CN112994019B - Flexible interconnected power distribution network system - Google Patents

Abstract

The invention relates to the technical field of power distribution networks, particularly provides a flexible internet power distribution system, and aims to solve the technical problem of improving the power supply reliability of a power distribution network. For this purpose, the system according to an embodiment of the present invention includes a plurality of power grid units that are connected to each other to form a cellular networking structure, each multi-station fusion unit in the power grid unit includes a management and control device and/or a multi-port flexible multi-state switch that is constructed based on a virtual power plant technology, and a feeder line connected to each port of the multi-port flexible multi-state switch is connected to a plurality of function stations. Based on above-mentioned management and control device not only can carry out unified coordinated control to all function stations in the distribution network system, improve the power supply reliability of system, can also carry out the power supply with the electric power market and coordinate, improve the economic nature of system. Meanwhile, based on the honeycomb networking structure, each multi-station fusion unit can not only operate independently, but also can be used for realizing power flow, and the power supply reliability of the system is further improved.

Description

Flexible interconnection distribution network system

technical field

The invention relates to the technical field of distribution network, in particular to a flexible interconnection distribution network system.

Background technique

Distributed power sources (such as distributed photovoltaic power generation and distributed wind power generation) and electric vehicles have great uncertainty in time and space distribution. If a large number of distributed power sources and electric vehicles are connected to the distribution network system, It will seriously affect the stability of the power flow in the distribution network system, and then reduce the power supply reliability of the distribution network system. The current conventional distribution network system is mainly composed of distributed power sources, loads and energy storage devices (electric vehicles can be used as special carriers for energy storage devices) into multiple micro-grids (Micro-Grid), and each micro-grid is used as The controlled unit of the distribution network system, in which each microgrid is an independent power generation and distribution system, so as to reduce the impact on the stability of the power flow in the system after a large number of distributed power sources and electric vehicles are connected to the distribution network system. Impact. However, the conventional distribution network system mainly uses series-parallel connection to connect each micro-grid to other grids. Since the power loop formed by series-parallel connection cannot be switched flexibly, the micro-grid cannot fully utilize its own resources (power supply and load). etc.) to participate in the power flow adjustment of the entire distribution network system, but it still cannot effectively improve the stability of the power flow in the distribution network system. Therefore, a new distribution network solution is needed in this field to solve the above problems.

Contents of the invention

In order to overcome the above defects, the present invention is proposed to provide a flexible interconnected distribution network system that solves or at least partially solves the technical problem of how to improve the reliability of power supply of the distribution network. The system includes a plurality of grid units, each of which The power grid units respectively include a plurality of multi-station fusion units; each of the multi-station fusion units includes a management and control device and/or a multi-port flexible multi-state switch based on virtual power plant technology; each of the management and control devices is configured as Perform function management and control on the preset functional stations in each multi-station fusion unit; connect multiple preset functional stations to the feeder connected to each port in the multi-port flexible multi-state switch; for each Each grid unit, each multi-port flexible multi-state switch in the grid unit is connected to each other in sequence, and each multi-port flexible multi-state switch is also connected to the multi-port flexible multi-state switch in other grid units, so that Each grid unit is interconnected to form a honeycomb network structure.

In a technical solution of the above-mentioned flexible interconnection distribution network system, the preset functional stations include power supply functional stations and/or grid functional stations and/or load functional stations and/or energy storage functional stations; the power supply functional stations Including a new energy power generation power supply function station and a hydrogen energy power generation power supply function station, the load function station includes an electric energy load function station and a hydrogen energy load function station, each of the hydrogen power generation power supply function stations is connected with each of the hydrogen energy load The functional stations are connected to each other to form a hydrogen energy interconnection network;

The control device is further configured to perform power control and/or hydrogen energy control on the preset functional stations respectively.

In one technical solution of the above-mentioned flexible interconnection distribution network system, the multi-port flexible multi-state switch includes a plurality of voltage source converters, and each of the voltage source converters includes a first bidirectional input/output side and a a second bidirectional input/output side;

The first bidirectional input/output sides of each of the voltage source converters are respectively connected in parallel;

The second bidirectional input/output side of each of the voltage source converters respectively forms each port of the multi-port flexible multi-state switch.

In a technical solution of the above-mentioned flexible interconnection distribution network system, the management and control device is further configured to separately control the multi-port flexible multi-state switch through the following operations according to the operating status of the feeder connected to each port of the multi-port flexible multi-state switch: The working mode of the voltage source converter corresponding to each port in the port flexible multi-state switch:

When each feeder is in normal operation state, control one voltage source converter to operate in U _dc _Q control mode, and control other voltage source converters to operate in P_Q control mode;

When it is detected that a feeder is faulty and loses power, obtain the voltage source converter corresponding to the feeder access port before the fault occurs, and use the voltage source converter as the fault side voltage source converter , using other voltage source converters as non-fault side voltage source converters;

If the fault-side voltage source converter adopts the P_Q control mode before the fault occurs, control the fault-side voltage source converter to switch to U _{ac_f} control mode operation, and control all The voltage source converter on the fault side is switched to the P_Q control mode again;

If the fault-side voltage source converter used the U _dc _Q control mode before the fault occurred, then control the fault-side voltage source converter to switch to U _ac _f control mode operation, and control a non-fault side voltage source converter is switched to U _dc _Q control mode to operate, and after the fault is recovered, control the fault side voltage source converter to switch to U _dc _Q control mode again, and control the one non-fault side The voltage source converter switches to the P_Q control mode again.

In a technical solution of the above-mentioned flexible interconnection distribution network system, the management and control device is further configured to perform the following operations:

Before the voltage source converter on the fault side is switched to the U _ac _f control mode, the voltage reference value and the frequency reference value of the U _ac _f control mode are respectively obtained using the secondary control strategy applied to the droop control, so that the When the voltage source converter on the fault side operates in the U _ac _f control mode according to the voltage reference value and the frequency reference value, it can make its AC side voltage amplitude and frequency, and the voltage source converter on the fault side The amplitude and frequency of the AC voltage on the feeder connection side of each functional station connected to the feeder connected to the corresponding port of the converter should be consistent.

In a technical solution of the above-mentioned flexible interconnection distribution network system, the grid unit also includes a public connection point, and the multi-port flexible multi-state switch in each multi-station fusion unit in the grid unit is respectively connected to the public connection point point connection, so as to connect with the external power grid through the public connection point.

The above-mentioned one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

In implementing the technical solution of the present invention, the flexible interconnection distribution network system may include multiple grid units, and each grid unit may include multiple multi-station fusion units; each multi-station fusion unit may include The management and control device and/or multi-port flexible multi-state switch; each management and control device can be configured to control the preset function stations in each multi-station fusion unit (including but not limited to: power supply function station, grid function station, load function station and energy storage function station) for function control. The feeder connected to each port of the multi-port flexible multi-state switch is respectively connected to multiple preset functional stations. Based on the above-mentioned management and control device, all functional stations in the flexible interconnected distribution network system can be unified and coordinated to realize the aggregation and coordination optimization of distributed power sources, energy storage systems, controllable loads, electric vehicles and other functional stations in the system. The power supply can be coordinated with the power market through the control device to improve the economy of the flexible interconnected distribution network system. In addition, for each grid unit, each multi-port flexible multi-state switch in the grid unit is connected to each other in sequence, and each multi-port flexible multi-state switch is also connected to a multi-port flexible multi-state switch in other grid units , so that each grid unit is interconnected to form a honeycomb network structure. Based on this honeycomb network structure, under the normal operation of the flexible interconnection distribution network system, each multi-station fusion unit can operate independently of each other, and the redundant power generated by the distributed power supply in the power supply function station in the multi-station fusion unit It can be transmitted to adjacent multi-station fusion units; in case of failure, the adjacent multi-station fusion units can perform power flow mutual aid, which improves the economy, reliability and flexibility of the entire flexible interconnection distribution network system.

Description of drawings

Describe the specific embodiment of the present invention below with reference to accompanying drawing, in the accompanying drawing:

Fig. 1 is the main structural block diagram of the flexible interconnection distribution network system according to an embodiment of the present invention;

Fig. 2 is a main structural block diagram of a multi-station fusion unit according to an embodiment of the present invention;

Fig. 3 is a schematic diagram of signal flow/energy flow between components in a multi-station fusion unit according to an embodiment of the present invention.

Detailed ways

Some embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention, and are not intended to limit the protection scope of the present invention.

In the description of the present invention, "module" and "unit" may include hardware, software or a combination of both. A module/unit may include hardware circuits, various suitable sensors, communication ports, memory, and may also include software parts, such as program codes, or a combination of software and hardware. The term "A and/or B" means all possible combinations of A and B, such as only A, only B or A and B.

Some terms involved in the present invention are firstly explained here.

A flexible multi-state switch (Flexible Multi-State Switch, FMSS) refers to a power electronic device based on power electronic devices with functions such as power flow mutual assistance and voltage support. According to the type of power conversion structure adopted, flexible multi-state switches include but are not limited to: flexible multi-state switches based on AC-DC-AC power conversion structure (AC/DC/AC), flexible multi-state switches based on AC-AC power conversion structure (AC/ AC) flexible multi-state switch, flexible multi-state switch based on alternating-direct power conversion structure (AC/DC), flexible multi-state switch based on direct-direct power conversion structure (DC/DC), etc. The multi-port flexible multi-state switch refers to a flexible multi-state switch with multiple power input/output ports.

Functional stations refer to systems, devices, and equipment related to power sources, grids, loads, and energy storage in energy systems such as power systems. Functional stations may include power supply functional stations and/or grid functional stations and/or load functional stations and/or energy storage functional stations. Power supply functional stations include but are not limited to hydrogen power generation power supply functional stations and new energy power generation functional stations such as photovoltaic power supply functional stations. Load function stations include but are not limited to hydrogen energy load function stations and electric energy load function stations such as electric vehicle charging stations. It should be noted that those skilled in the art can flexibly set the functional stations in the flexible interconnection distribution network system according to actual needs, as long as the functional stations can communicate and interact with external systems, and have the ability to send operating status to external systems and receive external system information. The functions such as the running command sent can be used. For example: In addition to the above-mentioned functional stations in the flexible interconnection power distribution system, heat supply stations and environmental monitoring stations can also be arranged. Under the premise of not deviating from the technical principle of the present invention, any technical solution that changes the number and/or type of functional stations in the flexible interconnection distribution network system falls within the scope of protection of the present invention.

The flexible interconnection distribution network system of the embodiment of the present invention will be specifically described below.

In the embodiment of the present invention, the flexible interconnection distribution network system may include multiple grid units, and each grid unit may include multiple multi-station fusion units. Each multi-station fusion unit may include a management and control device based on virtual power plant technology and/or a multi-port flexible multi-state switch. In addition, each multi-station fusion unit is also provided with a plurality of preset function stations, and each management and control device can be configured to perform function control on the preset function stations in each multi-station fusion unit. Taking a multi-station fusion unit equipped with a management and control device and a multi-port flexible multi-state switch as an example, the management and control device, multi-port flexible multi-state switch and function station in the multi-station fusion unit will be described in detail below.

1. Function station

In the embodiment of the present invention, the functional stations may include power supply functional stations and/or grid functional stations and/or load functional stations and/or energy storage functional stations. Further, in an implementation of the embodiment of the present invention, the power supply function station may include a new energy power generation power supply function station and a hydrogen energy generation power supply function station, and the load function station may include an electric energy load function station and a hydrogen energy load function station, wherein, Each hydrogen power generation power supply functional station is connected to each hydrogen energy load functional station to form a hydrogen energy interconnection network. Correspondingly, the management and control device may be further configured to perform power management and/or power management and control on the functional stations in the multi-station fusion unit. For example, the management and control device can control the power of the new energy power generation power station and/or the electric energy load function station and/or the grid function station and/or the energy storage The function station controls the hydrogen energy, that is to say, the control device not only has the function of controlling the power of the function station, but also has the function of controlling the hydrogen energy of the function station. It should be noted that those skilled in the art can flexibly set the specific control mode of power management and control in the management and control device and the specific control mode of hydrogen energy management and control according to actual needs, and control the power management and control of the management and control device without departing from the technical principles of the present invention. The changed/replaced technical solutions related to the specific control methods of hydrogen energy management and control all fall within the protection scope of the present invention.

2. Multi-port flexible multi-state switch

In the embodiment of the present invention, for each grid unit, each multi-port flexible multi-state switch in the grid unit is connected to each other in sequence, and each multi-port flexible multi-state switch is also connected to a multi-port flexible multi-state switch in other grid units. The flexible multi-state switch is connected so that each grid unit is interconnected to form a honeycomb network structure. In addition, in this embodiment, a plurality of preset functional stations are respectively connected to the feeder connected to each port of each multi-port flexible multi-state switch.

Referring to accompanying drawing 1, Fig. 1 is a main structural block diagram of a flexible interconnection distribution network system according to an embodiment of the present invention. Wherein, the flexible interconnected distribution network system includes multiple grid units, and each grid unit may include multiple multi-station fusion units. The following takes the grid unit composed of multi-station fusion units 1-6 shown on the right side of FIG. 1 as an example for specific description. As shown in FIG. 1 , multi-station fusion units 1-6 respectively include 3-port FMSS, 3-port FMSS, 4-port FMSS, 3-port FMSS, 3-port FMSS, and 4-port FMSS, and these FMSSs are connected to each other in sequence. In addition, each FMSS can also be connected with FMSSs in other grid units. For example, the 3-port FMSS in the multi-station fusion unit 1 can be connected to the 3-port FMSS in another grid unit adjacent to the upper side of the "current power grid unit" (the grid unit composed of multi-station fusion units 1-6). The 3-port FMSS in the station fusion unit 5 is connected to the 3-port FMSS in another power grid unit adjacent to the left side of the "current power grid unit", and the 4-port FMSS in the multi-station fusion unit 6 is connected to the left side of the "current power grid unit". 3-port FMSS connection in another adjacent grid unit, where the connection structure between the FMSS in the multi-station fusion unit 2-4 and the FMSS of other grid units is not shown in FIG. 1 . Through the above connection method, the multi-station fusion units 1-6 can form a basic unit (grid unit) in a honeycomb network structure, and these basic units are connected to each other to form a honeycomb network structure.

It should be noted that those skilled in the art can flexibly select flexible multi-state switches based on different power conversion structures according to actual needs. For example, flexible multi-state switches based on AC-DC power conversion structures or direct-direct power conversion structures can be selected. Such specific adjustments and changes to the flexible multi-state switch do not deviate from the principle and scope of the present invention, and should be limited within the protection scope of the present invention. In addition, those skilled in the art can flexibly set the number of multi-station fusion units according to actual needs. For example, the number of multi-station fusion units can be 7, 8, 9 or other values. Adjustments and changes that do not deviate from the principle and scope of the present invention should be limited within the protection scope of the present invention.

Further, in an implementation manner of the embodiment of the present invention, a voltage source converter (voltage source converter, VSC) may be used to construct a multi-port flexible multi-state switch. Specifically, in this embodiment, the multi-port flexible multi-state switch may include a plurality of voltage source converters, and each voltage source converter may include a first bidirectional input/output side and a second bidirectional input/output side side. For each multi-port flexible multi-state switch, the first bidirectional input/output side of each voltage source converter in the multi-port flexible multi-state switch is respectively connected in parallel, and the second bidirectional input side of each voltage source converter The /output side forms each port of the multi-port flexible multi-state switch separately. Referring to Fig. 2, Fig. 2 schematically shows a multi-station fusion unit constructed based on 4-port FMSS according to an embodiment of the present invention. As shown in FIG. 2 , four voltage source converters ( VSC1 , VSC2 , VSC3 and VSC4 ) respectively form four ports of a 4-port FMSS and each port is connected to feeders Bus1 to Bus4 respectively. Among them, the functional stations connected to the feeder Bus1 include data center station (Internet Data Center, IDC), conventional load (including but not limited to: enterprises, residents, factories and other electrical equipment), energy storage power station 1, hydrogen production station 1 and gas generators (hydrogen generators), the functional stations connected to the feeder Bus2 include conventional loads, 5G base stations, hydrogen production stations 2, energy storage power stations 2 and photovoltaic power stations, and the functional stations connected to the feeder Bus3 include conventional loads and For hydrogen fuel electric vehicles, the functional stations connected to the feeder Bus4 include conventional loads and pure electric vehicles. In addition, feeder lines Bus1 to feeder lines Bus4 are also respectively connected to adjacent multi-station fusion units 1 to 4, so as to perform electric energy/hydrogen energy interaction with adjacent multi-station fusion units 1 to 4 respectively.

3. Control device

In the embodiment of the present invention, the management and control device based on the virtual power plant technology can be configured to perform power management and/or hydrogen energy management and control on the preset functional stations in the multi-station fusion unit.

A virtual power plant (Virtual Power Plant, VPP) refers to a conventional system in the field of power technology that can realize the aggregation and coordination optimization of distributed power sources, energy storage systems, controllable loads, and electric vehicles through advanced information and communication technologies and software systems. , as a special power plant to participate in the power supply coordination management system of the power market and grid operation. The management and control device based on the virtual power plant technology refers to the device constructed by using the virtual power plant and having the functions of power control and hydrogen energy control of the functional station.

The management and control device in the multi-station fusion unit will be described below by taking the multi-station fusion unit built based on the 4-port FMSS shown in FIG. 2 as an example. Referring to accompanying drawing 3, Fig. 3 schematically shows the signal flow/energy flow between the management and control device and the functional stations in the multi-station fusion unit shown in Fig. 2 . Among them, the regional autonomous subsystem 1 refers to the electric energy subsystem formed by the energy storage power station 2 connected to the feeder Bus2, the photovoltaic power station, the conventional load and the 5G base station (not shown in Figure 3), and the regional autonomous subsystem 2 refers to the It is an electric energy subsystem formed by the energy storage power station 1 connected to the feeder Bus1, conventional loads and IDC (not shown in Figure 3). The regional autonomous subsystem 3 refers to the electric energy formed by the conventional load connected to the feeder Bus3. Subsystem, the regional autonomous subsystem 4 refers to the electric energy subsystem formed by the conventional load connected to the feeder Bus4 and the pure electric vehicle. In addition, hydrogen production station 1, hydrogen production station 2, gas engine and hydrogen fuel electric vehicle in the multi-station fusion unit can form a single hydrogen energy subsystem. As shown in Figure 3, the management and control device can be connected to the 4-port FMSS, the regional autonomous subsystem 1, the regional autonomous subsystem 2, the regional autonomous subsystem 3, the regional autonomous subsystem 4, and the hydrogen energy subsystem, so as to FMSS, Regional Autonomous Subsystem 1, Regional Autonomous Subsystem 2, Regional Autonomous Subsystem 3, and Regional Autonomous Subsystem 4 perform power control and hydrogen energy control for the hydrogen energy subsystem. In addition, the management and control device can also communicate with the external management center/electricity market, so as to receive the electric energy/hydrogen energy control command issued by the management center for corresponding electric energy/hydrogen energy control, or participate in the power supply coordination management of the electric power market to improve the system economy. Further, in the multi-station fusion unit shown in FIG. 2 , electric energy and hydrogen energy respectively maintain power balance (power conservation). Wherein, the calculation formulas of the power balance of electric energy and hydrogen energy can be shown in the following formulas (1) and (2) respectively.

The meanings of the parameters in formula (1) are as follows:

表示在t时刻第j个常规负载的电能输入功率，

表示第j个常规负载的功率系数，

表示在t时刻第j个储能电站的电能输入功率，

表示第j个储能电站的功率系数，

表示在t时刻纯电动汽车的电能输入功率，

表示纯电动汽车的功率系数，

表示在t时刻第j个制氢站的电能输入功率，

表示第j个制氢站的功率系数，P_PV(t)表示在t时刻光伏电站的电能输出功率，λ_PV表示光伏电站的功率系数，

表示在t时刻由第j个其他的多站融合单元输出至当前多站融合单元的电能功率，

表示第j个其他的多站融合单元的功率系数，P_GT(t)表示在t时刻燃气机的电能输出功率，λ_GT表示燃气机的功率系数。P _IDC (t) represents the electric energy input power of the data center station at time t, P _5G (t) represents the electric energy input power of the 5G base station at time t,

Indicates the electric energy input power of the jth conventional load at time t,

Indicates the power coefficient of the jth conventional load,

Indicates the electric energy input power of the jth energy storage power station at time t,

Indicates the power coefficient of the jth energy storage power station,

Indicates the electric energy input power of the pure electric vehicle at time t,

Indicates the power coefficient of pure electric vehicles,

Indicates the electric energy input power of the jth hydrogen production station at time t,

Indicates the power coefficient of the jth hydrogen production station, P _PV (t) represents the electric energy output power of the photovoltaic power station at time t, λ _PV represents the power coefficient of the photovoltaic power station,

Indicates the electric power output from the j-th other multi-station fusion unit to the current multi-station fusion unit at time t,

Indicates the power coefficient of the j-th other multi-station fusion unit, P _GT (t) represents the electric energy output power of the gas engine at time t, and λ _GT represents the power coefficient of the gas engine.

The meanings of the parameters in formula (2) are as follows:

表示在t时刻由其他的多站融合单元输出至当前多站融合单元的氢能功率，

表示在t时刻第j个氢燃料电动汽车的氢能输入功率，

表示第j个氢燃料电动汽车的功率系数，α表示预设的常数系数。η ₁ represents the efficiency that electric energy is converted into hydrogen energy, and η ₂ represents the efficiency that hydrogen energy is converted into electric energy,

Indicates the hydrogen power output from other multi-station fusion units to the current multi-station fusion unit at time t,

Indicates the hydrogen energy input power of the jth hydrogen fuel electric vehicle at time t,

Indicates the power coefficient of the jth hydrogen fuel electric vehicle, and α indicates a preset constant coefficient.

Further, in an implementation of the embodiment of the present invention, the management and control device can be further configured to adjust the multi-port flexible multi-state switch respectively by performing the following operations according to the running state of the feeder connected to each port in the multi-port flexible multi-state switch The working mode of the voltage source converter corresponding to each port in :

(1) When each feeder is in normal operation state, it can control one voltage source converter to operate in U _dc _Q control mode, and control other voltage source converters to operate in P_Q control mode.

(2) When it is detected that a feeder is faulty and loses power, it can be determined according to the type of control mode adopted by the voltage source converter (voltage source converter on the fault side) connected to the feeder before the fault occurs, to determine the The working mode of a voltage source converter:

When it is detected that a feeder fails and loses power, obtain the voltage source converter corresponding to the feeder access port (the port of the multi-port flexible multi-state switch) before the fault occurs, and convert the voltage source converter to As the voltage source converter on the fault side, the other voltage source converters are used as voltage source converters on the non-fault side. For example: referring to Figure 2, if it is detected that the feeder Bus1 has a fault and loses power, then VSC1 can be used as a voltage source converter on the fault side, and VSC2 to VSC4 can be used as voltage source converters on the non-fault side.

If the voltage source converter on the fault side is using the P_Q control mode before the fault occurs, the voltage source converter on the fault side is controlled to switch to the U _ac _f control mode, and the voltage source converter on the fault side is controlled after the fault is restored. The converter switches to P_Q control mode again.

If the voltage source converter on the fault side used the U _dc _Q control mode before the fault occurred, control the voltage source converter on the fault side to switch to the U _ac _f control mode, and control a voltage source converter on the non-fault side The converter is switched to the U _dc _Q control mode to operate, and after the fault is recovered, the voltage source converter on the fault side is controlled to switch to the U _dc _Q control mode again, and the non-fault side voltage source converter is controlled Switch to P_Q control mode again.

Continuing to refer to FIG. 2 , when the feeder Bus1 to the feeder Bus4 are in different states, the control mode of each VSC in the 4-port FMSS can be shown in Table 1 below.

Table 1

It should be noted that the U _dc _Q control mode, the P_Q control mode and the U _ac _f control mode are all conventional control modes in the field of electric power technology. Among them, the U _ac _f control mode belongs to the droop control, which mainly uses the droop characteristics to obtain stable AC voltage amplitude and frequency respectively. Specifically, the U _dc _Q control mode refers to the constant DC voltage and reactive power control mode. In the embodiment of the present invention, the U _dc _Q control mode mainly includes respectively controlling the DC bus voltage U of the voltage source converter on the fault side. _dc and the output reactive power Q are under constant control. The P_Q control mode refers to the constant power control mode. In the embodiment of the present invention, the P_Q control mode mainly includes constant control of active power P and reactive power Q output by the voltage source converter on the fault side. The U _{ac_f} control mode refers to the constant voltage and constant frequency control mode. In the embodiment of the present invention, the U _{ac_f} control mode mainly includes constant control of the AC side voltage amplitude and frequency of the voltage source converter on the fault side. For the sake of concise description, the specific control principles of the U _dc _Q control mode, the P_Q control mode and the U _ac _f control mode will not be repeated here.

In practical applications, one or more functional stations will be connected to the feeder connected to each port of the multi-port flexible state switch. When the voltage source converter on the fault side is switched to U _ac _f control mode, due to U _a The droop control characteristics of the _f control mode may cause the AC voltage amplitude/frequency at the feeder connection side of these functional stations (for example: a certain functional station is an energy storage power station, and the energy storage power station includes the energy storage power station body and AC/DC The DC side of the AC/DC device is connected to the main body of the energy storage power station, the AC side of the AC/DC device is connected to the feeder, and the AC/DC device converts the alternating current transmitted in the feeder into direct current and outputs it to the main body of the energy storage power station for electric energy storage Among them, the AC voltage amplitude/frequency of the feeder connection side in the energy storage power station refers to the AC voltage amplitude/frequency of the AC side of the AC/DC device), which is different from the AC side voltage amplitude of the voltage source converter on the fault side The value/frequency is inconsistent, and the deviation of these voltage amplitude/frequency will affect the stability of the multi-station fusion unit, which may affect the system stability of the entire flexible interconnection distribution network system. For example, when Bus2 fails and VSC2 switches to the U _ac _f control mode, the AC side voltage amplitude/frequency of VSC2, the AC voltage amplitude/frequency of the feeder connection side in the energy storage power station 2, and the feeder connection side of the photovoltaic power station Inconsistent AC voltage amplitude/frequency. In this regard, the secondary control strategy applied to droop control can be used to compensate the above-mentioned voltage amplitude/frequency deviation, so as to ensure the AC voltage amplitude/frequency of the fault-side voltage source converter and the functional stations connected to the corresponding feeder. The frequency remains the same. In one embodiment, the management and control device can be further configured to use the secondary control strategy applied to the droop control to obtain the voltage of the U _ac _f control mode respectively before the voltage source converter on the fault side is switched to the U _ac _f control mode Reference value and frequency reference value, so that the fault side voltage source converter can make its own _AC side voltage amplitude and frequency, and the fault side voltage source The amplitude and frequency of the AC voltage at the feeder connection side of each functional station connected to the feeder connected with the type converter shall be consistent respectively. Further, in this embodiment, the method "Secondary control of microgirds based on distributed cooperative control of multi-agent systems" disclosed by the Institute of Engineering Technology (IET) in 2013 can be used to obtain the voltage reference value and frequency reference value of the above-mentioned U _{ac_f} control mode respectively. value, that is, the voltage reference value and the frequency reference value of the above-mentioned U _ac _f control mode can be obtained respectively according to the method shown in the following formula (3):

The meanings of the parameters in formula (3) are as follows:

表示对第i个故障侧电压源型换流器对应的端口的无功功率测量值的微分。ω_ni表示第i个故障侧电压源型换流器对应的端口的频率参考值，u_ωi表示控制第i个故障侧电压源型换流器采用U_ac_f控制模式运行时进行频率下垂控制的辅助控制变量，m_i表示第i个故障侧电压源型换流器采用U_ac_f控制模式运行时进行频率下垂控制的下垂控制系数，

表示对第i个故障侧电压源型换流器对应的端口的有功功率测量值的微分。需要说明的是，上述各参数的具体获取方法均可以按照上述“Secondarycontrol of microgirds based on distributed cooperative control of multi-agentsystems”中记载的方法获取得到，在此不再赘述。U _refi represents the output voltage reference value of the port corresponding to the i-th fault-side voltage source converter in the multi-port flexible multi-state switch; u _vi represents the control of the i-th fault-side voltage source converter using U _ac _f Auxiliary control variable for voltage droop control when the control mode is running; n _i represents the droop control coefficient for voltage droop control when the i-th fault-side voltage source converter adopts U _ac _f control mode,

Indicates the differential of the reactive power measurement value of the port corresponding to the i-th fault-side voltage source converter. ω _ni represents the frequency reference value of the port corresponding to the voltage source converter on the i-th fault side, and u _ωi represents the frequency droop control function for controlling the voltage source converter on the i-th fault side to operate in the U _ac _f control mode Auxiliary control variable, _mi represents the droop control coefficient of frequency droop control when the ith fault-side voltage source converter adopts U _ac _f control mode,

Indicates the differential of the active power measurement value of the port corresponding to the i-th fault-side voltage source converter. It should be noted that the specific methods for obtaining the above parameters can be obtained according to the methods recorded in the above "Secondary control of microgirds based on distributed cooperative control of multi-agentsystems", and will not be repeated here.

Continuing to refer to Figure 1, in another embodiment according to the present invention, the grid units in the flexible conversion power distribution system may not only include the functional structures in the foregoing embodiments, each grid unit may also include a public connection point. For each grid unit, in the grid unit, the multi-port flexible multi-state switch in each multi-station fusion unit can be connected to the common connection point, so as to be connected to the external power grid through the common connection point. That is to say, if the flexible interconnected distribution network system as a whole is regarded as a grid layer, then grid units can not only communicate with other grid units in this grid layer, but also communicate with other grid units through common connection points. It is connected to other grid layers, that is, connected to external grids other than the flexible interconnected distribution grid system, to realize the power flow interaction between different grid layers.

So far, the technical solution of the present invention has been described in conjunction with an embodiment shown in the accompanying drawings, but those skilled in the art can easily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims (6)

1. The flexible interconnected power distribution network system is characterized by comprising a plurality of power grid units, wherein each power grid unit comprises a plurality of multi-station fusion units; each multi-station fusion unit comprises a management and control device and/or a multi-port flexible multi-state switch which are constructed based on the virtual power plant technology; the system comprises a multi-station fusion unit based on a 2-port flexible multi-state switch, a 3-port flexible multi-state switch and a 4-port flexible multi-state switch;

each management and control device is respectively configured to perform function management and control on a function station preset in each multi-station fusion unit;

a plurality of preset function stations are respectively connected to a feeder line connected with each port of the multi-port flexible multi-state switch; for each power grid unit, sequentially connecting each multi-port flexible multi-state switch in the power grid unit with each other, and respectively connecting each multi-port flexible multi-state switch with multi-port flexible multi-state switches in other power grid units, so that each power grid unit is connected with each other to form a honeycomb-shaped networking structure;

in a multi-station fusion unit based on a 4-port flexible multi-state switch, each port is respectively connected with feeder lines Bus1 to Bus4, functional stations accessed on the feeder lines Bus1 comprise an energy storage power station, a hydrogen generation station, a gas engine, a conventional load and a data center station, functional stations accessed on the feeder lines Bus2 comprise a hydrogen generation station, an energy storage power station, a photovoltaic power station, a conventional load and a 5G base station, functional stations accessed on the feeder lines Bus3 comprise a hydrogen fuel electric automobile and a conventional load, and functional stations accessed on the feeder lines Bus4 comprise a pure electric automobile and a conventional load;

in the multi-station fusion unit based on the 4-port flexible multi-state switch, a calculation formula of power balance of electric energy is shown as follows:

wherein, P _IDC (t) represents the electrical energy input power of the data center station at time t,P _5G (t) represents the power input power of the base station at time t 5G,

representing the electrical energy input power of the jth conventional load at time t,

represents the power coefficient of the jth conventional load,

representing the electrical energy input power of the first energy storage plant at time t,

representing the power coefficient of the jth energy storage plant,

the electric energy input power of the pure electric vehicle at the moment t is shown,

the power coefficient of the pure electric vehicle is shown,

represents the electric energy input power of the jth hydrogen generation station at the time t,

represents the power coefficient, P, of the jth hydrogen generation station _PV (t) represents the electrical energy output power of the photovoltaic plant at time t, λ _PV Represents the power coefficient of the photovoltaic power plant,

represents the electric energy power output by the j-th other multi-station fusion unit to the current multi-station fusion unit at the time t,

representing the power coefficient, P, of the jth other multi-station fusion unit _GT (t) represents the electrical output power of the gas engine at time t, λ _GT Representing the power coefficient of the gas engine;

in the multi-station fusion unit based on the 4-port flexible multi-state switch, a calculation formula of the power balance of hydrogen energy is shown as follows:

wherein eta is ₁ Representing the efficiency, eta, of conversion of electrical energy into hydrogen energy ₂ Indicating the efficiency of conversion of hydrogen energy into electrical energy,

represents the hydrogen energy power output by other multi-station fusion units to the current multi-station fusion unit at the time t,

represents the hydrogen energy input power of the jth hydrogen-fueled electric vehicle at the time t,

the power coefficient of the jth hydrogen fuel electric automobile is shown, and alpha is a preset constant coefficient.

2. The flexible internet power distribution system according to claim 1, wherein the preset function stations comprise a power supply function station and/or a power grid function station and/or a load function station and/or an energy storage function station, the power supply function station comprises a new energy power generation power supply function station and a hydrogen energy power generation power supply function station, and the load function station comprises an electrical energy load function station and a hydrogen energy load function station;

each hydrogen energy power generation power supply functional station and each hydrogen energy load functional station are respectively connected with each other to form a hydrogen energy interconnection network;

the management and control device is further configured to respectively perform power management and/or hydrogen energy management and control on the preset function stations.

3. The flexible interconnected power distribution system as set forth in claim 1, wherein said multi-port flexible multi-state switch comprises a plurality of voltage source converters, each of said voltage source converters comprising a first bidirectional input/output side and a second bidirectional input/output side, respectively;

the first bidirectional input/output sides of each voltage source type converter are respectively connected in parallel;

the second bidirectional input/output side of each of the voltage source converters forms each port of the multi-port flexible multi-state switch, respectively.

4. The flexible interconnected power distribution system according to claim 3, wherein the management and control device is further configured to control the operation mode of the voltage source type converter corresponding to each port in the multi-port flexible multi-state switch respectively according to the operation state of the feeder connected to each port in the multi-port flexible multi-state switch and through the following operations:

when each feeder line is in a normal operation state, controlling one voltage source type converter to adopt U _dc The Q control mode is operated, and other voltage source type converters are controlled to operate in a P-Q control mode;

when a feeder line is detected to have a fault and lose power, acquiring a voltage source type converter corresponding to the feeder line access port before the fault occurs, taking the voltage source type converter as a fault side voltage source type converter, and taking other voltage source type converters as non-fault side voltage source type converters;

controlling the fault side voltage source type converter to be switched to a U if the fault side voltage source type converter adopts a P _ Q control mode before the fault occurs _ac -f control mode operation and controlling the fault side voltage source converter to switch again to P-Q control mode operation after fault recovery；

If the fault side voltage source type converter adopts U before the fault occurs _dc A Q control mode is adopted, the fault side voltage source type converter is controlled to be switched to U _ac F control mode operation and control of a non-fault side voltage source inverter to switch to U _dc A Q control mode is operated, and the fault side voltage source type converter is controlled to be switched to the U again after the fault is recovered _dc -Q control mode and controlling said one non-fault side voltage source converter to switch to P-Q control mode again.

5. The flexible internet power distribution system of claim 4, wherein the policing apparatus is further configured to:

at the fault side the voltage source converter is switched to U _ac Before the f control mode, U is respectively acquired by using a secondary control strategy applied to droop control _ac -f controlling the voltage reference and the frequency reference of the mode so that the fault side voltage source converter adopts U according to the voltage reference and the frequency reference _ac The control mode operation can make the amplitude and the frequency of the alternating-current side voltage of the control mode operation and the amplitude and the frequency of the alternating-current voltage of the feeder connection side of each functional station connected to the feeder connected to the corresponding port of the fault side voltage source type converter respectively consistent.

6. The flexible interconnected power distribution system according to any one of claims 1-5, wherein the grid unit further comprises a common connection point to which the multi-port flexible multi-state switches in each multi-station fusion unit within the grid unit are respectively connected to connect with an external grid through the common connection point.

Images