Power flow cooperative control method and system for AC-DC conversion device

Abstract

The invention provides a power flow cooperative control method and system for an AC-DC conversion device, and the method comprises the steps: numbering transformer areas in the device, scanning the load power of each transformer area according to a numbering result, obtaining a load grade corresponding to the load power of each transformer area according to the load power of each transformer area, and carrying out the code scanning of the load power of each transformer area; determining a load type according to the load grade, and setting an initial power factor array as zero; acquiring current information, load power information and electricity price information of each transformer area every first preset time, evaluating each transformer area according to the current information, the load power information and the electricity price information, and judging whether an evaluation result meets a preset transformer area power flow adjustment condition or not; and if the evaluation result meets a preset transformer area power flow adjustment condition, performing power adjustment based on a preset transformer area power flow control strategy. According to the invention, reasonable and stable power output of each port can be ensured, and the overall performance, reliability and sustainability of the micro-grid are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power flow control, and in particular to a power flow coordinated control method and system for an AC / DC conversion device. Background Art

[0002] With the intensification of global energy shortages and environmental problems, how to effectively utilize renewable energy has become an important issue in the energy policies of various countries. The rise of microgrid technology has made it possible to integrate distributed renewable energy (such as solar energy and wind energy). This technology not only improves the reliability of local power supply, but also promotes the sustainable development of power. The operating characteristics of microgrids enable them to operate flexibly in a grid-connected or off-grid state to meet users' power and heat energy needs. In the implementation of microgrids, coordinated flow control is the key to ensuring the coordinated work of various power sources and loads. This process involves real-time monitoring and scheduling of power flow to optimize power distribution and improve the economy and reliability of the system.

[0003] In multi-port AC / DC conversion devices, the existing control methods mainly include master-slave control, adaptive control, etc. Although the existing technology is widely used in multi-port AC / DC conversion devices, there are still some technical defects: First, the response speed of traditional control methods is insufficient, and it is impossible to quickly respond to instantaneous load changes or fluctuations in renewable energy, affecting the stability of the power system. Secondly, in a multi-port system, if each port operates independently, it may cause power imbalance, affect the overall efficiency of the system, and cause some equipment to be overloaded or idle. In addition, the existing system has limited capabilities in real-time monitoring and scheduling, and cannot make full use of real-time data for optimized scheduling, affecting the overall economic benefits. In the future, with the increase in the amount of renewable energy access, the existing control system will lack scalability and will be difficult to adapt to the changing power demand. Summary of the invention

[0004] Based on this, the purpose of the present invention is to propose a power flow coordinated control method and system for an AC / DC conversion device, aiming to solve the above-mentioned problems by introducing a distributed power flow coordinated control method, to achieve efficient, stable and intelligent management of multi-port AC / DC conversion devices, to ensure that the power output of each port is reasonable and stable, thereby improving the overall performance and reliability of the microgrid.

[0005] In a first aspect, an embodiment of the present invention provides a power flow coordinated control method for an AC / DC conversion device, the method comprising: Numbering the substations in the device, and scanning the load power of each substation according to the numbering result, so as to obtain the load level corresponding to each substation according to the load power of each substation, determine the load type according to the load level, and set the initial power factor array to zero; Collecting current information, load power information and electricity price information of each substation at a first preset time interval, evaluating each substation according to the current information, the load power information and the electricity price information, and determining whether the evaluation result meets the preset substation power flow adjustment condition; If the evaluation result meets the preset area power flow adjustment conditions, power adjustment is performed based on the preset area power flow control strategy; Update the current power factor array of each area, and determine the power demand or margin of each area after power adjustment; and upload the power demand or margin.

[0006] Furthermore, the steps of numbering the substations in the device, scanning the load power of each substation according to the numbering result, obtaining the load level corresponding to the load power of each substation according to the load power of each substation, and determining the load type according to the load level include: The load levels include level 1, 2, ..., N from low to high, and the load types include critical load, ordinary load and non-critical load; When the load power is greater than or equal to the first preset power threshold, it is a critical load; When the load power is less than the first preset power threshold and greater than the second preset power threshold, it is a normal load; When the load power is less than or equal to the second preset power threshold, it is a non-critical load; Construct a pairwise correspondence table between load levels, load types, and load powers.

[0007] Furthermore, the step of collecting the current information, load power information and electricity price information of each substation at a first preset time interval to evaluate each substation according to the current information, the load power information and the electricity price information includes: The load fluctuation value is calculated according to the following formula: ΔP i (t) = [P i (t)-P i (t-1)] / P i (t-1) Among them, P i (t) is the storage power information of the ith station in the tth cycle, P i (t-1) is the storage power information of the ith station in the t-1th cycle, ΔP i (t) indicates the load fluctuation value of the ith substation in the tth cycle; The critical loads are sorted from large to small according to the load fluctuation value, the common loads are sorted in descending order according to the load fluctuation value, and the non-critical loads are sorted in descending order according to the load fluctuation value. Finally, the power factors M, M-1, ..., 1 corresponding to each load type are obtained according to the sequence number from high to low; The electricity price is assessed according to the following formula: ΣP PV (t)+P bat (t)+P net (t)=ΣP L (t)+ΣP Loss (t) Among them, ΣP PV (t) is the total active power generated by the photovoltaic power source at time t, P bat (t) is the active power of energy storage at time t, assuming that discharge is positive and charge is negative, P net (t) is the total active power exchanged between the multi-port device and the large power grid at time t. Assume that the power sent to the large power grid is positive, and the power sent to the large power grid is negative. L (t) is the total active power in the multi-port device, ΣP Loss (t) is the total active power loss in the multi-port device.

[0008] Furthermore, the step of judging whether the evaluation result meets the preset area power flow adjustment condition includes: Determine whether the power fluctuation of the power adjustment area is less than a first preset threshold, whether the load rate of the photovoltaic area is less than a second preset threshold, whether the load rate of the power adjustment area is within a first preset range, and whether the energy storage device is fault-free; If the power fluctuation of the power adjustment area is less than the first preset threshold, and the load rate of the photovoltaic area is less than the second preset threshold, and the load rate of the power adjustment area is within the first preset range, and the energy storage device has no faults, it is determined that the preset area flow adjustment conditions are met.

[0009] Furthermore, if the evaluation result satisfies the preset area power flow adjustment condition, the step of performing power adjustment based on the preset area power flow control strategy includes: In the power allocation process, the cost calculation formula is: Among them, P net (t) is the total active power exchanged between the multi-port device and the large power grid at time t, B(t) is the array data of the electricity price factor at time t, N i is the load level of the ith station area, M i (t) is the power factor array data of the ith area at time t; The loads are sorted according to the calculation results of the cost calculation formula, and the power is adjusted by sorting the loads from large to small according to the results.

[0010] Furthermore, the step of sorting the loads according to the calculation results of the cost calculation formula and adjusting the power by sorting the loads from large to small according to the results includes: The power exchange constraints between the AC / DC conversion device and the large power grid are: ΣP PV (t)+P bat (t)+P net (t)=ΣP L (t)+ΣP Loss (t); The photovoltaic power generation constraint in the i-th station is: 0≤P PV,i (t)≤P PVN,i (t); Among them, P PV,i (t) is the power generated by the photovoltaic power source in the i-th station at time t, P PVN,i (t) is the rated power of the photovoltaic power source in the i-th station; The state of charge constraint of the energy storage device is: S oc,min ≤S oc,t ≤S oc,max ; S oc,t is the battery charge state at time t, S oc,min S is the lower limit of the charge allowed for the energy storage device to discharge. oc,max The upper limit of the charge allowed for the energy storage device; The energy storage power limit constraint is: P CMAX ≤P bat (t)≤P DMAX ; Among them, P CMAX is the maximum discharge power of energy storage, P DMAX Maximum charging power of energy storage; The current working condition of the entire multi-port device is determined, the power reference value of each area is determined according to the algorithm, and power is allocated according to the power reference value.

[0011] Furthermore, the step of judging the current working condition of the entire multi-port device, determining the power reference value of each area according to an algorithm, and performing power distribution according to the power reference value includes: Condition 1: P bat (t) = 0; P net (t)=0;ΣP PV (t)=ΣP L (t)+ΣP Loss (t); S oc,t ≥S oc,maxWhen the energy storage device has reached the upper limit of charging, the photovoltaic output meets the load demand. At this time, the energy storage device is neither charging nor discharging, and the large power grid is not outputting power; Working condition 2: P net (t)=ΣP PV (t)-ΣP L (t)-ΣP Loss (t)>0;P bat (t)=0; when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t ≥S oc,max When the energy storage device has reached the upper limit of charging, the photovoltaic overflow power is transmitted to the large power grid, and the energy storage device is neither charged nor discharged; Condition 3: P bat (t)=ΣP L (t)+ΣP Loss (t)-ΣP PV (t)<0;P net (t)=0; when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t oc,max When P CMAX ≥ΣP PV (t)-ΣP L (t)-ΣP Loss (t), that is, at this time, the energy storage device can receive all the overflow power of the photovoltaic power source; Working condition 4: P bat (t)=-P CMAX ;P net (t)=ΣP L (t)+P bat (t)+ΣP Loss (t)-ΣP PV (t); when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t oc,max When P CMAX ≤ΣP PV (t)-ΣP L (t)-ΣP Loss (t), that is, at this time, the energy storage device is not sufficient to receive all the overflow power of the photovoltaic power source, so the energy storage device is charged according to the maximum input power, and the remaining overflow power is input into the large power grid; Condition 5: P bat (t)=ΣP L (t)+ΣP Loss (t)-ΣP​​PV (t)>0;P net (t)=0; when ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t >S oc,min When P DMAX ≥ΣP L (t)+ΣP Loss (t)-ΣP PV (t), that is, the photovoltaic output is less than the load and active power loss and the output of the energy storage device is sufficient to compensate for this shortfall. The energy storage device determines the output power based on the difference, and the multi-port device does not exchange power with the large power grid; Working condition 6: P bat (t) = P DMAX >0;P net (t) = P DMAX +ΣP PV (t)-ΣP L (t)+ΣP Loss (t)<0; When ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t >S oc,min When P DMAX <ΣP L (t)+ΣP Loss (t)-ΣP PV (t), that is, the photovoltaic output is less than the load and active power loss and the output of the energy storage device is not enough to compensate for this shortfall, then the energy storage device outputs at the maximum output power, and the remaining power shortfall is supplemented by the large power grid; Condition 7: P bat (t) = 0; P net (t)=ΣP PV (t)-ΣP L (t)+ΣP Loss (t)<0; when ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t oc,min When the photovoltaic output is less than the load and active power loss and the energy storage device has reached the lower limit of allowable discharge, the load power shortage is supplemented by the large power grid.

[0012] In a second aspect, an embodiment of the present invention further provides a power flow coordination control system for an AC / DC conversion device, the system comprising: ​The load level classification module is used to number the substations in the device, and scan the load power of each substation according to the numbering result, so as to obtain the load level corresponding to each substation according to the load power of each substation, determine the load type according to the load level, and set the initial power factor array to zero; A substation evaluation module, configured to collect current information, load power information, and electricity price information of each substation at a first preset time interval, evaluate each substation according to the current information, the load power information, and the electricity price information, and determine whether the evaluation result meets the preset substation power flow adjustment condition; A power regulation determination module is used to perform power regulation based on a preset area power flow control strategy if the evaluation result meets the preset area power flow adjustment condition; The array update module is used to update the current power factor array of each substation, and determine the power demand or margin of each substation after power adjustment; and upload the power demand or margin.

[0013] In a third aspect, an embodiment of the present invention further provides a storage medium, including one or more programs stored in the storage medium, which, when executed, implements the power flow coordinated control method for an AC / DC conversion device as described above.

[0014] In a fourth aspect, an embodiment of the present invention further provides an electronic device, the electronic device comprising a memory and a processor, wherein: The memory is used to store computer programs; When the processor is used to execute the computer program stored in the memory, the power flow coordinated control method for the AC / DC conversion device as described above is implemented.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The present invention is used to solve the problem that the photovoltaic overflow power cannot be absorbed in time due to the increase in the capacity of photovoltaic equipment in the microgrid. It can also reduce the impact of the large fluctuation of the output of distributed power sources on the stable operation of the power grid and loads.

[0016] 2. The present invention can achieve stable power output at each port of the system, and can effectively reduce the impact of load fluctuations and photovoltaic output changes on the stable operation of the microgrid.

[0017] 3. By calculating the load rate and electricity price in real time, the effective utilization of photovoltaic and energy storage equipment is ensured, the energy fed into the power grid is reduced, and the operating cost of the system is reduced. DSP and PLC are used in hardware to build a fully digital control system, which improves the control accuracy and response speed and realizes intelligent current and power control. The system is flexible in design and includes a human-computer interaction interface. Users can easily modify the control parameters. It can be expanded according to actual needs to adapt to power grid applications of different scales and types. The system can continuously monitor the operating status of each substation and adjust the flow according to real-time data to ensure the stability and reliability of the system. Efficient coordination between multiple ports is achieved, the problem of coordination between multiple devices is solved, and the overall work efficiency of the system is improved.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description or will be learned through embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an overall framework diagram of a power flow coordinated control method for an AC / DC conversion device in one embodiment of the present invention; Figure 2 It is a flow chart of a power flow coordinated control method for an AC / DC conversion device in one embodiment of the present invention; Figure 3 It is a structural schematic diagram of a power flow cooperative control system for an AC / DC conversion device in one embodiment of the present invention.

[0020] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0023] The applicant found that master-slave control manages all ports uniformly through the master controller. This method can provide a global perspective, but it has a slow response speed when facing real-time changing loads and fluctuating distributed power output, which can easily lead to low system efficiency. Adaptive control dynamically adjusts control parameters based on real-time data. Although it improves the flexibility of the system, it is difficult to implement adaptive control for complex multi-port systems and requires high algorithm processing capabilities.

[0024] In addition, the shortcomings of existing technologies are mainly reflected in three aspects: first, the traditional control method has a slow response speed and cannot respond to load changes or fluctuations in renewable energy in a timely manner, resulting in unstable power systems; second, if each port operates independently, it may cause power imbalance, affect overall efficiency, and may cause equipment to be overloaded or idle. In addition, traditional control mainly focuses on improving system stability, but does not consider how to effectively reduce equipment operating costs.

[0025] Based on this, in view of the above shortcomings, the purpose of the present invention is to introduce a method for coordinated flow control. Through a two-layer multi-port device, the upper layer uses a central controller to coordinate the output of distributed power sources, energy storage equipment, and load supply and demand to ensure the stable operation of the system, and the lower layer uses a local controller to achieve coordinated control of the flow, realize power distribution, and ensure multi-port power balance. At the same time, when coordinating the flow for power scheduling, the electricity price information is considered in real time to achieve efficient, stable, low-cost and intelligent management of the multi-port AC / DC conversion device, thereby ensuring that the power output of each port is reasonable and stable, and improving the overall performance, reliability and sustainability of the microgrid.

[0026] The method includes a power control link, a current control link, a power optimization scheduling control link and a human-machine interface link.

[0027] like Figure 1 As shown in the figure, all links are realized by programming a fully digital control system that combines a control board with TI's TMS320F28335 digital signal processor DSP as the core control chip and Siemens' programmable logic device PLC CPU1215C. The multi-port AC / DC conversion device is divided into two layers. The upper layer is the central controller, which is responsible for coordinating the energy of the power grid, managing the lower layer controller and classifying the load. The lower layer is the local controller, which is responsible for directly coordinating the photovoltaic output, energy storage equipment and monitoring the load operation status.

[0028] The power control link is the control link used to realize the output DC voltage of the central controller, and provides DC voltage for the DC side interconnection of the multi-port AC / DC conversion device. This link mainly includes data acquisition and conversion module, power outer loop current inner loop control module, and pulse width modulation PWM output module. These modules collect and convert the grid synchronization voltage and grid input current into digital quantities, and output the amplitude and angle of the voltage to the pulse width modulation PWM output module through the dual closed-loop control module of the power outer loop and the current inner loop, and finally control the power device to output DC voltage, realize AC to DC conversion, realize DC voltage output for other ports, and ensure the constant DC bus voltage of the microgrid.

[0029] The current control link is the link used to realize the power and current controllable of the local controller in the case of a shared DC bus. This link mainly includes the input current acquisition conversion module, the current loop control module and the pulse width modulation PWM module.

[0030] The power optimization scheduling control link includes a current direction determination module, a load rate calculation module, and a power optimization scheduling module. The current direction determination module can determine the current flowing in or out of each port in real time according to the phase relationship of the three-phase current, and calculate the effective value of the three-phase current, the inflow port is positive, and the outflow port is negative. The load rate calculation module calculates the load rate of each port in real time by collecting parameters such as the active power and reactive power of the total transformer of each port. The purpose of the power optimization scheduling module is to adjust the load rate of each port to a reasonable range, and at the same time, adjust the power of each port under the comprehensive judgment of the electricity price factor and the load power imbalance to ensure the power balance of the four ports, and finally output the updated power reference values ​​to the AC / DC conversion device of each port, and the AC / DC conversion device of each port performs the output according to the new output target.

[0031] The human-machine interface is connected to the touch screen through the PLC network port, and the communication protocol uses the Profinet protocol. The control parameters of the power flow system in each module can be modified through the human-machine interface.

[0032] The present invention provides a functionally complete and intelligent method for coordinated power flow control of a multi-port AC / DC conversion device, which integrates power flow calculation optimization control functions such as DC voltage control, real-time current calculation and judgment, power calculation and distribution, etc. It has the characteristics of good scalability, powerful functions and precise control, solves the problems of coordination and collaborative work between multiple ports, enables them to operate in a coordinated manner, and ensures that the power output of each port is reasonable, stable and reliable. It has been successfully applied to provincial power grid projects.

[0033] like Figure 2 As shown, an embodiment of the present invention provides a power flow coordinated control method for an AC / DC conversion device, the method comprising steps S101 to S104, wherein: Step S101: numbering the substations in the device, and scanning the load power of each substation according to the numbering result, so as to obtain the load level corresponding to each substation according to the load power of each substation, determine the load type according to the load level, and set the initial power factor array to zero; In this step, the load levels include level 1, 2, ..., N from low to high, and the load types include critical load, common load and non-critical load; When the load power is greater than or equal to the first preset power threshold, it is a critical load; when the load power is less than the first preset power threshold and greater than the second preset power threshold, it is a normal load; when the load power is less than or equal to the second preset power threshold, it is a non-critical load; and then a pairwise correspondence table of load levels, load types and load powers is constructed.

[0034] For example, a load with a rated power greater than or equal to 50kW is a critical load, a load with a rated power less than or equal to 25kW is a non-critical load, and the rest are ordinary loads. The load levels are sorted from large to small according to the load rated power, and the serial number is used as the load level. The corresponding relationship is shown in Table 1 below: Table 1 The electricity price factor array is arranged in descending order according to the electricity price, and the electricity price is directly used as the electricity price factor array data, as shown in Table 2 below, taking the general industrial and commercial time-of-use electricity price below 1kV in a certain place as an example: Table 2 Time peak peak Flat section Lows Electricity price (yuan / kWh) 1.4223 1.2930 0.7673 0.2939 Electricity price factor array 1.4223 1.2930 0.7673 0.2939 In addition, the power factor array ranks the loads by comprehensively considering the load level and load power fluctuation, and the initial value is set to 0.

[0035] Step S102: collecting current information, load power information and electricity price information of each substation at a first preset time interval, evaluating each substation according to the current information, the load power information and the electricity price information, and determining whether the evaluation result meets the preset substation power flow adjustment condition; It should be noted that before evaluating each substation, it is necessary to use the local controller to collect the substation voltage, current, active power, and photovoltaic output information in real time, and at the same time, according to the current value I collected by the current sensor x Determine the inflow and outflow of current in each area, I x >0 means it flows into the station area, I x When <0, it flows out of the station area. When calculating the load rate of the station area, the rated current of the secondary side of the station area transformer is I 2N , the current value collected by the current sensor is I 2 , according to β=I 2N / I 2×100% to calculate the load factor, and upload the area load power information, energy storage equipment output information, photovoltaic equipment output information and load factor information to the central controller.

[0036] In addition, in some embodiments, the central controller receives and saves the load rate information and key load power information uploaded by the local controller, calculates and evaluates the key load power fluctuation and photovoltaic output. The key load power in the substation area must always meet user needs, and the non-key load power can be adjusted and allocated in real time according to the power of each substation area (here it only explains the load nature, and does not involve adjustment, as long as it points out that the key load power should be adjusted first when it fluctuates), and refreshes the power factor array according to the load situation.

[0037] For example, the central controller updates the load power information every 10 minutes and uses the power values ​​of the two time periods to calculate the power fluctuation of each load. i (t) is the power information stored in the ith station at the current moment, P i (t-1) is the power information stored in the area 10 minutes ago. The load fluctuation calculation formula is [P i (t)-P i (t-1)] / P i (t-1). After obtaining the load fluctuation value, first sort the key loads by power fluctuation from large to small, then sort the common loads by power fluctuation value in descending order, and finally sort the non-key loads by power fluctuation value in descending order, and finally get the power factor array of each load in descending order. An example is shown in Table 3: Table 3 Load fluctuation 7％ 5％ 3％ 8％ ... 10％ 8％ Load level N-2 N N-1 5 ... 1 2 Load Type key key key ordinary ... Non-critical Non-critical Power Factor M M-1 M-2 M-3 ... 2 1 The central controller then obtains electricity price information in real time and refreshes the electricity price factor array. To reduce system costs, the system should make photovoltaic output and energy storage output meet load requirements as much as possible, and reduce the energy fed into the large power grid as much as possible to reduce system operating costs. The power exchange constraint between the multi-port AC / DC converter and the large power grid is: ΣP PV (t)+P bat (t)+P net (t)=ΣP L (t)+ΣP Loss (t); where ΣP PV (t) is the total active power generated by the photovoltaic power source at time t; P bat (t) is the active power of energy storage at time t, assuming that discharge is positive and charge is negative; P net (t) is the total active power exchanged between the multi-port device and the large power grid at time t, assuming that the power sent to the large power grid is positive, and vice versa is negative; ΣP L (t) is the total active power in the multi-port device; ΣP Loss(t) is the total active power loss in the multi-port device. Under this constraint, the total active power on the load side ΣP L (t)+ΣP Loss (t) is almost a constant value. Increasing the photovoltaic power source and energy storage output, that is, increasing ΣP PV (t)+P bat (t), which can reduce P net (t), reducing grid-side feed-in energy and lowering operating costs.

[0038] Step S103: If the evaluation result meets the preset area power flow adjustment condition, power adjustment is performed based on the preset area power flow control strategy; In this step, the central controller checks the power flow adjustment conditions of the substation: the power fluctuation degree of key loads, the overflow of photovoltaic output, the status of energy storage equipment, etc. If the conditions are met, the power adjustment calculation is entered, otherwise it enters the abnormal processing mode.

[0039] Specifically, it is determined whether the power fluctuation of the power adjustment area is less than the first preset threshold, and whether the load rate of the photovoltaic area is less than the second preset threshold, and whether the load rate of the power adjustment area is within the first preset range, and whether the energy storage device is fault-free; if the power fluctuation of the power adjustment area is less than the first preset threshold, and the load rate of the photovoltaic area is less than the second preset threshold, and the load rate of the power adjustment area is within the first preset range, and the energy storage device is fault-free, then it is determined that the preset area flow adjustment condition is met. Exemplarily, the preset area flow adjustment condition: the power fluctuation of the power adjustment area is less than 20%; the load rate of the photovoltaic area is less than 50%; the load rate of the power adjustment area is between 30% and 60%; the energy storage device is fault-free; at this time, flow coordination control can be performed. When the flow coordination control condition is not met, the central controller reads the relay protection device information of the local controller of the adjustment area. If the protection action cuts off the faulty area, the corresponding area local controller reports the fault state; if the protection does not act, then return to step S101.

[0040] In addition, in some embodiments, the central controller calculates and adjusts the system power flow direction based on the power flow coordination algorithm, giving priority to ensuring that the power required by the key loads in the substation area meets the demand. At the same time, the power at both ends of the power flow coordination controller needs to be balanced, and the power in the substation area is controlled to be within the limit. During the power distribution process, the central controller uses the cost calculation formula that introduces the electricity price factor and the power factor to sort the loads, and absorbs the photovoltaic overflow power in the order of loads. The equipment output target after power flow coordination will be sent by the central controller to the local controller, and the local controller will control the converter to perform output distribution, as follows: During the power allocation process, the cost calculation formula is: Among them, P net(t) is the total active power exchanged between the multi-port device and the large power grid at time t; B(t) is the array data of the electricity price factor at time t; N i is the load level of the ith station area, P i (t), P i-1 (t) are the power allocation values ​​of the ith station at time t and time t-1 respectively; M i (t) is the power factor array data of the ith area at time t. The loads are sorted according to the calculation results of the cost calculation formula, and the power is adjusted by sorting the loads from large to small according to the results.

[0041] The adjustment algorithm is as follows: 1. Constraints The power exchange constraints between the multi-port AC / DC converter and the large power grid are: ΣP PV (t)+P bat (t)+P net (t)=ΣP L (t)+ΣP Loss (t); The photovoltaic power generation constraint in the i-th station is: 0≤P PV,i (t)≤P PVN,i (t); Among them, P PV,i (t) is the power generated by the photovoltaic power source in the i-th station at time t, P PVN,i (t) is the rated power of the photovoltaic power source in the i-th station.

[0042] The state of charge constraint of the energy storage device is: S oc,min ≤S oc,t ≤S oc,max ; S oc,t is the battery charge state at time t, S oc,min S is the lower limit of the charge allowed for the energy storage device to discharge. oc,max The upper limit of the charge allowed for the energy storage device.

[0043] The energy storage power limit constraint is: P CMAX ≤P bat (t)≤P DMAX ; Among them, P CMAX is the maximum discharge power of energy storage; P DMAX Maximum charging power of energy storage.

[0044] 2. Adjustment methods under different working conditions Condition 1: P bat (t) = 0; P net(t)=0;ΣP PV (t)=ΣP L (t)+ΣP Loss (t); S oc,t ≥S oc,max At this time, the energy storage device has reached the upper limit of charging, and the photovoltaic output meets the load demand. At this time, the energy storage device is neither charging nor discharging, and the large power grid does not output power.

[0045] Condition 2: P net (t)=ΣP PV (t)-ΣP L (t)-ΣP Loss (t)>0;P bat (t)=0; when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t ≥S oc,max At this time, the energy storage device has reached the upper limit of charging, and the photovoltaic overflow power is transmitted to the large power grid. The energy storage device is neither charging nor discharging.

[0046] Condition 3: P bat (t)=ΣP L (t)+ΣP Loss (t)-ΣP PV (t)<0;P net (t)=0; when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t oc,max When P CMAX ≥ΣP PV (t)-ΣP L (t)-ΣP Loss (t), that is, at this time the energy storage device can receive all the overflow power of the photovoltaic power source.

[0047] Condition 4: P bat (t)=-P CMAX ;P net (t)=ΣP L (t)+P bat (t)+ΣP Loss (t)-ΣP PV (t); When ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t oc,max When P CMAX ≤ΣP PV ​​(t)-ΣP L (t)-ΣP Loss (t), that is, at this time the energy storage device is not sufficient to receive all the overflow power of the photovoltaic power source, so the energy storage device is charged according to the maximum input power, and the remaining overflow power is input into the large power grid.

[0048] Condition 5: P bat (t)=ΣP L (t)+ΣP Loss (t)-ΣP PV (t)>0;P net (t)=0; when ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t >S oc,min When P DMAX ≥ΣP L (t)+ΣP Loss (t)-ΣP PV (t), that is, the photovoltaic output is less than the load and active power loss and the output of the energy storage device is sufficient to compensate for this shortfall. The energy storage device determines the output power based on the difference, and the multi-port device does not exchange power with the large power grid.

[0049] Condition 6: P bat (t) = P DMAX >0;P net (t) = P DMAX +ΣP PV (t)-ΣP L (t)+ΣP Loss (t)<0; When ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t >S oc,min When P DMAX <ΣP L (t)+ΣP Loss (t)-ΣP PV (t), that is, the photovoltaic output is less than the load and active power loss and the output of the energy storage device is not enough to compensate for this shortfall. In this case, the energy storage device outputs at the maximum output power, and the remaining power shortfall is supplemented by the large power grid.

[0050] Condition 7: P bat (t) = 0; P net (t)=ΣP PV (t)-ΣP L (t)+ΣP Loss (t)<0; when ΣP PV (t)<ΣP L(t)+ΣP Loss (t); S oc,t oc,min When the photovoltaic output is less than the load and active power loss and the energy storage device has reached the lower limit of allowable discharge, the load power shortage is supplemented by the large power grid.

[0051] The central controller determines the current working condition of the entire multi-port device and determines the power reference value of each area according to the algorithm. The local controller of each area reads the reference value and distributes power accordingly. For example, assuming that the multi-port device is in working condition 6 at time t, the power reference value of each area allocated by the central controller is: The power reference value of the energy storage area is P bat (t) = P DMAX ; The output of the photovoltaic area remains unchanged; The power reference value of the large power grid area is P net (t) = P DMAX +ΣP PV (t)-ΣP L (t)+ΣP Loss (t).

[0052] In addition, in some embodiments, after redistributing power according to the adjusted power flow coordination target, the local controller updates the information of each array in the substation, recalculates the load rate, updates the power factor array, and determines the state of the energy storage device. After the power flow coordination, the central controller re-determines the photovoltaic overflow situation. If the photovoltaic output still has overflow and the energy storage device has margin, the overflow power is absorbed by the energy storage device. If the photovoltaic device still has power overflow, the local controller limits the photovoltaic output.

[0053] According to the above working conditions, in order to reduce the power obtained by multi-port devices from the large power grid, energy storage devices need to actively participate in power regulation. In other words, in order to reduce the occurrence of working condition 7, the status of the energy storage device is crucial, so it is necessary to ensure that the energy storage device has sufficient power as much as possible. If overflow power occurs in the system, the status of the energy storage device should be checked as soon as possible and the energy storage should be charged in time. Therefore, when judging the working condition of the multi-port device, the central controller will give priority to judging whether it is in working condition 3 or working condition 4. If it is, the power allocation indicator corresponding to the working condition will be executed immediately. If it is not, the central controller will determine whether it is in other working conditions.

[0054] Step S104: Update the current power factor array of each area, and determine the power demand or margin of each area after power adjustment; and upload the power demand or margin to In this step, the local controller updates the current power factor array of each area converter, and then determines the power demand and margin of each area after the power flow coordination. The information is uploaded to the central controller for status monitoring and preparation for the next power flow coordination.

[0055] The power of each area at time t is P i,t ​; The rated power of each area is P iN , the difference between the current power and the rated power is ΔP=P iN -P i,t ; If ΔP>0, it is the power demand; ΔP<0 is the power margin. After the system is stable, the central controller records the information uploaded by the local controllers of each substation and the inflow and outflow conditions of the current at both ends of each current coordination controller. Store the real-time power value, real-time electricity price factor and various data for subsequent use, so as to repeat the monitoring and adjustment continuously to achieve the coordinated control of the current.

[0056] In summary, the power flow coordinated control method for an AC / DC conversion device proposed in the embodiment of the present invention has the following advantages: (1) Improving response speed and system stability: By introducing a double-layer structure of a central controller and a local controller, the present invention can quickly respond to instantaneous load changes and fluctuations in renewable energy. Compared with traditional master-slave control and adaptive control methods, this structure realizes real-time data collection and processing, significantly improves the response speed of the system, and thus enhances the stability of the power system.

[0057] (2) Optimize power distribution and improve system efficiency: The present invention optimizes power scheduling by calculating load rate and electricity price information in real time to ensure balanced power output of each port. This optimization not only reduces the risk of equipment overload or idleness, but also reduces the energy fed into the power grid, thereby effectively reducing system operating costs and improving the overall system efficiency.

[0058] (3) Strong flexibility and scalability: The design of the present invention fully considers the flexibility and scalability of the system, and can adapt to grid applications of different sizes and types. Through the human-computer interaction interface, users can easily modify control parameters. The system also supports continuous monitoring of the operating status of each substation and makes adjustments based on real-time data to ensure that it adapts to the ever-changing power demand. This flexibility enables the system to remain efficient and reliable under different operating conditions.

[0059] like Figure 3 As shown, an embodiment of the present invention further provides a power flow coordination control system for an AC / DC conversion device, the system comprising: The load level classification module 10 is used to number the substations in the device, and scan the load power of each substation according to the numbering result, so as to obtain the load level corresponding to each substation according to the load power of each substation, determine the load type according to the load level, and set the initial power factor array to zero; The substation evaluation module 20 is used to collect the current information, load power information and electricity price information of each substation at a first preset time interval, evaluate each substation according to the current information, the load power information and the electricity price information, and determine whether the evaluation result meets the preset substation power flow adjustment condition; The power regulation determination module 30 is used to perform power regulation based on the preset area power flow control strategy if the evaluation result meets the preset area power flow adjustment condition; The array updating module 40 is used to update the current power factor array of each substation, and determine the power demand or margin of each substation after power adjustment; and upload the power demand or margin.

[0060] On the other hand, the present invention further proposes a computer storage medium on which one or more programs are stored, and when the program is executed by a processor, the above-mentioned power flow coordinated control method for an AC / DC conversion device is implemented.

[0061] On the other hand, the present invention also proposes an electronic device, including a memory and a processor, wherein the memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to implement the above-mentioned power flow coordinated control method for AC / DC conversion devices.

[0062] Those skilled in the art will appreciate that the logic and / or steps represented in the flowchart or otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For purposes of this specification, "computer-readable medium" may be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0063] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0064] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or a combination thereof: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A power flow coordinated control method for an AC / DC conversion device, characterized in that: The method comprises: Numbering the substations in the device, and scanning the load power of each substation according to the numbering result, so as to obtain the load level corresponding to each substation according to the load power of each substation, determine the load type according to the load level, and set the initial power factor array to zero; Collecting current information, load power information and electricity price information of each substation at a first preset time interval, evaluating each substation according to the current information, the load power information and the electricity price information, and determining whether the evaluation result meets the preset substation power flow adjustment condition; If the evaluation result meets the preset area power flow adjustment conditions, power adjustment is performed based on the preset area power flow control strategy; Update the current power factor array of each area, and determine the power demand or margin of each area after power adjustment; and upload the power demand or margin.

2. The power flow coordinated control method for an AC / DC conversion device according to claim 1, characterized in that: The steps of numbering the substations in the device, scanning the load power of each substation according to the numbering result, obtaining the load level corresponding to each substation according to the load power of each substation, and determining the load type according to the load level include: The load levels include level 1, 2, ..., N from low to high, and the load types include critical load, ordinary load and non-critical load; When the load power is greater than or equal to the first preset power threshold, it is a critical load; When the load power is less than the first preset power threshold and greater than the second preset power threshold, it is a normal load; When the load power is less than or equal to the second preset power threshold, it is a non-critical load; Construct a pairwise correspondence table between load levels, load types, and load powers.

3. The power flow coordinated control method for an AC / DC conversion device according to claim 2 is characterized in that: The step of collecting the current information, load power information and electricity price information of each substation at a first preset time interval to evaluate each substation according to the current information, the load power information and the electricity price information includes: The load fluctuation value is calculated according to the following formula: ΔP i (t)=[P i (t)-P i (t-1)] / P i (t-1) Among them, P i (t) is the storage power information of the ith station in the tth cycle, P i (t-1) is the storage power information of the ith station in the t-1th cycle, ΔP i (t) indicates the load fluctuation value of the ith substation in the tth cycle; The critical loads are sorted from large to small according to the load fluctuation value, the common loads are sorted in descending order according to the load fluctuation value, and the non-critical loads are sorted in descending order according to the load fluctuation value. Finally, the power factors M, M-1, ..., 1 corresponding to each load type are obtained according to the sequence number from high to low; The electricity price is assessed according to the following formula: ΣP PV (t)+P bat (t)+P net (t)=ΣP L (t)+ΣP Loss (t) Among them, ΣP PV (t) is the total active power generated by the photovoltaic power source at time t, P bat (t) is the active power of energy storage at time t, assuming that discharge is positive and charge is negative, P net (t) is the total active power exchanged between the multi-port device and the large power grid at time t. Assume that the power sent to the large power grid is positive, and the power sent to the large power grid is negative. L (t) is the total active power in the multi-port device, ΣP Loss (t) is the total active power loss in the multi-port device.

4. The power flow coordinated control method for an AC / DC conversion device according to claim 3 is characterized in that: The step of judging whether the evaluation result meets the preset area power flow adjustment condition comprises: Determine whether the power fluctuation of the power adjustment area is less than a first preset threshold, whether the load rate of the photovoltaic area is less than a second preset threshold, whether the load rate of the power adjustment area is within a first preset range, and whether the energy storage device is fault-free; If the power fluctuation of the power adjustment area is less than the first preset threshold, and the load rate of the photovoltaic area is less than the second preset threshold, and the load rate of the power adjustment area is within the first preset range, and the energy storage device has no faults, it is determined that the preset area flow adjustment conditions are met.

5. The power flow coordinated control method for an AC / DC conversion device according to claim 3, characterized in that: If the evaluation result satisfies the preset area power flow adjustment condition, the step of adjusting the power based on the preset area power flow control strategy includes: in the power allocation process, the cost calculation formula is: Among them, P net (t) is the total active power exchanged between the multi-port device and the large power grid at time t, B(t) is the array data of the electricity price factor at time t, N i is the load level of the ith station area, M i (t) is the power factor array data of the ith area at time t; The loads are sorted according to the calculation results of the cost calculation formula, and the power is adjusted by sorting the loads from large to small according to the results.

6. The power flow coordinated control method for an AC / DC conversion device according to claim 5, characterized in that: The steps of sorting the loads according to the calculation results of the cost calculation formula and adjusting the power by sorting the loads from large to small according to the results include: The power exchange constraints between the AC / DC conversion device and the large power grid are: ΣP PV (t)+P bat (t)+P net (t)=ΣP L (t)+ΣP Loss (t); The photovoltaic power generation constraint in the i-th station is: 0≤P PV,i (t)≤P PVN,i (t); Among them, P PV,i (t) is the power generated by the photovoltaic power source in the i-th station at time t, P PVN,i (t) is the rated power of the photovoltaic power source in the i-th station; The state of charge constraint of the energy storage device is: S oc,min ≤S oc,t ≤S oc,max ; S oc,t is the battery charge state at time t, S oc,min S is the lower limit of the charge allowed for the energy storage device to discharge. oc,max The upper limit of the charge allowed for the energy storage device; The energy storage power limit constraint is: P CMAX ≤P bat (t)≤P DMAX ; Among them, P CMAX is the maximum discharge power of energy storage, P DMAX Maximum charging power of energy storage; The current working condition of the entire multi-port device is determined, the power reference value of each area is determined according to the algorithm, and power is allocated according to the power reference value.

7. The power flow coordinated control method for an AC / DC conversion device according to claim 6, characterized in that: The step of judging the current working condition of the entire multi-port device, determining the power reference value of each area according to an algorithm, and performing power distribution according to the power reference value comprises: Condition 1: P bat (t) = 0; P net (t)=0;ΣP PV (t)=ΣP L (t)+ΣP Loss (t); S oc,t ≥S oc,max At this time, the energy storage device has reached the upper limit of charging, and the photovoltaic output meets the load demand. At this time, the energy storage device is neither charging nor discharging, and the large power grid does not output power; Condition 2: P net (t)=ΣP PV (t)-ΣP L (t)-ΣP Loss (t)>0;P bat (t)=0; when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t ≥S oc,max When the energy storage device has reached the upper limit of charging, the photovoltaic overflow power is transmitted to the large power grid, and the energy storage device is neither charged nor discharged; Condition 3: P bat (t)=ΣP L (t)+ΣP Loss (t)-ΣP PV (t)<0;P net (t)=0; when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t oc,max When P CMAX ≥ΣP PV (t)-ΣP L (t)-ΣP Loss (t), that is, at this time, the energy storage device can receive all the overflow power of the photovoltaic power source;​ Condition 4: P bat (t)=-P CMAX ;P net (t)=ΣP L (t)+P bat (t)+ΣP Loss (t)-ΣP PV (t); when ΣP PV (t)>ΣP L (t)+ΣP Loss (t); S oc,t oc,max When P CMAX ≤ΣP PV (t)-ΣP L (t)-ΣP Loss (t), that is, at this time, the energy storage device is not sufficient to receive all the overflow power of the photovoltaic power source, so the energy storage device is charged according to the maximum input power, and the remaining overflow power is input into the large power grid;​ Condition 5: P bat (t)=ΣP L (t)+ΣP Loss (t)-ΣP PV (t)>0;P net (t)=0; when ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t >S oc,min When P DMAX ≥ΣP L (t)+ΣP Loss (t)-ΣP PV (t), that is, the photovoltaic output is less than the load and active power loss and the output of the energy storage device is sufficient to compensate for the shortfall. The energy storage device determines the output power based on the difference, and the multi-port device does not exchange power with the large power grid; Operating condition 6: P bat (t) = P DMAX > 0; P net (t) = P DMAX + ΣP PV (t) - ΣP L (t) + ΣP Loss (t) < 0; When ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t >S oc,min When P DMAX <ΣP L (t)+ΣP Loss (t)-ΣP PV (t), that is, the photovoltaic output is less than the load and active power loss and the output of the energy storage device is not enough to compensate for this shortfall, then the energy storage device outputs at the maximum output power, and the remaining power shortfall is supplemented by the large power grid; Condition 7: P bat (t) = 0; P net (t)=ΣP PV (t)-ΣP L (t)+ΣP Loss (t)<0; when ΣP PV (t)<ΣP L (t)+ΣP Loss (t); S oc,t oc,min When the photovoltaic output is less than the load and active power loss and the energy storage device has reached the lower limit of allowable discharge, the load power shortage is supplemented by the large power grid.​ 8. A power flow coordinated control system for an AC / DC conversion device, characterized in that: The system comprises: The load level classification module is used to number the substations in the device, and scan the load power of each substation according to the numbering result, so as to obtain the load level corresponding to each substation according to the load power of each substation, determine the load type according to the load level, and set the initial power factor array to zero; A substation evaluation module, configured to collect current information, load power information, and electricity price information of each substation at a first preset time interval, evaluate each substation according to the current information, the load power information, and the electricity price information, and determine whether the evaluation result meets the preset substation power flow adjustment condition; A power regulation determination module is used to perform power regulation based on a preset area power flow control strategy if the evaluation result meets the preset area power flow adjustment condition; The array update module is used to update the current power factor array of each substation, and determine the power demand or margin of each substation after power adjustment; and upload the power demand or margin.

9. A storage medium, characterized in that: include: The storage medium stores one or more programs, which, when executed by the processor, implement the power flow coordinated control method for an AC / DC conversion device as described in any one of claims 1-7.

10. An electronic device, characterized in that: The electronic device comprises a memory and a processor, wherein: The memory is used to store computer programs; When the processor is used to execute the computer program stored in the memory, it implements the power flow coordinated control method for an AC / DC conversion device described in any one of claims 1-7.

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