Combined system of split-phase impedance and split-phase flexible interconnection device and control method

Abstract

The embodiment of the invention discloses a split-phase impedance and split-phase flexible interconnection device combination system and a control method, and the method comprises the steps: enabling a first power distribution network to be a heavy-load side power distribution network, and enabling a second power distribution network to be a light-load side power distribution network; the split-phase impedance group absorbs light-load three-phase imbalance treatment power corresponding to an adjustable impedance group value of the split-phase impedance group from the first power distribution network and transmits the light-load three-phase imbalance treatment power to the second power distribution network; the split-phase flexible interconnection device absorbs the target governance power from the second power distribution network according to a first preset control signal and a second preset control signal corresponding to the target governance power, and transmits the target governance power to the first power distribution network; by introducing the split-phase impedance group, the split-phase impedance group and the split-phase flexible interconnection device are ingeniously combined, the problems that an existing split-phase flexible interconnection device is limited in capacity, large in capacity expansion difficulty, low in efficiency and insufficient in operation flexibility are solved, and on the premise that extra cost is not increased, the split-phase flexible interconnection device can be applied to the field of flexible interconnection. And the power supply problems of heavy load, light load, three-phase imbalance and the like are effectively treated.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality governance, and particularly to a combined system and control method of a split-phase impedance and a split-phase flexible interconnection device. Background Art

[0002] With the acceleration of the construction of a new power system, a large number of new power sources and loads such as distributed photovoltaics, small wind power, electric vehicles, and electric flue-cured tobacco are being connected to the low-voltage distribution network substations. This transformation has greatly enriched the diversity and flexibility of energy utilization, but at the same time has brought unprecedented challenges to the operation of the distribution network. The inconsistency of the spatio-temporal characteristics of power sources and loads has led to a series of power supply problems, such as heavy overload, extreme light load, and three-phase imbalance. These problems seriously affect the stability and power supply quality of the distribution network. To solve these problems, the industry has tried to apply split-phase flexible interconnection devices in distribution network substations and achieved certain results.

[0003] However, the existing technologies still face multiple dilemmas: First, the key components of the split-phase flexible interconnection device use power electronic devices, and the costs of these devices are high, resulting in difficulty in initially investing in large-capacity split-phase flexible interconnection devices in practical applications, thus limiting the on-site applicability; Second, with the continuous change of power sources and loads in the distribution network, when the change of power sources and loads in the distribution network exceeds the rated capacity of the split-phase flexible interconnection device, the device will no longer be able to operate effectively; In addition, the split-phase flexible interconnection device has great difficulty in expansion, high cost, low efficiency, and the operation flexibility cannot fully meet the complex requirements of the new distribution network. Summary of the Invention

[0004] Based on this, it is necessary to address the above problems and propose a combined system and control method of a split-phase impedance and a split-phase flexible interconnection device to solve the problems of limited capacity, great difficulty in expansion, low efficiency, and insufficient operation flexibility of the existing split-phase flexible interconnection device, and to effectively manage power supply problems such as heavy load, light load, and three-phase imbalance without increasing additional costs.

[0005] To achieve the above object, in a first aspect, the present invention provides a combined system of a split-phase impedance and a split-phase flexible interconnection device, the system comprising a split-phase impedance group and a split-phase flexible interconnection device;

[0006] The split-phase flexible interconnection device is connected to the split-phase impedance 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 heavy - load side distribution network and the second distribution network is the light - load side distribution network, the phase - splitting impedance group is used to absorb the light - load three - phase unbalance governance power corresponding to the adjustable impedance group value of the phase - splitting impedance group from the first distribution network and transmit it to the second distribution network;

[0008] The phase - splitting flexible interconnection device is used to absorb the target governance power from the second distribution network according to the first preset control signal and the second preset control signal corresponding to the target governance power and transmit it to the first distribution network;

[0009] Among them, the target governance power includes the heavy - load three - phase unbalance governance power and the heavy - light load rate imbalance governance power, and the sum of the heavy - load three - phase unbalance governance power and the heavy - light load rate imbalance governance power is equal to the difference between the power to be transferred between the first distribution network and the second distribution network and the light - load three - phase unbalance governance 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 is connected to the phase - splitting impedance group through the first circuit breaker and forms a first distribution network access end, and the phase - splitting flexible interconnection device is connected to the phase - splitting impedance group 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 phase - splitting impedance group includes a first phase - splitting impedance, a second phase - splitting impedance and a third phase - splitting impedance;

[0015] One end of the first phase - splitting impedance 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. 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 phase - splitting impedance 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. 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 split-phase impedance 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 connect to the B-phase line of the first distribution network. The other end of the second split-phase impedance 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 connect to the B-phase line of the second distribution network;

[0017] One end of the third split-phase impedance 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 split-phase impedance 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 impedance group value according to the first load voltage of the first distribution network, and the second negative sequence current of the second load voltage and the second load current of the second distribution network.

[0020] To achieve the above object, in a second aspect, the present invention provides a control method for a combined system of split-phase impedance and split-phase flexible interconnection device. The method is applied to the combined system of split-phase impedance and split-phase flexible interconnection device according to any one of the first aspects. The method includes:

[0021] When the first distribution network is a heavy-load side distribution network and the second distribution network is a light-load side distribution network, measure the first load voltage of the first distribution network, and the second load voltage and the second load current of the second distribution network, and determine the target impedance group value according to the first load voltage, the second load voltage, and the second negative sequence current of the second load current;

[0022] Adjust the adjustable impedance group value of the split-phase impedance group in the system according to the target impedance group value, so that the split-phase impedance group absorbs the light-load three-phase unbalance control power corresponding to the adjustable impedance group value from the first distribution network and transmits it to the second distribution network;

[0023] Obtain a first preset control signal and a second preset control signal corresponding to the target governance power, and input the first preset control signal and the second preset control signal into a first converter on the first power distribution network side and a second converter on the second power distribution network side of the split-phase flexible interconnection device respectively, so that the split-phase flexible interconnection device absorbs the target governance power from the second power distribution network according to the first preset control signal and the second preset control signal and transmits it to the first power distribution network;

[0024] Wherein, the target governance power includes a heavy-load three-phase unbalance governance power and a light-heavy load rate imbalance governance power, and the sum of the heavy-load three-phase unbalance governance power and the light-heavy load rate imbalance governance power is equal to the difference between the power to be transferred between the first power distribution network and the second power distribution network and the light-load three-phase unbalance governance power.

[0025] Optionally, the obtaining of the first preset control signal and the second preset control signal corresponding to the target governance power includes:

[0026] Measure the first interconnection voltage at the interconnection point of the first power distribution network, as well as the re-measured second load current of the second power distribution network and the second interconnection voltage at the interconnection point;

[0027] Determine a first current reference value of the constant power control part of the first converter according to the first interconnection voltage and the target governance power;

[0028] Input the first current reference value into a first predictive control model to obtain the first preset control signal;

[0029] Determine a second current reference value of the unbalance control part of the second converter, as well as a zero-sequence current reference value and a regulated voltage current reference value of the DC voltage control part according to the re-measured second load current and the second interconnection voltage;

[0030] Input the second current reference value, the zero-sequence current reference value, the regulated voltage current reference value, and the light-load three-phase unbalance governance current corresponding to the light-load three-phase unbalance governance power into a second predictive control model to obtain the second preset control signal.

[0031] Optionally, the determining of the first current reference value of the constant power control part of the first converter according to the first interconnection voltage and the target governance power includes:

[0032] Obtain the first current phase angle of the first power distribution network through a phase-locked loop;

[0033] Determine the d-axis current reference value and q-axis current reference value of the first converter according to the d-axis component and q-axis component of the first interconnected voltage, and the target governance power;

[0034] Use the first current phase angle to perform an inverse Park transformation on the d-axis current reference value and q-axis current reference value of the first converter to obtain the first current reference value.

[0035] Optionally, the determining the second current reference value of the unbalanced control part of the second converter, and the zero-sequence current reference value and regulated voltage current reference value of the DC voltage control part according to the retested second load current and the second interconnected voltage includes:

[0036] Obtain the second current phase angle of the second distribution network through a phase-locked loop, and measure the capacitor voltages of the two split capacitors of the second converter;

[0037] Use the negative of the second current phase angle to perform a Park transformation on the retested second load current to obtain second dq components;

[0038] Obtain the second DC component in the second dq components through a low-pass mean filter;

[0039] Use the negative of the second current phase angle to perform an inverse Park transformation on the second DC component to obtain the retested second negative-sequence current;

[0040] Determine the second zero-sequence current according to the retested second load current;

[0041] Determine the second current reference value according to the second zero-sequence current and the retested second negative-sequence current;

[0042] Determine the DC-side voltage and the first DC-side voltage error according to the capacitor voltages of the two split capacitors of the second converter;

[0043] Input the first DC-side voltage error into a first PI controller to obtain the zero-sequence current reference value;

[0044] Determine the second DC-side voltage error according to the DC-side voltage and the DC-side voltage reference value of the second converter;

[0045] Input the second DC-side voltage error into a second PI controller to obtain the DC-side current;

[0046] Determine the d-axis current reference value of the second converter according to the DC-side current, the DC-side voltage, and the d-axis component of the second interconnected voltage;

[0047] The d-axis current reference value of the second converter is subjected to an inverse Pike transformation using the second current phase angle to obtain the regulated current reference value.

[0048] Optionally, the first predictive control model includes a first output current prediction model of the first converter and a first objective function, and the step of inputting the first current reference value into the first predictive control model to obtain the first preset control signal includes:

[0049] measuring an output current of the first converter;

[0050] 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;

[0051] Determining first target values ​​corresponding to different switching function combinations according to first output current prediction values ​​corresponding to different switching function combinations and the first current reference values ​​by using the first objective function;

[0052] 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;

[0053] The second predictive control model includes a second output current prediction model and a second objective function of the second converter, and the second current reference value, the zero-sequence current reference value, the voltage regulated current reference value, and the light-load three-phase unbalanced governance current corresponding to the light-load three-phase unbalanced governance power are input into the second predictive control model to obtain the second preset control signal, including:

[0054] measuring an output current of the second converter;

[0055] 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;

[0056] Using the second objective function, determine the second target value corresponding to different switching function combinations according to the second output current prediction value corresponding to different switching function combinations, the second current reference value, the zero-sequence current reference value, the voltage regulation current reference value and the light-load three-phase unbalanced control current;

[0057] 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.

[0058] Optionally, the expression of the first output current prediction model is:

[0059] The expression of the first objective function is: G 1,m =(i a1,ref,k+1 -i a1,m,k+1 ) 2 +(i b1,ref,k+1 -i b1,m,k+1 ) 2

[0060] +(i c1,ref,k+1 -i c1,m,k+1 ) 2 ;

[0061] The expression of the second output current prediction model is:

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

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

[0064] Among them, 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, T s1 is the control period of the first converter, L1 is the filter inductor of the first converter, U abc1,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 load voltage corresponding to the k-th moment, i abc1,k is the output current of the first converter corresponding to the k-th moment, G 1,m is the first target value corresponding to the m-th switching function combination, i a1,ref,k+1 , i b1,ref,k+1 and i c1,ref,k+1 are respectively the A-phase current reference value, B-phase current reference value and C-phase current reference value in the first current reference value corresponding to the (k + 1)-th moment, i a1,m,k+1 , i b1,m,k+1 and i c1,m,k+1 are respectively the A-phase current reference value, B-phase current reference value and C-phase current reference value in the first predicted output current corresponding to the m-th switching function combination at the (k + 1)-th moment, 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, T s2is the control period of the second converter, L2 is the filter inductor of the second converter, U abc2,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 load voltage corresponding to the k-th moment, i abc2 (k) is the output current of the second converter corresponding to the k-th moment, G 2,m is the first target value corresponding to the m-th switching function combination, i a2,ref,k+1 、i b2,ref,k+1 and i c2,ref,k+1 are respectively the A-phase current reference value, B-phase current reference value, and C-phase current reference value in the sum of the second current reference value, zero-sequence current reference value, regulated current reference value, and light-load three-phase unbalance control current corresponding to the (k + 1)-th moment, i a2,m,k+1 、i b2,m,k+1 and i c2,m,k+1 are respectively the A-phase current reference value, B-phase current reference value, and 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.

[0065] To achieve the above object, the present invention provides, in a third aspect, a control device for a combined system of a split-phase impedance and a split-phase flexible interconnection device. The device is applied to the combined system of a split-phase impedance and a split-phase flexible interconnection device according to any one of the first aspect. The device includes:

[0066] A measurement and determination module, configured to measure the first load voltage of the first distribution network, the second load voltage and the second load current of the second distribution network when the first distribution network is a heavy-load side distribution network and the second distribution network is a light-load side distribution network, and determine a target impedance group value according to the second negative sequence current of the first load voltage, the second load voltage and the second load current;

[0067] An impedance transfer module, configured to adjust the adjustable impedance group value of the split-phase impedance group in the system according to the target impedance group value, so that the split-phase impedance group absorbs the light-load three-phase unbalance control power corresponding to the adjustable impedance group value from the first distribution network and transmits it to the second distribution network;

[0068] The interconnected power transfer module is used to obtain a first preset control signal and a second preset control signal corresponding to the target power regulation, and input the first preset control signal and the second preset control signal into a first converter on the first power distribution network side and a second converter on the second power distribution network side in the split-phase flexible interconnected device respectively, so that the split-phase flexible interconnected device absorbs the target power regulation from the second power distribution network according to the first preset control signal and the second preset control signal, and transmits it to the first power distribution network;

[0069] Wherein, the target power regulation includes a heavy-load three-phase unbalance power regulation and a light / heavy-load rate imbalance power regulation, and the sum of the heavy-load three-phase unbalance power regulation and the light / heavy-load rate imbalance power regulation is equal to the difference between the power transfer required between the first power distribution network and the second power distribution network and the light-load three-phase unbalance power regulation.

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

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

[0072] The embodiment of the present invention has the following beneficial effects: the above-mentioned system includes a phase-splitting impedance group and a phase-splitting flexible interconnection device, the phase-splitting flexible interconnection device is connected to the phase-splitting impedance group and forms 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 and the second distribution network is a light-load side distribution network, the phase-splitting impedance group is used to absorb the light-load three-phase unbalanced control power corresponding to the adjustable impedance group value of the phase-splitting impedance group from the first distribution network, and transmit it to the second distribution network. The phase-splitting flexible interconnection device is used to absorb the target control power from the second distribution network according to the first preset control signal and the second preset control signal corresponding to the target control power, and transmit it to the first distribution network, wherein the target control power includes The heavy-load three-phase imbalance control power and the light-heavy load load rate imbalance control power, the sum of the heavy-load three-phase imbalance control power and the light-heavy load load rate imbalance control power is equal to the difference between the required transfer power between the first distribution network and the second distribution network and the light-load three-phase imbalance control power; that is, the system introduces a phase-split impedance group, cleverly combines the phase-split impedance group with the phase-split flexible interconnection device, and uses the phase-split impedance group to control the three-phase imbalance of the light-load side distribution network, and uses the phase-split flexible interconnection device to control the three-phase imbalance of the heavy-load side distribution network, and the load rate imbalance of the light-heavy side distribution network. This not only solves the problems of limited capacity, difficulty in expansion, low efficiency and insufficient operation flexibility of the existing phase-split flexible interconnection device, but also can achieve effective control of power supply problems such as heavy load, light load and three-phase imbalance without increasing additional costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0074] in:

[0075] Figure 1 It is a schematic diagram of a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device in an embodiment of the present application;

[0076] Figure 2 Another schematic diagram of a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device in an embodiment of the present application;

[0077] Figure 3 Schematic diagram of a control method for a combined system of a phase split impedance and a phase split flexible interconnection device in an embodiment of the present application

[0078] Figure 4 Schematic diagram of the control strategy process of the first preset control signal in the embodiment of the present application;

[0079] Figure 5 Schematic diagram of the control strategy process of the second preset control signal in the embodiment of the present application;

[0080] Figure 6 Simulation waveform diagram in the embodiment of the present application;

[0081] Figure 7 Schematic diagram of the control device of a combined system of a phase - separated impedance and a phase - separated flexible interconnection device in the embodiment of the present application;

[0082] Figure 8 Internal structure diagram of a computer device in some embodiments. Specific 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 acceleration of the construction of the new power system, a large number of new power sources and loads such as distributed photovoltaics, small - scale wind power, electric vehicles, and electric flue - cured tobacco are being connected to the low - voltage distribution network substations. This transformation has greatly enriched the diversity and flexibility of energy utilization, but at the same time has brought unprecedented challenges to the operation of the distribution network. The inconsistency of the spatio - temporal characteristics of power sources and loads has led to a series of power supply problems, such as heavy overload, extreme light load, and three - phase imbalance. These problems seriously affect the stability and power supply quality of the distribution network. To solve these problems, the industry has tried to apply phase - separated flexible interconnection devices in the distribution network substations and achieved certain results.

[0085] However, the existing technology still faces multiple dilemmas: First, the key components of the phase - separated flexible interconnection device use power electronic devices, and the cost of these devices is high, resulting in difficulty in initially investing in a large - capacity phase - separated flexible interconnection device in actual applications, thus limiting the on - site applicability; Second, with the continuous change of the power sources and loads in the distribution network, when the change of the power sources and loads in the distribution network exceeds the rated capacity of the phase - separated flexible interconnection device, the device will no longer be able to operate effectively; In addition, the phase - separated flexible interconnection device has great difficulty in expansion, high cost, low efficiency, and its operation flexibility cannot fully meet the complex requirements of the new distribution network.

[0086] In view of the above problems, the present application proposes a combined system and control method of a split-phase impedance and a split-phase flexible interconnection device to solve the problems of limited capacity, difficult capacity expansion, low efficiency, and insufficient operation flexibility of existing split-phase flexible interconnection devices, and can effectively manage power supply problems such as heavy load, light load, and three-phase imbalance without incurring additional costs. The specific implementation principle will be described in detail in the following embodiments.

[0087] In a first aspect, the present application provides a combined system of a split-phase impedance and a split-phase flexible interconnection device.

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

[0089] Among them, the split-phase flexible interconnection device 110 is connected to the split-phase impedance group 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 heavy-load side distribution network and the second distribution network 140 is a light-load side distribution network, the split-phase impedance group 120 is used to absorb the light-load three-phase imbalance management power corresponding to the adjustable impedance group value of the split-phase impedance group 120 from the first distribution network 130 and transmit it to the second distribution network 140; the split-phase flexible interconnection device 110 is used to absorb the target management power from the second distribution network 140 according to the first preset control signal and the second preset control signal corresponding to the target management power and transmit it to the first distribution network 130; wherein, the target management power includes heavy-load three-phase imbalance management power and heavy-light load rate imbalance management power, and the sum of the heavy-load three-phase imbalance management power and the heavy-light load rate imbalance management power is equal to the power to be transferred between the first distribution network 130 and the second distribution network 140 minus the light-load three-phase imbalance management power.

[0091] Among them, the power to be transferred refers to the situation where 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, and there is a three-phase imbalance between the first distribution network 130 and the second distribution network 140 due to the heavy and light loads. In order to eliminate the three-phase imbalance between the first distribution network 130 and the second distribution network 140 and make the load rates of the first distribution network 130 and the second distribution network 140 reach the balanced load state, the power that needs to be transferred between the first distribution network 130 and the second distribution network 140; for example, the load rate and the three-phase unbalance degree of the first distribution network 130 are 1.07 and 6.45% respectively. The load rate of the first distribution network 130 is greater than 1, which is significantly overloaded and there is a three-phase unbalance degree of 6.45%. The load rate and the three-phase unbalance degree of the second distribution network 140 are 0.23 and 32.55% respectively. The load rate of the second distribution network 140 is much less than 1, which is significantly extremely lightly loaded and there is a three-phase unbalance degree of 32.55%. At this time, power needs to be transferred between the first distribution network 130 and the second distribution network 140 to eliminate the three-phase imbalance between the first distribution network 130 and the second distribution network 140 and make the load rates of the first distribution network 130 and the second distribution network 140 reach the balanced 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; both the first preset control signal and the second preset control signal are switch signals, and the first preset control signal and the second preset control signal are used to control the switch states of the converters in the phase-splitting flexible interconnection device 110.

[0093] In some embodiments, the phase-splitting impedance group 120 can be composed of one or more devices with impedance. The impedance value of the devices in the phase-splitting impedance group 120 can be adjusted to adjust the adjustable impedance group value of the phase-splitting impedance group 120, and then adjust the power for governing the three-phase imbalance of the light load, so as to meet the requirements of eliminating different three-phase unbalance degrees.

[0094] Regarding the determination method of the first preset control signal and the second preset control signal, in some embodiments, the target governing power can be determined according to the power to be transferred and the power for governing the three-phase imbalance of the light load, and then the first preset control signal and the second preset control signal corresponding to the target governing power can be determined according to the target governing power; further, existing control strategies can be adopted to determine the first preset control signal and the second preset control signal according to the target governing power.

[0095] In the embodiment of the present application, by introducing the split-phase impedance group 120, the split-phase impedance group 120 is ingeniously combined with the split-phase flexible interconnection device 110. The split-phase impedance group 120 is used to control the three-phase imbalance of the lightly loaded side distribution network, and the split-phase flexible interconnection device 110 is used to control the three-phase imbalance of the heavily loaded side distribution network, as well as to control the uneven load rate of the lightly and heavily loaded side distribution networks. This not only solves the problems of limited capacity, difficult capacity expansion, low efficiency, and insufficient operation flexibility of the existing split-phase flexible interconnection device 110, but also can effectively control the power supply problems such as heavy load, light load, and three-phase imbalance without increasing additional costs.

[0096] In addition, by precisely adjusting the split-phase impedance group 120 and the split-phase flexible interconnection device 110, the energy in the distribution network can be balanced and scheduled more flexibly, avoiding energy waste. Especially in the case of the access of new energy sources such as distributed photovoltaics and small-scale wind power, these intermittent and volatile energy sources can be utilized more effectively.

[0097] Based on Figure 1 , please refer to Figure 2 , which is another schematic diagram of a combined system of a split-phase impedance and a split-phase flexible interconnection device 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 split-phase impedance 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 split-phase impedance 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 be connected 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 be connected 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 the first converter CV1 and the second converter CV2 in the split-phase flexible interconnection device 110 respectively. 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 the A-phase line, B-phase line, C-phase line, and neutral line of the first distribution network 130 respectively, and A2, B2, C2, and N2 are the A-phase line, B-phase line, C-phase line, and neutral line of the second distribution network 140 respectively.

[0100] It should be noted that since each circuit breaker is distributed among the connection points, it is possible to accurately control the closing and opening of each connection point according to the different load rates and the requirements for balancing the three-phase unbalance degree; 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 the split-phase impedance group 120 needs to perform power transfer, control the first circuit breaker S1 and the second circuit breaker S2 to close, etc.

[0101] 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, it is possible to achieve accurate control of different scenario requirements according to the different load rates and the requirements for balancing the three-phase unbalance degree.

[0102] Please continue to refer to Figure 2 , the split-phase impedance group 120 includes a first split-phase impedance, a second split-phase impedance, and a third split-phase impedance (not labeled in the figure).

[0103] In a feasible implementation, one end of the first split-phase impedance 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 split-phase impedance 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 split-phase impedance 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 split-phase impedance 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 split-phase impedance 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 split-phase impedance 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.

[0104] It should be noted that since each phase line of the three-phase line is correspondingly connected to a split-phase impedance, the impedance values of the split-phase impedances connected to different phase lines can be adjusted according to different three-phase unbalance control requirements to achieve precise control.

[0105] In the embodiment of the present application, by introducing the split-phase impedance group 120 including the first split-phase impedance, the second split-phase impedance, and the third split-phase impedance, and respectively connecting to each phase in the three-phase line, precise control and adjustment of different phase lines can be achieved, effectively solving the three-phase unbalance problem of the second distribution network 140 (light load side) to improve the power quality management of the system.

[0106] In a feasible implementation, the system further includes a controller (not shown). The controller is used to determine the adjustable impedance group value according to the first load voltage of the first distribution network 130, the second load voltage of the second distribution network 140, and the second negative sequence current of the second load current.

[0107] In some embodiments, the controller is connected to the split-phase impedance group 120 and is used to adjust the adjustable impedance group value of the split-phase impedance group 120. Further, the adjustable impedance group value includes the impedance values of each split-phase impedance. The controller is also respectively connected to the split-phase impedances in the split-phase impedance group 120 and is used to adjust the impedance values of each split-phase impedance.

[0108] In some embodiments, the controller is respectively connected to 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, and is configured to control the opening and closing of each circuit breaker.

[0109] In the embodiments of the present application, by introducing a controller, the impedance values of the individual phase-separated impedances in the phase-separated impedance group 120 can be accurately adjusted according to the first load voltage of the first distribution network 130, as well as the second negative sequence current of the second load voltage and the second load current of the second distribution network 140, so as to solve the problems of limited capacity, difficult capacity expansion, low efficiency, and insufficient operation flexibility of the existing phase-separated flexible interconnection device 110, and effectively manage power supply problems such as heavy load, light load, and three-phase imbalance without increasing additional costs.

[0110] In addition, the controller can automatically adjust the adjustable impedance group value of the phase-separated impedance group 120 according to the load voltage and load current information of the first distribution network 130 and the second distribution network 140 monitored in real time, which greatly improves the automation level of the system, reduces the need for manual intervention, and reduces the operation and maintenance costs.

[0111] The present application provides a control method for a combined system of a phase-separated impedance and a phase-separated flexible interconnection device in a second aspect.

[0112] Please refer to Figure 3 , which is a schematic diagram of a control method for a combined system of a phase-separated impedance and a phase-separated flexible interconnection device in the embodiments of the present application. This method is applied to the combined system of a phase-separated impedance and a phase-separated flexible interconnection device according to any one of the first aspects. The method includes:

[0113] Step 310: When the first distribution network is a heavy-load side distribution network and the second distribution network is a light-load side distribution network, measure the first load voltage of the first distribution network, as well as the second load voltage and the second load current of the second distribution network, and determine the target impedance group value according to the first load voltage, the second load voltage, and the second load current.

[0114] For the determination method of the target impedance group value, in some embodiments, the formula can be used to determine the target impedance group value; where Z abc is the target impedance group value, U s,abc1 is the first load voltage, U s,abc2 is the second load voltage, I s,abc2 is the second negative sequence current of the second load current; the abc in the subscript corresponds to phase A, phase B, and phase C. For example, Z a corresponds to the impedance value of the first phase-separated impedance of phase A.

[0115] Step 320: Adjust the adjustable impedance group value of the split-phase impedance group in the system according to the target impedance group value, so that the split-phase impedance group absorbs the light-load three-phase unbalance control power corresponding to the adjustable impedance group value from the first distribution network and transmits it to the second distribution network.

[0116] Among them, the adjustable impedance group value includes the impedance values of each split-phase impedance in the split-phase impedance group.

[0117] In some embodiments, the adjustable impedance group value of the split-phase impedance group can be adjusted to the target impedance group value; of course, in other embodiments, a preset error value can also be obtained first, and then the impedance value in the adjustable impedance group value of the split-phase impedance group is adjusted to the sum value between the impedance value in the target impedance group value and the preset error value, or the impedance value in the adjustable impedance group value of the split-phase impedance group is adjusted to the difference value between the impedance value in the target impedance group value and the preset error value; among them, 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] Step 330: Obtain the first preset control signal and the second preset control signal corresponding to the target control power, and 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 in the split-phase flexible interconnection device respectively, so that the split-phase flexible interconnection device absorbs the target control power from the second distribution network according to the first preset control signal and the second preset control signal and transmits it to the first distribution network.

[0119] Among them, the target control power includes the heavy-load three-phase unbalance control power and the light / heavy load rate imbalance control power, and the sum of the heavy-load three-phase unbalance control power and the light / heavy load rate imbalance control power is equal to the difference between the power to be transferred between the first distribution network and the second distribution network and the light-load three-phase unbalance control power.

[0120] 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.

[0121] In some embodiments, both the first preset control signal and the second preset control signal can be set by the operator in advance according to the transfer of the target control power of the split-phase flexible interconnection device.

[0122] 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.

[0123] In the embodiments of the present application, by measuring the load voltages and load currents of the first distribution network and the second distribution network, and determining the target impedance group value accordingly, the adjustable impedance group value of the split-phase impedance group can be accurately adjusted, so as to effectively solve the three-phase imbalance problem of the second distribution network (light load side). At the same time, combined with the target control power of the split-phase flexible interconnection device, the heavy-load three-phase imbalance and the imbalance of heavy and light load rates of the first distribution network (heavy load side) can be further solved, realizing a comprehensive and accurate treatment of the power supply problem.

[0124] In addition, this method also has the following advantages: by dynamically adjusting the working states of the split-phase impedance group and the split-phase flexible interconnection device, it can flexibly cope with the continuous changes of the power grid source and load, avoiding the low operation efficiency caused by problems such as limited capacity and difficult capacity expansion in the traditional method. At the same time, through accurate control strategies, it can ensure that the system can maintain efficient and stable operation in different scenarios; without increasing additional costs, it realizes the effective treatment of power supply problems such as heavy load, light load, and three-phase imbalance. By optimizing the use of the split-phase impedance group and the split-phase flexible interconnection device, it reduces the dependence on traditional large-capacity equipment and lowers the construction and operation and maintenance costs of the system.

[0125] In a feasible implementation manner, step 330 in the above embodiment, obtaining the first preset control signal and the second preset control signal corresponding to the target control power, includes: measuring the first interconnection voltage at the interconnection point of the first distribution network, and the retested second load current and the second interconnection voltage at the interconnection point of the second distribution network; determining the first current reference value of the constant power control part of the first converter according to the first interconnection voltage and the target control power; inputting the first current reference value into the first predictive control model to obtain the first preset control signal; determining the second current reference value of the imbalance control part of the second converter, and the zero-sequence current reference value and the voltage stabilizing current reference value of the DC voltage control part according to the retested second load current and the second interconnection voltage; inputting the second current reference value, the zero-sequence current reference value, the voltage stabilizing current reference value, and the light-load three-phase imbalance control current corresponding to the light-load three-phase imbalance control power into the second predictive control model to obtain the second preset control signal.

[0126] Among them, 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 the first preset control signal according to the input first current reference value, and the second predictive control model can predict and output the second preset control signal according to the input second current reference value, zero-sequence current reference value, voltage stabilizing current reference value, and light-load three-phase imbalance control current.

[0127] Regarding 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.

[0128] It should be noted that in this application, the unbalance control part also refers to the power quality part; the interconnection point between the first distribution network and the second distribution network also refers to the grid connection point. It can be understood that the interconnection points of the phase-splitting flexible interconnection device with the first distribution network and the second distribution network are both selected at their grid connection points.

[0129] In the embodiments of this application, through precise measurement, calculation and prediction, precise control of the phase-splitting flexible interconnection device and the phase-splitting impedance group is achieved, thereby effectively solving power supply problems such as heavy load, light load and three-phase unbalance.

[0130] In addition, by inputting the first current reference value into the first predictive control model, an accurate first preset control signal can be obtained. By inputting the second current reference value, zero-sequence current reference value, voltage-stabilizing current reference value and light-load three-phase unbalance control current into the second predictive control model, an accurate second preset control signal can be obtained. This method makes full use of the prediction ability of the predictive control model and can adjust the switching states of the first converter and the second converter in the phase-splitting flexible interconnection device in advance, thereby effectively controlling the three-phase unbalance and uneven load rate of the heavy-load side distribution network.

[0131] In a feasible implementation manner, the determining of the first current reference value of the constant power control part of the first converter according to the first interconnection voltage and the target control power in the above embodiments includes: obtaining the first current phase angle of the first distribution network through a phase-locked loop; determining the d-axis current reference value and q-axis current reference value of the first converter according to the d-axis component and q-axis component of the first interconnection voltage and the target control power; performing an inverse Park transformation on the d-axis current reference value and q-axis current reference value of the first converter by using the first current phase angle to obtain the first current reference value.

[0132] For the determining method of the d-axis component and q-axis component of the first interconnection voltage, in some embodiments, a Park transformation can be performed on the first interconnection voltage to obtain the dq components corresponding to the first interconnection voltage; wherein, the dq components include the d-axis component and q-axis component. Since the voltage of the distribution network has a directional characteristic, the calculation result of the q-axis component of the first interconnection voltage is 0.

[0133] For the determining method of the d-axis current reference value and q-axis current reference value of the first 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 first converter; wherein, i dref1 and i qref1 are respectively the d-axis current reference value and q-axis current reference value of the first converter, p ref1 and q ref1 are respectively the active power and reactive power in the target control power, Vsd1 and V sq1 are respectively the d-axis component and the q-axis component of the first interconnection voltage.

[0134] In the embodiment of the present application, preferably through the above method, the current reference value required for the constant power control part of the first converter can be accurately obtained, that is, through accurate measurement, calculation and prediction, combined with advanced control strategies, the accurate control of the split-phase flexible interconnection device and the split-phase impedance group is realized, effectively solving the power supply problems such as heavy load, light load and three-phase imbalance, and improving the stability and power supply quality of the system.

[0135] In a feasible implementation manner, determining the second current reference value of the unbalance control part of 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 according to the re-measured second load current and the second interconnection voltage in the above embodiment includes: obtaining the second current phase angle of the second distribution network through a phase-locked loop, and measuring the capacitor voltages of the two split capacitors of the second converter; performing Park transformation on the re-measured 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 re-measured second negative-sequence current; determining the second zero-sequence current according to the re-measured second load current; determining the second current reference value according to the second zero-sequence current and the re-measured second 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 second 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 second 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 of the second converter according to the DC side current, the DC side voltage and the d-axis component of the second interconnection voltage; performing inverse Park transformation on the d-axis current reference value of the second converter using the second current phase angle to obtain the regulated voltage current reference value.

[0136] For the determination method of the second zero-sequence current, in some embodiments, the quotient obtained by dividing the sum value of the three-phase line currents in the second load current by 3 can be used as the second zero-sequence current.

[0137] For the determination method of the second current reference value, in some embodiments, the sum value between the second zero-sequence current and the second negative-sequence current can be used as the second current reference value.

[0138] For the determination method of the DC side voltage, in some embodiments, the sum value between the capacitor voltages of the two split capacitors of the second converter can be used as the DC side voltage.

[0139] 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 second converter can be used as the first DC-side voltage error.

[0140] 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 its quotient value is used as the zero-sequence current reference value.

[0141] 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 second converter can be used as the second DC-side voltage error.

[0142] For the determination method of the d-axis current reference value of the second converter, in some embodiments, the formula can be used to determine the d-axis current reference value of the second converter; where, i dref2 is the d-axis current reference value of the second converter, v dcup +v dcdn is the DC-side voltage (i.e., the sum value of the capacitor voltages of the two split capacitors of the second converter), i dc is the DC-side current, and V sd2 is the d-axis component of the second interconnection voltage.

[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 second converter can be accurately obtained, that is, through accurate measurement, calculation and prediction, combined with advanced control strategies, the accurate control of the split-phase flexible interconnection device and the split-phase impedance group is realized, effectively solving the power supply problems such as heavy load, light load and three-phase imbalance, and improving the stability and power supply quality of the system.

[0144] In a feasible implementation manner, the first prediction control model in the above embodiments includes the first output current prediction model of the first converter and the first objective function. Inputting the first current reference value into the first prediction control model to obtain the 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 the first output current prediction values of the first converter corresponding to different switching function combinations; using the first objective function to determine the first objective values corresponding to different switching function combinations according to the first output current prediction values and the first current reference value corresponding to different switching function combinations; among the first objective values corresponding to all switching function combinations, the switching function combination corresponding to the smallest first objective value is used as the first preset control signal.

[0145] The second predictive control model in the above embodiments includes a second output current prediction model of the second converter and a second objective function. Inputting the second current reference value, zero-sequence current reference value, regulated current reference value, and the unbalanced three-phase load management current corresponding to the unbalanced three-phase load management power into the second predictive control model to obtain a second preset control signal, including: 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 the predicted values of the second output current of the second converter corresponding to different switching function combinations; using the second objective function to 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, the second current reference value, zero-sequence current reference value, regulated current reference value, and unbalanced three-phase load management current; among the second objective values corresponding to all switching function combinations, taking the switching function combination corresponding to the smallest second objective value as the second preset control signal.

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

[0147] In the embodiments of the present application, through the predictive control model (including the first predictive control model and the second predictive control model), accurate prediction of the output current of the converter can be achieved. This predictive ability enables the switching function combination to be adjusted in advance to adapt to different operating conditions, which not only improves the control accuracy, response speed, energy efficiency, stability, and power quality of the system, but also reduces the operation and maintenance costs, which is of great significance for solving power supply problems such as heavy load, light load, and three-phase imbalance in the new power system.

[0148] In a feasible implementation manner, the expression of the first output current prediction model in the above embodiments is:

[0149] The expression of the first objective function is: G 1,m =(i a1,ref,k+1 -i a1,m,k+1 ) 2 +(i b1,ref,k+1 -i b1,m,k+1 ) 2 +(i c1,ref,k+1 -i c1,m,k+1 ) 2 ;

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

[0151] The expression of the second objective function is: G 2,m =(i a2,ref,k+1 -i a2,m,k+1 ) 2 +(i b2,ref,k+1 -i b2,m,k+1 ) 2 +(i c2,ref,k+1 -i c2,m,k+1 ) 2 ;

[0152] 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, T s1 is the control period of the first converter, L1 is the filter inductor of the first converter, U abc1,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 load voltage corresponding to the k-th moment, i abc1,k is the output current of the first converter corresponding to the k-th moment, G 1,m is the first target value corresponding to the m-th switching function combination, i a1,ref,k+1 , i b1,ref,k+1 and i c1,ref,k+1 are the phase A current reference value, phase B current reference value, and phase C current reference value in the first current reference value corresponding to the (k + 1)-th moment 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, 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, T s2 is the control period of the second converter, L2 is the filter inductor of the second converter, U abc2,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 load voltage corresponding to the k-th moment, i abc2 (k) is the output current of the second converter corresponding to the k-th moment, G 2,m is the first target value corresponding to the m-th switching function combination, i a2,ref,k+1 , i b2,ref,k+1 and i c2,ref,k+1They are the reference current values of phase A, phase B, and phase C in the sum of the second current reference value, zero-sequence current reference value, regulated current reference value, and light-load three-phase unbalance control current corresponding to the (k + 1)-th moment, respectively, i a2,m,k+1 、i b2,m,k+1 and i c2,m,k+1 are the reference current values of phase A, phase B, and phase C in the second predicted output current corresponding to the m-th switch function combination at the (k + 1)-th moment, respectively.

[0153] In the embodiments of the present application, a rigorous output current prediction model and an expression of the objective function are provided from a mathematical perspective. From the rigor of the mathematical logic, the accuracy of the predicted output current and the calculated target value can be ensured. Moreover, by preferably showing the above expressions, it is convenient for technicians to provide references, understand, and calculate, etc.; in addition, by using the above expressions to predict the output current, a relatively accurate output predicted current can be obtained. By using the above calculation formula to calculate the target value, an optimal switch function combination can be sought to obtain a more accurate converter control signal.

[0154] 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.

[0155] Figure 4 The shown p ref1 and q ref1 are the active power and reactive power in the target governance power respectively, V sd1 is the d-axis component of the first interconnection voltage, i dref1 and i qref1 are the d-axis current reference value and q-axis current reference value of the first converter respectively, θ1 is the first current phase angle, dq0 / abc is the inverse Park transformation, i babc1 is the output current of the first converter, i refabc1 is the first current reference value;

[0156] Figure 5 The shown i za2 、i zb2 and i zc2are respectively the three-phase currents in the light-load three-phase unbalanced control current (note, the light-load three-phase unbalanced control current preferably uses the light-load three-phase unbalanced control current obtained by measurement. Of course, the light-load three-phase unbalanced control current obtained by calculation can also be used, that is, the difference between the three-phase mean current of the second load current and the second load current), i an2 、i bn2 and i cn2 are the three-phase currents in the second current reference value, i babc1 is the output current of the second converter, i refabc2 is the sum of the second current reference value, the zero-sequence current reference value, the voltage-stabilizing current reference value and the light-load three-phase unbalanced control current, V dc_ref is the DC side voltage reference value of the second converter, V dcup and V dcdn are the capacitor voltages of the two split capacitors of the second converter, V sd2 is the d-axis component of the second interconnection voltage, and θ2 is the second current phase angle.

[0157] In order to better reflect the technical effect brought about by this method of the present application, the present application is explained in conjunction with the simulation waveform diagram obtained through simulation.

[0158] See also Figure 6 , is a simulation waveform diagram in the embodiment of the present application, Figure 6 In the simulation waveform diagram shown, the five waveforms in the list correspond to the output current of the first converter, the output current of the second converter, the supply current of the first distribution network (i.e., the first load current), the supply current of the second distribution network (i.e., the second load current), and the load rate changes of the first distribution network and the second distribution network.

[0159] When the phase-splitting impedance management and phase-splitting flexible interconnection device were not put into operation, the three-phase imbalance of the first distribution network and the second distribution network were 6.45% and 32.55% respectively, and the load factors were 1.07 and 0.23 respectively, indicating that the first distribution network was heavily overloaded and had three-phase imbalance, while the second distribution network was extremely lightly loaded and had a high three-phase imbalance.

[0160] At 0.1s, after the phase-splitting impedance group was put into use and the power quality of the second distribution network was managed, the three-phase imbalance of the second distribution network was significantly reduced to 0.08%, and its power supply current became three-phase symmetrical. However, the three-phase imbalance of the first distribution network was affected by the phase-splitting impedance group, and its three-phase imbalance increased to 11.84%, and the load rate of the first distribution network and the second distribution network did not change significantly.

[0161] At 0.15 s, the split-phase flexible interconnection device is put into operation. After the power quality of the first distribution network is improved, the three-phase unbalance degree of the first distribution network drops significantly to 0.0076%, and its supply current becomes three-phase symmetric. The three-phase unbalance degree of the second distribution network remains unchanged at 0.08%, and the load rates of the first and second distribution networks do not change significantly.

[0162] At 0.2 s, the split-phase flexible interconnection device starts power transmission for unbalanced load rate governance between heavy and light loads. At this time, the load rates of the first and second distribution networks are adjusted to 0.646 and 0.645 respectively, and the load rates of the two distribution networks are balanced and both are in an economic operation state. At the same time, the three-phase unbalance degrees of the first and second distribution networks do not change significantly, indicating that the system has effectively solved the problems of three-phase unbalance and load imbalance.

[0163] Therefore, by introducing a combined system of split-phase impedance groups and split-phase flexible interconnection devices and precisely adjusting their operating parameters, effective governance of power supply problems such as heavy loads, light loads, and three-phase unbalance can be achieved, while improving the energy utilization efficiency and operating flexibility of the distribution network.

[0164] It should be noted that the target governance current of the split-phase flexible interconnection device can be reflected by the output currents of the first converter and the second converter.

[0165] In a third aspect of the present application, a control device for a combined system of split-phase impedance and split-phase flexible interconnection devices is provided.

[0166] Please refer to Figure 7 , which is a schematic diagram of a control device for a combined system of split-phase impedance and split-phase flexible interconnection devices in an embodiment of the present application. The device 710 is applied to a combined system of split-phase impedance and split-phase flexible interconnection devices according to any item in the first aspect. The device 710 includes:

[0167] A measurement and determination module 711, configured to measure the first load voltage of the first distribution network, the second load voltage and the second load current of the second distribution network when the first distribution network is a heavy-load side distribution network and the second distribution network is a light-load side distribution network, and determine the target impedance group value according to the first load voltage, the second load voltage and the second load current;

[0168] An impedance transfer module 712, configured to adjust the adjustable impedance group value of the split-phase impedance group in the system according to the target impedance group value, so that the split-phase impedance group absorbs the light-load three-phase unbalance governance power corresponding to the adjustable impedance group value from the second distribution network and transmits it to the first distribution network;

[0169] The interconnected power transfer module 713 is configured to obtain a first preset control signal and a second preset control signal corresponding to the target governance power, and input the first preset control signal and the second preset control signal into a first converter on the first power distribution network side and a second converter on the second power distribution network side in the split-phase flexible interconnection device respectively, so that the split-phase flexible interconnection device absorbs the target governance power from the second power distribution network according to the first preset control signal and the second preset control signal, and transmits it to the first power distribution network;

[0170] In the embodiment of the present application, the relevant content of the above measurement and determination module 711, impedance power transfer module 712 and interconnected power transfer module 713 can refer to Figure 3 the content in the shown embodiment, which will not be elaborated here.

[0171] 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.

[0172] In the embodiment of the present application, by measuring the load voltage and load current of the first power distribution network and the second power distribution network, and determining the target impedance group value accordingly, the adjustable impedance group value of the split-phase impedance group can be accurately adjusted, so as to effectively manage the three-phase imbalance problem of the second power distribution network (light load side). At the same time, combined with the target governance power control of the split-phase flexible interconnection device, the heavy-load three-phase imbalance and the imbalance of heavy and light load rates of the first power distribution network (heavy load side) can be further solved, realizing a comprehensive and accurate governance of the power supply problem.

[0173] In addition, this method also has the following advantages: by dynamically adjusting the working states of the split-phase impedance group and the split-phase flexible interconnection device, it can flexibly cope with the continuous changes of the power grid source and load, avoiding the low operation efficiency caused by problems such as limited capacity and difficult capacity expansion in the traditional method. At the same time, through precise control strategies, it can ensure that the system can maintain efficient and stable operation in different scenarios; without increasing additional costs, it realizes the effective governance of power supply problems such as heavy load, light load and three-phase imbalance. By optimizing the use of the split-phase impedance group and the split-phase flexible interconnection device, it reduces the dependence on traditional large-capacity equipment and lowers the construction and operation and maintenance costs of the system.

[0174] In the fourth aspect of the present application, a computer-readable storage medium is further provided, storing a computer program, which when executed by a controller, causes the controller to execute the control method of a combined system of a split-phase impedance and a split-phase flexible interconnection device in the above method embodiment.

[0175] In a fifth aspect, the present application also provides a computer device, including a memory and a controller. The memory stores a computer program, and when the computer program is executed by the controller, the controller is caused to execute the control method of a combined system of a split-phase impedance and a split-phase flexible interconnection device in the above method embodiment.

[0176] Figure 8 The internal structure diagram of the computer device in some embodiments is shown. The computer device may 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.

[0177] 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 controller, the controller can implement each step in the above method embodiment. The internal memory may also store a computer program. When the computer program is executed by the controller, the controller can execute each step in the above method embodiment. Those skilled in the art can understand that Figure 8 the structure shown in

[0178] merely represents a block diagram of some parts of the structure 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 parts than those shown in the figure, or combine some parts, or have different component arrangements.

[0179] 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 memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. 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.

[0180] 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.

[0181] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent 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 should be subject to the appended claims.

Claims

1. A combined system of phase split impedance and phase split flexible interconnection device, characterized in that: The system includes a phase-separated impedance group and a phase-separated flexible interconnection device; The phase-splitting flexible interconnection device is connected to the phase-splitting impedance 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 heavy-load side distribution network and the second distribution network is a light-load side distribution network, the phase-splitting impedance group is used to absorb the light-load three-phase unbalanced control power corresponding to the adjustable impedance group value of the phase-splitting impedance group from the first distribution network and transmit it to the second distribution network; The phase-split flexible interconnection device is used to absorb the target management power from the second distribution network according to the first preset control signal and the second preset control signal corresponding to the target management power, and transmit it to the first distribution network; Among them, the target control power includes heavy load three-phase unbalanced control power and light and heavy load load rate unbalanced control power. The sum of the heavy load three-phase unbalanced control power and the light and heavy load load rate unbalanced control power is equal to the difference between the required transfer power between the first distribution network and the second distribution network and the light load three-phase unbalanced control 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 is connected to the phase-splitting impedance group through the first circuit breaker to form a first distribution network access end, and the phase-splitting flexible interconnection device is connected to the phase-splitting impedance group through the second circuit breaker to form a second distribution network access end; 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 phase-splitting impedance group includes a first phase-splitting impedance, a second phase-splitting impedance and a third phase-splitting impedance; One end of the first phase-splitting impedance 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 phase-splitting impedance 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 phase-splitting impedance 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 connect to the B-phase line of the first distribution network, and the other end of the second phase-splitting impedance 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 connect to the B-phase line of the second distribution network; One end of the third phase-splitting impedance 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 phase-splitting impedance 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 impedance group according to the first load voltage of the first distribution network, the second load voltage of the second distribution network, and the second negative sequence current of the second load current.

5. A control method for a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device, the method being applied to the combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device as claimed in any one of claims 1 to 4, characterized in that: The method comprises: When the first distribution network is a heavy-load side distribution network and the second distribution network is a light-load side distribution network, a first load voltage of the first distribution network, and a second load voltage and a second load current of the second distribution network are measured, and a target impedance group value is determined according to the first load voltage, the second load voltage and a second negative sequence current of the second load current; Adjusting the adjustable impedance group value of the phase impedance group in the system according to the target impedance group value, so that the phase impedance group absorbs the light-load three-phase unbalanced control power corresponding to the adjustable impedance group value from the first distribution network, and transmits it to the second distribution network; Obtaining a first preset control signal and a second preset control signal corresponding to the target governance power, and inputting the first preset control signal and the 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 in the phase-split flexible interconnection device, respectively, so that the phase-split flexible interconnection device absorbs the target governance power from the second distribution network according to the first preset control signal and the second preset control signal, and transmits it to the first distribution network; Among them, the target control power includes heavy load three-phase unbalanced control power and light and heavy load load rate unbalanced control power. The sum of the heavy load three-phase unbalanced control power and the light and heavy load load rate unbalanced control power is equal to the difference between the required transfer power between the first distribution network and the second distribution network and the light load three-phase unbalanced control power.

6. The method according to claim 5, characterized in that The obtaining of the first preset control signal and the second preset control signal corresponding to the target governance power includes: measuring a first interconnection voltage at an interconnection point of the first distribution network, and a remeasured second load current and a second interconnection voltage at an interconnection point of the second distribution network; Determining a first current reference value of a constant power control part of the first converter according to the first interconnection voltage and the target management power; Inputting the first current reference value into a first predictive control model to obtain the first preset control signal; Determine a second current reference value of an unbalanced control part of the second converter, and a zero-sequence current reference value and a regulated current reference value of a DC voltage control part according to the remeasured second load current and the second interconnection voltage; The second current reference value, the zero-sequence current reference value, the voltage regulation current reference value and the light-load three-phase unbalanced control current corresponding to the light-load three-phase unbalanced control power are input into the second predictive control model to obtain the second preset control signal.

7. The method according to claim 6, characterized in that The determining a first current reference value of a constant power control part of the first converter according to the first interconnection voltage and the target management power comprises: Acquire a first current phase angle of the first distribution network through a phase-locked loop; Determining a d-axis current reference value and a q-axis current reference value of the first converter according to a d-axis component and a q-axis component of the first interconnection voltage and the target governance power; An inverse Pike transform is performed on a d-axis current reference value and a q-axis current reference value of the first converter using the first current phase angle to obtain the first current reference value.

8. The method according to claim 6, characterized in that The method of determining the second current reference value of the unbalanced control part of the second converter, and the zero-sequence current reference value and the regulated current reference value of the DC voltage control part according to the re-measured second load current and the second interconnection voltage includes: Acquiring a second current phase angle of the second distribution network through a phase-locked loop, and measuring capacitor voltages of two split capacitors of the second converter; Performing a Park transformation on the remeasured 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 remeasured second negative sequence current; Determine a second zero-sequence current according to the remeasured second load current; determining the second current reference value according to the second zero-sequence current and the remeasured second 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 second 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 second 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 of the second converter according to the DC side current, the DC side voltage and a d-axis component of the second interconnection voltage; The d-axis current reference value of the second converter is subjected to an inverse Pike transformation using the second current phase angle to obtain the regulated current reference value.

9. 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 is 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, by using the first objective function, first target values ​​corresponding to different switching function combinations according to first output current prediction values ​​corresponding to different switching function combinations and the first current reference values; 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 and a second objective function of the second converter, and the second current reference value, the zero-sequence current reference value, the voltage regulated current reference value, and the light-load three-phase unbalanced governance current corresponding to the light-load three-phase unbalanced governance power are 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; Using the second objective function, determine the second target value corresponding to different switching function combinations according to the second output current prediction value corresponding to different switching function combinations, the second current reference value, the zero-sequence current reference value, the voltage regulation current reference value and the light-load three-phase unbalanced control current; 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.

10. The method according to claim 9, characterized in that The expression of the first output current prediction model is: The expression of the first objective function is: 1,m =(i a1,ref,k+1 -i a1,m,k+1 ) 2 +(i b1,ref,k+1 -i b1,m,k+1 ) 2 +(i c1,ref,k+1 -i c1,m,k+1 ) 2 ; The expression of the second output current prediction model is: The expression of the second objective function is: 2,m =(i a2,ref,k+1 -i a2,m,k+1 ) 2 +(i b2,ref,k+1 -i b2,m,k+1 ) 2 +(i c2,ref,k+1 -i c2,m,k+1 ) 2 ; Among them, i abc1,m,k+1 is the first predicted output current corresponding to the mth switch function combination at the k+1th time, T s1 is the control period of the first converter, L1 is the filter inductance of the first converter, U abc1,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 load voltage corresponding to the kth moment, i abc1,k is the output current of the first converter corresponding to the kth moment, G 1,m is the first target value corresponding to the mth switch function combination, i a1,ref,k+1 、i b1,ref,k+1 and i c1,ref,k+1 are respectively the A-phase current reference value, the B-phase current reference value and the C-phase current reference value of the first current reference value corresponding to the k+1th moment, 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, i abc2,m,k+1 is the second predicted output current corresponding to the mth switch function combination at the k+1th time, T s2 is the control period of the second converter, L2 is the filter inductance of the second converter, U abc2,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 load voltage corresponding to the kth moment, i abc2 (k) is the output current of the second converter corresponding to the kth moment, G 2,m is the first target value corresponding to the mth switch function combination, i a2,ref,k+1 、i b2,ref,k+1 and i c2,ref,k+1 are respectively the A-phase current reference value, the B-phase current reference value and the C-phase current reference value of the second current reference value, the zero-sequence current reference value, the voltage-stabilizing current reference value and the light-load three-phase unbalanced governance current corresponding to the k+1th moment, 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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