A method and system for operating simulation of a direct current power distribution system with energy storage devices

Abstract

The application provides a method and system for simulating operation of a direct current power distribution system with an energy storage device, comprising: setting an initial value of a direct current voltage in the direct current power distribution system; reading a control mode of a voltage source converter and the energy storage device in the direct current power distribution system and a state of charge of the energy storage device; adjusting the control mode of the voltage source converter and the energy storage device according to the initial value of the direct current voltage in the direct current power distribution system and the state of charge of the energy storage device; and performing power flow simulation calculation on the power distribution system after the control mode of the voltage source converter and the energy storage device is adjusted. The method and system can effectively cope with the characteristics of the energy storage device in the direct current power distribution system, such as the changeable state of charge and the flexible adjustment of the control mode, and meet the power flow calculation requirements of the direct current power distribution system with the energy storage device.

Description

Technical Field

[0001] The present invention belongs to the technical field of operation simulation calculation of a DC power distribution system, and in particular relates to an operation simulation method and system for a DC power distribution system with an energy storage device. Background Art

[0002] With the rapid development and widespread application of new energy, new materials, and power electronics technologies, users are increasingly demanding power supply quality, reliability, and operational efficiency. Existing AC distribution networks are facing significant challenges, including the diversification of power demand, the large-scale integration of distributed generation, and the complexity of coordinated power flow control. On the one hand, the type and number of power-consuming devices in distribution networks have changed significantly, with a large number of DC-powered devices such as electric vehicles, energy storage devices, and LED lighting becoming widely used. On the other hand, the use of DC-connected distributed generation, such as photovoltaics and fuel cells, can eliminate the need for conversion and improve overall operational efficiency. These shifts in the power demands of DC devices have necessitated the development of DC distribution technology.

[0003] DC power distribution system uses DC voltage (U dc ) control, voltage droop characteristic (Droop) control, and constant power (P) control. There are various control methods. When running simulation calculations, it is necessary to take into account the adjustments between different control methods and perform equivalent node processing for power flow calculations for different control methods.

[0004] At the same time, due to the access of the energy storage device, its flexible power control capability provides strong support for the system operation. It is worth noting that the energy storage device is affected by its own SOC, and the control method cannot be adjusted arbitrarily. It is necessary to consider the operating status of the energy storage device and make reasonable adjustments on this basis to complete the DC distribution system operation simulation calculation.

[0005] In view of this, it is very necessary to invent an operation control method for a DC power distribution system with an energy storage device. Summary of the Invention

[0006] To overcome the above-mentioned deficiencies of the prior art, the present invention proposes an operation simulation method for a DC power distribution system with an energy storage device, the improvement of which includes:

[0007] Set the initial value of the DC voltage in the DC distribution system;

[0008] Read the control mode and charge state of the voltage source converter and energy storage device in the DC power distribution system;

[0009] adjusting a control mode of the voltage source converter and the energy storage device according to an initial value of the DC voltage in the DC power distribution system and a charge state of the energy storage device;

[0010] The power flow simulation calculation is performed on the distribution system after adjusting the control mode of the voltage source converter and energy storage device.

[0011] Preferably, adjusting the control mode of the voltage source converter and the energy storage device according to the initial value of the DC voltage in the DC power distribution system and the state of charge of the energy storage device includes:

[0012] Step 1: Determine whether the initial value of the DC voltage in the DC power distribution system is higher than the stability threshold: if so, execute step 2; otherwise, execute step 3;

[0013] Step 2: Determine whether the state of charge of the energy storage device is higher than the low alarm value: If so, maintain the voltage source converter and energy storage device control mode and execute step 3; otherwise, switch the energy storage device control mode to the first constant power control mode and execute step 3;

[0014] Step 3: Determine whether the state of charge of the energy storage device is lower than the stable first upper limit. If so, proceed to step 4. Otherwise, switch the control mode of the energy storage device to the second constant power control mode and then execute step 4.

[0015] Step 4: Determine whether the state of charge of the energy storage device is lower than the stable second upper limit: If so, execute step 5; otherwise, switch the control mode of the energy storage device to the DC voltage control mode, and convert the voltage source converter to the constant power control mode or exit operation and execute step 5;

[0016] Step 5: Determine whether the state of charge of the energy storage device is lower than the stability limit: If so, an alarm is issued and the simulation ends; otherwise, the energy storage device control mode is switched to the voltage droop characteristic control mode, and the voltage source converter is switched to the voltage droop characteristic control mode or exits operation;

[0017] The stable first upper limit is greater than the stable second upper limit.

[0018] Preferably, the calculation formula for the initial power value of the energy storage device in the first constant power control mode is as follows:

[0019]

[0020] Where, P dc01 represents the initial power value of the energy storage device in the first constant power control mode, SOC represents the state of charge, P bess represents the rated power of the energy storage device, C is the set of voltage source converters, k represents the kth voltage source converter, P krepresents the rated power of the kth voltage source converter; α is the primary loss fitting coefficient, β is the secondary loss fitting coefficient; U dc0 is the initial value of DC voltage.

[0021] Preferably, the calculation formula for the initial power value of the energy storage device in the second constant power control mode is as follows:

[0022]

[0023] Where, P dc02 represents the initial power value of the energy storage device in the second constant power control mode, SOC represents the state of charge, P bess Represents the rated power of the energy storage device, P l Represents the total power of DC load, P dg represents the total power of distributed power; α is the primary loss fitting coefficient, β is the secondary loss fitting coefficient; U dc0 is the initial value of DC voltage.

[0024] Preferably, the initial value of the DC voltage in the DC voltage control mode is set as:

[0025] U dc01 =U dcref

[0026] Where U dc01 is the initial value of DC voltage in DC voltage control mode, U dcref is the DC voltage reference value.

[0027] Preferably, the calculation formula of the initial value of the DC voltage in the voltage droop characteristic control mode is as follows:

[0028] U dc02 =U dcref +k p0 (P dc0 -P ref );

[0029] Where U dc02 is the initial value of DC voltage in voltage droop characteristic control mode, U dcref is the DC voltage reference value, k p0 represents the droop coefficient, P dc0 Indicates the initial value of power, P ref Indicates the active power reference value of the energy storage device, k p0 represents the droop coefficient;

[0030] Droop coefficient k p0 The calculation formula is as follows:

[0031]

[0032] Among them: Udcmin Indicates the minimum allowable DC voltage, P bess represents the rated power of the energy storage device; SOC represents the state of charge; α is the primary loss fitting coefficient, and β is the secondary loss fitting coefficient.

[0033] Preferably, the power flow simulation calculation of the power distribution system after adjusting the control mode of the voltage source converter and the energy storage device includes:

[0034] According to the adjusted control mode of the voltage source converter and the energy storage device, the DC distribution system parameters are updated and a DC distribution system Y matrix is ​​generated;

[0035] Performing DC power distribution system power flow calculation according to the DC power distribution system Y matrix;

[0036] Determine whether the power flow calculation results converge. If so, output the simulation results and end; otherwise, adjust the control mode of the voltage source converter and the energy storage device according to the DC distribution system parameters and the charge state of the energy storage device and continue the power flow simulation calculation until the power flow calculation results converge.

[0037] Based on the same inventive concept, the present invention also provides an operation simulation system of a DC power distribution system with an energy storage device, the improvement of which is that it includes: an initialization module, a data reading module, a mode adjustment module and a power flow calculation module;

[0038] The initialization module is used to set the initial value of the DC voltage in the DC power distribution system;

[0039] The data reading module is used to read the control mode of the voltage source converter and the energy storage device in the DC power distribution system and the charge state of the energy storage device;

[0040] The mode adjustment module is configured to adjust the control mode of the voltage source converter and the energy storage device according to the initial value of the DC voltage in the DC power distribution system and the state of charge of the energy storage device;

[0041] The power flow calculation module is used to perform power flow simulation calculation on the power distribution system after adjusting the control mode of the voltage source converter and the energy storage device.

[0042] Preferably, the mode adjustment module includes: a first judgment unit, a second judgment unit, a third judgment unit, a fourth judgment unit and a fifth judgment unit;

[0043] The first judgment unit is configured to judge whether the initial value of the DC voltage in the DC power distribution system is higher than a stability threshold: if so, calling the second judgment unit; otherwise, calling the third judgment unit;

[0044] The second judgment unit is used to judge whether the state of charge of the energy storage device is higher than the low alarm value: if so, maintain the voltage source converter and the energy storage device control mode and call the third judgment unit; otherwise, switch the energy storage device control mode to the first constant power control mode and call the third judgment unit;

[0045] The third judgment unit is used to judge whether the state of charge of the energy storage device is lower than the stable first upper limit, and if so, call the fourth judgment unit; otherwise, switch the control mode of the energy storage device to the second constant power control mode and then call the fourth judgment unit;

[0046] The fourth judgment unit is configured to judge whether the state of charge of the energy storage device is lower than the stable second upper limit: if so, calling the fifth judgment unit; otherwise, switching the control mode of the energy storage device to the DC voltage control mode, and converting the voltage source converter to the constant power control mode or exiting operation and calling the fifth judgment unit;

[0047] The fifth judgment unit is used to judge whether the state of charge of the energy storage device is lower than the stability limit: if so, an alarm is issued and the simulation is terminated; otherwise, the control mode of the energy storage device is switched to a control mode based on the voltage droop characteristic, and the voltage source converter is switched to a control mode based on the voltage droop characteristic or exits operation;

[0048] The stable first upper limit is greater than the stable second upper limit.

[0049] Preferably, the power flow calculation module includes: a matrix generation unit, a power flow calculation unit and a convergence judgment unit;

[0050] The matrix generation unit is configured to update the DC power distribution system parameters and generate a Y matrix of the DC power distribution system according to the adjusted control mode of the voltage source converter and the energy storage device;

[0051] The power flow calculation unit is used to perform power flow calculation of the DC power distribution system according to the DC power distribution system Y matrix;

[0052] The convergence judgment unit is used to judge whether the power flow calculation result converges, and if so, output the simulation result and end; otherwise, call the mode adjustment module and continue the power flow simulation calculation until the power flow calculation result converges.

[0053] Compared with the closest prior art, the present invention has the following beneficial effects:

[0054] The present invention provides an operation simulation method and system for a DC power distribution system with an energy storage device, comprising: setting an initial value of the DC voltage in the DC power distribution system; reading the control mode and state of charge of the voltage source converter and energy storage device in the DC power distribution system; adjusting the control mode of the voltage source converter and energy storage device based on the initial value of the DC voltage in the DC power distribution system and the state of charge of the energy storage device; and performing power flow simulation calculations on the power distribution system after adjusting the control mode of the voltage source converter and energy storage device. This method and system can effectively address the characteristics of the energy storage device in the DC power distribution system, such as the variable state of charge and flexible adjustment of the control mode, and meet the power flow calculation requirements of the DC power distribution system containing the energy storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic flow chart of an operation simulation method for a DC power distribution system with an energy storage device provided by the present invention;

[0056] Figure 2 This is a structural diagram of a single-bus DC power distribution system including an energy storage device according to the present invention;

[0057] Figure 3 A schematic diagram of an embodiment of a method for simulating the operation of a DC power distribution system with an energy storage device provided by the present invention;

[0058] Figure 4 This is a structural diagram of another single-bus DC power distribution system including an energy storage device according to the present invention;

[0059] Figure 5 A schematic diagram of the basic structure of an operation simulation system of a DC power distribution system with an energy storage device provided by the present invention;

[0060] Figure 6 A detailed structural diagram of an operation simulation system of a DC power distribution system with an energy storage device provided by the present invention. DETAILED DESCRIPTION

[0061] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0062] The present invention considers the operation state of the energy storage device and the DC distribution system operation simulation calculation method under different control modes, and calculates the DC voltage (U dc ) control, voltage droop control, and constant power (P) control. By utilizing equivalent node processing for the corresponding control methods, this method completes DC distribution system operation simulation. This method effectively addresses the complex operating conditions of energy storage devices in DC distribution systems, the need for flexible control adjustments, and the lack of effective power flow simulation.

[0063] Example 1:

[0064] The flow chart of the operation simulation method of a DC power distribution system with an energy storage device provided by the present invention is as follows: Figure 1 Shown, including:

[0065] Step 1: Set the initial value of the DC voltage in the DC distribution system;

[0066] Step 2: Read the control mode of the voltage source converter and energy storage device in the DC power distribution system and the state of charge of the energy storage device;

[0067] Step 3: Adjust the control mode of the voltage source converter and the energy storage device according to the initial value of the DC voltage in the DC distribution system and the charge state of the energy storage device;

[0068] Step 4: Perform power flow simulation calculation on the distribution system after adjusting the control mode of the voltage source converter and the energy storage device.

[0069] An example of a single bus DC distribution system structure with energy storage device is as follows: Figure 2 As shown in the figure, it mainly consists of a voltage source converter (VSC) that is responsible for the interconnection of AC and DC power grids, an energy storage device (such as a battery energy storage system (BESS),) a constant power DC load, a local DC load, and a distributed power source (such as photovoltaics).

[0070] When the DC power distribution system runs a simulation calculation, the parameters of the DC power distribution system are first initialized, including setting the initial value of the DC voltage in the DC power distribution system, and then reading the VSC and energy storage device control mode and the energy storage device state of charge (SOC); then the VSC and energy storage device control mode are adjusted, and the energy storage device SOC is set to U according to the method of the present invention. dc Node, Droop node and P node, that is, the control mode of VSC and energy storage device is set to DC voltage control mode, voltage droop characteristic control mode and constant power control mode respectively. The specific process of setting the control mode is as follows:

[0071] Step 31: Determine the initial value U of the DC voltage for this power flow calculation dc0 , if U dc0 Above the stability threshold U dc,stab , then go to step 32; otherwise, go to step 33.

[0072] Step 32: If the energy storage device SOC is higher than the low alarm value SOC alarm , keep the control mode unchanged; if the energy storage device SOC is lower than the low alarm value SOCalarm , the energy storage device control mode is switched to the first constant power (P) control. At this time, the energy storage device is the P node, which absorbs power, and the initial power value is P dc01 Set to:

[0073]

[0074] In the above formula, P bess represents the rated power of the energy storage battery system, C is the VSC set, k represents the kth VSC, P k represents the rated power of the kth VSC; α is the primary loss fitting coefficient, β is the secondary loss fitting coefficient; U dc0 is the initial value of the DC voltage. The VSC and energy storage device control modes are adjusted.

[0075] Step 33: If the energy storage device SOC is lower than the stable first upper limit, i.e. the stable upper limit SOC stabhupper , then go to step 34. If the energy storage device SOC is higher than the upper limit SOC stabhupper , the energy storage device control mode is switched to the second constant power (P) control. At this time, the energy storage device is a P node, which releases power. The initial power value is P dc02 Set to:

[0076]

[0077] In the above formula, P bess Represents the rated power of the energy storage battery system, P l Represents the total power of DC load, P dg represents the total power of distributed power; α is the primary loss fitting coefficient, β is the secondary loss fitting coefficient; U dc0 is the initial value of the DC voltage. The VSC and energy storage device control modes are adjusted.

[0078] Step 34: If the energy storage device SOC is lower than the stable second upper limit, that is, the stable upper limit SOC stabupper , then go to step 35; if the energy storage device SOC is higher than the upper limit SOC stabupper , switch the energy storage device control mode to DC voltage (U dc ) control, at this time the energy storage device is U dc Node, controls DC voltage and balances active power in the network, that is, the balance node, the initial value of DC voltage is U dc01 Set to:

[0079] U dc01 =U dcref

[0080] In the above formula, U dcref= is the DC voltage reference value. Simultaneously, each VSC switches to constant power (P) control (at this point, each VSC is a P node, and the initial power value remains the same as before the switch) or exits operation. The VSC and energy storage device control modes are adjusted.

[0081] Step 35: If the energy storage device SOC is lower than the stability limit SOC stab , then the alarm will exit the calculation; if the energy storage device SOC is higher than the stability limit SOC stab , the energy storage device control mode is switched to voltage droop control. At this time, the energy storage device is a droop node, and power sharing is achieved according to the DC power-voltage slope to ensure DC voltage stability. Its initial DC voltage value U dc02 and the initial power value P dc0 satisfy:

[0082] U dc02 =U dcref +k p0 (P dc0 -P ref )

[0083] Droop coefficient k p0 satisfy:

[0084]

[0085] Where: k p0 Indicates the droop coefficient, U dcref and U dcmin Respectively represent the DC voltage reference value and the DC voltage minimum allowable value, P ref and P bess α represents the active power reference value of the energy storage device and the rated power of the energy storage battery system, respectively; α is the primary loss fitting coefficient, and β is the secondary loss fitting coefficient. Simultaneously, each VSC switches to voltage droop control. At this point, each VSC becomes a droop node and calculates its initial power value based on its preset droop coefficient, or exits operation. The VSC and energy storage device control modes are adjusted.

[0086] Example 2:

[0087] A specific embodiment of an operation simulation method for a DC power distribution system with an energy storage device is given below.

[0088] The operation simulation method of the DC distribution system with energy storage device is as follows: Figure 3 As shown, first initialize the DC power distribution system parameters, read the VSC and energy storage device control mode, energy storage device SOC; then adjust the VSC and energy storage device control mode, and use the method of the present invention to set it to U according to the energy storage device SOC.dc Nodes, Droop nodes, and P nodes; then update the parameters to generate the Y matrix of the DC distribution system; further use the Newton-Raphson algorithm (NR) and other methods to calculate the DC distribution system power flow. If convergence is achieved, the simulation calculation results are output; otherwise, the VSC and energy storage device control mode adjustments are entered.

[0089] The structure of a single busbar DC distribution system with energy storage device is as follows: Figure 4 As shown in the figure, it mainly consists of a voltage source converter (VSC) responsible for the interconnection of AC and DC power grids, an energy storage device (such as a battery energy storage system (BESS),) local DC loads, and distributed generation (DG).

[0090] Figure 4 In the figure, the parameter subscripts e, vsc, and dc represent the physical quantities of the voltage control VSC, power control VSC, and DC bus, respectively. e , i1 represent the output voltage and DC current of voltage control VSC, U vsc 、i2、C vsc 、P vsc They represent the DC voltage, DC current, DC side capacitance, and active power of the power control VSC, respectively. dc 、C dc Respectively represent the DC bus voltage and the DC side capacitance of the energy storage DC / DC converter. r1 and r2 are the resistance values ​​of each line, L1 and L2 are the reactance values ​​of each line. b , P l , P dg They are the energy storage DC / DC converter power, the total DC load power and the total distributed power supply power.

[0091] Figure 3 In the embodiment, the specific process of adjusting the control mode of the VSC and the energy storage device is the same as the control mode adjustment method in Example 1 and will not be repeated here.

[0092] After the VSC and energy storage device control mode adjustments are completed, the parameters are updated to generate the DC distribution system Y matrix:

[0093] Assuming that the DC distribution system model has n nodes, the injection current model is used, that is, the current injected into DC node i can be expressed as the expression of the current flowing through the other n-1 nodes in the DC distribution system, which is:

[0094]

[0095] Where I i 、U iis the DC current and DC voltage of node i; j represents the jth node, n represents the total number of nodes; Y ij is the admittance between nodes ij; U j is the DC voltage at node j.

[0096] If the current is written in matrix form, it satisfies:

[0097] I=YU

[0098] Where I is the DC current vector, Y is the DC node admittance matrix, and U is the DC voltage vector.

[0099] Active power P injected into node i i It can be expressed as:

[0100]

[0101] Using the Newton-Raphson algorithm (NR) to solve, we can get the mth iteration:

[0102]

[0103] The Newton-Raphson algorithm (NR) and other methods are used to calculate the DC distribution system power flow. If convergence is achieved, the simulation calculation results are output; otherwise, the VSC and energy storage device control modes are adjusted.

[0104] Example 3:

[0105] Based on the same inventive concept, the present invention also provides an operation simulation system for a DC power distribution system with an energy storage device. Since the principles of these devices for solving technical problems are similar to the operation simulation method for a DC power distribution system with an energy storage device, the repeated parts will not be repeated.

[0106] The basic structure of the system is as follows Figure 5 As shown, it includes: initialization module, data reading module, mode adjustment module and power flow calculation module;

[0107] The initialization module is used to set the initial value of the DC voltage in the DC power distribution system;

[0108] A data reading module, used to read the control mode of the voltage source converter and energy storage device in the DC power distribution system and the charge state of the energy storage device;

[0109] A mode adjustment module, configured to adjust the control mode of the voltage source converter and the energy storage device according to the initial value of the DC voltage in the DC power distribution system and the state of charge of the energy storage device;

[0110] The power flow calculation module is used to perform power flow simulation calculations on the power distribution system after adjusting the control modes of the voltage source converter and the energy storage device.

[0111] The detailed structure of the operation simulation system of the DC distribution system with energy storage device is as follows: Figure 6 shown.

[0112] The mode adjustment module includes: a first judgment unit, a second judgment unit, a third judgment unit, a fourth judgment unit and a fifth judgment unit;

[0113] The first judgment unit is used to judge whether the initial value of the DC voltage in the DC power distribution system is higher than the stability threshold: if so, calling the second judgment unit; otherwise calling the third judgment unit;

[0114] a second determination unit, configured to determine whether the state of charge of the energy storage device is higher than a low alarm value; if so, maintaining the voltage source converter and the energy storage device control mode and invoking the third determination unit; otherwise, switching the energy storage device control mode to the first constant power control mode and invoking the third determination unit;

[0115] a third judgment unit, configured to judge whether the state of charge of the energy storage device is lower than a stable first upper limit, and if so, call the fourth judgment unit; otherwise, switch the control mode of the energy storage device to the second constant power control mode and then call the fourth judgment unit;

[0116] a fourth determination unit, configured to determine whether the state of charge of the energy storage device is lower than a stable second upper limit: if so, calling the fifth determination unit; otherwise, switching the control mode of the energy storage device to a DC voltage control mode, and converting the voltage source converter to a constant power control mode or exiting operation and calling the fifth determination unit;

[0117] a fifth judgment unit, configured to judge whether the state of charge of the energy storage device is lower than the stability limit; if so, an alarm is issued and the simulation is terminated; otherwise, the control mode of the energy storage device is switched to a voltage droop characteristic control mode, and the voltage source converter is switched to a voltage droop characteristic control mode or exits operation;

[0118] The stable first upper limit is greater than the stable second upper limit.

[0119] The power flow calculation module includes: a matrix generation unit, a power flow calculation unit and a convergence judgment unit;

[0120] a matrix generation unit, configured to update the DC power distribution system parameters and generate a Y matrix of the DC power distribution system according to the adjusted control mode of the voltage source converter and the energy storage device;

[0121] A power flow calculation unit is used to perform power flow calculation of the DC distribution system according to the Y matrix of the DC distribution system;

[0122] The convergence judgment unit is used to judge whether the power flow calculation result converges. If so, the simulation result is output and the process ends; otherwise, the mode adjustment module is called and the power flow simulation calculation continues until the power flow calculation result converges.

[0123] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0124] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0125] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0126] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit its scope of protection. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading this application, those skilled in the art may still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the application.

Claims

1. A method for simulating the operation of a DC power distribution system with an energy storage device, characterized in that: include: Set the initial value of the DC voltage in the DC distribution system; Read the control mode and charge state of the voltage source converter and energy storage device in the DC power distribution system; adjusting a control mode of the voltage source converter and the energy storage device according to an initial value of the DC voltage in the DC power distribution system and a charge state of the energy storage device; Perform power flow simulation calculations on the distribution system after adjusting the control modes of the voltage source converter and energy storage device; The adjusting the control mode of the voltage source converter and the energy storage device according to the initial value of the DC voltage in the DC power distribution system and the charge state of the energy storage device includes: Step 1: Determine whether the initial value of the DC voltage in the DC power distribution system is higher than the stability threshold: if so, execute step 2; otherwise, execute step 3; Step 2: Determine whether the state of charge of the energy storage device is higher than the low alarm value: If so, maintain the voltage source converter and energy storage device control mode and execute step 3; otherwise, switch the energy storage device control mode to the first constant power control mode and execute step 3; Step 3: Determine whether the state of charge of the energy storage device is lower than the stable first upper limit. If so, proceed to step 4. Otherwise, switch the control mode of the energy storage device to the second constant power control mode and then execute step 4. Step 4: Determine whether the state of charge of the energy storage device is lower than the stable second upper limit: If so, execute step 5; otherwise, switch the control mode of the energy storage device to the DC voltage control mode, and convert the voltage source converter to the constant power control mode or exit operation and execute step 5; Step 5: Determine whether the state of charge of the energy storage device is lower than the stability limit: If so, an alarm is issued and the simulation ends; otherwise, the energy storage device control mode is switched to the voltage droop characteristic control mode, and the voltage source converter is switched to the voltage droop characteristic control mode or exits operation; The stable first upper limit is greater than the stable second upper limit.

2. The method according to claim 1, wherein The calculation formula for the initial power value of the energy storage device in the first constant power control mode is as follows: Where, P dc01 represents the initial power value of the energy storage device in the first constant power control mode, SOC represents the state of charge, P bess represents the rated power of the energy storage device, C is the set of voltage source converters, k represents the kth voltage source converter, P k represents the rated power of the kth voltage source converter; α is the primary loss fitting coefficient, β is the secondary loss fitting coefficient; U dc0 is the initial value of DC voltage.

3. The method according to claim 1, wherein The calculation formula for the initial power value of the energy storage device in the second constant power control mode is as follows: Where, P dc02 represents the initial power value of the energy storage device in the second constant power control mode, SOC represents the state of charge, P bess Represents the rated power of the energy storage device, P l Represents the total power of DC load, P dg represents the total power of distributed power; α is the primary loss fitting coefficient, β is the secondary loss fitting coefficient; U dc0 is the initial value of DC voltage.

4. The method according to claim 1, wherein In DC voltage control mode, the initial value of DC voltage is set as: IN dc01 =U dcref Where U dc01 is the initial value of DC voltage in DC voltage control mode, U dcref is the DC voltage reference value.

5. The method according to claim 1, wherein The calculation formula for the initial value of DC voltage in voltage droop characteristic control mode is as follows: IN dc02 =U dcref +k p0 (P dc0 -P ref ); Where U dc02 is the initial value of DC voltage in voltage droop characteristic control mode, U dcref is the DC voltage reference value, k p0 represents the droop coefficient, P dc0 Indicates the initial value of power, P ref Indicates the active power reference value of the energy storage device, k p0 represents the droop coefficient; Droop coefficient k p0 The calculation formula is as follows: Among them: U dcmin Indicates the minimum allowable DC voltage, P bess represents the rated power of the energy storage device; SOC represents the state of charge; α is the primary loss fitting coefficient, and β is the secondary loss fitting coefficient.

6. The method according to claim 1, wherein The power flow simulation calculation of the power distribution system after adjusting the control mode of the voltage source converter and the energy storage device includes: According to the adjusted control mode of the voltage source converter and the energy storage device, the DC distribution system parameters are updated and a DC distribution system Y matrix is ​​generated; Performing DC power distribution system power flow calculation according to the DC power distribution system Y matrix; Determine whether the power flow calculation results converge. If so, output the simulation results and end; otherwise, adjust the control mode of the voltage source converter and the energy storage device according to the DC distribution system parameters and the charge state of the energy storage device and continue the power flow simulation calculation until the power flow calculation results converge.

7. An operation simulation system of a DC power distribution system with an energy storage device, characterized in that: include: Initialization module, data reading module, mode adjustment module and power flow calculation module; The initialization module is used to set the initial value of the DC voltage in the DC power distribution system; The data reading module is used to read the control mode of the voltage source converter and the energy storage device in the DC power distribution system and the charge state of the energy storage device; The mode adjustment module is configured to adjust the control mode of the voltage source converter and the energy storage device according to the initial value of the DC voltage in the DC power distribution system and the state of charge of the energy storage device; The power flow calculation module is used to perform power flow simulation calculation on the power distribution system after adjusting the control mode of the voltage source converter and the energy storage device; The mode adjustment module includes: a first judgment unit, a second judgment unit, a third judgment unit, a fourth judgment unit and a fifth judgment unit; The first judgment unit is configured to judge whether the initial value of the DC voltage in the DC power distribution system is higher than a stability threshold: if so, calling the second judgment unit; otherwise, calling the third judgment unit; The second judgment unit is used to judge whether the state of charge of the energy storage device is higher than the low alarm value: if so, maintain the voltage source converter and the energy storage device control mode and call the third judgment unit; otherwise, switch the energy storage device control mode to the first constant power control mode and call the third judgment unit; The third judgment unit is used to judge whether the state of charge of the energy storage device is lower than the stable first upper limit, and if so, call the fourth judgment unit; otherwise, switch the control mode of the energy storage device to the second constant power control mode and then call the fourth judgment unit; The fourth judgment unit is configured to judge whether the state of charge of the energy storage device is lower than the stable second upper limit: if so, calling the fifth judgment unit; otherwise, switching the control mode of the energy storage device to the DC voltage control mode, and converting the voltage source converter to the constant power control mode or exiting operation and calling the fifth judgment unit; The fifth judgment unit is used to judge whether the state of charge of the energy storage device is lower than the stability limit: if so, an alarm is issued and the simulation is terminated; otherwise, the control mode of the energy storage device is switched to a control mode based on the voltage droop characteristic, and the voltage source converter is switched to a control mode based on the voltage droop characteristic or exits operation; The stable first upper limit is greater than the stable second upper limit.

8. The system according to claim 7, wherein: The power flow calculation module includes: a matrix generation unit, a power flow calculation unit and a convergence judgment unit; The matrix generation unit is configured to update the DC power distribution system parameters and generate a Y matrix of the DC power distribution system according to the adjusted control mode of the voltage source converter and the energy storage device; The power flow calculation unit is used to perform power flow calculation of the DC power distribution system according to the DC power distribution system Y matrix; The convergence judgment unit is used to judge whether the power flow calculation result converges, and if so, output the simulation result and end; otherwise, call the mode adjustment module and continue the power flow simulation calculation until the power flow calculation result converges.

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