Capacity-adjustable power distribution network interconnection system and regulation and control method thereof

Abstract

The capacity-adjustable power distribution network interconnection system comprises the steps that when a first power distribution network is a heavy load side power distribution network, a second power distribution network is a light load 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, the first power distribution network is connected with the second power distribution network; the split-phase flexible interconnection device absorbs the maximum transfer power corresponding to the interconnection capacity from the second power distribution network and transmits the maximum transfer power to the first power distribution network, and the coordination impedance absorbs the adjustable transfer power corresponding to the adjustable impedance value of the coordination impedance from the second power distribution network and transmits the adjustable transfer power to the first power distribution network; the coordination impedance is introduced, so that when the interconnection capacity of the split-phase flexible interconnection device is not enough to support the load of the transfer overload side power distribution network, the coordination impedance can be utilized to ensure that the heavy load side power distribution network and the light load side power distribution network reach a real balanced load state under the condition that no extra power electronic device needs to be added.

Description

Technical Field

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

[0002] With the development of the new power system, the access ratio of distributed generation in the distribution network has increased significantly. Although this phenomenon has brought about diversified energy utilization, it has also caused a series of problems, especially the seasonal heavy overload and extreme light load phenomena in the distribution network have become more and more serious. During certain periods, some distribution networks are overloaded, resulting in long-term overheating of distribution transformers, affecting their safe and stable operation, while some distribution networks are lightly loaded, making the resources of distribution transformers not fully utilized. This unbalanced load state not only affects the economic operation efficiency of distribution transformers, but also poses a serious threat to their service life.

[0003] Currently, to solve this problem, the load rate of different distribution networks can be balanced through a split-phase flexible interconnection device, that is, part of the load of the heavily loaded distribution network is supplied by the lightly loaded distribution network through the split-phase flexible interconnection device, so that both the heavily loaded distribution network and the lightly loaded distribution network reach a balanced load state. However, the capacity of the split-phase flexible interconnection device is usually limited, which to a certain extent restricts its complete transfer ability for that part of the load of the overloaded distribution network. When the interconnection capacity of the split-phase flexible interconnection device is not enough to support the transfer of that part of the load of the overloaded distribution network, it is impossible to make both the heavily loaded distribution network and the lightly loaded distribution network reach a truly balanced load state. Summary of the Invention

[0004] Based on this, in view of the above problems, it is necessary to propose a capacity-adjustable distribution network interconnection system and its control method, which can ensure that both the heavily loaded distribution network and the lightly loaded distribution network reach a truly balanced load state by using coordinated impedance without adding additional power electronic devices.

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

[0006] The split-phase flexible interconnection device is connected to the coordinated impedance 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 a heavily loaded distribution network, the second distribution network is a lightly loaded distribution network, and the interconnection capacity of the phase-splitting flexible interconnection device is less than the power to be transferred 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;

[0008] The coordinated impedance is used to absorb the adjustable transfer power corresponding to the adjustable impedance value of the coordinated impedance from the second distribution network and transmit it to the first distribution network;

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

[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 phase-splitting flexible interconnection device and the coordinated impedance are connected through the first circuit breaker to form a first distribution network access end, and the phase-splitting flexible interconnection device and the coordinated impedance are connected through the second circuit breaker to form 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 system further includes a controller;

[0015] The controller is used to determine the adjustable impedance value according to the first interconnection voltage at the interconnection point of the first distribution network and the second interconnection voltage at the interconnection point of the second distribution network.

[0016] To achieve the above object, the present invention provides a control method for a distribution network interconnection system with adjustable capacity in a second aspect. The method is applied to the distribution network interconnection system with adjustable capacity according to any one of the first aspect, and the method includes:

[0017] When the first distribution network is a heavy-load distribution network, the second distribution network is a light-load distribution network, and the interconnection capacity of the phase-splitting flexible interconnection device in the system is less than the power to be transferred of the first distribution network, input the first preset control signal and the second preset control signal into the first converter on the side of the first distribution network and the second converter on the side of the second distribution network in the phase-splitting flexible interconnection device respectively, 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;

[0018] Measure the first interconnection voltage at the interconnection point of the first distribution network and the second interconnection voltage at the interconnection point of the second distribution network;

[0019] Determine the target impedance value according to the first interconnection voltage, the second interconnection voltage, the first impedance value of the first distribution network and the second impedance value of the second distribution network;

[0020] Adjust the adjustable impedance value of the coordinated impedance in the system according to the target impedance value, so that the coordinated impedance absorbs the adjustable transfer power corresponding to the adjustable impedance value from the second distribution network and transmits it to the first distribution network.

[0021] Optionally, the determining the target impedance value according to the first interconnection voltage, the second interconnection voltage, the first impedance value of the first distribution network and the second impedance value of the second distribution network includes:

[0022] Use the formula to determine the target impedance value;

[0023] where Z abc is the target impedance value, is the first interconnection voltage, is the second interconnection voltage, Z abc1 is the first impedance, Z abc2 is the second impedance.

[0024] Optionally, the method further includes:

[0025] Obtain the first current reference value of the unbalanced control part of the first converter, the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part, and the second current reference value of the unbalanced control part of the second converter;

[0026] Input the first current reference value, the zero-sequence current reference value and the regulated voltage current reference value into the first predictive control model to obtain the first preset control signal;

[0027] Input the second current reference value into the second predictive control model to obtain the second preset control signal.

[0028] Optionally, obtaining the first current reference value of the unbalanced control part of the first converter, the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part, and the second current reference value of the unbalanced control part of the second converter includes:

[0029] Obtain the first current phase angle of the first distribution network through a phase-locked loop, and measure the first load current of the first distribution network and the capacitor voltages of the two split capacitors of the first converter;

[0030] Perform Park transformation on the first load current using the negative of the first current phase angle to obtain the first dq components;

[0031] Obtain the first DC component in the first dq components through a low-pass mean filter;

[0032] Perform inverse Park transformation on the first DC component using the negative of the first current phase angle to obtain the first negative-sequence current;

[0033] Determine the first zero-sequence current according to the first load current;

[0034] Determine the first current reference value according to the first zero-sequence current and the first negative-sequence current;

[0035] Determine the DC side voltage and the first DC side voltage error according to the capacitor voltages of the two split capacitors of the first converter;

[0036] Input the first DC side voltage error into a first PI controller to obtain the zero-sequence current reference value;

[0037] Determine the second DC side voltage error according to the DC side voltage and the DC side voltage reference value of the first converter;

[0038] Input the second DC side voltage error into a second PI controller to obtain the DC side current;

[0039] Determine the d-axis current reference value according to the DC side current, the DC side voltage and the d-axis component of the first interconnection voltage;

[0040] Perform inverse Park transformation on the d-axis current reference value using the first current phase angle to obtain the regulated voltage current reference value;

[0041] Obtain the second current phase angle of the second distribution network through a phase-locked loop, and measure the second load current of the second distribution network;

[0042] The Park transformation is performed on the second load current by using the negative of the second current phase angle to obtain second dq components;

[0043] The second DC component in the second dq components is obtained through a low-pass mean filter;

[0044] The inverse Park transformation is performed on the second DC component by using the negative of the second current phase angle to obtain a second negative-sequence current;

[0045] A second zero-sequence current is determined according to the second load current;

[0046] The second current reference value is determined according to the second zero-sequence current and the second negative-sequence current.

[0047] Optionally, the first predictive control model includes a first output current prediction model and a first objective function of the first converter. The step of inputting the first current reference value, the zero-sequence current reference value, and the regulated voltage current reference value into the first predictive control model to obtain the first preset control signal includes:

[0048] Measure the output current of the first converter;

[0049] The output current of the first converter is input into the first output current prediction model to obtain first output current prediction values corresponding to different switching function combinations of the first converter;

[0050] Using the first objective function, first objective values corresponding to different switching function combinations are determined according to the first output current prediction values corresponding to different switching function combinations, the first current reference value, the zero-sequence current reference value, and the regulated voltage current reference value;

[0051] Among the first objective values corresponding to all switching function combinations, the switching function combination corresponding to the minimum first objective value is used as the first preset control signal;

[0052] The second predictive control model includes a second output current prediction model and a second objective function of the second converter. The step of inputting the second current reference value into the second predictive control model to obtain the second preset control signal includes:

[0053] Measure the output current of the second converter;

[0054] The output current of the second converter is input into the second output current prediction model to obtain second output current prediction values corresponding to different switching function combinations of the second converter;

[0055] Using the second objective function, determine the second objective values corresponding to different switching function combinations according to the predicted values of the second output current corresponding to different switching function combinations and the second current reference value;

[0056] Among the second objective values corresponding to all switching function combinations, take the switching function combination corresponding to the minimum second objective value as the second preset control signal.

[0057] Optionally, the expression of the first output current prediction model is:

[0058]

[0059] The expression of the second output current prediction model is:

[0060] where, i abc1,m,k+1 is the first predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment, i abc1,k is the output current of the first converter corresponding to the k-th moment, T s1 is the control period of the first converter, L1 is the filter inductor of the first converter, U 0,1,m,k is the output voltage of the first converter corresponding to the m-th switching function combination at the k-th moment, U s,abc1,k is the first interconnection voltage corresponding to the k-th moment, R1 is the parasitic resistance of the first converter, i abc2,m,k+1 is the second predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment, i abc2,k is the output current of the second converter corresponding to the k-th moment, T s2 is the control period of the second converter, L2 is the filter inductor of the second converter, U 0,2,m,k is the output voltage of the second converter corresponding to the m-th switching function combination at the k-th moment, U s,abc2,k is the second interconnection voltage corresponding to the k-th moment, R2 is the parasitic resistance of the second converter.

[0061] Optionally, the expression of the first objective function is: g 1,m =(i a1,ref -i a1,m,k+1 ) 2 +(i b1,ref -i b1,m,k+1 ) 2 +(i c1,ref -i c1,m,k+1 ) 2 ;

[0062] The expression of the second objective function is: g 2,m =(i a2,ref -i a2,m,k+1 ) 2 +(i b2,ref -i b2,m,k+1 ) 2

[0063] +(i c2,ref -i c2,m,k+1 ) 2 ;

[0064] where g 1,m is the first objective value corresponding to the m-th switching function combination, i a1,ref , i b1,ref and i c1,ref are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the sum of the first current reference value, the zero-sequence current reference value, and the regulated current reference value respectively, i a1,m,k+1 , i b1,m,k+1 and i c1,m,k+1 are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the first predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment respectively, g 2m is the second objective value corresponding to the m-th switching function combination, i a2,ref , i b2,ref and i c2,ref are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the second current reference value respectively, i a2,m,k+1 , i b2,m,k+1 and i c2,m,k+1 are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the second predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment respectively.

[0065] To achieve the above object, in a third aspect, the present invention provides a control 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:

[0066] A transfer power supply judgment module, 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 of the split-phase flexible interconnection device in the case that the first distribution network is a heavily loaded distribution network, the second distribution network is a lightly loaded 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;

[0067] A measurement module, configured to measure a first interconnection voltage at an interconnection point of the first distribution network and a second interconnection voltage at an interconnection point of the second distribution network;

[0068] A determination module, configured to determine a target impedance value according to the first interconnection voltage, the second interconnection voltage, a first impedance value of the first distribution network, and a second impedance value of the second distribution network;

[0069] An adjusted transfer power supply module, configured to adjust an adjustable impedance value of a coordinated impedance in the system according to the target impedance value, so that the coordinated impedance absorbs an adjustable transfer power corresponding to the adjustable impedance value from the second distribution network and transmits it to the first distribution network.

[0070] To achieve the above object, in a third aspect of the present invention, there is provided a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the processor is caused to execute the method according to any one of the first aspects.

[0071] To achieve the above object, in a fourth aspect of the present invention, there is provided a computer device including a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, the processor is caused to execute the method according to any one of the first aspects.

[0072] Adopting the embodiment of the present invention has the following beneficial effects: The above system includes a split-phase flexible interconnection device and a coordinated impedance. The split-phase flexible interconnection device is connected to the coordinated impedance and forms two distribution network access ends. The first distribution network access end is connected to the three-phase line of the first distribution network, and the second distribution network access end is connected to the three-phase line of the second distribution network. When the first distribution network is the heavy-load side distribution network, the second distribution network is the light-load side distribution network, and the interconnection capacity of the split-phase flexible interconnection device is less than the required transfer power of the first distribution network, the split-phase 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 coordinated impedance is used to absorb the adjustable transfer power corresponding to the adjustable impedance value of the coordinated impedance from the second distribution network and transmit it to the first distribution network, where the required transfer power is the sum of the maximum transfer power and the adjustable transfer power; that is, by introducing the coordinated impedance, when the interconnection capacity of the split-phase flexible interconnection device is insufficient to support that part of the load of the overloaded side distribution network, without the need to add additional power electronic devices, the remaining part of the load of the overloaded side distribution network can be transferred by adjusting the adjustable impedance value of the coordinated impedance to ensure the full transfer of the remaining overloaded side load and ensure that both the heavy-load side distribution network and the light-load side distribution network reach a truly balanced load state. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] 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 drawings in the following description 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.

[0074] Wherein:

[0075] Figure 1 is a schematic diagram of a distribution network interconnection system with adjustable capacity in an embodiment of the present application;

[0076] Figure 2 is another schematic diagram of a distribution network interconnection system with adjustable capacity in an embodiment of the present application;

[0077] Figure 3 is a schematic diagram of a control method for a distribution network interconnection system with adjustable capacity in an embodiment of the present application

[0078] Figure 4 is a schematic diagram of the control strategy process of the first preset control signal in an embodiment of the present application;

[0079] Figure 5 is a schematic diagram of the control strategy process of the second preset control signal in an embodiment of the present application;

[0080] Figure 6 This is the simulation waveform diagram in the embodiment of the present application;

[0081] Figure 7 This is a schematic diagram of a control device for a capacity - adjustable distribution network interconnection system in the embodiment of the present application;

[0082] Figure 8 This is the internal structure diagram of a computer device in some embodiments. Detailed implementation manners

[0083] 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.

[0084] With the development of the new power system, the access ratio of distributed generation in the distribution network has increased significantly. Although this phenomenon has brought about the diversification of energy utilization, it has also caused a series of problems. In particular, the seasonal heavy overload and extreme light load phenomena in the distribution network have become more and more serious. During certain periods, some distribution networks have long - term overheating of distribution transformers due to heavy loads, affecting their safe and stable operation. While some distribution networks have under - utilized distribution transformer resources due to light loads. This unbalanced load state not only affects the economic operation efficiency of the distribution transformer but also poses a serious threat to its service life.

[0085] Currently, to solve this problem, the load rate of different distribution networks can be balanced through a split - phase flexible interconnection device, that is, part of the load of the heavily - loaded distribution network is supplied by the lightly - loaded distribution network through the split - phase flexible interconnection device, so that both the heavily - loaded distribution network and the lightly - loaded distribution network reach a balanced load state. However, the split - phase flexible interconnection device usually has a limited capacity, which to a certain extent limits its full - transfer ability for that part of the load on the overloaded distribution network. When the interconnection capacity of the split - phase flexible interconnection device is not enough to support the transfer of that part of the load on the overloaded distribution network, it is impossible to make both the heavily - loaded distribution network and the lightly - loaded distribution network reach a truly balanced load state.

[0086] To address the above problems, the present application proposes a capacity - adjustable distribution network interconnection system and its control method, which can ensure that both the heavily - loaded distribution network and the lightly - loaded distribution network reach a truly balanced load state by using coordinated impedance without adding additional power electronic devices. The specific implementation principle will be described in detail in the following embodiments.

[0087] In the first aspect of the application, a capacity - adjustable distribution network interconnection system is provided.

[0088] Please refer to Figure 1 , which is a schematic diagram of a capacity-adjustable distribution network interconnection system in an embodiment of the present application. The system includes a split-phase flexible interconnection device 110 and a coordination impedance 120.

[0089] Among them, the split-phase flexible interconnection device 110 is connected to the coordination impedance 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.

[0090] In a feasible implementation manner, when the first distribution network 130 is a heavily loaded distribution network, the second distribution network 140 is a lightly loaded distribution network, and the interconnection capacity of the split-phase flexible interconnection device 110 is less than the power transfer requirement of the first distribution network 130, the split-phase 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 coordination impedance 120 is used to absorb the adjustable power transfer corresponding to the adjustable impedance value of the coordination impedance 120 from the second distribution network 140 and transmit it to the first distribution network 130; where the power transfer requirement is the sum of the maximum power transfer and the adjustable power transfer.

[0091] Among them, the power transfer requirement refers to the situation where the distribution transformer of the first distribution network 130 is heavily overloaded, while the distribution transformer of the second distribution network 140 is extremely lightly loaded. In order to make the load rates of the first distribution network 130 and the second distribution network 140 reach an equilibrium load state, the second distribution network 140 needs to transfer power to the first distribution network 130; for example, the load rate of the first distribution network 130 is 1.075, the load rate of the first distribution network 130 is greater than 1 and is significantly heavily overloaded, the load rate of the second distribution network 140 is 0.238, the load rate of the second distribution network 140 is much less than 1 and is significantly extremely lightly loaded. At this time, the second distribution network 140 needs to transfer power to the first distribution network 130 so that the load rates of the first distribution network 130 and the second distribution network 140 both reach an equilibrium state.

[0092] It should be noted that in this application, the load refers to the same as 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.

[0093] In some embodiments, the coordination impedance 120 can be composed of one or more devices with impedance. By adjusting the impedance value of the devices in the coordination impedance 120, the adjustable impedance value of the coordination impedance 120 can be adjusted, and then the adjustable power transfer can be adjusted to meet the requirements of different load rates to reach equilibrium.

[0094] In the embodiment of the present application, by introducing the coordinated impedance 120, when the interconnection capacity of the split-phase flexible interconnection device 110 is insufficient to support the part of the load on the overload side distribution network, the remaining part of the load on the overload side distribution network can be transferred without adding additional power electronic devices by adjusting the adjustable impedance value of the coordinated impedance 120, so as to ensure the full transfer of the remaining overload side load and ensure that both the heavy-load side distribution network and the light-load side distribution network reach a truly balanced load state.

[0095] Further, when the distribution transformer of the first distribution network 130 is severely overloaded while the distribution transformer of the second distribution network 140 is extremely lightly loaded, through the double-layer coordinated control of the split-phase flexible interconnection device 110 and the coordinated impedance 120, the transfer power can be stabilized in a short time, and compared with the existing method, the time required for stable transfer is greatly shortened.

[0096] In addition, by adjusting the coordinated impedance 120 to carry the remaining load beyond the capacity, the working pressure of the split-phase flexible interconnection device 110 is relieved, the problem of capacity overrun caused by over-reliance on a single device is avoided, the service life of the equipment is extended, 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, thus reducing the economic burden of power grid maintenance and management.

[0097] Based on Figure 1 , please refer to Figure 2 , which is another schematic diagram of a capacity-adjustable distribution network interconnection system in the embodiment of the present application. The system 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.

[0098] In a feasible implementation manner, the split-phase flexible interconnection device 110 and the coordinated impedance 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 coordinated impedance 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.

[0099] 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 split capacitors on the side of the first converter CV1, and C3 and C4 are two split 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.

[0100] It should be noted that since each circuit breaker is distributed between each connection point, therefore, for the demand situation where different load rates need to achieve balance, the closing and opening of each connection point can be accurately controlled; for example, when there is no need for power transfer, control the third circuit breaker S3 and the fourth circuit breaker S4 to open, and when it is necessary to coordinate the impedance 120 for power transfer, control the first circuit breaker S1 and the second circuit breaker S2 to close, etc.

[0101] Furthermore, since each phase line of the three-phase line corresponds to one end of the coordinated impedance 120, therefore, for the demand where different load rates need to achieve balance, the impedance value of the device in the coordinated impedance 120 corresponding to the different phase lines can be adjusted to achieve accurate control.

[0102] 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, for the demand where different load rates need to achieve balance, accurate control of different scenario requirements can be achieved.

[0103] In addition, since each phase line of the three-phase line corresponds to one end point of the coordinated impedance 120, therefore, the impedance value of the device in the coordinated impedance 120 can be accurately adjusted according to the different demands of different phase loads, achieving the goal of balancing different load rates and improving the balance and efficiency of the system.

[0104] In a feasible implementation manner, the system in the above embodiment further includes a controller (not shown in the figure), and the controller is used to determine the adjustable impedance value according to the first interconnection voltage at the interconnection point of the first distribution network 130 and the second interconnection voltage at the interconnection point of the second distribution network 140.

[0105] It should be noted that the interconnection point between the first distribution network 130 and the second distribution network 140 also refers to the grid connection point. It can be understood that the interconnection points of the phase-splitting flexible interconnection device 110 with the first distribution network 130 and the second distribution network 140 are both selected at their grid connection points.

[0106] In some embodiments, the controller is connected to the coordination impedance 120 and is used to adjust the adjustable impedance value of the coordination impedance 120.

[0107] 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.

[0108] In the embodiments of the present application, by introducing a controller, the impedance values of the respective devices in the coordination impedance 120 can be accurately adjusted according to the first interconnection voltage and the second interconnection voltage, so as to ensure that in the case where the interconnection capacity of the phase-splitting flexible interconnection device 110 is insufficient to support, through accurate adjustment, the transferred power reaches the required level, and ensure that both the heavy-load side distribution network and the light-load side distribution network reach a truly balanced load state.

[0109] In addition, the controller can adjust the value of the coordination impedance 120 according to the real-time load condition, ensure that the load rates of the two distribution networks can quickly reach an equilibrium state, improve the dynamic response ability of the system, and can accurately calculate the required adjustable impedance value according to the specific operation condition of the distribution network, so as to achieve precise load balancing.

[0110] The present application provides a control method for a capacity-adjustable distribution network interconnection system in a second aspect.

[0111] Please refer to Figure 3 , which is a schematic diagram of a control method for a capacity-adjustable distribution network interconnection system in the embodiments of the present application. This method is applied to the capacity-adjustable distribution network interconnection system in the above embodiments. This method includes:

[0112] Step 310: When the first distribution network is a heavy-load side distribution network, the second distribution network is a light-load side distribution network, and the interconnection capacity of the phase-splitting flexible interconnection device in the system is less than the required transferred 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 phase-splitting flexible interconnection device respectively, so that the phase-splitting flexible interconnection device absorbs the maximum transferred power corresponding to the interconnection capacity from the second distribution network and transmits it to the first distribution network.

[0113] 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 switching state of the first converter, while the second preset control signal is used to control the switching state of the second converter.

[0114] In some embodiments, both the first preset control signal and the second preset control signal can be set in advance by an operator according to the maximum transfer power for transferring power by the control split-phase flexible interconnection device.

[0115] 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.

[0116] Step 320: Measure the first interconnection voltage at the interconnection point of the first distribution network and the second interconnection voltage at the interconnection point of the second distribution network.

[0117] Step 330: Determine the target impedance value according to the first interconnection voltage, the second interconnection voltage, the first impedance value of the first distribution network, and the second impedance value of the second distribution network.

[0118] It should be noted that the purpose of this application is to make the load rates of the first distribution network and the second distribution network reach equilibrium. Therefore, in some embodiments, when the load rates of the first distribution network and the second distribution network reach equilibrium, the relationship that the load current of the first distribution network is equal to the load current of the second distribution network can be utilized, and the target impedance value can be determined in combination with the first interconnection voltage, the second interconnection voltage, the first impedance value of the first distribution network, and the second impedance value of the second distribution network.

[0119] Step 340: Adjust the adjustable impedance value of the coordination impedance in the system according to the target impedance value, so that the coordination impedance absorbs the adjustable transfer power corresponding to the adjustable impedance value from the second distribution network and transmits it to the first distribution network.

[0120] Among them, the adjustable impedance value includes the impedance values of each device in the coordination impedance.

[0121] In some embodiments, the adjustable impedance value of the coordination impedance can be adjusted to the target impedance value. Of course, in other embodiments, the preset error value can also be obtained first, and then the impedance value in the adjustable impedance value of the coordination impedance can be adjusted to the sum value between the impedance value in the target impedance value and the preset error value, or the impedance value in the adjustable impedance value of the coordination impedance can be adjusted to the difference value between the impedance value in the target impedance value and the preset error value. Among them, the preset error value can be obtained by an operator based on a large amount of experience, experiments, or statistics, or can also be set by the operator according to actual needs.

[0122] In the embodiments of the present application, by calculating an appropriate adjustable impedance value, it is possible to ensure that when the interconnection capacity of the split-phase flexible interconnection device is insufficient to support all power transfer, the adjustable performance of the coordinated impedance is utilized to effectively transfer the remaining load, so as to ensure that both the heavy-load side distribution network and the light-load side distribution network reach a truly balanced load state.

[0123] In a feasible implementation manner, step 330 in the above embodiment, determining the target impedance value according to the first interconnection voltage, the second interconnection voltage, the first impedance value of the first distribution network, and the second impedance value of the second distribution network, includes:

[0124] Using the formula to determine the target impedance value;

[0125] where Z abc is the target impedance value, is the first interconnection voltage, is the second interconnection voltage, Z abc1 is the first impedance, Z abc2 is the second impedance.

[0126] In the embodiments of the present application, a rigorous calculation formula for the target impedance value is provided from a mathematical perspective. The accuracy of the calculated target impedance value can be ensured from the rigor of the mathematical logic, and by preferably showing the above calculation formula, it is convenient for technicians to provide reference, understanding, calculation, etc.; in addition, by using the above calculation formula to calculate the target impedance value, a relatively accurate target impedance value can be obtained to determine an appropriate adjustable impedance value, which can effectively transfer the remaining load, so as to ensure that both the heavy-load side distribution network and the light-load side distribution network reach a truly balanced load state.

[0127] In a feasible implementation manner, the method in the above embodiment further includes: obtaining the first current reference value of the unbalanced control part of the first converter, the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part, and the second current reference value of the unbalanced control part of the second converter; inputting the first current reference value, the zero-sequence current reference value and the regulated voltage current reference value into the first predictive control model to obtain a first preset control signal; inputting the second current reference value into the second predictive control model to obtain a second preset control signal.

[0128] Wherein, both the first predictive control model and the second predictive control model are models preset by the operator; the first predictive control model can predict and output a first preset control signal according to the input first current reference value, zero-sequence current reference value and regulated voltage current reference value, and the second predictive control model can predict and output a second preset control signal according to the input second current reference value.

[0129] For the acquisition methods of the first predictive control model and the second predictive control model, in some embodiments, they can be obtained by pre-training using a deep learning network or machine learning.

[0130] It should be noted that in this application, the unbalance control part also refers to the power quality part.

[0131] In the embodiments of this application, by obtaining the current reference values of the unbalance control parts of the first converter and the second converter, as well as the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part, the control signal can be predicted more accurately, and further ensure that the phase-splitting flexible interconnection device performs power transfer more precisely.

[0132] In addition, by predicting the control signals of the first converter and the second converter using the predictive control model, not only the real-time performance and accuracy of the control are improved, but also the control signal can be dynamically adjusted better to adapt to the change of the load rate, thereby effectively improving the efficiency of the load balancing process.

[0133] In a feasible implementation manner, obtaining the first current reference value of the unbalanced control part of the first converter, the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part, and the second current reference value of the unbalanced control part of the second converter in the above embodiments includes: obtaining the first current phase angle of the first distribution network through a phase-locked loop, and measuring the first load current of the first distribution network and the capacitor voltages of the two split capacitors of the first converter; performing Park transformation on the first load current using the negative first current phase angle to obtain the first dq components; obtaining the first DC component in the first dq components through a low-pass mean filter; performing inverse Park transformation on the first DC component using the negative first current phase angle to obtain the first negative-sequence current; determining the first zero-sequence current according to the first load current; determining the first current reference value according to the first zero-sequence current and the first negative-sequence current; determining the DC-side voltage and the first DC-side voltage error according to the capacitor voltages of the two split capacitors of the first converter; inputting the first DC-side voltage error into a first PI controller to obtain the zero-sequence current reference value; determining the second DC-side voltage error according to the DC-side voltage and the DC-side voltage reference value of the first converter; inputting the second DC-side voltage error into a second PI controller to obtain the DC-side current; determining the d-axis current reference value according to the DC-side current, the DC-side voltage and the d-axis component of the first interconnection voltage; performing inverse Park transformation on the d-axis current reference value using the first current phase angle to obtain the regulated voltage current reference value; obtaining the second current phase angle of the second distribution network through a phase-locked loop, and measuring the second load current of the second distribution network; performing Park transformation on the second load current using the negative second current phase angle to obtain the second dq components; obtaining the second DC component in the second dq components through a low-pass mean filter; performing inverse Park transformation on the second DC component using the negative second current phase angle to obtain the second negative-sequence current; determining the second zero-sequence current according to the second load current; determining the second current reference value according to the second zero-sequence current and the second negative-sequence current.

[0134] For the determination method of the first zero-sequence current, in some embodiments, the quotient obtained by dividing the sum of the three-phase line currents in the first load current by 3 can be used as the first zero-sequence current.

[0135] For the determination method of the first current reference value, in some embodiments, the sum of the first zero-sequence current and the first negative-sequence current can be used as the first current reference value.

[0136] For the determination method of the DC-side voltage, in some embodiments, the sum of the capacitor voltages of the two split capacitors of the first converter can be used as the DC-side voltage.

[0137] For the determination method of the first DC-side voltage error, in some embodiments, the difference between the capacitor voltages of the two split capacitors of the first converter can be used as the first DC-side voltage error.

[0138] For the determination method of the zero-sequence current reference value, in some embodiments, after inputting the first DC-side voltage error into the first PI controller, the output value of the first PI controller needs to be divided by 3, and then the quotient value is used as the zero-sequence current reference value.

[0139] For the determination method of the second DC-side voltage error, in some embodiments, the difference between the DC-side voltage and the DC-side voltage reference value of the first converter can be used as the second DC-side voltage error.

[0140] For the determination method of the d-axis current reference value, in some embodiments, the formula can be used to determine the d-axis current reference value; where, i dref is the d-axis current reference value, v dcup +v dcdn is the DC-side voltage, i dc is the DC-side current, and e d is the d-axis component of the first interconnection voltage.

[0141] For the determination method of the second zero-sequence current, in some embodiments, the quotient value obtained by dividing the sum of the three-phase line currents in the second load current by 3 can be used as the second zero-sequence current.

[0142] For the determination method of the second current reference value, in some embodiments, the sum of the second zero-sequence current and the second negative-sequence current can be used as the second current reference value.

[0143] In the embodiments of the present application, preferably through the above methods, the current reference values required for the unbalanced control part and the DC voltage control part of the converter can be accurately obtained, that is, through a series of processing steps involving measurement and transformation processing, from the phase tracking of the distribution network to the extraction of current components, and then to the calculation of specific current components, accurate control signals can be provided for the converter, thereby realizing more accurate and efficient load transfer.

[0144] In a feasible implementation manner, the first predictive control model in the above embodiment includes a first output current prediction model of the first converter and a first objective function. Inputting the first current reference value, zero-sequence current reference value, and regulated voltage current reference value into the first predictive control model to obtain a first preset control signal includes: measuring the output current of the first converter; inputting the output current of the first converter into the first output current prediction model to obtain first output current prediction values of the first converter corresponding to different switching function combinations; using the first objective function to determine first objective values corresponding to different switching function combinations according to the first output current prediction values, first current reference value, zero-sequence current reference value, and regulated voltage current reference value corresponding to different switching function combinations; among the first objective values corresponding to all switching function combinations, taking the switching function combination corresponding to the minimum first objective value as the first preset control signal.

[0145] The second predictive control model in the above embodiment includes a second output current prediction model of the second converter and a second objective function. Inputting the second current reference value into the second predictive control model to obtain a second preset control signal includes: measuring the output current of the second converter; inputting the output current of the second converter into the second output current prediction model to obtain second output current prediction values of the second converter corresponding to different switching function combinations; using the second objective function to determine second objective values corresponding to different switching function combinations according to the second output current prediction values and second current reference value corresponding to different switching function combinations; among the second objective values corresponding to all switching function combinations, taking the switching function combination corresponding to the minimum second objective value as the second preset control signal.

[0146] It should be noted that different switching function combinations include combinations of conduction and cutoff of the three-phase upper-arm power devices of the converter and combinations of conduction and cutoff of the three-phase lower-arm power devices; for example, S a 、S b and S c respectively represent conduction and cutoff of the three phases. When the value is 1, it means the phase corresponding to the upper-arm power device of the converter is conducting, and when the value is 0, it means the phase corresponding to the lower-arm power device of the converter is conducting, otherwise, it is cutoff.

[0147] In the embodiments of the present application, the output current is predicted through the output current prediction model, and the optimal switching function combination is sought in combination with the objective function as the preset control signal, which can provide a more accurate control signal for the converter, thereby realizing more accurate and efficient load transfer.

[0148] In addition, the output current prediction model can dynamically adjust the control signal to ensure that the system can quickly adapt to changes in the load rate, effectively improving the load balancing efficiency and the stability of the system.

[0149] In a feasible implementation manner, the expression of the first output current prediction model in the above embodiment is:

[0150] The expression of the second output current prediction model is:

[0151] where, i abc1,m,k+1 is the first predicted output current corresponding to the m-th switch function combination at the (k + 1)-th moment, i abc1,k is the output current of the first converter corresponding to the k-th moment, T s1 is the control period of the first converter, L1 is the filter inductor of the first converter, U 0,1,m,k is the output voltage of the first converter corresponding to the m-th switch function combination at the k-th moment, U s,abc1,k is the first interconnection voltage corresponding to the k-th moment, R1 is the parasitic resistance of the first converter, i abc2,m,k+1 is the second predicted output current corresponding to the m-th switch function combination at the (k + 1)-th moment, i abc2,k is the output current of the second converter corresponding to the k-th moment, T s2 is the control period of the second converter, L2 is the filter inductor of the second converter, U 0,2,m,k is the output voltage of the second converter corresponding to the m-th switch function combination at the k-th moment, U s,abc2,k is the second interconnection voltage corresponding to the k-th moment, and R2 is the parasitic resistance of the second converter.

[0152] In the embodiments of the present application, the expression of the rigorous output current prediction model is provided from a mathematical perspective. From the rigor of the mathematical logic, the accuracy of the predicted output current can be ensured. In addition, by preferably showing the above expression, it is convenient for technicians to provide reference, understanding, calculation, etc.; furthermore, by using the above expression to predict the output current, a relatively accurate output predicted current can be obtained to obtain a more precise converter control signal.

[0153] In a feasible implementation manner, the expression of the first objective function in the above embodiment is: g 1,m =(i a1,ref -i a1,m,k+1 ) 2 +(i b1,ref -i b1,m,k+1 ) 2 +(i c1,ref -i c1,m,k+1 ) 2 ;

[0154] The expression of the second objective function is: g 2,m =(i a2,ref -i a2,m,k+1 ) 2 +(i b2,ref -i b2,m,k+1 ) 2

[0155] +(i c2,ref -i c2,m,k+1 ) 2 ;

[0156] where g 1,m is the first objective value corresponding to the m-th switching function combination, i a1,ref , i b1,ref and i c1,ref are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the sum of the first current reference value, zero-sequence current reference value, and regulated current reference value respectively, i a1,m,k+1 , i b1,m,k+1 and i c1,m,k+1 are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the first predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment respectively, g 2,m is the second objective value corresponding to the m-th switching function combination, i a2,ref , i b2,ref and i c2,ref are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the second current reference value respectively, i a2,m,k+1 , i b2,m,k+1 and i c2,m,k+1 are the phase-A current reference value, phase-B current reference value, and phase-C current reference value in the second predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment respectively.

[0157] In the embodiments of the present application, the expression of the rigorous objective function is provided from a mathematical perspective. From the rigor of the mathematical logic, the accuracy of the calculated objective value can be ensured, and by preferably showing the above calculation formula, it is convenient for technicians to provide reference, understanding, calculation, etc.; in addition, by using the above calculation formula to calculate the objective value, the optimal switching function combination can be found to obtain a more accurate converter control signal.

[0158] To better intuitively understand the control strategy process of the first preset control signal and the second preset control signal in the above embodiments of the present application, the present application will be described in conjunction with Figure 4 and Figure 5 . Please refer to Figure 4 , which is a schematic diagram of the control strategy process of the first preset control signal in the embodiments of the present application. Please refer to Figure 5, which is a schematic diagram of the control strategy process of the second preset control signal in the embodiments of the present application.

[0159] Figure 4 The shown i a01 , i b01 and i c01 are respectively the three-phase currents in the first zero-sequence current, i an1 , i bn1 and i cn1 are respectively the three-phase currents in the first negative-sequence current, i feed1 is the output current of the first converter, i ref1 is the sum of the first current reference value, the zero-sequence current reference value and the regulated voltage current reference value, dq0 / abc is the inverse Park transformation, θ1 is the first current phase angle, V dc_ref is the DC-side voltage reference value of the first converter, V dcup and V dcdn are respectively the capacitor voltages of the two split capacitors of the first converter, u d2 is the d-axis component of the interconnected voltage of the second distribution network; Figure 5 The shown i a02 , i b02 and i c02 are respectively the three-phase currents in the second zero-sequence current, i an2 , i bn2 and i cn2 are respectively the three-phase currents in the second negative-sequence current, i feed2 is the output current of the second converter, i ref2 is the second current reference value.

[0160] In order to better reflect the technical effects brought by this method of the present application, the present application will be explained in combination with the simulation waveform diagram obtained through simulation.

[0161] Please refer to Figure 6 , which is the simulation waveform diagram in the embodiments of the present application. In Figure 6 the shown simulation waveform diagram, the five waveforms in the list respectively correspond to the output current of the first converter, the output current of the second converter, the power supply current of the first distribution network, the power supply current of the second distribution network, and the load rate change of the first distribution network and the second distribution network.

[0162] Before 0.1 s, the split-phase flexible interconnection device is not put into operation, and there are significant imbalance problems in the power supply currents of the first distribution network and the second distribution network. At the same time, there are also large differences in the load rates of the two distribution networks; among them, the load rate of the first distribution network is as high as 1.075, in an overloaded state, while the load rate of the second distribution network is only 0.238, in a light-loaded state.

[0163] At 0.1 s, the phase - splitting flexible interconnection device is controlled to be put into operation, and then the three - phase unbalance of the supply currents of the two distribution networks is rectified. Although the current unbalance problem is alleviated to a certain extent, the load rates of the two distribution networks are not effectively balanced.

[0164] At 0.15 s, in addition to continuing to rectify the three - phase unbalance of the supply current, the phase - splitting flexible interconnection device also starts to transfer a certain amount of interconnection power to further balance the load rates of the two ends of the distribution network. However, due to the limitation of the interconnection capacity of the phase - splitting flexible interconnection device, it is unable to transfer a large enough interconnection power to completely balance the load rates of the two distribution networks. Nevertheless, after this adjustment, the difference in the load rates between the first distribution network and the second distribution network still decreases, but there is still a large deviation between their load rates. The first distribution network is still in an overloaded state, while the second distribution network is still in a light - loaded state.

[0165] At 0.2 s, the control - coordinated impedance is put into operation. At this time, the main task of the phase - splitting flexible interconnection device returns to only rectifying the three - phase unbalance of the distribution network, and the load - rate balance of the two distribution networks is achieved through the coordinated impedance.

[0166] It can be seen that after the coordinated impedance is put into operation, the load rate of the first distribution network is reduced to 0.741, and the load rate of the second distribution network is increased to 0.744, and their load rates reach an equilibrium state. This result shows that the method provided in this application can effectively balance the load rates of the two distribution networks.

[0167] It should be particularly noted that the transfer current of the phase - splitting flexible interconnection device can be reflected by the output currents of the first converter and the second converter.

[0168] In the third aspect of this application, a control device for a capacity - adjustable distribution - network interconnection system is provided.

[0169] Please refer to Figure 7 , which is a schematic diagram of a control device for a capacity - adjustable distribution - network interconnection system in an embodiment of this application. The device 710 is applied to the capacity - adjustable distribution - network interconnection system as described in the above embodiment. The device 710 includes:

[0170] A judgment and transfer module 711, configured to input a first preset control signal and a second preset control signal into a first converter on the side of the first distribution network and a second converter on the side of the second distribution network in the phase - splitting flexible interconnection device respectively when the first distribution network is the over - loaded side distribution network, the second distribution network is the light - loaded 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, 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;

[0171] A measurement module 712 for measuring a first interconnection voltage at an interconnection point of a first distribution network and a second interconnection voltage at an interconnection point of a second distribution network;

[0172] A determination module 713 for determining a target impedance value based on the first interconnection voltage, the second interconnection voltage, a first impedance value of the first distribution network, and a second impedance value of the second distribution network;

[0173] An adjustment and power transfer module 714 for adjusting an adjustable impedance value of a coordination impedance in the system according to the target impedance value, so that the coordination impedance absorbs an adjustable power transfer corresponding to the adjustable impedance value from the second distribution network and transmits it to the first distribution network.

[0174] In the embodiments of the present application, the relevant content of the above-mentioned power transfer judgment module 711, measurement module 712, determination module 713, and adjustment and power transfer module 714 can be referred to Figure 3 the content in the illustrated embodiments, and will not be elaborated here.

[0175] 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 embodiments.

[0176] In the embodiments of the present application, by calculating a suitable adjustable impedance value, it can be ensured that when the interconnection capacity of the split-phase flexible interconnection device is insufficient to support all power transfers, the adjustable performance of the coordination impedance is utilized to effectively transfer the remaining load, so as to ensure that both the heavy-load side distribution network and the light-load side distribution network reach a truly balanced load state.

[0177] The present application also provides a computer-readable storage medium in a fourth aspect, storing a computer program, which when executed by a processor, causes the processor to execute a regulation method for a capacity-adjustable distribution network interconnection system in the above method embodiments.

[0178] The present application also provides a computer device in a fifth aspect, including a memory and a processor, the memory storing a computer program, which when executed by the processor, causes the processor to execute a regulation method for a capacity-adjustable distribution network interconnection system in the above method embodiments.

[0179] Figure 8 shows an internal structural diagram of a computer device in some embodiments. The computer device may specifically be a terminal, a server, or a gateway. As Figure 8 shown, the computer device includes a processor, a memory, and a network interface connected through a system bus.

[0180] 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 may also store a computer program. When the computer program is executed by the processor, the processor can implement each step in the above method embodiments. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can execute each step in the above method embodiments. Those skilled in the art can understand that Figure 8 The structure shown in Figure 8 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.

[0181] Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it may include the processes of the above method embodiments.

[0182] Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided by 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 an external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0183] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of 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.

[0184] 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 to 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 fall within 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-separated flexible interconnection device and a coordinated impedance; The phase-splitting flexible interconnection device is connected to the coordination impedance 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 heavy-load side distribution network, the second distribution network is a light-load 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 coordination impedance is used to absorb the adjustable transfer power corresponding to the adjustable impedance value of the coordination impedance from the second distribution network, and transmit it to the first distribution network; The required transfer power is the sum of the maximum transfer power and the adjustable transfer power.

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 and the coordination impedance are connected through the first circuit breaker to form a first distribution network access terminal, and the phase-splitting flexible interconnection device and the coordination impedance are connected 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 any one of claims 1 to 2, characterized in that: The system also includes a controller; The controller is used to determine the adjustable impedance value according to a first interconnection voltage at an interconnection point of the first distribution network and a second interconnection voltage at an interconnection point of the second distribution network.

4. A control 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 3, characterized in that: The method comprises: In the case where the first distribution network is a heavy-load side distribution network, the second distribution network is a light-load 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; measuring a first interconnection voltage at an interconnection point of the first distribution network and a second interconnection voltage at an interconnection point of the second distribution network; determining a target impedance value according to the first interconnection voltage, the second interconnection voltage, a first impedance value of the first distribution network, and a second impedance value of the second distribution network; The adjustable impedance value of the coordination impedance in the system is adjusted according to the target impedance value, so that the coordination impedance absorbs the adjustable transfer power corresponding to the adjustable impedance value from the second distribution network and transmits it to the first distribution network.

5. The method according to claim 4, characterized in that The determining a target impedance value according to the first interconnection voltage, the second interconnection voltage, a first impedance value of the first distribution network, and a second impedance value of the second distribution network includes: Using the formula determining the target impedance value; Among them, Z abc is the target impedance value, is the first interconnect voltage, is the second interconnect voltage, Z abc1 is the first impedance, Z abc2 is the second impedance.

6. The method according to claim 4, characterized in that The method further comprises: Acquire a first current reference value of an unbalanced control part of the first converter, a zero-sequence current reference value and a regulated current reference value of a DC voltage control part, and a second current reference value of an unbalanced control part of the second converter; Inputting the first current reference value, the zero-sequence current reference value and the regulated current reference value into a first predictive control model to obtain the first preset control signal; The second current reference value is input into a second predictive control model to obtain the second preset control signal.

7. The method according to claim 6, characterized in that The obtaining of the first current reference value of the unbalanced control part of the first converter, the zero-sequence current reference value and the regulated current reference value of the DC voltage control part, and the second current reference value of the unbalanced control part of the second converter comprises: Acquire a first current phase angle of the first distribution network through a phase-locked loop, and measure a first load current of the first distribution network and a capacitor voltage of two split capacitors of the first converter; Performing a Park transformation on the first load current using the negative first current phase angle to obtain a first dq component; Obtaining a first DC component in the first dq component through a low-pass mean filter; Performing an inverse Park transformation on the first DC component using the negative first current phase angle to obtain a first negative sequence current; determining a first zero-sequence current according to the first load current; determining the first current reference value according to the first zero-sequence current and the first negative-sequence current; Determining a DC link voltage and a first DC link voltage error according to capacitor voltages of two split capacitors of the first converter; Inputting the first DC side voltage error into a first PI controller to obtain the zero-sequence current reference value; determining a second DC link voltage error according to the DC link voltage and a DC link voltage reference value of the first converter; Inputting the second DC side voltage error into a second PI controller to obtain a DC side current; determining a d-axis current reference value according to the DC side current, the DC side voltage and a d-axis component of the first interconnection voltage; Performing an inverse Pike transformation on the d-axis current reference value using the first current phase angle to obtain the regulated current reference value; Acquiring a second current phase angle of the second distribution network through a phase-locked loop, and measuring a second load current of the second distribution network; Performing a Park transformation on the second load current using the negative second current phase angle to obtain a second dq component; Obtaining a second DC component in the second 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 second negative sequence current; determining a second zero-sequence current according to the second load current; The second current reference value is determined according to the second zero-sequence current and the second negative-sequence current.

8. The method according to claim 6, characterized in that The first predictive control model includes a first output current prediction model of the first converter and a first objective function, and the first current reference value, the zero-sequence current reference value and the regulated current reference value are input into the first predictive control model to obtain the first preset control signal, including: measuring an output current of the first converter; Inputting the output current of the first converter into the first output current prediction model to obtain first output current prediction values ​​of the first converter corresponding to different switching function combinations; Determine the first target value corresponding to different switching function combinations by using the first objective function according to the first output current prediction value corresponding to different switching function combinations, the first current reference value, the zero-sequence current reference value and the regulated current reference value; Among the first target values ​​corresponding to all the switch function combinations, the switch function combination corresponding to the smallest first target value is used as the first preset control signal; The second predictive control model includes a second output current prediction model of the second converter and a second objective function, and the second current reference value is input into the second predictive control model to obtain the second preset control signal, including: measuring an output current of the second converter; Inputting the output current of the second converter into the second output current prediction model to obtain second output current prediction values ​​of the second converter corresponding to different switching function combinations; Determine the second target value corresponding to the different switching function combinations according to the second output current prediction value corresponding to the different switching function combinations and the second current reference value by using the second objective function; Among the second target values ​​corresponding to all the switching function combinations, the switching function combination corresponding to the smallest second target value is used as the second preset control signal.

9. The method according to claim 8, characterized in that The expression of the first output current prediction model is: The expression of the second output current prediction model is: Among them, i abc1,m,k+1 is the first predicted output current corresponding to the mth switch function combination at the k+1th moment, i abc1,k is the output current of the first converter corresponding to the kth moment, T s1 is the control period of the first converter, L1 is the filter inductance of the first converter, U 0,1,m,k is the output voltage of the first converter corresponding to the mth switching function combination at the kth moment, U s,abc1,k is the first interconnection voltage corresponding to the kth moment, R1 is the parasitic resistance of the first converter, i abc2,m,k+1 is the second predicted output current corresponding to the mth switch function combination at the k+1th moment, i abc2,k is the output current of the second converter corresponding to the kth moment, T s2 is the control period of the second converter, L2 is the filter inductance of the second converter, U 0,2,m,k is the output voltage of the second converter corresponding to the mth switching function combination at the kth moment, U s,abc2,k is the second interconnection voltage corresponding to the kth moment, and R2 is the parasitic resistance of the second converter.

10. The method according to claim 8, characterized in that The expression of the first objective function is: 1,m =(i a1,ref -i a1,m,k+1 ) 2 +(i b1,ref -i b1,m,k+1 ) 2 +(i c1,ref -i c1,m,k+1 ) 2 ; The expression of the second objective function is: 2,m =(i a2,ref -i a2,m,k+1 ) 2 +(i b2,ref -i b2,m,k+1 ) 2 +(i c2,ref -i c2,m,k+1 ) 2 ; Among them, g 1,m is the first target value corresponding to the mth switch function combination, i a1,ref 、i b1,ref and i c1,ref are respectively the A-phase current reference value, the B-phase current reference value and the C-phase current reference value of the sum of the first current reference value, the zero-sequence current reference value and the regulated current reference value, i a1,m,k+1 、i b1,m,k+1 and i c1,m,k+1 are respectively the A-phase current reference value, the B-phase current reference value and the C-phase current reference value in the first predicted output current corresponding to the m-th switching function combination at the k+1th moment, 2,m is the second target value corresponding to the mth switch function combination, i a2,ref 、i b2,ref and i c2,ref are respectively the A phase current reference value, the B phase current reference value and the C phase current reference value in the second current reference value, i a2,m,k+1 、i b2,m,k+1 and i c2,m,k+1 They are respectively the A-phase current reference value, the B-phase current reference value and the C-phase current reference value in the second predicted output current corresponding to the m-th switching function combination at the k+1-th moment.

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