A power control method for a multi-voltage-level direct current power distribution network

Abstract

A power control method of a multi-voltage-level DC power distribution network comprises the following steps: S1, determining the structure of the multi-voltage-level DC power distribution network; S2, determining whether the switched converter between adjacent buses is turned on according to the current voltage deviation per unit of each bus and the set minimum deviation voltage per unit, if there is a switched converter turned on, turning to step S3, if none of the switched converters is turned on, turning to step S4; S3, determining whether the working converter between each adjacent bus is turned off according to the predicted voltage deviation per unit of each bus and the set minimum deviation voltage per unit of each bus, if there is a working converter not turned off, repeating step S3, if all the working converters are turned off, turning to step S4; S4, each bus is independently operated, and turning to step S2. According to the deviation degree of the voltage per unit of the bus and the size of the mutual power between adjacent buses, the control mode suitable for the current bus is determined, and the coordinated operation of each voltage-level bus in the DC power distribution network can be effectively realized.

Description

Technical Field

[0001] This invention relates to the field of power quality control technology for power distribution networks, and in particular to a power control method for multi-voltage-level DC power distribution networks. Background Technology

[0002] In recent years, with the continuous development of DC power sources and loads, the proportion of DC elements in power distribution systems has been increasing. These DC elements are connected to the AC power distribution network through energy conversion equipment such as inverters and rectifiers, increasing energy loss and grid connection difficulties. In contrast, DC power distribution technology has gradually demonstrated its advantages in efficiency, economy, and reliability. DC power distribution systems have stronger power supply capabilities, better controllability, and the ability to integrate renewable energy.

[0003] With the increase in the types of DC loads and distributed power sources, the system is gradually exhibiting characteristics of multiple converters and multiple voltage levels. The multi-voltage-level DC power distribution system consists of multiple subsystems with different voltage levels, which not only facilitates the integration of various distributed power sources to meet diverse load demands, but also allows for flexible adjustment of power distribution and transmission at each voltage level, achieving coordination between local power supply and cross-regional energy mobilization, and significantly improving energy utilization efficiency.

[0004] Currently, voltage control technology for single-voltage-level DC systems is relatively mature, but energy coordination in multi-voltage-level systems remains insufficient, hindering the overall stable operation of the entire system. By controlling power transfer between different voltage levels, the overall voltage quality of the system can be effectively improved, enabling flexible coordination between multi-voltage-level systems.

[0005] Patent application No. 202410063463.6 discloses a control method and related equipment for a DC islanded microgrid. It can distribute power among various battery energy storage main systems, but it can only control the voltage of a single DC bus equipped with energy storage units, and cannot distribute power among multiple DC buses, thus limiting its application scope and making it unsuitable for systems with multiple voltage levels. Patent application No. 202411032598.2 discloses a voltage regulation method that achieves balanced and coordinated voltage regulation by setting up coordinated voltage regulation for each voltage level. However, it only targets the highest voltage level bus, and the judgment criterion is only whether the highest voltage level bus is above the upper voltage limit or below the lower voltage limit, failing to maintain the voltage of each voltage level bus at a reasonable level. Patent application No. 202311405833.1 discloses a distributed economic control method for low-resistivity AC / DC hybrid microgrid groups, which achieves autonomous and economical operation between AC and DC microgrids, but requires a common connection bus, increasing line costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a power control method for a multi-voltage-level DC distribution network. The method designs two operating modes: droop control when the bus operates independently and mutual power assistance between adjacent buses when the bus voltage deviation is too large. The applicable operating mode of the bus is determined based on the degree of deviation after the bus voltage is normalized and the magnitude of the mutual power assistance between adjacent buses. This enables the coordinated operation of buses of different voltage levels in the DC distribution network, avoids large changes in bus voltage due to faults, and improves the stability of the DC distribution network operation.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical method: a power control method for a multi-voltage level DC distribution network, comprising:

[0008] Step S1: Determine the structure of the multi-voltage level DC distribution network, and denote each bus in the distribution network as a bus. , For the total number of buses, set the adjacent buses to be enabled. Transformer between Time bus or busbar Minimum deviation voltage value required or Using the per-unit method to and Processed as minimum deviation voltage per unit value and , , ;

[0009] Step S2: Real-time acquisition of voltage of each bus, calculation of voltage deviation of each bus using per-unit method, obtaining per-unit value of voltage deviation of each bus, and determining whether the transformer between adjacent buses is turned on according to criterion #1. If any transformer is turned on, proceed to step S3; if none are turned on, proceed to step S4.

[0010] Criterion #1: For a switched-off converter Determine whether the busbar requirement is met. The absolute value of the voltage deviation per unit is greater than or busbar The absolute value of the voltage deviation per unit is greater than If at least one of these conditions is met, the system will determine the bus based on the following: The voltage deviation per unit value determines the converter. The control signal of the bridge arm switch turns on the converter. busbar Establish power mutual assistance between them; if neither is satisfied, the converter... Busbar not turned on The spaces are not connected;

[0011] Step S3: Real-time detection of system operating parameters; Determine whether each converter operating between adjacent buses has exited based on criterion #2. If any converter has not exited, repeat step S3. If all converters have exited, proceed to step S4.

[0012] Criterion #2: Assuming the converter is in operation Exit, predict bus The per-unit value of the voltage deviation, if the predicted busbar The absolute value of the voltage deviation per unit is less than And the predicted busbar The absolute value of the voltage deviation per unit is less than converter Exit, otherwise, converter Keep it on;

[0013] Step S4: Each busbar operates independently, then proceed to step S2.

[0014] Furthermore, step S1 also includes classifying the distributed power sources contained in the multi-voltage level DC distribution network into dispatchable distributed power sources and intermittent distributed power sources according to their output power characteristics. The dispatchable distributed power sources include fuel cells and micro gas turbines, and the intermittent distributed power sources include photovoltaic cells and wind turbines.

[0015] In step S4, each bus operates independently. Droop control is used to control the power output of the dispatchable distributed power sources on each bus, and maximum power point tracking control is used to achieve the maximum power output of the intermittent distributed power sources on each bus.

[0016] Furthermore, the criterion #1 is:

[0017] For the off converter Determine the current busbar per-unit voltage deviation , Does it satisfy the following formula (1)? If it does, then the system will first set the voltage deviation per unit value. per-unit value of voltage deviation The difference is then input into the first PI proportional-integral controller to obtain the converter. Reference current Then the converter Reference current With inductor current measurement value The difference is then input to the second PI proportional-integral controller to obtain the duty cycle signal. Finally, through a pulse width modulation algorithm, the converter is obtained. The control signals for the upper and lower bridge arms are used to start the converter. busbar Establish power mutual assistance; if not, the converter Busbar not turned on The spaces are not connected;

[0018] (1).

[0019] Furthermore, the criterion #2 is:

[0020] For the converter in operation Assuming it exits, predict the bus length according to the following formula. per-unit voltage deviation , ;

[0021] (2)

[0022] In the formula, , These are the current busbars. The per-unit value of voltage deviation; , They represent the busbars respectively. After the converter To the bus Transmitted power; , They represent the converters respectively. At the bus The equivalent droop coefficient for the side is given by the following formula:

[0023] (3)

[0024] (4)

[0025] In the formula, Indicates busbar With busbar The connection status of the busbar If the converters between adjacent buses are all working, it indicates that the bus... With busbar There is a connection. =1, if any converter between adjacent buses is not working, it indicates that the bus... With busbar No connection exists. =0; in solving During the process, and Consider it as 1, because of the assumption of the converter quit, and Consider it as 0; Indicates busbar Maximum allowable deviation voltage value Indicates busbar The equivalent droop coefficient is given by the following formula:

[0026] (5)

[0027] In the formula, Indicates busbar Upper The droop control coefficient of a schedulable distributed power source; Indicates busbar The number of schedulable distributed power sources;

[0028] Judgment of the prediction and Does it satisfy the following equation (6)? If it does, the converter... Exit; if not satisfied, converter Keep it on;

[0029] (6).

[0030] Preferably, the formulas for calculating the minimum deviation voltage per unit value and the voltage deviation per unit value of the bus are as follows:

[0031] (7)

[0032] (8)

[0033] In the formula, , To enable Time bus The minimum per-unit deviation voltage value that needs to be exceeded; , To enable Time bus The minimum deviation voltage value required to be exceeded; , They represent the busbars respectively. Maximum allowable deviation voltage value; Indicates busbar The per-unit value of voltage deviation; Indicates busbar voltage, Indicates busbar The rated voltage.

[0034] The power control method for multi-voltage level DC distribution networks proposed in this invention first uses a per-unit method to determine the degree of voltage deviation of each bus in the multi-voltage level DC distribution network, which can effectively quantify the deviation level of each bus voltage. Then, based on the difference in per-unit voltage deviation of the buses on both sides of the converter, mutual bus voltage control is performed, which can realize that the voltage deviation of the buses on both sides reaches the same level, avoids a large voltage drop caused by a temporary fault, and improves system stability. Finally, this invention calculates an equivalent droop coefficient to represent the droop equivalent characteristics of the bus on one side of the converter and multiple buses in its connection state, and predicts the voltage deviation level of the buses on both sides after the converter is taken out of operation. This realizes the normal exit of mutual control after fault recovery, avoids the converter from working for a long time, reduces converter losses, and extends the service life of the converter. Attached Figure Description

[0035] Figure 1 This is a flowchart of the power control method for multi-voltage level DC distribution networks involved in this invention;

[0036] Figure 2 This is a block diagram of the adjacent bus voltage mutual assistance control in the power control method for multi-voltage level DC distribution networks involved in this invention;

[0037] Figure 3 This is a diagram of the DC distribution network structure used in the simulation experiment of this invention.

[0038] Figure 4 The following are per-unit waveforms of voltage deviation for each bus during the simulation process in this embodiment of the invention (where (a), (b), (c), (d), and (e) are per-unit waveforms of voltage deviation for buses 1, 2, 3, 4, and 5, respectively, during the simulation process).

[0039] Figure 5 This is a schematic diagram of the connection status of each adjacent busbar during the simulation process in an embodiment of the present invention (where (a) is the connection status F of busbars 1 and 2 during the simulation process). 12 (a) is a schematic diagram; (b) shows the connection state F of busbars 2 and 3 during the simulation. 23 (c) is a schematic diagram; (d) shows the connection state F of busbars 2 and 4 during the simulation. 24 (d) is a schematic diagram of the connection state F of busbars 4 and 5 during the simulation. 45 (A schematic diagram). Detailed Implementation

[0040] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0041] like Figure 1As shown, the power control method for multi-voltage level DC distribution networks provided by the present invention mainly includes the following steps.

[0042] Step S1: Determine the structure of the multi-voltage-level DC distribution network.

[0043] Each busbar in the distribution network is denoted as a busbar. , The number of busbars for each voltage level is denoted as follows: The rated voltage of each busbar for each voltage level is denoted as follows: Any adjacent busbar The converter between them is denoted as Enable settings Time bus or busbar Minimum deviation voltage value required or Using the per-unit method to and Processed as minimum deviation voltage per unit value and , , As shown in the following formula:

[0044] (7)

[0045] In the formula, , To enable Time bus The minimum per-unit deviation voltage value that needs to be exceeded; , To enable Time bus The minimum deviation voltage value required to exceed; , They represent the busbars respectively. Maximum allowable deviation voltage value.

[0046] Based on the operating status of the converters between adjacent busbars in the distribution network, the connection status between each busbar is recorded. The connection relationships between busbars include direct connections and indirect connections.

[0047] Direct connection: any adjacent busbars With busbar Connection status Depends on the converter between the two The working state of the converter When working, the busbar With busbar Direct connection, remember However, if the converter If it is not working, then the busbar With busbar No connection, remember ;

[0048] Indirect connection: The connection state of any two non-adjacent buses is the product of the connection states of all adjacent buses between them. For example: assuming bus... With busbar Adjacent, busbar With busbar Adjacent, if the converter and If all are enabled, then , , indicating busbar With busbar Indirect connection, while if the converter or converter If not enabled, or , , indicating busbar With busbar No connection.

[0049] Distributed power sources in multi-voltage DC distribution networks are classified into dispatchable distributed power sources and intermittent distributed power sources according to their output power characteristics. Dispatchable distributed power sources include fuel cells, micro gas turbines, etc., while intermittent distributed power sources include photovoltaic cells, wind turbines, etc.

[0050] Step S2: Determine whether the converters that are shut down between adjacent buses are turned on.

[0051] S201: Real-time acquisition of voltage of each bus, calculation of voltage deviation of each bus using per-unit method, obtaining the current per-unit value of voltage deviation of each bus, monitoring the connection status of each adjacent bus in DC distribution network, if the adjacent bus is not connected, it means that the converter between the adjacent bus has been turned off, proceed to step S202, if the adjacent bus is connected, it means that there is power mutual assistance between the adjacent bus, proceed to step S3;

[0052] Preferably, the formula used in this invention to calculate the per-unit value of bus voltage deviation is as follows:

[0053] (8)

[0054] In the formula, Indicates busbar The per-unit value of voltage deviation; Indicates busbar The voltage; Indicates busbar The rated voltage; Indicates busbar The maximum allowable deviation voltage value. When the bus voltage deviation is less than the maximum allowable deviation voltage value, the per-unit value range of the voltage deviation is (-1, 1).

[0055] S202, determine whether the converters between adjacent buses are turned on according to criterion #1. If any converter is turned on, proceed to step S3. If none of them need to be turned on, proceed to step S4.

[0056] Criterion #1, i.e., the converter activation criterion, is as follows:

[0057] For the off converter Determine whether the busbar requirement is met. The absolute value of the voltage deviation per unit is greater than or meet the requirements of the busbar The absolute value of the voltage deviation per unit is greater than See formula (1) below;

[0058] (1).

[0059] If at least one of them is satisfied, such as Figure 2 As shown, the system first sets the voltage deviation per unit value. per-unit value of voltage deviation The difference is then input into the first PI proportional-integral controller to obtain the converter. Reference current Then the reference current With converter Inductor current measurement value The difference is then input to the second PI proportional-integral controller to obtain the duty cycle signal. Finally, through a pulse width modulation algorithm, the converter is obtained. The control signals for the upper and lower bridge arms are used to start the converter. busbar Establish power mutual assistance and upgrade busbars Connection status If not satisfied, the converter No need to turn on the bus. Keep the connection open.

[0060] It is worth noting that in multi-voltage level DC distribution networks, there are two types of busbars:

[0061] Type 1 busbar: There is only one adjacent busbar. For this type of busbar, only one minimum deviation voltage per unit value needs to be determined.

[0062] The second type of bus: There are multiple adjacent buses. In order to enable different converters to be activated for this type of bus to establish power mutual assistance with different adjacent buses in the event of a fault, this invention sets different minimum deviation voltage per-unit values ​​for different converters to be activated for this type of bus according to the importance and reserve capacity of the adjacent buses. Preferably, the less important the adjacent bus or the larger the reserve capacity, the smaller the minimum deviation voltage per-unit value set for this type of bus to activate the converter between it and the adjacent bus, and vice versa. In this way, when the voltage deviation of this type of bus is too large, if the system has already activated one converter to provide power mutual assistance for the bus, but the voltage deviation of the bus is still worsening, the system can continue to activate other converters to add other adjacent buses to the mutual assistance state, thereby effectively stabilizing the voltage deviation of the bus and improving the reliability of system operation.

[0063] Step S3: Determine whether the converters operating between adjacent buses have exited.

[0064] The system operates in real time, calculates the per-unit voltage deviation of the current bus and the transmission power of the converter, and determines whether the converters operating between adjacent buses have exited according to criterion #2. If there are converters that have not exited, repeat step S3. If all converters have exited, proceed to step S4.

[0065] Criterion #2, i.e., the converter exit criterion, is as follows:

[0066] For the converter in operation Assuming it exits, the busbar is predicted according to the following formula (2). per-unit voltage deviation , ;

[0067] (2)

[0068] In the formula, , These are the current busbars. The per-unit value of voltage deviation; , They represent the busbars respectively. After the converter To the bus Transmitted power; , They represent the converters respectively. At the bus The equivalent droop coefficient on the side represents the converter. The sag equivalent characteristics of one busbar and multiple busbars in their connected states are as follows:

[0069] (3)

[0070] (4)

[0071] In the formula, Indicates busbar With busbar The connection state, in solving During the process, and Consider it as 1, because of the assumption of the converter quit, and Consider it as 0; Indicates busbar Maximum allowable deviation voltage value Indicates busbar The equivalent droop coefficient is given by the following formula:

[0072] (5)

[0073] In the formula, Indicates busbar Upper The droop control coefficient of a schedulable distributed power source; Indicates busbar The number of schedulable distributed power sources;

[0074] Judgment of the prediction and Does it satisfy the following equation (6)? If it does, then the converter... Exit, busbar Intermittently disconnect and update the bus. Connection status If not satisfied, then the converter Unable to exit, busbar Maintain mutual power assistance;

[0075] (6).

[0076] This invention designs an equivalent droop coefficient calculation method, which can calculate the equivalent droop coefficient of each bus during the operation of different converters. The per-unit voltage change caused by power mutual assistance between adjacent buses is equal to the power transmitted from the bus to the adjacent bus through the converter multiplied by the equivalent droop coefficient of the converter on that bus side. Therefore, this invention can predict the per-unit voltage deviation of the two buses after a certain converter is shut down by calculating the sum of the current per-unit voltage deviation of the bus and the per-unit voltage change caused by mutual power. This allows the system to correctly determine whether the converter can be shut down, avoiding the misjudgment that "the converter can be shut down" which would lead to an excessively large bus voltage deviation and the restarting of the converter, resulting in unstable power quality. At the same time, it avoids the misjudgment that "the converter cannot be shut down" which would cause the converter to continue to operate in mutual assistance mode, reducing converter losses and extending the service life of the converter.

[0077] Step S4: Each busbar operates independently, then proceed to step S2.

[0078] When each busbar operates independently, droop control is used to control the power output of the dispatchable distributed power sources on each busbar, and maximum power point tracking control is used to achieve the maximum power output of the intermittent distributed power sources on each busbar.

[0079] Specifically, for busbars The schedulable distributed power source uses droop control, and its expression is:

[0080] (9)

[0081] in, Indicates busbar The voltage; Indicates busbar Upper The droop control coefficient of a schedulable distributed power source. Indicates busbar Upper The output power of each dispatchable distributed power source, the droop control coefficient, allows each dispatchable distributed power source to output power inversely proportional to the droop control coefficient. Therefore, the bus... voltage and bus Total output power of the schedulable distributed power source The relationship is:

[0082] (10)

[0083] In the formula, busbar The equivalent droop coefficient.

[0084] As can be seen from the above, the distribution network in this invention adopts a droop control working mode when the busbar operates independently, and starts a power mutual assistance control working mode when the busbar voltage deviation is large. This can effectively avoid a large drop in busbar voltage caused by a temporary fault, thus improving system stability.

[0085] The following implementation method establishes the following... Figure 3 The DC distribution network topology shown was used for simulation experiments.

[0086] The busbars are numbered 1, 2, 3, 4, and 5 respectively; the rated voltages of the busbars at each voltage level are 600V, 750V, 400V, 440V, and 220V respectively; the maximum allowable voltage deviation values ​​for each busbar are 20V, 50V, 20V, 30V, and 20V respectively; the equivalent sag coefficients for each busbar are 0.0005, 0.02, 0.01, 0.01, and 0.005 respectively; and the converters between adjacent busbars are C... 12 C 23 C 24 C 45 The minimum per-unit deviation voltage of each busbar is: η 12 =0.4, η 21 =0.4, η 23 =0.42, η 24 =0.6, η 32 =0.42, η 42 =0.2, η 45 =0.6, η 54 =0.6; Each bus is equipped with several dispatchable distributed power sources and intermittent distributed power sources, which can keep each bus operating within the voltage deviation range under normal operating conditions.

[0087] During the simulation experiment, such as Figure 4 and Figure 5 As shown: Busbar 2 experiences a load power drop of approximately 7kW during the 3s-5s period, and busbar 5 experiences a load power drop of approximately 2kW during the 4s-6s period; at 3s, due to the voltage drop at busbar 2, based on the minimum deviation voltage per unit value, C... 12 Start, busbars 1 and 2 cooperate, F 12 =1, the voltage of bus 2 is effectively controlled; at 4s, due to the voltage drop of bus 5, according to the minimum deviation voltage per unit value, C 45 With C 24 The buses are activated sequentially, with buses 1, 2, 4, and 5 operating in coordination. (F) 12 =F 24 =F 45 =1; At 5s, the fault on bus 2 is resolved, and after a period of time, C 12 Withdraw from mutual aid, F 12=0, at this time busbars 2, 4, and 5 cooperate with each other, F 24 =F 45 =1; At time 6s, the fault on bus 5 is resolved, C 24 With C 45 Disconnect sequentially, then F 24 =F 45 =0, each bus resumes independent operation; throughout the process, the voltage of each bus does not exceed the maximum allowable deviation voltage value of that bus, which proves that the method proposed in this invention can effectively deal with the voltage sag problem of multi-voltage level DC distribution network and realize the power control of multi-voltage level DC distribution network.

[0088] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

[0089] To facilitate understanding by those skilled in the art of the improvements of this invention over the prior art, some of the accompanying drawings and descriptions have been simplified, and for clarity, some other elements have been omitted from this application. Those skilled in the art should realize that these omitted elements may also constitute the content of this invention.

Claims

1. A power control method for a multi-voltage-level DC distribution network, characterized in that, include: Step S1: Determine the structure of the multi-voltage level DC distribution network, and denote each bus in the distribution network as a bus. , For the total number of buses, set the adjacent buses to be enabled. Interconverter Time bus or busbar Minimum deviation voltage value required or Using the per-unit method to and Processed as minimum deviation voltage per unit value and , , The distributed power sources contained in the multi-voltage level DC distribution network are classified into dispatchable distributed power sources and intermittent distributed power sources according to their output power characteristics. The dispatchable distributed power sources include fuel cells and micro gas turbines, and the intermittent distributed power sources include photovoltaic cells and wind turbines. Step S2: Real-time acquisition of voltage of each bus, calculation of voltage deviation of each bus using per-unit method, obtaining per-unit value of voltage deviation of each bus, and determining whether the transformer between adjacent buses is turned on according to criterion #1. If any transformer is turned on, proceed to step S3; if none are turned on, proceed to step S4. The criterion #1 is: For the off converter Determine the current busbar per-unit voltage deviation , Does it satisfy the following formula (1)? If it does, then the system will first set the voltage deviation per unit value. per-unit value of voltage deviation The difference is then input into the first PI proportional-integral controller to obtain the converter. Reference current Then the converter Reference current The measured value of the inductor current on the input side The difference is then input to the second PI proportional-integral controller to obtain the duty cycle signal. Finally, through a pulse width modulation algorithm, the converter is obtained. The control signals for the upper and lower bridge arms are used to start the converter. busbar Establish power mutual assistance; if not, the converter Busbar not turned on The spaces are not connected; （1） Step S3: Real-time detection and calculation of the operating parameters of the system, prediction of the per-unit voltage deviation of the busbars on both sides of the converter in operation, and determination of whether the converters operating between adjacent buses have exited based on the predicted per-unit voltage deviation of the busbars and the corresponding minimum deviation voltage per-unit value that has not been set. If any converter has not exited, repeat step S3. If all converters have exited, proceed to step S4. Step S4: Each bus operates independently. Droop control is used to control the power output of the dispatchable distributed power sources on each bus. Maximum power point tracking control is used to achieve the maximum power output of the intermittent distributed power sources on each bus. Proceed to step S2.

2. The power control method for multi-voltage level DC distribution networks according to claim 1, characterized in that: In step S3, the operating parameters of the computing system are detected in real time, and the converters working between adjacent buses are determined one by one according to criterion #2. If any converter has not exited, step S3 is repeated. If all converters have exited, the process proceeds to step S4. The criterion #2 is: For the converter in operation Assuming it exits, predict the bus length according to the following formula. per-unit voltage deviation , ; （2） In the formula, , These are the current busbars. The per-unit value of voltage deviation; , They represent the busbars respectively. After the converter To the bus Transmitted power; , They represent the converters respectively. At the bus The equivalent droop coefficient on the side is given by the following formula: （3） （4） In the formula, Indicates busbar With busbar The connection status of the busbar If the converters between adjacent buses are all working, it indicates that the bus... With busbar There is a connection. =1, if any converter between adjacent buses is not working, it indicates that the bus... With busbar No connection exists. =0; in solving During the process, and Consider it as 1, because of the assumption of the converter quit, and Consider it as 0; Indicates busbar Maximum allowable deviation voltage value Indicates busbar The equivalent droop coefficient is given by the following formula: （5） In the formula, Indicates busbar Upper The droop control coefficient of a schedulable distributed power source; Indicates busbar The number of schedulable distributed power sources; Judgment of the prediction and Does it satisfy the following equation (6)? If it does, the converter... Exit; if not satisfied, converter Keep it on; （6）。 3. The power control method for multi-voltage level DC distribution networks according to claim 1 or 2, characterized in that: The formulas for calculating the minimum deviation voltage per unit value and the voltage deviation per unit value of the bus are as follows: （7） （8） In the formula, , To enable Time bus The minimum per-unit deviation voltage value that needs to be exceeded; , To enable Time bus The minimum deviation voltage value required to exceed; , They represent the busbars respectively. Maximum allowable deviation voltage value; Indicates busbar The per-unit value of voltage deviation; Indicates busbar voltage, Indicates busbar The rated voltage.

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