Privacy protection secondary control method for direct current microgrid and direct current microgrid system

Abstract

The application discloses a privacy protection secondary control method for a direct current microgrid and a direct current microgrid system, belongs to the secondary control technical field of the direct current microgrid, and is characterized in that a secondary control signal u i (t) is divided into two components and is only transmitted to a neighbor and is invisible to the neighbor, the integrity and authenticity of the privacy signal are protected because the neighbor cannot obtain the complete privacy signal due to the fact that only a partial privacy signal is contained, and the neighbor cannot obtain output current data and acquire privacy information of the local power supply unit, thereby greatly improving the privacy and security of the direct current microgrid system.

Description

Technical Field

[0001] This invention belongs to the field of secondary control technology for DC microgrids, and more specifically, relates to a privacy protection secondary control method and a DC microgrid system for DC microgrids. Background Technology

[0002] In recent years, DC microgrids have been widely promoted by academic and industrial communities both domestically and internationally, and are extensively used for power supply management in facilities such as data centers, 5G base stations, smart buildings, and electric ships. For DC microgrids with multiple power supply units, designing a suitable multi-source collaborative power supply scheme is crucial to ensuring the stable and economical operation of the system. Secondary control is a key means of multi-source collaborative power supply. By applying a distributed secondary controller on top of droop control, power supply units interact with each other through a communication network to achieve microgrid bus voltage regulation and current sharing output of power supply units. During the secondary control process, the privacy protection of power supply units needs to be considered. On the one hand, privacy protection can prevent the leakage of private information such as the operating conditions and generation costs of power supply units, safeguarding the interests of the power supply units; on the other hand, privacy protection can improve the safety of grid operation and avoid power supply security risks caused by the leakage of private data. Therefore, researching a privacy-protected secondary control method for DC microgrids to achieve bus voltage regulation and current sharing output of power supply units while protecting the privacy information of power supply units is of great significance.

[0003] Existing secondary control methods for privacy protection in DC microgrids are often based on differential privacy or incorporate random noise. However, these methods can alter the system state, easily causing power quality problems and, in severe cases, system instability. For example, adding random noise to the original state can mask the true value of the local state and achieve privacy protection, but the introduction of noise, a random variable, can easily cause system disturbances and affect power quality. If the noise range becomes too large and exceeds the system's tolerance, instability will result. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a privacy protection secondary control method and DC microgrid system for DC microgrids, so as to solve the technical problems of power quality degradation and power supply instability in the existing technology.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a privacy-preserving secondary control method for DC microgrids, comprising the following steps:

[0006] S1. The secondary control signal u of the i-th DC converter in the DC microgrid is respectively... i The component of (t) and Perform initialization and set the virtual voltage drop of the i-th DC-DC converter. Decomposed into pressure drop components and in, n represents the total number of DC-DC converters in the DC microgrid;

[0007] S2, Using the formula Calculate intermediate variables Using formula Calculate intermediate variables Where k and r are preset control parameters, and k > 0, 0 < r < 1; a ij The communication weight between the i-th DC-DC converter and the j-th DC-DC converter;

[0008] S3, based on and The sum of components Update based on and The sum of components Update and transfer the updated components. Assigned to secondary control signal To regulate bus voltage;

[0009] S4. Repeat steps S2-S3 iteratively until the DC microgrid bus voltage approaches or reaches its rated value, and the ratio of the output currents of any two DC converters that can communicate approaches or reaches the preset ratio.

[0010] More preferably, in step S3 above, the component is... Updated to Components Updated to

[0011] More preferably, in step S3 above, the component is... Updated to Components Updated to Where δi is a random number.

[0012] More preferably, if the i-th DC-DC converter and the j-th DC-DC converter can communicate, then a ij >0, otherwise, a ij =0; where, when i=j, a ii =0.

[0013] More preferably, the virtual voltage drop of the i-th DC-DC converter is:

[0014]

[0015] Among them, R iLet m be the transmission line impedance between the i-th DC converter and the DC bus; i I is the droop control gain of the i-th DC-DC converter; i (t) represents the output current of the i-th DC-DC converter.

[0016] More preferably, the method for adjusting the bus voltage includes:

[0017] A voltage reference signal is generated for the i-th DC-DC converter based on droop control. Among them, V * This refers to the rated value of the bus voltage; m i I is the droop control gain of the i-th DC-DC converter; i (t) represents the output current of the i-th DC-DC converter;

[0018] A PWM signal is generated for the i-th DC-DC converter based on dual closed-loop control, so that the output voltage of the i-th DC-DC converter tracks its voltage reference signal. This allows for the regulation of the bus voltage.

[0019] Secondly, the present invention provides a DC microgrid system, comprising: a distributed power supply unit, a DC converter, and a controller; each power supply unit is used to connect to a DC bus through a corresponding DC converter to supply power to the DC bus.

[0020] The controller is used to execute the privacy protection secondary control method provided in the first aspect of the present invention.

[0021] More preferably, for any DC-DC converter, after each update of its secondary control signal, the controller is also used to generate a corresponding voltage reference signal for the DC-DC converter based on droop control, and to generate a PWM signal for the DC-DC converter based on dual closed-loop control, so that its output voltage tracks its voltage reference signal, thereby realizing the regulation of the bus voltage.

[0022] The voltage reference signal for the i-th DC-DC converter is: V * This refers to the rated value of the bus voltage; m i I is the droop control gain of the i-th DC-DC converter; i (t) represents the output current of the i-th DC-DC converter.

[0023] Thirdly, the present invention also provides a computer-readable storage medium comprising a stored computer program, wherein the computer program, when executed by a processor, controls the device containing the storage medium to perform the privacy protection secondary control method provided in the first aspect of the present invention.

[0024] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0025] 1. This invention provides a privacy-protecting secondary control method for DC microgrids. Under the control framework of bus voltage regulation and current sharing output of power supply units within the error range, the secondary control signal u of the DC converter is... i (t) is divided into two components and There is only one decomposition signal locally. Another decomposed signal is transmitted to the neighboring DC-DC converter. Not visible to neighboring DC-DC converters, because Only contains partial privacy signals This prevents neighboring DC-DC converters from acquiring complete privacy signals. State decomposition can protect privacy signals. The integrity and authenticity of the output current value I are protected. i (t) The neighbor cannot obtain the output current data and the privacy information of the local power supply unit, which protects the main interests of the power supply unit and prevents the power supply safety hazards caused by the leakage of privacy information, greatly improving the privacy and security of the DC microgrid system; moreover, the present invention does not change the system state, and while ensuring privacy and security, it can also solve the technical problems of power quality degradation and power supply instability in the prior art.

[0026] 2. Furthermore, the privacy protection secondary control method for DC microgrids provided by this invention is based on... and The sum of components Update, and based on and The sum of components During the update process, a random number δ was introduced. i , the portion Updated to Components Updated to random number δ i The introduction of this feature causes random offsets in the transmitted information, making it impossible for neighboring DC-DC converters to infer the true privacy signal. This further enhances the privacy and security of DC microgrid systems.

[0027] 3. Furthermore, the privacy protection secondary control method for DC microgrids provided by this invention does not require the acquisition of bus voltage signal V. bus (t) only requires sampling local signals and transmitting neighbor signals, which greatly reduces the number of sensors and makes the controller easy to use and operate. Attached Figure Description

[0028] Figure 1 This is a hierarchical control framework diagram of a DC microgrid power supply unit provided in Embodiment 1 of the present invention;

[0029] Figure 2 This is a schematic diagram of a privacy protection secondary control method for DC microgrids provided in Embodiment 1 of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] like Figure 1 As shown, this embodiment establishes a hierarchical control framework for a DC microgrid. At the physical layer, the power supply unit connects to the DC bus via a DC-DC converter and transmission lines. The converter is equipped with a PWM module to implement a boost function. Let the output voltage and current of the i-th DC-DC converter be Vi and Vi, respectively. i and I i The transmission line impedance between the i-th DC converter and the DC bus is R. i The bus voltage is V bus The rated bus voltage is V * Then the bus voltage V bus (t)=V i (t)-R i I i (t).

[0033] The primary control layer includes droop control and dual closed-loop control. The droop control generates a voltage reference signal for the i-th DC-DC converter. In the formula m i Let u be the droop control gain of the i-th DC-DC converter. i (t) represents the secondary control signal for the i-th DC-DC converter. The dual-loop control generates a PWM signal for the converter, specifically through two PI control modules that drive the DC-DC converter's output voltage to track its voltage reference signal within a fast timescale. Specifically, the virtual voltage drop of the i-th DC-DC converter is The expression for the bus voltage at this time is as follows:

[0034]

[0035] In the secondary control layer, a secondary control algorithm is designed based on a state decomposition mechanism. Specifically, as follows: Figure 2 As shown, the privacy protection secondary control method for DC microgrids provided by this invention includes the following steps:

[0036] S1. Initialize the preset control parameters k and r, where k > 0, 0 < r < 1. In this embodiment, k = 10 and r = 0.9. Then, initialize the secondary control signal u of the i-th DC-DC converter in the DC microgrid. i The component of (t) and Perform initialization and set the virtual voltage drop of the i-th DC-DC converter. Decomposed into pressure drop components and in, n represents the total number of DC-DC converters in the DC microgrid; where, the components... It exchanges information with neighboring DC-DC converters, while components It evolves locally and is not transmitted to its neighbors; specifically, a communication network is established. For the i-th DC-DC converter, if it can receive information from the j-th DC-DC converter, then the j-th DC-DC converter is a neighbor of the i-th DC-DC converter, and the communication weight between them is greater than 0.

[0037] S2. Obtain information (local information) of the i-th DC-DC converter. and And information about neighboring DC converters q∈N i ∈{1, 2, ..., n} indicates that the q-th DC-DC converter is a neighbor of the i-th DC-DC converter; the formula is used. Calculate intermediate variables Using formula Calculate intermediate variables Among them, a ij Let a be the communication weight between the i-th DC-DC converter and the j-th DC-DC converter; where, if the i-th DC-DC converter and the j-th DC-DC converter can communicate, then a ij >0, otherwise, a ij =0; where, when i=j, a ii =0.

[0038] S3, based on and The sum of components The update is performed and sent to neighboring DC-DC converters via a communication network, based on... and The sum of components The update is performed, and this signal is stored locally and not sent to neighboring DC-DC converters; additionally, the updated component is also... Assigned to the secondary control signal u i (t), and added to the droop control to regulate the bus voltage;

[0039] Specifically, in one optional implementation, the components Updated to Components Updated to

[0040] In another alternative implementation, the components Updated to Components Updated to Where, δ i The result is a random number, which can also be initialized in step S1.

[0041] Furthermore, in one alternative implementation, the method for adjusting the bus voltage includes:

[0042] A voltage reference signal is generated for the i-th DC-DC converter based on droop control. Among them, V * This refers to the rated value of the bus voltage; m i I is the droop control gain of the i-th DC-DC converter; i (t) represents the output current of the i-th DC-DC converter;

[0043] A PWM signal is generated for the i-th DC-DC converter based on dual closed-loop control, so that the output voltage V of the i-th DC-DC converter is... i (t) Track its voltage reference signal Furthermore, based on V bus (t)=V i (t)-R i I i (t) to achieve bus voltage regulation.

[0044] S4. Repeat steps S2-S3 iteratively until the DC microgrid system is stable, i.e., the DC microgrid bus voltage approaches or reaches its rated value, and the ratio of the output currents of any two communicable DC converters approaches or reaches a preset ratio. Specifically, this is reflected in: And the output current sharing of each power supply unit, that is, the output current I corresponding to any two neighboring DC converters. i (t) and I j (t) satisfies Among them, V f and I f These represent the maximum permissible voltage regulation and current sharing deviation, respectively, Vf The value is generally taken to not exceed the rated voltage V. * 5% (V in this embodiment) * =400V, V f =20V, I f =10A), d i and d j The current sharing coefficients are (taking four converters connected to the grid as an example, d1=5, d2=d3=10, d4=20).

[0045] It should be noted that the secondary control method provided by this invention can achieve bus voltage regulation and current sharing output of the power supply unit within the error range, while protecting the privacy information of the power supply unit from being known by neighbors. The specific analysis is as follows:

[0046] First, define the systematic error and establish its state space:

[0047] For the i-th DC-DC converter, define in To determine the average value of the virtual voltage drop, the state-space model is established as follows:

[0048]

[0049] in,

[0050] Next, based on the state space, we analyze the steady state of the error:

[0051] definition Φ(t, s) = e -kH(t-s) The state space is solved using the differential equation method as follows:

[0052]

[0053] According to Schuler's complement theorem, when 0 < r < 1, matrix H is positive definite and all eigenvalues ​​are greater than 0. λ1 is the smallest eigenvalue of H. Assuming the virtual voltage drop and its decomposed signal values ​​are bounded and their rates of change are bounded, then... Substituting into the above formula, we get:

[0054]

[0055] In steady state, taking t→∞, then

[0056]

[0057] So

[0058]

[0059] It can be seen that the steady-state characteristic of the error is eventually bounded. By increasing k and taking r to approach 1, the range of the bound can be narrowed.

[0060] Finally, let's analyze voltage regulation and current sharing:

[0061] Define voltage regulation error e V (t)=V bus (t)-V * ,So

[0062]

[0063] then By adjusting k and r, g ≤ V f This enables bus voltage regulation.

[0064] Define flow sharing error

[0065]

[0066] then By adjusting k and r, we can make 2g≤I f This enables the power supply unit to output current in a balanced manner.

[0067] Therefore, when the system error eventually becomes bounded, voltage regulation and current sharing also become bounded. By adjusting the magnitude of these bounds, the control objective can be achieved. That is, the secondary control method provided by the present invention can realize bus voltage regulation and power supply unit current sharing output.

[0068] Furthermore, based on the ability to achieve bus voltage regulation and current sharing output of power supply units, this invention employs the designed state decomposition quadratic control algorithm, which can protect privacy signals. It will not be known to the neighbors. There is only one decomposition signal locally. Transmitted to the neighbor, another decomposed signal Invisible to neighbors, because Only contains partial privacy signals This prevents neighbors from obtaining complete privacy signals. This greatly improves the privacy and security of DC microgrid systems. Furthermore, due to the random number δ... i The introduction of this feature causes random offsets in the transmitted information, making it impossible for neighbors to infer the true privacy signal. Therefore, this invention can protect privacy signals through state decomposition and secondary control. The integrity and authenticity of the output current value I are protected. i(t) Neighboring DC converters cannot obtain output current data and access the privacy information of local power supply units, such as operating conditions, generation costs, and maximum allowable output power. In summary, the proposed privacy-protecting secondary control method for DC microgrids protects the interests of the power supply unit and prevents power supply security risks caused by privacy information leakage.

[0069] In summary, this invention, based on a state decomposition mechanism, designs a privacy-protecting secondary control method for DC microgrids. This method enables bus voltage regulation and current sharing output of power supply units within the error range, while simultaneously protecting the privacy of power supply units from being known by neighbors, such as operating conditions, generation costs, and maximum allowable output power. This protects the interests of the power supply units and prevents power supply safety hazards caused by privacy information leakage. Furthermore, this invention does not alter the system state, ensuring privacy and security while also addressing the technical problems of power quality degradation and unstable power supply found in existing technologies.

[0070] Example 2

[0071] A DC microgrid system includes: a distributed power supply unit, a DC converter, and a controller; each power supply unit is connected to a DC bus via a corresponding DC converter to supply power to the DC bus;

[0072] The controller is used to execute the privacy protection secondary control method provided in Embodiment 1 of the present invention.

[0073] Furthermore, for any DC-DC converter, after each update of its secondary control signal, the controller is also used to generate a corresponding voltage reference signal for the DC-DC converter based on droop control, and to generate a PWM signal for the DC-DC converter based on dual closed-loop control, so that its output voltage tracks its voltage reference signal, thereby realizing the regulation of the bus voltage.

[0074] The voltage reference signal for the i-th DC-DC converter is: V * This refers to the rated value of the bus voltage; m i I is the droop control gain of the i-th DC-DC converter; i (t) represents the output current of the i-th DC-DC converter.

[0075] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0076] Example 3

[0077] A computer-readable storage medium includes a stored computer program, wherein when the computer program is run by a processor, it controls the device where the storage medium is located to execute the privacy protection secondary control method provided in Embodiment 1 of the present invention.

[0078] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A privacy-preserving secondary control method for DC microgrids, characterized in that, Includes the following steps: S1, respectively, for the first in the DC microgrid i Secondary control signals of a DC-DC converter The amount and Perform initialization, and set the first i Virtual voltage drop of a DC-DC converter Decomposed into pressure drop components and ,in, ; n ; n The total number of DC-DC converters in a DC microgrid; components Interact with neighboring DC-DC converters; component It evolves locally and is not transmitted to its neighbors; S2, Using the formula Calculate intermediate variables ; Use formula Calculate intermediate variables ;in, k and r All are preset control parameters, and , ; For the first i The DC-DC converter and the first j Communication weights between DC-DC converters; The first in DC microgrid j The components of the secondary control signal of a DC-DC converter; S3, based on and The sum of components Updates are performed and transmitted to neighboring DC-DC converters via a communication network; based on and The sum of components Update the data; the updated data will be used for the next step. Stored locally and not sent to neighboring DC-DC converters; the updated components... Assigned to secondary control signal To regulate the bus voltage; S4. Repeat steps S2-S3 for iteration until the DC microgrid bus voltage approaches or reaches its rated value, and the ratio of the output currents of any two DC converters that can communicate approaches or reaches the preset ratio. No. i The virtual voltage drop of the DC-DC converter is: in, For the first i The transmission line impedance between the DC converter and the DC bus; For the first i The droop control gain of a DC-DC converter; For the first i The output current of a DC-DC converter.

2. The privacy protection secondary control method according to claim 1, characterized in that, In step S3, the components Updated to ,Will Updated to .

3. The privacy protection secondary control method according to claim 1, characterized in that, In step S3 above, the components Updated to ,Will Updated to ;in, It is a random number.

4. The privacy protection secondary control method according to claim 1, characterized in that, If the first i The DC-DC converter and the first j If the DC-DC converters can communicate with each other, then ,otherwise, Among them, when hour, .

5. The privacy protection secondary control method according to any one of claims 1-4, characterized in that, The method for adjusting the bus voltage includes: Based on droop control as the first i A DC-DC converter generates a voltage reference signal. ;in, This is the rated value of the bus voltage; For the first i The droop control gain of a DC-DC converter; For the first i The output current of a DC-DC converter; Based on dual closed-loop control, the first... i The DC-DC converter generates a PWM signal to make the first DC-DC converter generate a PWM signal. i The output voltage of a DC-DC converter tracks its voltage reference signal. This allows for the regulation of the bus voltage.

6. A DC microgrid system, characterized in that, include: Distributed power supply unit, DC-DC converter and controller; each power supply unit is connected to the DC bus through a corresponding DC-DC converter to supply power to the DC bus; The controller is used to execute the privacy protection secondary control method according to any one of claims 1-5.

7. The DC microgrid system according to claim 6, characterized in that, For any DC-DC converter, after each update of its secondary control signal, the controller is also used to generate a corresponding voltage reference signal for the DC-DC converter based on droop control, and to generate a PWM signal for the DC-DC converter based on dual closed-loop control, so that its output voltage tracks its voltage reference signal, thereby realizing the regulation of the bus voltage. Among them, the i The voltage reference signal for each DC-DC converter is: ; This is the rated value of the bus voltage; For the first i The droop control gain of a DC-DC converter; For the first i The output current of a DC-DC converter.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, it controls the device where the storage medium is located to perform the privacy protection secondary control method according to any one of claims 1-5.

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