Flexible interconnection power distribution area frequency out-of-limit coordination control system and method

Abstract

The invention belongs to the technical field of micro-grid control, and particularly discloses a frequency out-of-limit coordination control system and method for a flexible interconnection power distribution area, and the system comprises a control module, a DC bus system, and a plurality of voltage source converters connected to the DC bus system. Each voltage source converter is correspondingly connected with one power distribution area, and the power distribution areas and the voltage source converters are connected with the control module; the control module is used for determining the total difference of the active power of the out-of-limit power distribution transformer area in the plurality of power distribution transformer areas is not zero and the total difference of the active power of the power distribution transformer area is not less than the total output power of the internal optical storage system, according to the total difference of the active power of the power distribution transformer area and the rated capacity of each voltage source converter, determining the total difference of the active power of the out-of-limit power distribution transformer area. And adjusting the output power of each voltage source converter so as to enable the total difference of the active power of the power distribution area to be zero. According to the invention, the frequency stability of the flexible interconnection power distribution area can be improved, and the power fluctuation of the area can be balanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of micro-grid control, and more particularly to a flexible interconnected power distribution area frequency out-of-limit coordinated control system and method. BACKGROUND

[0002] With the large-scale application of distributed power sources, the independent establishment of micro-grid operation in power distribution areas has become an important development direction to improve power supply reliability and promote on-site consumption of new energy. However, in micro-grid areas with high penetration of photovoltaic and energy storage systems, the strong randomness and low inertia characteristics of distributed power sources can cause system frequency out-of-limit and stability problems.

[0003] In the prior art, the handling of the frequency out-of-limit problem in the power distribution area focuses on adjusting the frequency by controlling the internal source and storage resources of a single area, and ignores the collaborative control potential of flexible interconnection of other adjacent areas, resulting in unsatisfactory frequency adjustment effect of the out-of-limit area and the power fluctuation of the area cannot be effectively balanced.

[0004] Therefore, how to better control the frequency out-of-limit of the micro-grid power distribution area has become a technical problem to be solved in the industry. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to better control the frequency out-of-limit of the micro-grid power distribution area, and to solve the problem that the frequency adjustment effect of the out-of-limit area in the prior art is not ideal and the power fluctuation of the area cannot be effectively balanced.

[0006] To achieve the above purpose, in a first aspect, the present application provides a flexible interconnected power distribution area frequency out-of-limit coordinated control system applied to a micro-grid system, the micro-grid system comprising a plurality of power distribution areas, comprising: a control module, a DC bus system, and a plurality of voltage source converters connected to the DC bus system respectively; Each voltage source converter is connected to one power distribution area, and each power distribution area and voltage source converter is connected to the control module; The control module is configured to, when it is determined that the active power total difference of the out-of-limit power distribution area is not zero and the active power total difference of the out-of-limit power distribution area is not less than the total output power of the internal light storage system, adjust the output power of each voltage source converter according to the active power total difference of the out-of-limit power distribution area and the rated capacity of each voltage source converter, so that the active power total difference of the out-of-limit power distribution area is zero.

[0007] Optionally, the direct current bus system comprises a direct current bus, a direct current power supply system and a direct current voltage stabilizing capacitor; the direct current bus comprises a positive direct current bus and a negative direct current bus; the direct current voltage stabilizing capacitor is connected between the positive direct current bus and the negative direct current bus. The direct current power supply system is configured to supply power to the direct current bus. The direct current voltage stabilizing capacitor is configured to stabilize the output voltage of the direct current bus.

[0008] Optionally, the direct current power supply system comprises a DC / DC converter and an energy storage unit connected in sequence. The output end of the DC / DC converter is connected to the direct current bus. The DC / DC converter is configured to connect the energy storage unit to the direct current bus to supply power to the direct current bus.

[0009] In a second aspect, the present application provides a control method applied to the flexible interconnection power distribution area frequency out-of-limit coordination control system as described in any one of the preceding aspects, comprising: Step S1, determining the total active power difference of the out-of-limit power distribution area among the plurality of power distribution areas; Step S2, in the case that the total active power difference of the out-of-limit power distribution area is not zero and the total active power difference of the out-of-limit power distribution area is not less than the total output power of the internal optical storage system of the out-of-limit power distribution area, adjusting the output power of each voltage source converter according to the total active power difference of the out-of-limit power distribution area and the rated capacity of each voltage source converter, so as to make the total active power difference of the out-of-limit power distribution area zero.

[0010] Optionally, the internal optical storage system of each power distribution area comprises a plurality of photovoltaic converters and a plurality of energy storage converters; the step S2 specifically comprises: In the case that the total active power difference of the out-of-limit power distribution area is less than zero and the total active power difference of the out-of-limit power distribution area is not less than the total output power of the internal optical storage system of the out-of-limit power distribution area, adjusting the output power of each photovoltaic converter and the output power of each energy storage converter in the out-of-limit power distribution area according to the total active power difference of the out-of-limit power distribution area, the total output power of the internal optical storage system of the out-of-limit power distribution area, the current output power of each photovoltaic converter and the current output power of each energy storage converter in the out-of-limit power distribution area; adjusting the output power of each voltage source converter according to the total active power difference of the out-of-limit power distribution area, the total output power of the internal optical storage system of the out-of-limit power distribution area and the rated capacity of each voltage source converter.

[0011] Optionally, the adjusting the output power of each voltage source converter according to the total active power difference of the over-limit power distribution area, the total output power of the over-limit power distribution area and the rated capacity of each voltage source converter comprises: determining a first target output power according to the total active power difference of the over-limit power distribution area and the total output power of the over-limit power distribution area; adjusting the output power of the voltage source converter corresponding to the over-limit power distribution area according to the first target output power; adjusting the output power of the voltage source converter corresponding to each other power distribution area except the over-limit power distribution area according to the first target output power and the rated capacity of each voltage source converter.

[0012] Optionally, the step S2 specifically comprises: in a case where it is determined that the total active power difference of the over-limit power distribution area is greater than zero and the total active power difference of the over-limit power distribution area is not less than the total output power of the over-limit power distribution area, adjusting the output power of each voltage source converter according to the total active power difference of the over-limit power distribution area and the rated capacity of each voltage source converter.

[0013] Optionally, the adjusting the output power of each voltage source converter according to the total active power difference of the over-limit power distribution area, the total output power of the over-limit power distribution area and the rated capacity of each voltage source converter comprises: determining a second target output power according to the total active power difference of the over-limit power distribution area; adjusting the output power of the voltage source converter corresponding to the over-limit power distribution area according to the second target output power; adjusting the output power of the voltage source converter corresponding to each other power distribution area except the over-limit power distribution area according to the second target output power and the rated capacity of each voltage source converter.

[0014] In a third aspect, the present application provides a computer readable storage medium, which stores a computer program, when the computer program runs on a processor, the processor executes the method described in the first aspect or any possible implementation manner of the first aspect.

[0015] In a fourth aspect, the present application provides a computer program product, when the computer program product runs on a processor, the processor executes the method described in the first aspect or any possible implementation manner of the first aspect.

[0016] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects: The application provides a flexible interconnection power distribution area frequency overrun coordination control system and method, which fully excavates the cooperative control potential of adjacent flexible interconnection power distribution areas, realizes the physical interconnection between the power distribution areas by using a DC bus system and multiple voltage source converters, and dynamically regulates and controls the cross-area resources by controlling the communication control of the voltage source converters, so as to expand the equivalent regulation capacity of the micro-grid system, avoid the frequency instability risk caused by the limited capacity of the light storage resource in a single area, and realize the rapid suppression of the power shortage / surplus of the overrun area by using the cooperative control strategy of the flexible interconnection voltage source converter, so as to control the system frequency deviation within the rated range, improve the frequency stability of the flexible interconnection power distribution area, and effectively balance the power fluctuation of the power distribution area. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a structural schematic diagram of the flexible interconnection power distribution area frequency overrun coordination control system provided by the application; Figure 2 FIG. 2 is another structural schematic diagram of the flexible interconnection power distribution area frequency overrun coordination control system provided by the application; Figure 3 FIG. 3 is a control structure diagram of the DC / DC converter provided by the application; Figure 4 FIG. 4 is a control structure diagram of the VSC converter provided by the application; Figure 5 FIG. 5 is a flow schematic diagram of the flexible interconnection power distribution area frequency overrun coordination control method provided by the application; Figure 6 FIG. 6 is a first regulation and control effect schematic diagram of the flexible interconnection power distribution area frequency overrun coordination control method provided by the application; Figure 7 FIG. 7 is a second regulation and control effect schematic diagram of the flexible interconnection power distribution area frequency overrun coordination control method provided by the application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0019] The terms "first" and "second" and the like in the specification and claims of the application are used to distinguish different objects, rather than to describe a specific order of the objects. For example, the first target output power and the second target output power are used to distinguish the target output power in different situations, rather than to describe a specific order of the target output power.

[0020] In the embodiments of the present application, the word "exemplary" or "for example" is used to mean serving as an example, instance, or illustration. Any embodiment or design described in this application as "exemplary" or "for example" should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the embodied words are used to present concepts in a particular, concrete form that is easier to understand.

[0021] In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, for example, a plurality of voltage source converters means two or more voltage source converters, and the like, unless otherwise specified.

[0022] The embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0023] Figure 1 is one of the structural diagrams of the flexible interconnected power distribution area frequency overrun coordination control system provided by the embodiments of the present application, as Figure 1 indicated, the flexible interconnected control system can be applied to a micro-grid system, wherein the micro-grid system includes a plurality of power distribution areas 1, the control system 2 includes: a control module 21, a DC bus system 22, and a plurality of voltage source converters 23 connected to the DC bus system 22 respectively; Each voltage source converter 23 is connected to one power distribution area 1, and each power distribution area 1 and voltage source converter 23 are connected to the control module 21; The control module 21 is configured to, in a case where it is determined that the total difference of active power of the overrun power distribution area 1 in the plurality of power distribution areas 1 is not zero, and the total difference of active power of the overrun power distribution area 1 is not less than the total output power of the internal light storage system 11, adjust the output power of each voltage source converter 23 according to the total difference of active power of the overrun power distribution area 1 in the plurality of power distribution areas 1 and the rated capacity of each voltage source converter 23, so that the total difference of active power of the overrun power distribution area 1 is zero.

[0024] Specifically, in the embodiments of the present application, the flexible interconnected control system can be composed of a control module, a DC bus system, and a plurality of voltage source converters (VSC) connected to the DC bus system respectively, each VSC converter is connected to one power distribution area, and each power distribution area and each VSC converter are connected to the control module.

[0025] In the embodiments of the present application, the overall structure of the flexible interconnected power distribution area with light storage system access is as Figure 1As shown, it mainly comprises a plurality of normal grid-connected distribution areas, a distribution area independently configured for micro-grid operation, and a flexible interconnection control system. Among them, a plurality of distributed energy storage and distributed photovoltaic are connected in each area, and can transmit information bidirectionally with the control module through the communication network. The flexible interconnection control system comprises hardware circuit, software control and communication network. The hardware circuit mainly comprises a plurality of VSC converters and a DC bus system. Each VSC converter is connected to the AC feeder of the corresponding distribution area.

[0026] Figure 2 Figure 2 is a structural schematic diagram of a flexible interconnection distribution area frequency out-of-limit coordination control system provided by the embodiment of the present application, as shown in Figure 2 As an optional embodiment, the DC bus system 22 can include a DC bus 221, a DC power supply system 222 and a DC voltage stabilizing capacitor 223. The DC bus 221 includes positive and negative DC buses. The DC voltage stabilizing capacitor 223 is connected between the positive and negative DC buses. The DC power supply system 222 is used to supply power to the DC bus 221. The DC voltage stabilizing capacitor 223 is used to stabilize the output voltage of the DC bus 221.

[0027] Specifically, in the embodiment of the present application, the DC bus system mainly comprises a DC bus, a DC power supply system and a DC voltage stabilizing capacitor. The structure is simple, the operation is efficient, and the DC bus system can connect each distribution area and realize power transfer and coordination control between each distribution area.

[0028] Referring back to Figure 2 , based on the above embodiment, as an optional embodiment, the DC power supply system 222 comprises a DC / DC converter 2221 and an energy storage unit 2222 connected in sequence. The output end of the DC / DC converter 2221 is connected to the DC bus 221. The DC / DC converter 2221 is used to connect the energy storage unit 2222 to the DC bus 221 to supply power to the DC bus 221.

[0029] Specifically, in the embodiment of the present application, the energy storage unit is connected through the DC / DC converter, which can be controlled by a constant DC voltage to maintain the stability of the DC voltage of the DC bus. As shown in Figure 3 , the control strategy of the DC / DC converter can be expressed as: ; ; Among them, and U dc are the rated value and the actual value of the DC voltage, respectively. is the inner loop current reference value output by the outer loop voltage; and are the proportional and integral coefficients of the outer loop control, respectively; is the actual value of the current flowing through the inductor of the DC / DC converter; d is the duty cycle of the DC / DC converter; and are the proportional and integral coefficients of the inner loop control, respectively.

[0030] As shown in Figure 4 , in the embodiments of the present application, the VSC converter control strategy of the flexible interconnection control system is as follows: the VSC converter adopts virtual synchronous generator control and has the ability to independently build microgrid operation; in addition, it can also receive the power instruction issued by the control module, transmit the required active power, and thus participate in the frequency regulation of the microgrid station area. The control equation of the VSC converter is as follows:

[0031] ; ; wherein, J represents the virtual inertia coefficient, is the damping coefficient; ω and ωn correspond to the real-time rotational angular frequency and the rated value of the internal potential of the VSC converter, respectively; θ represents the phase angle of the internal potential of the VSC converter output by the active control link; E is the amplitude reference value of the internal potential of the VSC converter output by the reactive control link; E 0 is the initial value of the internal potential amplitude; Dq characterizes the integral coefficient of the reactive control link; is the Laplace operator; the active power and reactive power reference instruction values issued by the control module are denoted as Pref , Qref , and Pvsc , Qvsc are the actual active power and reactive power output by the VSC converter, with the direction from the VSC converter to the distribution station area being the positive direction.

[0032] wherein, the three-phase voltage reference value of the VSC converter can be represented as: ; According to the three-phase voltage reference value output by the VSC converter, a control signal for controlling the AC / DC converter can be generated.

[0033] It should be noted that, as Figure 2As shown, in the embodiments of the present application, the internal light storage system of each power distribution area includes a plurality of photovoltaic converters and a plurality of energy storage converters. The distributed light storage control strategy of each power distribution area is as follows: (1) Distributed energy storage converter control strategy: The distributed energy storage adopts fixed power control, and the power instruction is calculated by the software control unit of the flexible interconnection device and then issued through the communication network.

[0034] ; Among them, , represents the inner loop current reference value; , , , respectively represent the proportional and integral coefficients of the PI control unit; the active power and reactive power reference instruction values issued by the control module are respectively denoted as , ; and , are the actual active power and reactive power output by the energy storage converter, with the flow from the energy storage to the power distribution area as the positive direction.

[0035] (2) Distributed photovoltaic converter control strategy: In normal operation, the distributed photovoltaic adopts traditional maximum power point tracking (MPPT) control to ensure efficient use of light energy resources. When the power distribution area operates in an independent networking state and faces the risk of frequency overrun, the flexible interconnection device will generate a power adjustment instruction (denoted as P pv_ref ) based on the frequency stability requirements of the area, and issue it to each photovoltaic converter through the communication network. At this time, the distributed photovoltaic converter is in a fixed power control mode.

[0036] It should be noted that the overrun power distribution area refers to the power distribution area whose actual operating frequency deviates from its rated frequency; the total active power difference refers to the total active power difference required by the overrun power distribution area, which can be expressed as: ; Among them, P x is the total active power difference required by the power distribution area; is the actual operating frequency of the power distribution area collected by the sensor; is the rated frequency of the power distribution area, generally 50Hz; and are the proportional and integral coefficients of the PI control unit.

[0037] In the embodiments of the present application, the control module can process the operation information of the flexible interconnected distribution area and the output information of each distributed light storage on one hand, and can generate the operation mode and power instruction on line and issue them to each distributed light storage converter and voltage source converter through the communication network on the other hand.

[0038] More specifically, the control module can determine the target power finally output by each VSC converter according to the total active power difference of the over-limit distribution area and the rated capacity of each VSC converter, thereby adjusting the output power of each VSC converter, and transferring the power shortage or surplus to the distribution area at risk of frequency over-limit through the power transmission path between each adjacent VSC converter, DC bus and VSC converter connected with the over-limit distribution area, so as to adjust the frequency dynamics of the over-limit distribution area, make the total active power difference of the distribution area become zero, and control the system frequency deviation within the rated range, under the condition that the total active power difference of the over-limit distribution area in the plurality of distribution areas is not zero and is not less than the total output power of the internal light storage system.

[0039] The flexible interconnected distribution area frequency over-limit coordinated control system of the embodiments of the present application can fully tap the cooperative control potential of adjacent flexible interconnected distribution areas, realize the physical interconnection between each distribution area by using the DC bus system and a plurality of voltage source converters, and expand the equivalent adjustment capacity of the micro-grid system by dynamically regulating the cross-area resources through the communication control of the control module on each voltage source converter, thereby avoiding the frequency instability risk of a single distribution area due to the limited capacity of light storage resources. Meanwhile, when the frequency over-limit power imbalance occurs in a local distribution area, the cooperative control strategy of the flexible interconnected voltage source converter can quickly suppress the power shortage / surplus of the over-limit distribution area, control the system frequency deviation within the rated range, improve the frequency stability of the flexible interconnected distribution area, and effectively balance the power fluctuation of the distribution area.

[0040] The control method of the flexible interconnected distribution area frequency over-limit coordinated control system provided by the present application will be described below. The control method described below can be correspondingly referred to the flexible interconnected distribution area frequency over-limit coordinated control system described above.

[0041] Figure 5 The control method of the flexible interconnected distribution area frequency over-limit coordinated control system provided by the present application will be described below. The control method described below can be correspondingly referred to the flexible interconnected distribution area frequency over-limit coordinated control system described above. Step S1, determining the total active power difference of the over-limit distribution area in the plurality of distribution areas; Step S2, in the case that the total active power difference of the over-limit power distribution area is determined to be not zero and the total active power difference of the over-limit power distribution area is not less than the total output power of the internal optical storage system, the output power of each voltage source converter is adjusted according to the total active power difference of the over-limit power distribution area and the rated capacity of each voltage source converter, so that the total active power difference of the over-limit power distribution area is zero.

[0042] It can be understood that the specific implementation of each method step can refer to the introduction of the detailed function implementation of each unit / module of the flexible interconnected power distribution area frequency over-limit coordinated control system, which will not be repeated here. The flexible interconnected power distribution area frequency over-limit coordinated control method of the embodiment of the application fully excavates the cooperative control potential of adjacent flexible interconnected power distribution areas, realizes the physical interconnection between each power distribution area by using the DC bus system and multiple voltage source converters, and dynamically regulates and controls the cross-area resource through the communication control of the control module to each voltage source converter, thereby expanding the equivalent regulation capacity of the micro-grid system and avoiding the frequency instability risk caused by the limited capacity of the optical storage resource in a single area. At the same time, when the frequency over-limit power imbalance occurs in a local area, the cooperative control strategy of the flexible interconnected voltage source converter can quickly suppress the power shortage / surplus of the over-limit area and control the system frequency deviation within the rated range, thereby improving the frequency stability of the flexible interconnected power distribution area and effectively balancing the power fluctuation of the power distribution area.

[0044] Based on the above embodiment, as an optional embodiment, the internal optical storage system of each power distribution area includes multiple photovoltaic converters and multiple energy storage converters; and step S2 specifically includes: In the case that the total active power difference of the over-limit power distribution area is determined to be less than zero and the total active power difference of the over-limit power distribution area is not less than the total output power of the internal optical storage system, the output power of each photovoltaic converter and the output power of each energy storage converter in the over-limit power distribution area are adjusted according to the total active power difference of the over-limit power distribution area, the total output power of the internal optical storage system of the over-limit power distribution area, and the current output power of each photovoltaic converter and the current output power of each energy storage converter. The output power of each VSC converter is adjusted according to the total active power difference of the over-limit power distribution area, the total output power of the internal optical storage system of the over-limit power distribution area, and the rated capacity of each VSC converter.

[0045] Specifically, in the embodiment of the application, the control module of the flexible interconnected control system can judge the operation state of the interconnected power distribution area based on the collected operation information.

[0046] For example, when the total active power difference of the power distribution area is less than zeroP x =0, represents that the frequency of the distribution area is stable. At this time, there is no need to adjust the frequency, so it is not discussed.

[0047] When it is monitored that there is a risk of frequency out-of-limit at the grid-connected point of the distribution area x ( x =1, 2, …, N, where N is the total number of distribution areas), that is, the operating frequency is not its rated frequency, it is considered that the distribution area x is currently operating in an independent networking mode, and the frequency coordination control is triggered to start. The control module centrally calculates the total difference of active power of the out-of-limit distribution area x .

[0048] When the total difference of active power of the out-of-limit distribution area x is less than 0 P x , it is indicated that the operating frequency in the out-of-limit distribution area x is increased, the output of the distributed light storage system is excessive, and the redundant power in the area needs to be reduced to maintain the stability of the frequency of the area.

[0049] More specifically, first, the total output power of the distributed light storage system in the out-of-limit distribution area x at the current time is calculated , that is: ; wherein, Pout,i is the output power of the i-th (i=1, 2…) photovoltaic converter in the out-of-limit distribution area x ; i Pout,i is the output power of the i-th (i=1, 2…) energy storage converter in the out-of-limit distribution area i . n At this time, if x | i |<0, i then it is indicated that the frequency stability of the area m can be maintained only by reducing the output of the distributed light storage in the out-of-limit distribution area . The photovoltaic converter is switched to constant-power control, and the power instruction issued by the control module to each light storage converter is:

[0050] ; wherein, x P* is the power instruction of the control module to the i-th photovoltaic converter in the area x . x i ​​​​​​The power command value issued by the photovoltaic and energy storage converters.

[0051] If not satisfied | |< , that is, the total active power difference of the over-limit distribution area is not less than the total output power of its internal optical storage system, which means that at this time, only by reducing the over-limit distribution area x The distributed solar storage output is not enough to maintain the area x In order to stabilize the frequency, it is necessary to transmit redundant active power through a flexible interconnection control system to achieve effective control of the substation frequency.

[0052] At this point, the control module can continue to follow the above 、 The calculation method is based on the total active power difference of the over-limit distribution station area. , the total output power of the optical storage system within the cross-limit distribution area , and the current output power of each photovoltaic inverter inside it , the current output power of each energy storage converter , determine the area where the distribution is restricted x Middle i The power command values ​​issued by each photovoltaic and energy storage converter are used to adjust the output power of each internal photovoltaic converter and the output power of each energy storage converter.

[0053] Furthermore, the control module can x The total active power difference, the total output power of the photovoltaic storage system in the distribution area and the rated capacity of each VSC converter are used to calculate the power command value issued to each VSC converter, so as to adjust the output power of each VSC converter to ensure that the power supply in the distribution area that exceeds the limit is within 100%. x The total difference in active power is 0, which ensures that the distribution area x The operating frequency is stable.

[0054] The method of the embodiment of the present application, when it is determined that the total active power difference of the out-of-limit distribution station area is less than zero, and the total active power difference of the out-of-limit distribution station area is not less than the total output power of its internal photovoltaic storage system, distributes the output power of each VSC converter and each photovoltaic and storage converter within the out-of-limit distribution station area, so as to effectively coordinate the injection of the surplus power of the out-of-limit distribution station area into other adjacent stations across stations, dynamically coordinate the distributed photovoltaic storage resources within the microgrid station area and the mutual power between the flexible interconnected stations, realize the effective regulation of the frequency of the microgrid station area, and prevent the occurrence of frequency over-limit events.

[0055] Based on the content of the above embodiments, as an optional embodiment, according to the total difference of active power of the over-limit power distribution area, the total output power of the over-limit power distribution area and the rated capacity of each VSC converter, the output power of each VSC converter is adjusted, including: determining a first target output power according to the total difference of active power of the over-limit power distribution area and the total output power of the over-limit power distribution area; adjusting the output power of the VSC converter corresponding to the over-limit power distribution area according to the first target output power; adjusting the output power of the VSC converter corresponding to each other power distribution area except the over-limit power distribution area according to the first target output power and the rated capacity of each VSC converter.

[0056] Specifically, the first target output power described in the embodiments of the application refers to the output power of the VSC converter corresponding to the over-limit power distribution area finally running through over-limit coordination control in the case of surplus power of the power distribution area.

[0057] In the embodiments of the application, the first target output power is determined according to the total difference of active power of the power distribution area and the total output power of the light storage system in the power distribution area , the output power of the VSC converter corresponding to the power distribution area is adjusted, and the output power of the VSC converter corresponding to each other power distribution area is adjusted according to the first target output power and the rated capacity of each VSC converter.

[0058] For example, assuming that four VSC converters are used to realize the interconnection of four areas w, x, y, z , the over-limit power distribution area is area x , the control module issues power instructions to each VSC converter according to the first target output power and the rated capacity of each VSC converter, and the process can be represented as:

[0059]

[0060]

[0061] ; wherein, is the power instruction value issued by the control module to the VSC x converter connected to the over-limit power distribution area x ; Sw , Sy , Sz respectively, the VSCw、 VSC y、 VSC z rated capacity of the converter; power instruction value issued by the control module to the VSC w、 VSC x、 VSC y、 VSC z power instruction value issued by the converter.

[0062] At this time, by issuing opposite power instruction values to each VSC converter, the power surplus of the over-limit distribution area x VSC x converter-DC bus-VSC w / VSC y / VSC z power transmission path of the converter, to the distribution area w, y, z running in normal grid connection, to transport the excess active power. The specific process of power transmission is as follows: When the active power instruction is issued, the over-limit distribution area x side VSC x converter receives a negative active power instruction value, i.e. an instruction to "absorb excess active power", and immediately adjusts the switch state and modulation strategy of its power module, so that the over-limit distribution area x excess active power on the AC bus is efficiently converted into DC power, and is collected and transmitted through the DC bus of the flexible interconnection control system. At the same time, the VSC converter on the side of the distribution area w , y, z side VSC converter according to the opposite active power instruction, i.e. the instruction to "output active power", performs the opposite energy conversion process, and injects the power transmitted from the DC bus into the AC bus of the distribution area w, y, z . In this way, the surplus power of the over-limit distribution area x is dynamically and controllably "transported" to the distribution area w, y, z , reducing the redundant active power in the over-limit distribution area x and achieving effective regulation of the operating frequency of the distribution area x .

[0063] The method of the embodiments of the present application controls the power instruction issued to each VSC converter by means of energy conversion, so that the over-limit distribution area and each normally operating distribution area perform opposite energy conversion processes, which can make the surplus power of the over-limit distribution area cross-distribution area, effectively achieving effective regulation of the frequency of the over-limit distribution area.

[0064] ​​​Based on the content of the above embodiment, as an optional embodiment, step S2 specifically includes: When it is determined that the total active power difference of the out-of-limit distribution substation is greater than zero and the total active power difference of the out-of-limit distribution substation is not less than the total output power of its internal photovoltaic storage system, the output power of each VSC converter is adjusted according to the total active power difference of the out-of-limit distribution substation and the rated capacity of each VSC converter.

[0065] Specifically, in the embodiment of the present application, when the restricted radio area is exceeded, x The total active power difference When the radio is out of range, x The operating frequency of the distribution area is reduced, and the absolute value of the total active power difference of the distribution area is bound to be greater than the total output power of its internal solar storage system. Therefore, it is not possible to rely solely on the cross-limit distribution area. x The distributed solar storage output within the area is not enough to meet the load demand within the area, so it is necessary to increase the output to the over-limit distribution area through a flexible interconnection control system. x Injected active power to maintain the area x Power balance and frequency stability.

[0066] Furthermore, the control module can be configured according to the cross-limit distribution station area x The total active power difference and the rated capacity of each VSC converter are used to calculate the power command value issued to each VSC converter, so as to adjust the output power of each VSC converter.

[0067] The method of the embodiment of the present application, when it is determined that the total active power difference of the out-of-limit distribution station area is greater than zero, and the total active power difference of the out-of-limit distribution station area is not less than the total output power of its internal photovoltaic storage system, can effectively introduce the surplus power of the out-of-limit distribution station area from other adjacent stations across stations by distributing the output power of each VSC converter, dynamically coordinate the distributed photovoltaic storage resources within the microgrid station area and the mutual power between the flexible interconnected stations, realize the effective regulation of the microgrid station area frequency, and prevent the occurrence of frequency out-of-limit events.

[0068] Based on the above embodiment, as an optional embodiment, adjusting the output power of each VSC converter according to the total active power difference of the over-limit distribution station area and the rated capacity of each VSC converter includes: Determining a second target output power according to the total active power difference of the over-limit distribution station area; According to the second target output power, the output power of the VSC converter corresponding to the over-limit distribution station area is adjusted; According to the second target output power and the rated capacity of each VSC converter, the output power of each VSC converter corresponding to each distribution substation except the out-of-limit distribution substation is adjusted.

[0069] Specifically, the second target output power described in the embodiment of the present application refers to the output power at which the VSC converter corresponding to the out-of-limit distribution station area is finally operated through out-of-limit coordinated control when a power shortage occurs in the distribution station area.

[0070] In the embodiment of the present application, according to the cross-limit allocation station area x The total active power difference , determine the second target output power , and output power according to the second target , adjust the cross-limit distribution station area x Corresponding VSC x Here, for example, 4 VSC converters are used to realize 4 distribution substations ( w, x, y, z ) When interconnected, the control module sends the corresponding power command value to each VSC converter. The process can be expressed as: ;

[0071]

[0072] ; in, For the control module to the station area x Connected VSC x The power command value issued by the converter; 、 、 To control the module to normal grid operation and the substation area w, y, z Connected VSC w、 VSC y、 VSC z Power command value issued by the converter.

[0073] At this time, under the coordination of the control module, the normal grid-connected area w, y, z VSC through flexible interconnected control system w / VSC y / VSC z Converter-DC Bus-VSC x The power transmission path of the converter is to the distribution station area where there is a risk of frequency exceeding the limit. x Transmit the required active power and adjust the over-limit distribution station area x frequency dynamics.

[0074] The method of the embodiment of the present application controls the power instruction issued to each VSC converter by using energy conversion, so that the out-of-limit power supply area and each normal operation power supply area perform opposite energy conversion processes, the lack of power in the out-of-limit power supply area is introduced across the power supply areas, and the frequency of the out-of-limit power supply area is effectively adjusted.

[0075] In one specific embodiment of the present application, the distribution power supply area 1 and the distribution power supply area 2 are interconnected by the VSC1 converter and the VSC2 converter. Figure 6 and Figure 7 As shown in FIG. 1, at time 0 to 2s, the distribution power supply area 1 is independently formed into a micro-grid power supply area. When the time reaches 2s, the load of the distribution power supply area 1 suddenly increases, causing the operating frequency to decrease. At this time, the control module of the flexible interconnection control system dynamically calculates the power difference required by the out-of-limit distribution power supply area, and updates the corresponding power instruction value of the VSC1 converter and the VSC2 converter. Through the cross-area power coordination control strategy of the present application, the active power and the frequency of the micro-grid distribution power supply area 1 are maintained stable. Therefore, the control strategy proposed in the present application can effectively control the system frequency deviation of the out-of-limit distribution power supply area within the rated range, and balance the power fluctuation of the power supply area.

[0076] Based on the method in the above embodiment, the embodiment of the present application provides a computer readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0077] Based on the method in the above embodiment, the embodiment of the present application provides a computer program product, which, when running on a processor, causes the processor to execute the method in the above embodiment.

[0078] It can be understood that the processor in the embodiment of the present application can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor can be a microprocessor, or any conventional processor.

[0079] The method steps in the embodiments of the present application can be implemented by means of hardware, or by means of a processor executing software instructions. The software instructions can be composed of corresponding software modules, which can be stored in a Random Access Memory (RAM), a flash memory, a Read-only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically EPROM (EEPROM), a register, a hard disk, a mobile hard disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor, so that the processor can read information from the storage medium, and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0080] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented by software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted by the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. integrated with one or more available media. The available media can be magnetic media (such as floppy disk, hard disk, magnetic tape), optical media (such as DVD), or semiconductor media (such as Solid State Disk (SSD)), etc.

[0081] It can be understood that the various numerical numbers involved in the embodiments of the present application are only for the convenience of differentiation, and do not limit the scope of the embodiments of the present application.

[0082] It should be understood that the terms such as "include" and "may include" used in the present application represent the presence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In the present application, terms such as "include" and / or "have" can be interpreted to mean that a specific characteristic, number, operation, constituent element, component or a combination thereof is present, but can not be interpreted to exclude the presence or possibility of one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0083] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, "connection" can be detachable connection, or can be non-detachable connection; can be direct connection, or can be indirect connection through intermediate medium. Among them, "fixed connection" means that the relative positional relationship after connection is unchanged. "Rotary connection" means that the relative rotation is allowed after connection. "Sliding connection" means that the relative sliding is allowed after connection. The orientation language mentioned in the embodiments of the present application, such as "top", "bottom", "inner", "outer", "left", "right", etc., is only the direction of the reference drawing, therefore, the orientation language used is to better, more clearly illustrate and understand the embodiments of the present application, and is not to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore, it cannot be understood as a limitation on the embodiments of the present application.

[0084] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A frequency over-limit coordination control system for a flexible interconnected distribution station area, characterized in that: Applied to a microgrid system, the microgrid system includes multiple distribution substations, including: A control module, a DC bus system, and a plurality of voltage source converters respectively connected to the DC bus system; Each of the voltage source converters is connected to a corresponding distribution substation, and each of the distribution substations and the voltage source converter is connected to the control module; The control module is used to adjust the output power of each voltage source converter according to the total active power difference of the out-of-limit distribution substation among the multiple distribution substations and the rated capacity of each voltage source converter so that the total active power difference of the out-of-limit distribution substation is zero.

2. The frequency over-limit coordination control system for flexible interconnected distribution station area according to claim 1 is characterized in that: The DC bus system includes a DC bus, a DC power supply system and a DC voltage stabilizing capacitor; the DC bus includes a positive DC bus and a negative DC bus; the DC voltage stabilizing capacitor is connected between the positive DC bus and the negative DC bus; The DC power supply system is used to supply power to the DC bus; The DC voltage stabilizing capacitor is used to stabilize the output voltage of the DC bus.

3. The frequency over-limit coordination control system for flexible interconnected distribution station area according to claim 2 is characterized in that: The DC power supply system includes a DC / DC converter and an energy storage unit connected in sequence; The output end of the DC / DC converter is connected to the DC bus; The DC / DC converter is used to connect the energy storage unit to the DC bus to supply power to the DC bus.

4. A control method for a frequency over-limit coordination control system for a flexible interconnected distribution station area as claimed in any one of claims 1 to 3, characterized in that: include: Step S1, determining the total active power difference of the over-limit distribution substations among the plurality of distribution substations; Step S2, when it is determined that the total active power difference of the out-of-limit distribution station area is not zero, and the total active power difference of the out-of-limit distribution station area is not less than the total output power of its internal photovoltaic storage system, adjust the output power of each of the voltage source converters according to the total active power difference of the out-of-limit distribution station area and the rated capacity of each of the voltage source converters so that the total active power difference of the out-of-limit distribution station area is zero.

5. The control method according to claim 4, characterized in that: Each of the photovoltaic storage systems within the distribution substation includes multiple photovoltaic converters and multiple energy storage converters; the step S2 specifically includes: When it is determined that the total active power difference of the out-of-limit distribution substation is less than zero and the total active power difference of the out-of-limit distribution substation is not less than the total output power of the photovoltaic storage system within the out-of-limit distribution substation, the output power of each photovoltaic converter and the output power of each energy storage converter within the out-of-limit distribution substation are adjusted according to the total active power difference of the out-of-limit distribution substation, the total output power of the photovoltaic storage system within the out-of-limit distribution substation, and the current output power of each photovoltaic converter and the current output power of each energy storage converter within the out-of-limit distribution substation; The output power of each voltage source converter is adjusted according to the total active power difference of the out-of-limit distribution station area, the total output power of the photovoltaic storage system within the out-of-limit distribution station area and the rated capacity of each voltage source converter.

6. The control method according to claim 5, characterized in that: The adjusting the output power of each voltage source converter according to the total active power difference of the out-of-limit distribution station area, the total output power of the photovoltaic storage system within the out-of-limit distribution station area, and the rated capacity of each voltage source converter includes: Determining a first target output power according to the total active power difference of the out-of-limit distribution substation area and the total output power of the solar energy storage system within the out-of-limit distribution substation area; adjusting the output power of the voltage source converter corresponding to the out-of-limit distribution station area according to the first target output power; The output power of the voltage source converters corresponding to each of the power distribution substations except the out-of-limit power distribution substation is adjusted according to the first target output power and the rated capacity of each of the voltage source converters.

7. The control method according to claim 4, characterized in that: The step S2 specifically includes: When it is determined that the total active power difference of the out-of-limit distribution station area is greater than zero and the total active power difference of the out-of-limit distribution station area is not less than the total output power of its internal photovoltaic storage system, the output power of each voltage source converter is adjusted according to the total active power difference of the out-of-limit distribution station area and the rated capacity of each voltage source converter.

8. The control method according to claim 7, characterized in that: The adjusting the output power of each voltage source converter according to the total active power difference of the over-limit distribution station area and the rated capacity of each voltage source converter includes: determining a second target output power according to the total active power difference of the over-limit distribution station area; adjusting the output power of the voltage source converter corresponding to the out-of-limit distribution station area according to the second target output power; According to the second target output power and the rated capacity of each of the voltage source converters, the output power of the voltage source converters corresponding to each of the other power distribution substations except the out-of-limit power distribution substation is adjusted.

9. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method according to any one of claims 4 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed on a processor, the processor is caused to execute the method according to any one of claims 4 to 8.

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