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 combined 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 the adjustable impedance group value of the split-phase impedance group from the second power distribution network and transmits the light-load three-phase imbalance treatment power to the first 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 the new power system, a large number of new types of 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 split-phase flexible interconnection devices in the 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 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 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 of the present invention, a combined system of a split-phase impedance and a split-phase flexible interconnection device is provided, and the system includes 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 a heavily loaded distribution network and the second distribution network is a lightly loaded distribution network, the split-phase impedance group is used to absorb the light-load three-phase unbalance control power corresponding to the adjustable impedance group value of the split-phase impedance group from the second distribution network and transmit it to the first distribution network;

[0008] The split-phase 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;

[0009] Wherein, the target control power includes the heavily loaded three-phase unbalance control power and the imbalance control power of the heavy-light load rate. The sum of the heavily loaded three-phase unbalance control power and the imbalance control power of the heavy-light load rate is equal to the difference between the power to be transferred of the first distribution network and the light-load three-phase unbalance control 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 split-phase flexible interconnection device is connected to the split-phase impedance group through the first circuit breaker and forms a first access end of the distribution network. The split-phase flexible interconnection device is connected to the split-phase impedance group through the second circuit breaker and forms a second access end of the distribution network;

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

[0015] One end of the first split-phase impedance is connected to the first end of the split-phase flexible interconnection device and forms the first end of the first access end of the distribution network. The first end of the first access end of the distribution network is used to be connected to the A-phase line of the first distribution network. The other end of the first split-phase impedance is connected to the second end of the split-phase flexible interconnection device and forms the first end of the second access end of the distribution network. The first end of the second access end of the distribution network 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, the second load voltage, the second load current of the second distribution network, and the three-phase average current of the second load current.

[0020] To achieve the above object, in the 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, 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, the second load current, and the three-phase average 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 second distribution network and transmits it to the first distribution network;

[0023] Obtain the first preset control signal and the second preset control signal corresponding to the target governance 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 of the split-phase flexible interconnection device respectively, so that the split-phase 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;

[0024] Among them, the target governance power includes the heavy-load three-phase unbalance governance power and the unbalanced governance power of the light and heavy load rates. The sum of the heavy-load three-phase unbalance governance power and the unbalanced governance power of the light and heavy load rates is equal to the difference between the power to be transferred of the first distribution network and the light-load three-phase unbalance governance power.

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

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

[0027] Determine the first current reference value of the unbalanced control part of the first converter according to the first load current and the first interconnection voltage, and determine the second 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 and the second current reference value into the first predictive control model to obtain the first preset control signal;

[0029] Determine the zero-sequence current reference value and the voltage-stabilizing current reference value of the DC voltage control part of the second converter according to the retested second load current and the second interconnection voltage;

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

[0031] Optionally, the determining the first current reference value of the unbalanced control part of the first converter according to the first load current and the first interconnection voltage, and determining the second 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 distribution network through a phase-locked loop;

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

[0034] Obtain the first DC component in the first dq components through a low-pass mean filter;

[0035] Perform inverse Park transformation on the first DC component using the negative of the first current phase angle to obtain the first negative sequence current;

[0036] Determine the first zero sequence current according to the first load current;

[0037] Determine the first current reference value according to the first zero sequence current and the first negative sequence current;

[0038] 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 control power;

[0039] Perform inverse Park transformation on the d-axis current reference value and q-axis current reference value of the first converter using the first current phase angle to obtain the second current reference value.

[0040] Optionally, the determining the zero sequence current reference value and the regulated voltage current reference value of the DC voltage control part of the second converter according to the retested second load current and the second interconnected voltage includes:

[0041] Obtain the second current phase angle of the second distribution network through a phase-locked loop, and measure the capacitor voltages of two split capacitors of the second converter;

[0042] Determine the DC side voltage and the first DC side voltage error according to the capacitor voltages of 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] Inverse Park transformation is performed on the d-axis current reference value of the second converter 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 and a first objective function of the first converter. The step of inputting the first current reference value and the second current reference value into the first predictive control model to obtain the first preset control signal includes:

[0049] Measure the output current of the first converter;

[0050] Input the output current of the first converter into the first output current prediction model to obtain the predicted values of the first output current of the first converter corresponding to different switching function combinations;

[0051] Using the first objective function, determine the first objective values corresponding to different switching function combinations according to the predicted values of the first output current corresponding to different switching function combinations, the first current reference value, and the second current reference value;

[0052] Among the first objective values corresponding to all switching function combinations, take the switching function combination corresponding to the smallest first objective value 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. The step of inputting the zero-sequence current reference value, the regulated current reference value, and the zero-sequence current for light-load three-phase unbalance control corresponding to the light-load three-phase unbalance control power into the second predictive control model to obtain the second preset control signal includes:

[0054] Measure the output current of the second converter;

[0055] Input 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;

[0056] Using the second objective function, determine the second objective values corresponding to different switching function combinations according to the predicted values of the second output current corresponding to different switching function combinations, the zero-sequence current reference value, the regulated current reference value, and the zero-sequence current for light-load three-phase unbalance control;

[0057] Among the second objective values corresponding to all switching function combinations, take the switching function combination corresponding to the smallest second objective value 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] 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 A-phase current reference value, B-phase current reference value, and C-phase current reference value in the sum of the first current reference value and the second 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 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 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, Ts2 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 zero-sequence current reference value, the voltage-stabilizing current reference value and the light-load three-phase unbalanced control 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.

[0065] To achieve the above-mentioned object, the present invention provides, in a third aspect, a control device for a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device, the device being applied to a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device as described in any one of the first aspects, the device comprising:

[0066] A measurement and determination module, used to measure a first load voltage of the first distribution network, and a second load voltage and a 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 three-phase average current of the first load voltage, the second load voltage, the second load current and the second load current;

[0067] An impedance transfer module, used for 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 second distribution network, and transmits it to the first 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 management, 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 power management 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 management includes the heavy-load three-phase unbalance management power and the unbalanced management power of the light and heavy load rates, and the sum of the heavy-load three-phase unbalance management power and the unbalanced management power of the light and heavy load rates is equal to the difference between the power to be transferred of the first power distribution network and the light-load three-phase unbalance management power.

[0070] To achieve the above object, in a fourth aspect of the present invention, a computer-readable storage medium is provided, storing a computer program, when the computer program is executed by a controller, the controller is caused 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, a computer device is provided, including a memory and a controller, the memory stores a computer program, when the computer program is executed by the controller, the controller is caused to execute the method 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 second distribution network, and transmit it to the first 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 The power includes the heavy-load three-phase imbalance management power and the light-heavy load load rate imbalance management power. The sum of the heavy-load three-phase imbalance management power and the light-heavy load load rate imbalance management power is equal to the difference between the required transfer power of the first distribution network and the light-load three-phase imbalance management power; that is, the system introduces a phase-split impedance group, and cleverly combines the phase-split impedance group with the phase-split flexible interconnection device. The three-phase imbalance of the light-load side distribution network is managed through the phase-split impedance group, and the three-phase imbalance of the heavy-load side distribution network is managed through the phase-split flexible interconnection device, and the load rate imbalance of the light-heavy side distribution network is managed. 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 management 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 phase split impedance and 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 the combined system of the phase - splitting impedance and the phase - splitting 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 types of 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, extremely 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 - splitting flexible interconnection devices in the distribution network substations and achieved certain results.

[0085] However, the existing technologies still face multiple dilemmas: First, the key components of the phase - splitting flexible interconnection device use power electronic devices, and the cost of these devices is high, resulting in difficulty in initially investing in large - capacity phase - splitting flexible interconnection devices 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 - splitting flexible interconnection device, the device will no longer be able to operate effectively; In addition, the phase - splitting 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 for split-phase impedance and split-phase flexible interconnection devices to solve the problems of limited capacity, difficult capacity expansion, low efficiency, and insufficient operation flexibility of existing split-phase flexible interconnection devices, and to effectively manage power supply problems such as heavy load, light load, and three-phase imbalance without increasing 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 for split-phase impedance and split-phase flexible interconnection devices.

[0088] Please refer to Figure 1 , which is a schematic diagram of a combined system for split-phase impedance and split-phase flexible interconnection devices 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 second distribution network 140 and transmit it to the first distribution network 130; 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; where 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 difference between the power to be transferred of the first distribution network 130 and 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 three-phase unbalance degree of the first distribution network 130 are 0.83 and 6.74% respectively, and the load rate and three-phase unbalance degree of the second distribution network 140 are 0.23 and 21.92% respectively. The load rate of the first distribution network 130, 0.83, is much greater than the load rate of the second distribution network 140, 0.23. The load rates of the first distribution network 130 and the second distribution network 140 are unbalanced. The first distribution network 130 is significantly severely overloaded and has a three-phase unbalance degree of 6.45%, and the second distribution network 140 is significantly extremely lightly loaded and has 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 further adjust the power for governing the three-phase imbalance of the lightly loaded phase, 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 lightly loaded phase, 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, through the intelligent control of the combined system, the load changes and three-phase imbalance conditions in the distribution network can be responded to in real time, and the working states of the split-phase impedance group 120 and the split-phase flexible interconnection device 110 can be dynamically adjusted, so as to effectively avoid the phenomena of heavy overload and extreme light load of the distribution transformer and improve the reliability and stability of power supply.

[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 between each connection point, therefore, for different load rates and the requirement of achieving balance in the three-phase unbalance degree, the closing and opening of each connection point can be accurately controlled; for example, when there is no need for power transfer, control the third circuit breaker S3 and the fourth circuit breaker S4 to open, and when 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, for different load rates and the requirement of achieving balance in the three-phase unbalance degree, accurate control of different scenario requirements can be realized.

[0102] In addition, by introducing multiple circuit breakers (S1 to S6), the system can flexibly control the closing and opening of each connection point according to different operating requirements and fault conditions. This design enables the system to quickly respond, adjust the operating state, and ensure the stability of the distribution network and the power supply quality when facing different load changes, three-phase unbalance conditions, and fault states.

[0103] 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).

[0104] In a feasible implementation, one end of the first phase-splitting impedance is connected to the first end of the phase-splitting 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 phase-splitting impedance is connected to the second end of the phase-splitting 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 phase-splitting impedance is connected to the third end of the phase-splitting 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 phase-splitting impedance is connected to the fourth end of the phase-splitting 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 phase-splitting impedance is connected to the fourth end of the phase-splitting 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 phase-splitting impedance is connected to the fifth end of the phase-splitting 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.

[0105] It should be noted that since each phase line of the three-phase line is correspondingly connected to a phase-splitting impedance, the impedance values of the phase-splitting impedances connected to different phase lines can be adjusted according to different three-phase unbalance control requirements to achieve precise control.

[0106] In the embodiment of the present application, by introducing the phase-splitting impedance group 120 including the first phase-splitting impedance, the second phase-splitting impedance, and the third phase-splitting impedance, and respectively corresponding to each phase in the three-phase line, precise control and adjustment of different phase lines can be realized, 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.

[0107] In a feasible implementation, the system further includes a controller. The controller is used to determine the adjustable impedance group value according to the first load voltage of the first distribution network 130, as well as the second load voltage, the second load current, and the three-phase average current of the second load current of the second distribution network 140.

[0108] In some embodiments, the controller is connected to the phase-splitting impedance group 120 and is used to adjust the adjustable impedance group value of the phase-splitting impedance group 120. Further, the adjustable impedance group value includes the impedance values of each phase-splitting impedance. The controller is also respectively connected to the phase-splitting impedances in the phase-splitting impedance group 120 and is used to adjust the impedance values of each phase-splitting impedance.

[0109] 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.

[0110] In the embodiments of the present application, by introducing a controller, the adjustable impedance group value can be determined according to the first load voltage of the first distribution network 130, as well as the second load voltage, the second load current, and the three-phase average current of the second load current of the second distribution network 140, so as to solve the problems of limited capacity, high difficulty in capacity expansion, low efficiency, and insufficient operation flexibility of the existing single-phase flexible interconnection device 110, and effectively manage power supply problems such as heavy load, light load, and three-phase imbalance without increasing additional costs.

[0111] In addition, the introduction of the controller can dynamically adjust the adjustable impedance group value of the single-phase impedance group 120 according to the real-time load data (including voltage and current) of the first distribution network 130 and the second distribution network 140. This intelligent control ability enables the system to respond to load changes and three-phase imbalance conditions in the distribution network in real time, thereby ensuring the stability and quality of power supply.

[0112] The present application provides a control method for a combined system of a single-phase impedance and a single-phase flexible interconnection device in a second aspect.

[0113] Please refer to Figure 3 , which is a schematic diagram of a control method for a combined system of a single-phase impedance and a single-phase flexible interconnection device in the embodiments of the present application. This method is applied to the combined system of a single-phase impedance and a single-phase flexible interconnection device according to any one of the first aspect. The method includes:

[0114] Step 110: 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, the second load current, and the three-phase average current of the second load current.

[0115] 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 is the target impedance group value, is the second load voltage, is the first load voltage, is the three-phase average current of the second load current, is the second load current; the subscripts abc correspond to phase A, phase B, and phase C. For example, Z aThe impedance value of the first split-phase impedance corresponding to the A phase.

[0116] It should be noted that for the calculation formula of the target impedance group value in this embodiment, the first load voltage, the second load voltage, the second load current, and the three-phase average current of the second load current, etc., are all vector operations.

[0117] Step 120: 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 second distribution network and transmits it to the first distribution network.

[0118] Among them, the adjustable impedance group value includes the impedance values of each split-phase impedance in the split-phase impedance group.

[0119] 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 be obtained first, and then the impedance value in the adjustable impedance group value of the split-phase impedance group can be 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 can be 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.

[0120] Step 130: 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.

[0121] Among them, the target control power includes the heavy-load three-phase unbalance control power and the heavy-light load rate imbalance control power, and the sum of the heavy-load three-phase unbalance control power and the heavy-light load rate imbalance control power is equal to the difference between the power to be transferred of the first distribution network and the light-load three-phase unbalance control power.

[0122] 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.

[0123] 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 target control power for transferring power of the split-phase flexible interconnection device.

[0124] In some 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.

[0125] In the embodiments of the present application, by measuring the load voltage and load current 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 phase-splitting impedance group can be accurately adjusted, so as to effectively control 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 phase-splitting 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 control of the power supply problem.

[0126] In addition, this method also has the following advantages: by responding to the load changes and three-phase imbalance conditions in the distribution network in real time, dynamically adjusting the working states of the phase-splitting impedance group and the phase-splitting flexible interconnection device, effectively avoiding the phenomena of heavy overload and extreme light load of the distribution transformer. This intelligent regulation ability enables the system to adapt to the changes of the distribution network in real time, improving the stability and reliability of power supply; through the intelligent regulation of the combined system, the resources in the distribution network can be utilized more effectively, reducing unnecessary energy losses. The introduction of the phase-splitting impedance group reduces the demand for the capacity of the phase-splitting flexible interconnection device, thereby reducing the overall cost of the system; the controller can flexibly control the closing and opening of each circuit breaker according to different operating requirements and fault conditions, enabling the system to respond quickly when facing different load changes, three-phase imbalance conditions and fault states.

[0127] 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 load current of the first distribution network and the first interconnection voltage at the interconnection point, and the re-measured second load current of the second distribution network and the second interconnection voltage at the interconnection point; determining the first current reference value of the unbalanced control part of the first converter according to the first load current and the first interconnection voltage, and determining the second 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 and the second current reference value into the first predictive control model to obtain the first preset control signal; determining the zero-sequence current reference value and the voltage stabilizing current reference value of the DC voltage control part of the second converter according to the re-measured second load current and the second interconnection voltage; inputting 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.

[0128] Among them, both the first predictive control model and the second predictive control model are models preset by an operator; the first predictive control model can predict and output a first preset control signal according to the input first current reference value and second current reference value, and the second predictive control model can predict and output a second preset control signal according to the input zero-sequence current reference value, regulated voltage current reference value, and light-load three-phase unbalance control current.

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

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

[0131] In the embodiments of this application, through strategies such as precise measurement, intelligent prediction, and comprehensive governance, the control accuracy and adaptability of the combined system of the phase-splitting impedance and the phase-splitting flexible interconnection device are improved, providing strong support for the stable operation of the distribution network and the improvement of power quality.

[0132] It can be understood that precise control: by measuring the load currents of the first distribution network and the second distribution network and the voltage at the interconnection point, the operating state of the distribution network can be obtained in real time. According to these real-time data, the current reference values of the unbalance control part and the constant power control part of the first converter, as well as the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part of the second converter, can be determined. This control strategy based on real-time data can more precisely adjust the working state of the phase-splitting flexible interconnection device, thereby more effectively addressing power supply problems; intelligent prediction: introducing the first predictive control model and the second predictive control model, predicting and outputting control signals according to the input current reference values. This predictive control strategy can respond to changes in the distribution network in advance, improving the stability and reliability of the system; comprehensive governance: simultaneously considering the heavy-load three-phase unbalance governance and the imbalance governance of the heavy-light load rate of the first distribution network, as well as the light-load three-phase unbalance governance of the second distribution network, and through a comprehensive control strategy, achieving comprehensive and precise governance of power supply problems and improving power quality.

[0133] In a feasible implementation manner, determining the first current reference value of the unbalanced control part of the first converter according to the first load current and the first interconnection voltage, and determining the second current reference value of the constant power control part of the first converter according to the first interconnection voltage and the target governance power in the above embodiments includes: obtaining the first current phase angle of the first distribution network through a phase-locked loop; performing Park transformation on the first load current using the negative of the first current phase angle to obtain the first dq components; obtaining the first DC component in the first dq components through a low-pass mean filter; performing inverse Park transformation on the first DC component using the negative of the first current phase angle to obtain the first negative sequence current; determining the first zero sequence current according to the first load current; determining the first current reference value according to the first zero sequence current and the first negative sequence current; determining the d-axis current reference value and the q-axis current reference value of the first converter according to the d-axis component and the q-axis component of the first interconnection voltage and the target governance power; performing inverse Park transformation on the d-axis current reference value and the q-axis current reference value of the first converter using the first current phase angle to obtain the second current reference value.

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

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

[0136] For the determination method of the d-axis component and the q-axis component of the first interconnection voltage, in some embodiments, Park transformation can be performed on the first interconnection voltage to obtain the dq components corresponding to the first interconnection voltage; where the dq components include the d-axis component and the q-axis component. Since the voltage of the distribution network has a directional characteristic, the calculation result of the q-axis component of the first interconnection voltage is 0.

[0137] For the determination method of the d-axis current reference value and the 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 the q-axis current reference value of the first converter; where i dref1 and i qref1 are the d-axis current reference value and the q-axis current reference value of the first converter respectively, p ref1 and q ref1 are the active power and the reactive power in the target governance power respectively, V sd1 and V sq1 are the d-axis component and the q-axis component of the first interconnection voltage respectively.

[0138] In the embodiment of the present application, preferably through the above method, the current reference values required for the unbalanced control part and 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 of the system and the power supply quality.

[0139] In addition, through the design in terms of accurate control, comprehensive governance and flexibility, the control accuracy and adaptability of the split-phase flexible interconnection device are improved, providing strong support for the stable operation of the distribution network and the improvement of power quality. At the same time, this control method also reflects the development trend of the smart grid, that is, through advanced control strategies and algorithms, the intelligent management and optimized operation of the distribution network are realized.

[0140] In a feasible implementation manner, determining the zero-sequence current reference value and the regulated voltage current reference value of the DC voltage control part of the second converter according to the retested 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 two split capacitors of the second converter; determining the DC side voltage and the first DC side voltage error according to the 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 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; and performing an inverse Park transformation on the d-axis current reference value of the second converter by using the second current phase angle to obtain the regulated voltage current reference value.

[0141] For the determination method of the DC side voltage, in some embodiments, the sum value between the capacitor voltages of two split capacitors of the second converter can be used as the DC side voltage.

[0142] For the determination method of the first DC side voltage error, in some embodiments, the difference value between the capacitor voltages of two split capacitors of the second converter can be used as the first DC side voltage error.

[0143] For the determination method of the zero-sequence current reference value, in some embodiments, after inputting the first DC side voltage error into the first PI controller, the output value of the first PI controller needs to be divided by 3, and then the quotient value is used as the zero-sequence current reference value.

[0144] 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.

[0145] 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 first converter; where, i dref1 is the d-axis current reference value of the second converter, v dcup +v dcdn is the DC side voltage (i.e., the sum 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.

[0146] In the embodiments of the present application, preferably through the above method, the current reference value required for 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.

[0147] In addition, through the design in terms of precise control, comprehensive governance and flexibility, the control accuracy and adaptability of the split-phase flexible interconnection device are improved, providing strong support for the stable operation of the distribution network and the improvement of power quality. At the same time, this control method also reflects the development trend of the smart grid, that is, through advanced control strategies and algorithms, the intelligent management and optimized operation of the distribution network are realized.

[0148] In a feasible implementation manner, the first predictive 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 and the second current reference value into the first predictive control model, a first preset control signal is obtained, including: 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, the first current reference value and the second current reference value corresponding to different switching function combinations; among the first objective values corresponding to all switching function combinations, taking the switching function combination corresponding to the smallest first objective value as the first preset control signal.

[0149] 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 zero-sequence current reference value, the regulated current reference value, and the light-load three-phase unbalance control current corresponding to the light-load three-phase unbalance control power into the second predictive control model to obtain a second preset control signal, which includes: measuring the output current of the second converter; inputting the output current of the second converter into the second output current prediction model to obtain 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 zero-sequence current reference value, the regulated current reference value, and the light-load three-phase unbalance control 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.

[0150] It should be noted that different switching function combinations include the combinations of the three-phase conduction and cut-off of the upper-bridge power devices in the converter and the combinations of the three-phase conduction and cut-off of the lower-bridge power devices; 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 phase corresponding to the upper-bridge power device in the converter is conducting, and when the value is 0, it means the phase corresponding to the lower-bridge power device in the converter is conducting, otherwise, it is cut off.

[0151] 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 unbalance in the new power system.

[0152] In a feasible implementation manner, the expression of the first output current prediction model in the above embodiments is:

[0153] 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 ;

[0154] The expression of the second output current prediction model is as follows:

[0155] 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 ;

[0156] 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 A-phase current reference value, B-phase current reference value, and C-phase current reference value in the sum of the first current reference value and the second 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 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 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 values of the zero-sequence current, the regulated current, and the A-phase, B-phase, and C-phase current reference values in the sum of the light-load three-phase unbalance treatment currents 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 A-phase, B-phase, and C-phase current reference values in the second predicted output current corresponding to the m-th switch function combination at the (k + 1)-th moment, respectively.

[0157] 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.

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

[0159] Figure 4 The shown i za1 、i zb1 and i zc1 are the three-phase currents in the light-load three-phase unbalance treatment current (note that the light-load three-phase unbalance treatment current preferably uses the measured light-load three-phase unbalance treatment current. Of course, the calculated light-load three-phase unbalance treatment current, that is, the difference between the three-phase average current of the second load current and the second load current, can also be used). i an1 、i bn1 and i cn1 are the three-phase currents in the first current reference value, i babc1 is the output current of the first converter, i refabc1 is the sum of the first current reference value and the second current reference value, p ref1 and q ref1 are the active power and reactive power in the target treatment power, respectively. V sd1 is the d-axis component of the first interconnection voltage, i dref1 and iqref1 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, and dq0 / abc is the inverse Park transformation; Figure 5 The V shown 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 respectively, V sd2 is the d-axis component of the second interconnection voltage, θ2 is the second current phase angle, i babc2 is the output current of the second converter, i refabc2 is the sum of the zero-sequence current reference value, the voltage-stabilizing current reference value, and the current for mitigating three-phase unbalance under light load.

[0160] To better demonstrate the technical effects brought by this method of the present application, the present application will be explained in conjunction with the simulation waveform diagram obtained through simulation.

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

[0162] When the phase-separated impedance for governance and the phase-separated flexible interconnection device are not put into operation, the three-phase unbalance degrees of the first distribution network and the second distribution network are 6.74% and 21.92% respectively, and the load rates are 0.83 and 0.23 respectively. This indicates that the first distribution network is in heavy overload and there is three-phase unbalance, while the second distribution network is in extreme light load and has a relatively high three-phase unbalance degree.

[0163] At 0.1 s, when the phase-separated impedance group is put into operation and the power quality of the second distribution network is improved, the three-phase unbalance degree of the second distribution network is significantly reduced to 0.224%, and its power supply current becomes three-phase symmetric. However, affected by the phase-separated impedance group, the three-phase unbalance degree of the first distribution network increases to 9.35%. Moreover, the load rates of the first distribution network and the second distribution network do not change significantly, only with slight changes, that is, the load rate of the first distribution network drops to 0.75, and the load rate of the second distribution network rises to 0.31.

[0164] 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 0.559%, and its supply current becomes three-phase symmetrical. The three-phase unbalance degree of the second distribution network remains unchanged at 0.224%. The load rates of the first and second distribution networks do not change significantly, only some changes occur, that is, the load rate of the first distribution network drops to 0.68, and the load rate of the second distribution network rises to 0.37.

[0165] At 0.2 s, the split-phase flexible interconnection device starts to perform power transmission for unbalanced load rates between heavy and light loads. At this time, the load rates of the first and second distribution networks are adjusted to 0.54 and 0.53 respectively, and the load rates of the two distribution networks are balanced and both are in the 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 unbalanced load.

[0166] It can be seen that by introducing a combined system of split-phase impedance groups and split-phase flexible interconnection devices and precisely adjusting their operating parameters, effective improvement 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.

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

[0168] The present application provides a control device for a combined system of split-phase impedance and split-phase flexible interconnection devices in a third aspect.

[0169] 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 the combined system of split-phase impedance and split-phase flexible interconnection devices according to any one of the first aspects. The device 710 includes:

[0170] 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, the second load current, and the three-phase average current of the second load current;

[0171] 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 control power corresponding to the adjustable impedance group value from the second distribution network and transmits it to the first distribution network;

[0172] 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 power management, 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 management 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;

[0173] Wherein, the target power management includes a heavy-load three-phase unbalance management power and a light-heavy load rate imbalance management power, and the sum of the heavy-load three-phase unbalance management power and the light-heavy load rate imbalance management power is equal to the difference between the power to be transferred of the first power distribution network and the light-load three-phase unbalance management power.

[0174] In the embodiment of the present application, the relevant content of the above measurement and determination module 711, impedance transfer module 712 and interconnected power transfer module 713 can refer to Figure 3 the content in the illustrated embodiment, which will not be elaborated here.

[0175] It should be noted that the device 710 of the present application further includes some other modules. It can be understood that there is a one-to-one correspondence between the method and the device 710 of the present application. 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.

[0176] 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 unbalance problem of the second power distribution network (light-load side). At the same time, combined with the target power management control of the split-phase flexible interconnected device, the heavy-load three-phase unbalance and the light-heavy load rate imbalance problem of the first power distribution network (heavy-load side) can be further solved, realizing a comprehensive and accurate management of the power supply problem.

[0177] In addition, the method has the following advantages: by responding in real time to the load changes and three-phase imbalance in the distribution network, dynamically adjusting the working states of the phase-splitting impedance group and the phase-splitting flexible interconnection device, effectively avoiding the phenomena of heavy overload and extreme light load of the distribution transformer, this intelligent regulation ability enables the system to adapt to the changes of the distribution network in real time, improving the stability and reliability of power supply; through the intelligent regulation of the combined system, the resources in the distribution network can be utilized more effectively, reducing unnecessary energy losses. The introduction of the phase-splitting impedance group reduces the demand for the capacity of the phase-splitting flexible interconnection device, thereby reducing the overall cost of the system; the controller can flexibly control the closing and opening of each circuit breaker according to different operating requirements and fault conditions, enabling the system to respond quickly when facing different load changes, three-phase imbalance conditions and fault states.

[0178] In a fourth aspect, the present application also provides a computer-readable storage medium storing a computer program, which, when executed by a controller, causes the controller to execute the control method of a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device in the above method embodiment.

[0179] In a fifth aspect, the present application also provides a computer device including a memory and a controller. The memory stores a computer program, which, when executed by the controller, causes the controller to execute the control method of a combined system of a phase-splitting impedance and a phase-splitting flexible interconnection device in the above method embodiment.

[0180] 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.

[0181] 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, which, when executed by the controller, enables the controller to implement each step in the above method embodiment. The internal memory may also store a computer program, which, when executed by the controller, enables the controller to execute each step in the above method embodiment. Those skilled in the art can understand that Figure 8 the structure shown in

[0182] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods.

[0183] Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memories. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), 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.

[0184] 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.

[0185] 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 patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application 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 second distribution network and transmit it to the first 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 of the first 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 adjustable impedance group value according to the first load voltage of the first distribution network, and the second load voltage, the second load current and the three-phase average current of the second load current of the second distribution network.

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: In the case where the first distribution network is a heavy-load side distribution network and the second distribution network is a light-load side distribution network, measuring a first load voltage of the first distribution network, and a second load voltage and a second load current of the second distribution network, and determining a target impedance group value according to a three-phase average current of the first load voltage, the second load voltage, the second load current and 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 second distribution network, and transmits it to the first 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 of the first 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 load current of the first distribution network and a first interconnection voltage at an interconnection point, and re-measuring a second load current of the second distribution network and a second interconnection voltage at an interconnection point; Determine a first current reference value of an unbalanced control part of the first converter according to the first load current and the first interconnection voltage, and determine a second current reference value of a constant power control part of the first converter according to the first interconnection voltage and the target governance power; Inputting the first current reference value and the second current reference value into a first predictive control model to obtain the first preset control signal; Determine a zero-sequence current reference value and a regulated current reference value of a DC voltage control part of the second converter according to the remeasured second load current and the second interconnection voltage; The zero-sequence current reference value, the voltage-stabilizing 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 step of determining a first current reference value of an unbalanced control part of the first converter according to the first load current and the first interconnection voltage, and determining a second current reference value of a constant power control part of the first converter according to the first interconnection voltage and the target governance power, comprises: Acquire a first current phase angle of the first distribution network through a phase-locked loop; Performing a Park transformation on the first load current using the negative first current phase angle to obtain a first dq component; Obtaining a first DC component in the first dq component through a low-pass mean filter; Performing an inverse Park transformation on the first DC component using the negative first current phase angle to obtain a first negative sequence current; determining a first zero-sequence current according to the first load current; determining the first current reference value according to the first zero-sequence current and the first negative-sequence current; Determining a 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; The first current phase angle is used to perform an inverse Pike transformation on a d-axis current reference value and a q-axis current reference value of the first converter to obtain the second current reference value.

8. The method according to claim 6, characterized in that The method of determining the zero-sequence current reference value and the voltage stabilization current reference value of the DC voltage control part of the second converter according to the re-measured second load current and the second interconnection voltage comprises: 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; 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 and the second current reference value are input into the first predictive control model to obtain the first preset control signal, including: measuring an output current of the first converter; Inputting the output current of the first converter into the first output current prediction model to obtain first output current prediction values ​​of the first converter corresponding to different switching function combinations; Determine, 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, the first current reference value, and the second current reference value; Among the first target values ​​corresponding to all the switch function combinations, the switch function combination corresponding to the smallest first target value is used as the first preset control signal; The second predictive control model includes a second output current prediction model of the second converter and a second objective function, and the zero-sequence current reference value, the voltage stabilization 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 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 in the sum of the first current reference value and the second 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 switching 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 zero-sequence current reference value, the voltage-stabilizing current reference value and the light-load three-phase unbalanced control 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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