank is used to absorb an adjustable transfer current corresponding to the adjustable resistor bank value of the adjustable resistor bank from the second distribution network and transmit it to the first distribution network;

[0009] Wherein, the transfer current of the power to be transferred is the sum of the maximum transfer current of the maximum transfer power and the adjustable transfer current.

[0010] Optionally, the system further includes a first circuit breaker, a second circuit breaker, a third circuit breaker, a fourth circuit breaker, a fifth circuit breaker, and a sixth circuit breaker;

[0011] The split-phase flexible interconnection device is connected to the adjustable resistor bank through the first circuit breaker and forms a first distribution network access end, and the split-phase flexible interconnection device is connected to the adjustable resistor bank through the second circuit breaker and forms a second distribution network access end;

[0012] The first distribution network access end is used to be connected to the three-phase lines of the first distribution network through the third circuit breaker, and the second distribution network access end is used to be connected to the three-phase lines of the second distribution network through the fourth circuit breaker;

[0013] The three-phase lines of the first distribution network are connected to the first distribution network through the fifth circuit breaker, and the three-phase lines of the second distribution network are connected to the second distribution network through the sixth circuit breaker.

[0014] Optionally, the adjustable resistor bank includes a first adjustable resistor, a second adjustable resistor, and a third adjustable resistor;

[0015] One end of the first adjustable resistor is connected to the first end of the split-phase flexible interconnection device and forms the first end of the first distribution network access end. The first end of the first distribution network access end is used to be connected to the A-phase line of the first distribution network. The other end of the first adjustable resistor is connected to the second end of the split-phase flexible interconnection device and forms the first end of the second distribution network access end. The first end of the second distribution network access end is used to be connected to the A-phase line of the second distribution network;

[0016] One end of the second adjustable resistor is connected to the third end of the split-phase flexible interconnection device and forms the second end of the first distribution network access end. The second end of the first distribution network access end is used to be connected to the B-phase line of the first distribution network. The other end of the second adjustable resistor is connected to the fourth end of the split-phase flexible interconnection device and forms the second end of the second distribution network access end. The second end of the second distribution network access end is used to be connected to the B-phase line of the second distribution network;

[0017] One end of the third adjustable resistor is connected to the fourth end of the split-phase flexible interconnection device and forms the third end of the first distribution network access end. The third end of the first distribution network access end is used to connect to the C-phase line of the first distribution network. The other end of the third adjustable resistor is connected to the fifth end of the split-phase flexible interconnection device and forms the third end of the second distribution network access end. The third end of the second distribution network access end is used to connect to the C-phase line of the second distribution network.

[0018] Optionally, the system further includes a controller;

[0019] The controller is used to determine the adjustable resistor group value according to the maximum transfer current and the required transfer current.

[0020] To achieve the above object, in a second aspect, the present invention provides a power transfer method for a capacity-adjustable distribution network interconnection system. The method is applied to the capacity-adjustable distribution network interconnection system described in any one of the first aspects. The method includes:

[0021] When the first distribution network is the fault-side distribution network, the second distribution network is the non-fault-side distribution network, and the interconnection capacity of the split-phase flexible interconnection device in the system is less than the required transfer power of the first distribution network, input the first preset control signal and the second preset control signal into the first converter on the first distribution network side and the second converter on the second distribution network side of the split-phase flexible interconnection device respectively, so that the split-phase flexible interconnection device absorbs the maximum transfer power corresponding to the interconnection capacity from the second distribution network and transmits it to the first distribution network;

[0022] Determine the target resistor group value according to the maximum transfer current corresponding to the maximum transfer power, the required transfer current corresponding to the required transfer power, and the impedance value of the split-phase flexible interconnection device;

[0023] Adjust the adjustable resistor group value of the adjustable resistor group in the system according to the target resistor group value, so that the adjustable resistor group absorbs the adjustable transfer current corresponding to the adjustable resistor group value from the second distribution network and transmits it to the first distribution network.

[0024] Optionally, the method further includes:

[0025] Determine the first preset control signal by adopting a constant AC voltage control strategy;

[0026] Determine the second preset control signal by adopting a constant power control strategy.

[0027] Optionally, the determining the first preset control signal by adopting a constant AC voltage control strategy includes:

[0028] Obtain the output voltage reference value of the AC voltage control part of the first converter and the first DC-side voltage;

[0029] Determine the modulation wave according to the output voltage reference value, the first DC-side voltage, and a preset carrier amplitude;

[0030] Input the modulation wave into a PWM signal generator to obtain the first preset control signal.

[0031] Optionally, the obtaining the output voltage reference value of the AC voltage control part of the first converter and the first DC-side voltage includes:

[0032] Obtain the first current phase angle of the first distribution network through a phase-locked loop, and measure the first load voltage of the first distribution network;

[0033] Perform Park transformation on the first load voltage using the first current phase angle to obtain the first dq components;

[0034] Determine the voltage error according to the first dq components and the second dq components of the load voltage reference value of the first distribution network;

[0035] Input the voltage error into a first PI controller to obtain a voltage error gain;

[0036] Determine the third dq components according to the voltage error gain and the first dq components;

[0037] Perform inverse Park transformation on the third dq components using the first current phase angle to obtain the output voltage reference value;

[0038] Determine the first DC-side voltage according to the capacitor voltages of the two floating capacitors of the first converter.

[0039] Optionally, the determining the second preset control signal by adopting a constant power control strategy includes:

[0040] Obtain the first current reference value of the power transmission control part of the second converter, the second current reference value of the harmonic control part, the third current reference value of the unbalance control part, as well as the zero-sequence current reference value and the regulated current reference value of the DC voltage control part;

[0041] Determine the output current reference value of the power control part of the second converter according to the first current reference value, the second current reference value, the third current reference value, the zero-sequence current reference value, and the regulated current reference value;

[0042] Input the output current reference value into a hysteresis control to obtain the second preset control signal.

[0043] Optionally, obtaining the first current reference value of the power transfer control part of the second converter, the second current reference value of the harmonic control part, the third current reference value of the unbalance control part, and the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part includes:

[0044] Obtaining the second current phase angle of the second distribution network through a phase-locked loop, measuring the interconnected voltage and the second load current at the interconnection point of the second distribution network, and measuring the capacitor voltages of the two floating capacitors of the second converter;

[0045] Determining the d-axis current reference value and the q-axis current reference value of the second converter according to the d-axis component and the q-axis component of the interconnected voltage and the maximum transfer power;

[0046] Performing an inverse Park transformation on the d-axis current reference value and the q-axis current reference value of the second converter by using the second current phase angle to obtain the first current reference value;

[0047] Performing a Park transformation on the second load current by using the second current phase angle to obtain a fourth dq component;

[0048] Obtaining a first DC component in the fourth dq component through a low-pass mean filter;

[0049] Performing an inverse Park transformation on the first DC component by using the second current phase angle to obtain a fundamental current;

[0050] Determining the second current reference value according to the fundamental current and the second load current;

[0051] Performing a Park transformation on the second load current by using a negative of the second current phase angle to obtain a fifth dq component;

[0052] Obtaining a second DC component in the fifth dq component through a low-pass mean filter;

[0053] Performing an inverse Park transformation on the second DC component by using a negative of the second current phase angle to obtain a negative-sequence current;

[0054] Determining a zero-sequence current according to the second load current;

[0055] Determining the third current reference value according to the zero-sequence current and the negative-sequence current;

[0056] Determining a second DC-side voltage and a DC-side voltage error according to the capacitor voltages of the two floating capacitors of the second converter;

[0057] Input the DC-side voltage error into a second PI controller to obtain the zero-sequence current reference value;

[0058] Determine the DC voltage error based on the second DC-side voltage and the DC-side voltage reference value of the second converter;

[0059] Input the DC voltage error into a third PI controller to obtain the DC-side current;

[0060] Determine the first d-axis current reference value based on the DC-side current, the second DC-side voltage, and the d-axis component of the interconnection voltage;

[0061] Perform an inverse Park transformation on the first d-axis current reference value using the second current phase angle to obtain the regulated current reference value.

[0062] To achieve the above object, the present invention provides a power transfer device for a capacity-adjustable distribution network interconnection system in a third aspect. The device is applied to the capacity-adjustable distribution network interconnection system described in any one of the first aspects. The device includes:

[0063] A transfer judgment module, configured to input a first preset control signal and a second preset control signal into a first converter located on the first distribution network side and a second converter located on the second distribution network side of the split-phase flexible interconnection device in the system when the first distribution network is a fault-side distribution network, the second distribution network is a non-fault-side distribution network, and the interconnection capacity of the split-phase flexible interconnection device in the system is less than the required power transfer of the first distribution network, so that the split-phase flexible interconnection device absorbs the maximum power transfer corresponding to the interconnection capacity from the second distribution network and transmits it to the first distribution network;

[0064] A determination module, configured to determine a target resistor group value based on the maximum power transfer current corresponding to the maximum power transfer, the required power transfer current corresponding to the required power transfer, and the impedance value of the split-phase flexible interconnection device;

[0065] An adjustable transfer module, configured to adjust the adjustable resistor group value of the adjustable resistor group in the system according to the target resistor group value, so that the adjustable resistor group absorbs the adjustable transfer current corresponding to the adjustable resistor group value from the second distribution network and transmits it to the first distribution network.

[0066] To achieve the above object, the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a controller, the controller executes the method described in any one of the second aspects.

[0067] To achieve the above object, in a fifth aspect, the present invention provides a computer device, including a memory and a controller. The memory stores a computer program. When the computer program is executed by the controller, the controller is caused to execute the method described in any one of the second aspect.

[0068] Adopting the embodiment of the present invention has the following beneficial effects: The above system includes a phase-splitting flexible interconnection device and an adjustable resistor group. The phase-splitting flexible interconnection device is connected to the adjustable resistor group and forms two distribution network access ends. The first distribution network access end is used to connect to the three-phase lines of the first distribution network, and the second distribution network access end is used to connect to the three-phase lines of the second distribution network. When the first distribution network is the fault-side distribution network, the second distribution network is the non-fault-side distribution network, and the interconnection capacity of the phase-splitting flexible interconnection device is less than the required transfer power of the first distribution network, the phase-splitting flexible interconnection device is used to absorb the maximum transfer power corresponding to the interconnection capacity from the second distribution network and transmit it to the first distribution network. The adjustable resistor group is used to absorb the adjustable transfer current corresponding to the adjustable resistor group value from the second distribution network and transmit it to the first distribution network. Among them, the required transfer current of the required transfer power is the sum of the maximum transfer current of the maximum transfer power and the adjustable transfer current. That is, by introducing the adjustable resistor group, when the interconnection capacity of the phase-splitting flexible interconnection device is not enough to support the transfer of all the fault-side loads, without the need to add additional power electronic devices, the remaining fault-side loads can be transferred by adjusting the adjustable resistor group value of the adjustable resistor group, so as to ensure the full transfer of the remaining fault-side loads, effectively solving the problems of economic losses and adverse effects caused by the inability to transfer all the fault-side loads due to insufficient interconnection capacity. Description of the Drawings

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0070] Among them:

[0071] Figure 1 It is a schematic diagram of a distribution network interconnection system with adjustable capacity in an embodiment of the present application;

[0072] Figure 2 It is another schematic diagram of a distribution network interconnection system with adjustable capacity in an embodiment of the present application;

[0073] Figure 3 It is a schematic diagram of a power transfer method for a distribution network interconnection system with adjustable capacity in an embodiment of the present application

[0074] Figure 4 Schematic diagram for determining the first preset control signal by the fixed AC voltage control strategy in the embodiment of the present application;

[0075] Figure 5 Schematic diagram for determining the second preset control signal by the fixed power control strategy in the embodiment of the present application;

[0076] Figure 6 Simulation waveform diagram in the embodiment of the present application;

[0077] Figure 7 Schematic diagram of the power transfer device of a capacity - adjustable distribution network interconnection system in the embodiment of the present application;

[0078] Figure 8 Internal structure diagram of a computer device in some embodiments. Detailed implementation manners

[0079] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0080] In recent years, with the continuous development of active distribution networks, the large - scale access of distributed energy has led to inconsistent spatio - temporal characteristics of power sources and loads in the distribution network, exacerbating typical problems such as inherent heavy overload, extreme light load, and three - phase imbalance in the distribution network. To effectively solve these problems, using a phase - separated flexible interconnection device to achieve the interconnection between different distribution networks has become an important means. The phase - separated flexible interconnection device can not only improve the inconsistent load rates of distribution networks, but also effectively control the power quality and improve the overall operation efficiency of the system.

[0081] In practical applications, when a fault occurs at one end of the distribution network, resulting in the distribution network at the fault side stopping power supply to the load, the load of the distribution network at the fault side can be powered by the distribution network at the non - fault side through the phase - separated flexible interconnection device to ensure continuous power supply to the load. However, the capacity of the phase - separated flexible interconnection device is usually limited, which to a certain extent restricts its full power transfer ability to the load at the fault side. When the interconnection capacity of the phase - separated flexible interconnection device is insufficient to support the transfer of all loads at the fault side, the remaining loads at the fault side need to be cut off from power, resulting in huge economic losses and affecting the normal operation of citizens' lives and many fields.

[0082] In view of the above problems, the present application proposes a capacity-adjustable interconnected distribution network system and its power transfer method, which can effectively solve the problems of economic losses and adverse effects caused by the inability to transfer all the load on the faulty side due to insufficient interconnection capacity without adding additional power electronic devices. The specific implementation principle will be described in detail in the following embodiments.

[0083] In the first aspect, the present application provides a capacity-adjustable interconnected distribution network system.

[0084] Please refer to Figure 1 , which is a schematic diagram of a capacity-adjustable interconnected distribution network system in an embodiment of the present application. The system includes a phase-splitting flexible interconnection device 110 and an adjustable resistor bank 120.

[0085] Among them, the phase-splitting flexible interconnection device 110 is connected to the adjustable resistor bank 120 and forms two distribution network access ends. The first distribution network access end is used to connect to the three-phase lines of the first distribution network 130, and the second distribution network access end is used to connect to the three-phase lines of the second distribution network 140.

[0086] In a feasible implementation manner, when the first distribution network 130 is a faulty-side distribution network, the second distribution network 140 is a non-faulty-side distribution network, and the interconnection capacity of the phase-splitting flexible interconnection device 110 is less than the power transfer requirement of the first distribution network 130, the phase-splitting flexible interconnection device 110 is used to absorb the maximum power transfer corresponding to the interconnection capacity from the second distribution network 140 and transmit it to the first distribution network 130; the adjustable resistor bank 120 is used to absorb the adjustable power transfer current corresponding to the adjustable resistor value of the adjustable resistor bank 120 from the second distribution network 140 and transmit it to the first distribution network 130; among them, the power transfer current of the power transfer requirement is the sum of the maximum power transfer current of the maximum power transfer and the adjustable power transfer current.

[0087] Among them, the power transfer requirement refers to the total electrical energy demand that needs to be transferred to the first distribution network 130 when the first distribution network 130 fails; for example, when the first distribution network 130 has a three-phase imbalance problem, the power transfer requirement at this time is the compensation amount required to solve the three-phase imbalance of the first distribution network 130. When a ground fault occurs in the C-phase line of the first distribution network 130, the power transfer requirement at this time includes the load current of the C-phase line of the first distribution network 130 and the load currents required by other phase lines.

[0088] It should be noted that in the present application, the load refers to the load; for example, the load current can also be called the load current, and the load voltage can also be called the load voltage.

[0089] In some embodiments, the adjustable resistor group 120 may be composed of one or more adjustable resistors. By adjusting the resistance value of the adjustable resistors in the adjustable resistor group 120, the adjustable resistor group value of the adjustable resistor group 120 can be adjusted, and then the adjustable transfer supply current can be adjusted to meet different transfer supply requirements.

[0090] In the embodiments of the present application, by introducing the adjustable resistor group 120, when the interconnection capacity of the split-phase flexible interconnection device 110 is insufficient to support the transfer supply of all the load on the faulty side, without the need to add additional power electronic devices, the remaining load on the faulty side can be transferred by adjusting the adjustable resistor group value of the adjustable resistor group 120 to ensure the full transfer supply of the remaining load on the faulty side, effectively solving the problems of economic losses and adverse effects caused by the inability to transfer supply all the load on the faulty side due to insufficient interconnection capacity.

[0091] Furthermore, when a sudden fault occurs in the distribution network, through the double-layer cooperative control of the split-phase flexible interconnection device 110 and the adjustable resistor group 120, the power can be stably transferred within a short time. Compared with the existing methods, the time required for stable transfer supply is greatly shortened.

[0092] In addition, by adjusting the adjustable resistor group 120 to regulate the remaining load exceeding the capacity, the working pressure of the split-phase flexible interconnection device 110 is relieved, avoiding the problem of capacity overrun caused by over-reliance on a single device, prolonging the service life of the equipment, and since there is no need to purchase additional large-capacity power electronic devices or other expensive equipment, the construction and operation costs are saved, thereby reducing the economic burden of power grid maintenance and management.

[0093] Based on Figure 1 , please refer to Figure 2 , which is another schematic diagram of a distribution network interconnection system with adjustable capacity in the embodiments of the present application. The system in the above embodiments further includes a first circuit breaker S1, a second circuit breaker S2, a third circuit breaker S3, a fourth circuit breaker S4, a fifth circuit breaker S5, and a sixth circuit breaker S6.

[0094] In a feasible implementation manner, the split-phase flexible interconnection device 110 and the adjustable resistor group 120 are connected through the first circuit breaker S1 to form a first distribution network access end, and the split-phase flexible interconnection device 110 and the adjustable resistor group 120 are connected through the second circuit breaker S2 to form a second distribution network access end; the first distribution network access end is used to connect to the three-phase lines of the first distribution network 130 through the third circuit breaker S3, and the second distribution network access end is used to connect to the three-phase lines of the second distribution network 140 through the fourth circuit breaker S4; the three-phase lines of the first distribution network 130 are connected to the first distribution network 130 through the fifth circuit breaker S5, and the three-phase lines of the second distribution network 140 are connected to the second distribution network 140 through the sixth circuit breaker S6.

[0095] Among them, CV1 and CV2 are respectively the first converter CV1 and the second converter CV2 in the split-phase flexible interconnection device 110. Both the first converter CV1 and the second converter CV2 are composed of six IGBTs with anti-parallel diodes; C1 and C2 are two floating capacitors on the side of the first converter CV1, and C3 and C4 are two floating capacitors on the side of the second converter CV1; LC1 is the filter LC1 on the side of the first converter CV1, and LC2 is the filter LC2 on the side of the second converter CV2. The filter LC1 on the side of the first converter CV1 and the filter LC2 on the side of the second converter CV2 are both composed of three inductors and three capacitors; A1, B1, C1, and N1 are respectively the A-phase line, B-phase line, C-phase line, and neutral line of the first distribution network 130, and A2, B2, C2, and N2 are respectively the A-phase line, B-phase line, C-phase line, and neutral line of the second distribution network 140.

[0096] It should be noted that since each circuit breaker is distributed between each connection point, therefore, for different fault situations, the closing and opening of each connection point can be accurately controlled; for example, when a ground fault occurs in the C-phase line of the first distribution network 130, control the fifth circuit breaker S5 to disconnect the connection between the first distribution network 130 and the C-phase line of the first distribution network 130. When there is no need for power transfer, control the third circuit breaker S3 and the fourth circuit breaker S4 to disconnect. When adjustable resistor group 120 is required for power transfer, control the first circuit breaker S1 and the second circuit breaker S2 to close, etc.

[0097] In the embodiment of the present application, by introducing the first circuit breaker S1, the second circuit breaker S2, the third circuit breaker S3, the fourth circuit breaker S4, the fifth circuit breaker S5, and the sixth circuit breaker S6, accurate control of different fault scenario requirements can be achieved in the event of a fault.

[0098] Please continue to refer to Figure 2 , the adjustable resistor group 120 in the above embodiment includes a first adjustable resistor, a second adjustable resistor, and a third adjustable resistor (not labeled in the figure).

[0099] In a feasible implementation, one end of the first adjustable resistor is connected to the first end of the split-phase flexible interconnection device 110 and forms the first end of the first distribution network access end. The first end of the first distribution network access end is used to connect to the A-phase line of the first distribution network 130. The other end of the first adjustable resistor is connected to the second end of the split-phase flexible interconnection device 110 and forms the first end of the second distribution network access end. The first end of the second distribution network access end is used to connect to the A-phase line of the second distribution network 140. One end of the second adjustable resistor is connected to the third end of the split-phase flexible interconnection device 110 and forms the second end of the first distribution network access end. The second end of the first distribution network access end is used to connect to the B-phase line of the first distribution network 130. The other end of the second adjustable resistor is connected to the fourth end of the split-phase flexible interconnection device 110 and forms the second end of the second distribution network access end. The second end of the second distribution network access end is used to connect to the B-phase line of the second distribution network 140. One end of the third adjustable resistor is connected to the fourth end of the split-phase flexible interconnection device 110 and forms the third end of the first distribution network access end. The third end of the first distribution network access end is used to connect to the C-phase line of the first distribution network 130. The other end of the third adjustable resistor is connected to the fifth end of the split-phase flexible interconnection device 110 and forms the third end of the second distribution network access end. The third end of the second distribution network access end is used to connect to the C-phase line of the second distribution network 140.

[0100] It should be noted that since each phase line of the three-phase line is correspondingly connected to an adjustable resistor, the resistance value of the adjustable resistor connected to different phase lines can be adjusted according to different fault conditions and control requirements to achieve precise control.

[0101] In the embodiment of the present application, by introducing the adjustable resistor group 120 including the first adjustable resistor, the second adjustable resistor, and the third adjustable resistor, and respectively connecting them to each phase of the three-phase line, precise control and adjustment of the load on different phase lines can be achieved, effectively alleviating the three-phase imbalance problem and the uneven load distribution problem between different phase lines, so as to improve the power quality of the system.

[0102] In a feasible implementation, the system in the above embodiment further includes a controller (not shown), and the controller is used to determine the adjustable resistor group value according to the maximum transfer current and the transfer current required.

[0103] In some embodiments, the controller is connected to the adjustable resistor group 120 and is used to adjust the adjustable resistor group value of the adjustable resistor group 120.

[0104] In some embodiments, the controller is respectively connected to the first circuit breaker S1, the second circuit breaker S2, the third circuit breaker S3, the fourth circuit breaker S4, the fifth circuit breaker S5, and the sixth circuit breaker S6, and is used to control the opening and closing of each circuit breaker.

[0105] In the embodiment of the present application, by introducing a controller, the resistance values of the adjustable resistors in the adjustable resistor group 120 can be accurately adjusted according to the maximum power transfer current and the power transfer current required, so as to ensure that when the interconnection capacity of the split-phase flexible interconnection device 110 is insufficient to support, through accurate adjustment, the transferred power reaches the required level, maximizing the continuous power supply to the load on the fault side and reducing the losses caused by power outages.

[0106] In addition, the controller can monitor the system operation state in real time. When detecting a change in the power transfer power required in the case of a fault, it can quickly calculate the new adjustable resistor group value and make adjustments. This real-time performance and self-adaptability improve the flexibility and response speed of the system, better adapting to the complex and changeable operation environment of the distribution network.

[0107] The present application provides a power transfer method for a distribution network interconnection system with adjustable capacity in a second aspect.

[0108] Please refer to Figure 3 , which is a schematic diagram of a power transfer method for a distribution network interconnection system with adjustable capacity in the embodiment of the present application. This method is applied to the distribution network interconnection system with adjustable capacity in the above embodiment. The method includes:

[0109] Step 310: When the first distribution network is the fault-side distribution network, the second distribution network is the non-fault-side distribution network, and the interconnection capacity of the split-phase flexible interconnection device in the system is less than the power transfer power required by the first distribution network, input the first preset control signal and the second preset control signal into the first converter on the first distribution network side and the second converter on the second distribution network side of the split-phase flexible interconnection device respectively, so that the split-phase flexible interconnection device absorbs the maximum power transfer power corresponding to the interconnection capacity from the second distribution network and transmits it to the first distribution network.

[0110] It should be noted that both the first preset control signal and the second preset control signal are switch signals. The first preset control signal is used to control the switch state of the first converter, while the second preset control signal is used to control the switch state of the second converter.

[0111] In some embodiments, both the first preset control signal and the second preset control signal can be set by an operator in advance according to controlling the split-phase flexible interconnection device to transfer power according to the maximum power transfer power.

[0112] In other embodiments, the first preset control signal and the second preset control signal are variable at each moment to meet different control requirements. Therefore, existing control strategies can also be used to determine the first preset control signal and the second preset control signal at each moment.

[0113] Step 320: Determine the target resistor group value according to the maximum transfer current corresponding to the maximum transfer power, the required transfer current corresponding to the required transfer power, and the impedance value of the split-phase flexible interconnection device.

[0114] In some embodiments, the formula can be used to determine the target resistor group value; where R abc is the target resistor group value, I n,abc is the maximum transfer current, I L,abc is the required transfer current, and Z is the impedance value of the split-phase flexible interconnection device; the subscripts abc correspond to phase A, phase B, and phase C. For example, R a corresponds to the resistance value of the first adjustable resistor in phase A.

[0115] Step 330: Adjust the adjustable resistor group value of the adjustable resistor group in the system according to the target resistor group value, so that the adjustable resistor group absorbs the adjustable transfer current corresponding to the adjustable resistor group value from the second distribution network and transmits it to the first distribution network.

[0116] Wherein, the adjustable resistor group value includes the resistance values of the respective adjustable resistors in the adjustable resistor group.

[0117] In some embodiments, the adjustable resistor group value of the adjustable resistor group can be adjusted to the target resistor group value; of course, in other embodiments, a preset error value can be obtained first, and then the resistance value in the adjustable resistor group value of the adjustable resistor group can be adjusted to the sum of the resistance value in the target resistor group value and the preset error value, or the resistance value in the adjustable resistor group value of the adjustable resistor group can be adjusted to the difference between the resistance value in the target resistor group value and the preset error value; wherein, the preset error value can be obtained by the operator based on a large amount of experience, experiments, or statistics, or can also be set by the operator according to actual needs.

[0118] In the embodiments of the present application, by calculating a suitable adjustable resistor group value, it can be ensured that when the interconnection capacity of the split-phase flexible interconnection device is not sufficient to support all transfers, the adjustable performance of the adjustable resistor group is used to effectively transfer the remaining load, avoiding the economic losses caused by power outages and ensuring the power supply continuity of users.

[0119] In a feasible implementation manner, the method in the above embodiments further includes: determining a first preset control signal by adopting a constant AC voltage control strategy; determining a second preset control signal by adopting a constant power control strategy.

[0120] In the embodiments of the present application, by controlling the switching state of the first converter by adopting a constant AC voltage control strategy and controlling the regulation of the second converter by adopting a constant power control strategy, it can be ensured that the voltage of the first distribution network can be maintained at a stable level under fault conditions and the absorbed power can be accurately controlled, thereby improving the stability and power quality of the entire system.

[0121] In a feasible implementation manner, determining the first preset control signal by adopting a fixed AC voltage control strategy in the above embodiment includes: obtaining the output voltage reference value of the AC voltage control part of the first converter and the first DC side voltage; determining the modulation wave according to the output voltage reference value, the first DC side voltage, and the preset carrier amplitude; inputting the modulation wave into a PWM signal generator to obtain the first preset control signal.

[0122] Among them, the preset carrier amplitude can be set by an operator according to a large amount of experience or actual requirements.

[0123] In some embodiments, the present application preferably sets the preset carrier amplitude to 1.

[0124] For the determination method of the modulation wave, in some embodiments, the modulation wave can be determined by using the formula where v m is the modulation wave, u abc is the output voltage reference value, U dc is the first DC side voltage, and v tri is the preset carrier amplitude.

[0125] In the embodiment of the present application, by obtaining the output voltage reference value of the AC voltage control part of the first converter and the first DC side voltage, and combining the preset carrier amplitude to determine the modulation wave, and then obtaining the first preset control signal, it is possible to stabilize the output voltage of the AC voltage control part of the first converter, ensure that the voltage of the first distribution network remains at a stable level in case of a fault, and reduce the influence of voltage fluctuations on power quality and the power supply stability of users.

[0126] In a feasible implementation manner, obtaining the output voltage reference value of the AC voltage control part of the first converter and the first DC side voltage in the above embodiment includes: obtaining the first current phase angle of the first distribution network through a phase-locked loop, and measuring the first load voltage of the first distribution network; performing a Park transformation on the first load voltage by using the first current phase angle to obtain the first dq component; determining the voltage error according to the first dq component and the second dq component of the load voltage reference value of the first distribution network; inputting the voltage error into a first PI controller to obtain the voltage error gain; determining the third dq component according to the voltage error gain and the first dq component; performing an inverse Park transformation on the third dq component by using the first current phase angle to obtain the output voltage reference value; determining the first DC side voltage according to the capacitor voltages of the two floating capacitors of the first converter.

[0127] For the determination method of the voltage error, in some embodiments, the difference between the second dq component and the first dq component can be used as the voltage error.

[0128] For the determination method of the third dq component, in some embodiments, the sum value between the voltage error gain and the first dq component may be used as the third dq component.

[0129] For the determination method of the first DC-side voltage, in some embodiments, the quotient obtained by dividing the sum value between the capacitor voltages of the two floating capacitors of the first converter by 2 may be used as the first DC-side voltage.

[0130] In the embodiments of the present application, preferably, the output voltage reference value of the AC voltage control part of the first converter and the first DC-side voltage are obtained in the above manner to achieve precise control, ensuring that the voltage can be stabilized at a safe level under the condition of a distribution network fault, and reducing the influence of voltage fluctuations on the power quality and the power supply stability of users.

[0131] In a feasible implementation manner, determining the second preset control signal by using the constant power control strategy in the above embodiments includes: obtaining the first current reference value of the power transmission control part of the second converter, the second current reference value of the harmonic control part, the third current reference value of the unbalance control part, as well as the zero-sequence current reference value and the voltage stabilization current reference value of the DC voltage control part; determining the output current reference value of the power control part of the second converter according to the first current reference value, the second current reference value, the third current reference value, the zero-sequence current reference value, and the voltage stabilization current reference value; inputting the output current reference value into the hysteresis control to obtain the second preset control signal.

[0132] It should be noted that in the present application, the harmonic control part and the unbalance control part of the second converter together constitute the power quality control part of the second converter.

[0133] For the determination method of the output current reference value, in some embodiments, the sum value between the first current reference value, the second current reference value, the third current reference value, the zero-sequence current reference value, and the voltage stabilization current reference value may be used as the output current reference value.

[0134] In the embodiments of the present application, by obtaining multiple reference values of the power transmission control part, the harmonic control part, the unbalance control part, and the DC voltage control part to determine the output current reference value of the power control part of the second converter, and thus obtaining the second preset control signal, the absorbed power can be precisely controlled to ensure that stable and required power transfer is provided to the fault side.

[0135] Furthermore, by obtaining the current reference values of the harmonic control part and the unbalance control part to participate in the calculation of the second preset control signal, the current harmonics generated during system operation can be effectively reduced, and the load unbalance under fault conditions can be alleviated, improving the power quality and reducing power losses.

[0136] In addition, by using the hysteresis control mechanism, compared with other control mechanisms, hysteresis control can respond faster to power changes in the system, which is particularly important when dealing with transient changes such as grid faults. It can quickly adjust power absorption and transfer and rapidly restore power quality.

[0137] In a feasible implementation manner, obtaining the first current reference value of the power transmission control part of the second converter, the second current reference value of the harmonic control part, the third current reference value of the unbalance control part, as well as the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part in the above embodiments includes: obtaining the second current phase angle of the second distribution network through a phase-locked loop, measuring the interconnected voltage and the second load current at the interconnection point of the second distribution network, and measuring the capacitor voltages of the two floating capacitors of the second converter; determining the d-axis current reference value and the q-axis current reference value of the second converter according to the d-axis component and the q-axis component of the interconnected voltage and the maximum transfer power; performing an inverse Park transformation on the d-axis current reference value and the q-axis current reference value of the second converter by using the second current phase angle to obtain the first current reference value; performing a Park transformation on the second load current by using the second current phase angle to obtain the fourth dq component; obtaining the first DC component in the fourth dq component through a low-pass mean filter; performing an inverse Park transformation on the first DC component by using the second current phase angle to obtain the fundamental current; determining the second current reference value according to the fundamental current and the second load current; performing a Park transformation on the second load current by using the negative second current phase angle to obtain the fifth dq component; obtaining the second DC component in the fifth dq component through a low-pass mean filter; performing an inverse Park transformation on the second DC component by using the negative second current phase angle to obtain the negative-sequence current; determining the zero-sequence current according to the second load current; determining the third current reference value according to the zero-sequence current and the negative-sequence current; determining the second DC-side voltage and the DC-side voltage error according to the capacitor voltages of the two floating capacitors of the second converter; inputting the DC-side voltage error into the second PI controller to obtain the zero-sequence current reference value; determining the DC voltage error according to the second DC-side voltage and the DC-side voltage reference value of the second converter; inputting the DC voltage error into the third PI controller to obtain the DC-side current; determining the first d-axis current reference value according to the DC-side current, the second DC-side voltage, and the d-axis component of the interconnected voltage; performing an inverse Park transformation on the first d-axis current reference value by using the second current phase angle to obtain the regulated voltage current reference value.

[0138] It should be noted that the interconnection point of the second distribution network also refers to the connection point of the second distribution network. It can be understood that the interconnection point of the split-phase flexible interconnection device and the second distribution network is selected at its connection point.

[0139] For the determination method of the d-axis component and q-axis component of the interconnected voltage of the second distribution network, in some embodiments, Park transformation can be performed on the interconnected voltage of the second distribution network to obtain the dq components corresponding to the interconnected voltage of the second distribution network; where the dq components include the d-axis component and the q-axis component. Since the voltage of the distribution network has a directional characteristic, the calculated result of the q-axis component of the interconnected voltage of the second distribution network is 0.

[0140] For the determination method of the d-axis current reference value and q-axis current reference value of the second converter, in some embodiments, the formula can be used to determine the d-axis current reference value and q-axis current reference value of the second converter; where i dref2 and i qref2 are the d-axis current reference value and q-axis current reference value of the second converter respectively, p ref2 and q ref2 are the active power and reactive power in the maximum transfer power respectively, u d2 and u q2 are the d-axis component and q-axis component of the interconnected voltage of the second distribution network respectively.

[0141] For the determination method of the second current reference value, in some embodiments, the difference between the second load current and the fundamental current can be used as the second current reference value.

[0142] For the determination method of the zero-sequence current, in some embodiments, the quotient obtained by dividing the sum of the three-phase line currents in the second load current by 3 can be used as the zero-sequence current.

[0143] For the determination method of the third current reference value, in some embodiments, the sum of the zero-sequence current and the negative-sequence current can be used as the third current reference value.

[0144] For the determination method of the second DC-side voltage, in some embodiments, the sum of the capacitor voltages of the two floating capacitors of the second converter can be used as the second DC-side voltage.

[0145] For the determination method of the DC-side voltage error, in some embodiments, the difference between the capacitor voltages of the two floating capacitors of the second converter can be used as the DC-side voltage error.

[0146] For the determination method of the zero-sequence current reference value, in some embodiments, after inputting the DC-side voltage error into the second PI controller, the output value of the second PI controller needs to be divided by 3, and then the quotient is used as the zero-sequence current reference value.

[0147] For the determination method of the DC voltage error, in some embodiments, the difference between the second DC-side voltage and the DC-side voltage reference value can be used as the DC voltage error.

[0148] For the determination method of the first d-axis current reference value, in some embodiments, the formula can be used to determine the first d-axis current reference value; where, i 1,dref2 is the first d-axis current reference value, v dcup2 + v dcdn2 is the second DC-side voltage, i dc2 is the DC-side current, and u d2 is the d-axis component of the interconnection voltage of the second distribution network.

[0149] In the embodiments of the present application, preferably, the first current reference value of the power transmission control part of the second converter, the second current reference value of the harmonic control part, the third current reference value of the unbalance control part, and the zero-sequence current reference value and the voltage stabilization current reference value of the DC voltage control part are obtained through the above method, that is, through a detailed current reference value acquisition algorithm, for precise control in the case of a distribution network fault, effective allocation is achieved, and the power absorption and transfer of the second converter can be controlled more precisely, ensuring the continuity of the user's power supply.

[0150] To better intuitively understand the process of determining the first preset control signal by using the fixed AC voltage control strategy and determining the second preset control signal by using the fixed power control strategy in the above embodiments of the present application, the present application will be described in conjunction with Figure 4 and Figure 5 for illustration. Please refer to Figure 4 , which is a schematic diagram of determining the first preset control signal by the fixed AC voltage control strategy in the embodiments of the present application. Please refer to Figure 5 , which is a schematic diagram of determining the second preset control signal by the fixed power control strategy in the embodiments of the present application.

[0151] Figure 4 The shown V dref1 is the second dq component of the load voltage reference value of the first distribution network, V Labc1 is the first load voltage, θ1 is the first current phase angle, abc / dq0 is the Park transformation, dq0 / abc is the inverse Park transformation, and V dcup1 and V dcdn1 are the capacitor voltages of the two floating capacitors of the first converter respectively; Figure 5 The shown i dref2 and i qref2 are the d-axis current reference value and the q-axis current reference value of the second converter respectively, θ2 is the second current phase angle, i ah2 , i bh2 and i ch2 are the three-phase currents in the second current reference value respectively, and i a02 , i b02 and i c02They are the three-phase currents in the zero-sequence current, i an2 , i bn2 and i cn2 They are the three-phase currents in the negative-sequence current, V dc_ref is the DC-side voltage reference value of the second converter, V dcup2 and V dcdn2 are the capacitor voltages of the two floating capacitors of the second converter respectively, u d2 is the d-axis component of the interconnected voltage of the second distribution network.

[0152] To better reflect the technical effects brought by this method of the present application, the present application is explained in conjunction with the simulation waveform diagram obtained through simulation.

[0153] Please refer to Figure 6 , which is the simulation waveform diagram in the embodiment of the present application. In Figure 6 shown in the simulation waveform diagram, the four waveforms in the list respectively correspond to the supply voltage, supply current, output current of the split-phase flexible interconnection device, and the change of the load current of the first distribution network.

[0154] At 0.05 s, due to the three-phase unbalance problem in the first distribution network, the split-phase flexible interconnection device is controlled to start operating to compensate for the three-phase current unbalance of the first distribution network, and 46.65 kW of active power is transmitted from the second distribution network to the first distribution network.

[0155] At 0.15 s, a ground fault occurs in phase C1 of the first distribution network. Its supply voltage is not affected, and the supply currents of phases A1 and B1 also remain unchanged. However, due to the ground fault in phase C1, its current increases significantly.

[0156] At 0.2 s, the fifth circuit breaker is controlled to act quickly to cut off the faulty section of the line, making the first distribution network enter the no-load state. At this time, the supply current of the first distribution network drops to 0, and the first converter of the split-phase flexible interconnection device switches to the voltage source mode to provide AC voltage for the load of the first distribution network. However, due to the limitation of the interconnection capacity of the split-phase flexible interconnection device, it is impossible to transfer all the loads of the first distribution network, and it can only be transferred to its maximum capacity limit. In this case, the split-phase flexible interconnection device provides a three-phase AC voltage of 220 V and a current of 168 A for the load of distribution network 1, and the maximum transfer power is 110 kW. This means that 110 kW of the load of the first distribution network is transferred and supplied by the second distribution network through the split-phase flexible interconnection device, while the remaining 28.38 kW of the load cannot be transferred due to the limitation of the interconnection capacity of the split-phase flexible interconnection device.

[0157] To solve this problem, at 0.3 seconds, the first circuit breaker and the second circuit breaker at both ends of the adjustable resistor bank were closed. At this time, the transfer power of the split-phase flexible interconnection device still remained at the maximum power level that it could transfer, while the remaining 28.38 kW of power was transferred through the adjustable resistor bank. Therefore, the load of the distribution network on the faulty side was completely transferred, and the load current (i.e., the transfer current required in the power to be transferred) reached 211 A.

[0158] The present application provides a power transfer device for a capacity-adjustable distribution network interconnection system in a third aspect.

[0159] Please refer to Figure 7 , which is a schematic diagram of a power transfer device for a capacity-adjustable distribution network interconnection system in an embodiment of the present application. The device 710 is applied to the capacity-adjustable distribution network interconnection system as described in the above embodiment. The device 710 includes:

[0160] A judgment transfer module 711, configured to input a first preset control signal and a second preset control signal into a first converter on the first distribution network side and a second converter on the second distribution network side in the split-phase flexible interconnection device respectively when the first distribution network is the faulty-side distribution network, the second distribution network is the non-faulty-side distribution network, and the interconnection capacity of the split-phase flexible interconnection device in the system is less than the power to be transferred of the first distribution network, so that the split-phase flexible interconnection device absorbs the maximum transfer power corresponding to the interconnection capacity from the second distribution network and transmits it to the first distribution network;

[0161] A determination module 712, configured to determine a target resistor bank value according to the maximum transfer current corresponding to the maximum transfer power, the transfer current required corresponding to the power to be transferred, and the impedance value of the split-phase flexible interconnection device;

[0162] An adjustment transfer module 713, configured to adjust the adjustable resistor bank value of the adjustable resistor bank in the system according to the target resistor bank value, so that the adjustable resistor bank absorbs the adjustable transfer current corresponding to the adjustable resistor bank value from the second distribution network and transmits it to the first distribution network.

[0163] In the embodiment of the present application, the relevant content of the above judgment transfer module 711, determination module 712, and adjustment transfer module 713 can refer to Figure 3 the content in the embodiment shown, and will not be elaborated here.

[0164] It should be noted that the device 710 of the present application further includes some other modules. It can be understood that there is a one-to-one correspondence between the method of the present application and the device 710. Therefore, some other modules of the device 710 of the present application are the corresponding content of the method of the present application in the above embodiment.

[0165] In the embodiments of the present application, by calculating an appropriate adjustable resistor group value, it is possible to ensure that when the interconnection capacity of the split-phase flexible interconnection device is insufficient to support all transfer power supplies, the adjustable performance of the adjustable resistor group is used to effectively transfer the remaining load, avoiding the economic losses caused by power outages and ensuring the power supply continuity for users.

[0166] The present application also provides a computer-readable storage medium in a fourth aspect, storing a computer program, which when executed by a controller, causes the controller to execute the power transfer method of a capacity-adjustable distribution network interconnection system in the above method embodiments.

[0167] The present application also provides a computer device in a fifth aspect, including a memory and a controller. The memory stores a computer program, which when executed by the controller, causes the controller to execute the power transfer method of a capacity-adjustable distribution network interconnection system in the above method embodiments.

[0168] Figure 8 The internal structure diagram of the computer device in some embodiments is shown. The computer device can specifically be a terminal, a server, or a gateway. As Figure 8 shown, the computer device includes a controller, a memory, and a network interface connected through a system bus.

[0169] Among them, the memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and can also store a computer program, which when executed by the controller, can cause the controller to implement each step in the above method embodiments. The internal memory can also store a computer program, which when executed by the controller, can cause the controller to execute each step in the above method embodiments. Those skilled in the art can understand that Figure 8 the structure shown in is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0170] Those of ordinary skill in the art can understand that to implement all or part of the processes in the above method embodiments, it can be completed by instructing relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the above method embodiments.

[0171] Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application may include non-volatile and / or volatile memories. The non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. The volatile memory may 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), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0172] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, 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, it should be considered as the scope described in this specification.

[0173] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A capacity-adjustable distribution network interconnection system, characterized in that: The system includes a phase-splitting flexible interconnection device and an adjustable resistance group; The phase-splitting flexible interconnection device is connected to the adjustable resistor group to form two distribution network access terminals, the first distribution network access terminal is used to connect to the three-phase line of the first distribution network, and the second distribution network access terminal is used to connect to the three-phase line of the second distribution network; When the first distribution network is a fault-side distribution network, the second distribution network is a non-fault-side distribution network, and the interconnection capacity of the phase-split flexible interconnection device is less than the required transfer power of the first distribution network, the phase-split flexible interconnection device is used to absorb the maximum transfer power corresponding to the interconnection capacity from the second distribution network and transmit it to the first distribution network; The adjustable resistor group is used to absorb the adjustable transfer current corresponding to the adjustable resistor group value of the adjustable resistor group from the second distribution network, and transmit it to the first distribution network; The required transfer current of the required transfer power is the sum of the maximum transfer current of the maximum transfer power and the adjustable transfer current.

2. The system according to claim 1, characterized in that The system further comprises a first circuit breaker, a second circuit breaker, a third circuit breaker, a fourth circuit breaker, a fifth circuit breaker and a sixth circuit breaker; The phase-splitting flexible interconnection device is connected to the adjustable resistor group through the first circuit breaker to form a first distribution network access terminal, and the phase-splitting flexible interconnection device is connected to the adjustable resistor group through the second circuit breaker to form a second distribution network access terminal; The first distribution network access terminal is used to connect to the three-phase line of the first distribution network through the third circuit breaker, and the second distribution network access terminal is used to connect to the three-phase line of the second distribution network through the fourth circuit breaker; The three-phase line of the first distribution network is connected to the first distribution network through the fifth circuit breaker, and the three-phase line of the second distribution network is connected to the second distribution network through the sixth circuit breaker.

3. The system according to claim 1, characterized in that The adjustable resistor group includes a first adjustable resistor, a second adjustable resistor and a third adjustable resistor; One end of the first adjustable resistor is connected to the first end of the phase-splitting flexible interconnection device and forms the first end of the first distribution network access end, and the first end of the first distribution network access end is used to be connected to the A-phase line of the first distribution network, and the other end of the first adjustable resistor is connected to the second end of the phase-splitting flexible interconnection device and forms the first end of the second distribution network access end, and the first end of the second distribution network access end is used to be connected to the A-phase line of the second distribution network; One end of the second adjustable resistor is connected to the third end of the phase-splitting flexible interconnection device and forms the second end of the first distribution network access end, and the second end of the first distribution network access end is used to be connected to the B-phase line of the first distribution network, and the other end of the second adjustable resistor is connected to the fourth end of the phase-splitting flexible interconnection device and forms the second end of the second distribution network access end, and the second end of the second distribution network access end is used to be connected to the B-phase line of the second distribution network; One end of the third adjustable resistor is connected to the fourth end of the phase-splitting flexible interconnection device and forms the third end of the first distribution network access end, and the third end of the first distribution network access end is used to be connected to the C-phase line of the first distribution network. The other end of the third adjustable resistor is connected to the fifth end of the phase-splitting flexible interconnection device and forms the third end of the second distribution network access end, and the third end of the second distribution network access end is used to be connected to the C-phase line of the second distribution network.

4. The system according to any one of claims 1 to 3, characterized in that: The system also includes a controller; The controller is used to determine the value of the adjustable resistance group according to the maximum transferred current and the required transferred current.

5. A power transfer method for a capacity-adjustable distribution network interconnection system, the method being applied to the capacity-adjustable distribution network interconnection system as claimed in any one of claims 1 to 4, characterized in that: The method comprises: In the case where the first distribution network is a fault-side distribution network, the second distribution network is a non-fault-side distribution network, and the interconnection capacity of the phase-splitting flexible interconnection device in the system is less than the required transfer power of the first distribution network, a first preset control signal and a second preset control signal are respectively input into a first converter located on the first distribution network side and a second converter located on the second distribution network side in the phase-splitting flexible interconnection device, so that the phase-splitting flexible interconnection device absorbs the maximum transfer power corresponding to the interconnection capacity from the second distribution network, and transmits it to the first distribution network; Determine a target resistance group value according to a maximum transfer current corresponding to the maximum transfer power, a required transfer current corresponding to the required transfer power, and an impedance value of the phase-splitting flexible interconnection device; The adjustable resistance group value of the adjustable resistance group in the system is adjusted according to the target resistance group value, so that the adjustable resistance group absorbs the adjustable transfer current corresponding to the adjustable resistance group value from the second distribution network and transmits it to the first distribution network.

6. The method according to claim 5, characterized in that The method further comprises: Determining the first preset control signal by adopting a constant AC voltage control strategy; A constant power control strategy is adopted to determine the second preset control signal.

7. The method according to claim 6, characterized in that The adopting a constant AC voltage control strategy to determine the first preset control signal includes: Acquire an output voltage reference value of an AC voltage control part of the first converter and a first DC side voltage; Determine a modulation wave according to the output voltage reference value, the first DC side voltage and a preset carrier amplitude; The modulated wave is input into a PWM signal generator to obtain the first preset control signal.

8. The method according to claim 7, characterized in that The obtaining of the output voltage reference value of the AC voltage control part of the first converter and the first DC side voltage includes: Acquiring a first current phase angle of the first distribution network through a phase-locked loop, and measuring a first load voltage of the first distribution network; Performing a Park transformation on the first load voltage using the first current phase angle to obtain a first dq component; determining a voltage error according to the first dq component and a second dq component of a load voltage reference value of the first distribution network; Inputting the voltage error into a first PI controller to obtain a voltage error gain; Determine the third dq component according to the voltage error gain and the first dq component; Performing an inverse Pike transform on the third dq component using the first current phase angle to obtain the output voltage reference value; The first DC link voltage is determined according to the capacitance voltages of two suspension capacitors of the first converter.

9. The method according to claim 6, characterized in that The adopting a constant power control strategy to determine the second preset control signal includes: Acquire a first current reference value of a power transmission control part, a second current reference value of a harmonic control part, a third current reference value of an unbalanced control part, and a zero-sequence current reference value and a regulated current reference value of a DC voltage control part of the second converter; Determine an output current reference value of a power control part of the second converter according to the first current reference value, the second current reference value, the third current reference value, the zero-sequence current reference value and the regulated current reference value; The output current reference value is input into the hysteresis control to obtain the second preset control signal.

10. The method according to claim 9, characterized in that The obtaining of the first current reference value of the power transmission control part of the second converter, the second current reference value of the harmonic control part, the third current reference value of the unbalanced control part, and the zero-sequence current reference value and the regulated current reference value of the DC voltage control part includes: Acquiring a second current phase angle of the second distribution network through a phase-locked loop, measuring an interconnection voltage and a second load current at an interconnection point of the second distribution network, and measuring a capacitor voltage of two suspension capacitors of the second converter; Determining a d-axis current reference value and a q-axis current reference value of the second converter according to the d-axis component and the q-axis component of the interconnection voltage and the maximum transfer power; Performing an inverse Pike transformation on a d-axis current reference value and a q-axis current reference value of the second converter using the second current phase angle to obtain the first current reference value; Performing a Park transformation on the second load current using the second current phase angle to obtain a fourth dq component; Obtaining a first DC component in the fourth dq component through a low-pass mean filter; Performing an inverse Park transformation on the first DC component using the second current phase angle to obtain a fundamental current; determining the second current reference value according to the fundamental current and the second load current; Performing a Park transformation on the second load current using the negative second current phase angle to obtain a fifth dq component; Acquire a second DC component in the fifth dq component through a low-pass mean filter; Performing an inverse Park transformation on the second DC component using the negative second current phase angle to obtain a negative sequence current; determining a zero-sequence current according to the second load current; Determine the third current reference value according to the zero-sequence current and the negative-sequence current; Determine a second DC link voltage and a DC link voltage error according to the capacitance voltages of the two suspension capacitors of the second converter; Inputting the DC side voltage error into a second PI controller to obtain the zero-sequence current reference value; determining a DC voltage error according to the second DC link voltage and a DC link voltage reference value of the second converter; Inputting the DC voltage error into a third PI controller to obtain a DC side current; determining a first d-axis current reference value according to the DC link current, the second DC link voltage and a d-axis component of the interconnection voltage; The first d-axis current reference value is subjected to an inverse Park transformation using the second current phase angle to obtain the regulated current reference value.

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