Optical storage collaborative transient voltage control method and system

Abstract

The invention discloses an optical storage collaborative transient voltage control method and system. The method comprises the following steps: step 1, observing a grid-connected point voltage amplitude change rate, a grid-connected point voltage frequency and a grid-connected point voltage frequency change rate by using a complex frequency lock loop (CFLL); step 2, in a fault detection module, generating a fault control signal by using the grid-connected point voltage amplitude change rate, the grid-connected point voltage amplitude deviation, the grid-connected point voltage frequency change rate and the deviation between the grid-connected point voltage frequency and a reference value; and step 3, according to the fault control signal output by the fault detection module, performing optical storage cooperative transient voltage control. According to the method, high-performance dynamic support on the system voltage can be realized in a disturbance scene, and the voltage stability in a transient scene is improved.

Description

Technical Field

[0001] This invention relates to the field of power system voltage control technology, and specifically to a transient voltage control method for a distribution network with a high proportion of photovoltaic power. Background Technology

[0002] With the advancement of the global energy transition, photovoltaic (PV) power has been widely integrated into the power grid due to its advantages such as being clean and renewable. However, the intermittency and volatility of PV power pose challenges to the stable operation of the power grid. The high proportion of PV power integration leads to a decrease in the system's voltage support capacity, especially under fault conditions such as DC blocking, exposing the power grid to the risk of transient voltage fluctuations.

[0003] Currently, methods for transient voltage control in DC receiving-end power grids mainly include reactive power compensation, DC modulation, and retaining compensation capacitors at converter stations. Reactive power compensation is achieved by installing devices such as synchronous condensers, static var compensators (SVCs), and static synchronous compensators (STATCOMs). While this method effectively controls voltage, it incurs high investment costs. Furthermore, these methods primarily focus on transmission network voltage control and do not fully consider the potential for coordinated regulation of photovoltaic and energy storage systems in the distribution network.

[0004] In existing technologies, the conditions for initiating transient voltage control are typically based on voltage and frequency deviations. However, in practical applications, relying solely on these conditions may not be sufficient to comprehensively capture abnormal grid conditions, especially for transient voltage problems caused by reactive power disturbances, where existing methods have insufficient detection and response capabilities. Furthermore, existing technologies typically only use voltage deviation droop to provide reactive power support under transient conditions, which is insufficient for supporting system voltage. Therefore, a comprehensive method for photovoltaic and energy storage fault detection and transient support control that integrates multiple initiation conditions and operating parameters is of great significance. Summary of the Invention

[0005] The technical problem to be solved by this invention is that the existing transient voltage control methods for DC receiving-end near-area distribution networks have insufficient detection and support capabilities. The invention aims to improve the transient voltage support performance of the power grid by comprehensively considering four starting conditions: voltage change rate, frequency change rate, frequency deviation, and voltage deviation. Furthermore, it aims to improve the transient voltage support performance of the power grid by simultaneously employing voltage deviation droop and voltage change rate droop control under transient conditions.

[0006] To address the aforementioned technical problems, this invention provides a method for controlling the transient voltage of a photovoltaic-storage system in synergy, comprising: Step 1: Use a complex frequency-locked loop (CFLL) to observe the rate of change of voltage amplitude at the grid connection point, the voltage frequency at the grid connection point, and the rate of change of voltage frequency at the grid connection point. Step 2. In the fault detection module, a fault control signal is generated using the rate of change of the grid connection point voltage amplitude, the deviation of the grid connection point voltage amplitude, the rate of change of the grid connection point voltage frequency, and the deviation of the grid connection point voltage frequency from the reference value. Step 3. Perform photovoltaic-storage collaborative transient voltage control based on the fault control signal output by the fault detection module.

[0007] The aforementioned photovoltaic-storage coordinated transient voltage control method includes, in step 1: 1) Define the complex phase angle and complex frequency : (1) (2) in Voltage amplitude, The voltage phase angle, It is the voltage angular frequency. The normalized rate of change of voltage amplitude, superscript Denotes the derivative. For complex units; 2) In Fundamental positive sequence voltage in coordinate system Represented as: (3) At this time, the fundamental positive sequence voltage The derivative satisfies the following relationship: (4)

[0008] To estimate the fundamental positive sequence voltage A complex frequency reduced-order generalized integrator CF-ROGI is designed to achieve voltage observation: (5) In the formula, For voltage observations, The normalized voltage change rate observation, These are frequency observations. These are complex frequency observations. For voltage observation error, This is the gain coefficient; Transfer function of complex frequency reduced-order generalized integrator for: (6) In the formula, For Laplace variables.

[0009] At this point, the voltage observation error is dynamically expressed as: (7) In the formula, This represents the observation error of complex frequencies; From the above formula, it can be seen that when = 0 and gain coefficient If the voltage is large enough, the voltage observation error will decay to 0; Design a complex frequency observation loop: (8) Where * denotes the conjugate operation. As an auxiliary variable, For complex frequency observation gain; A complex frequency locking loop (CFLL) is constructed by a CF-ROGI voltage observer and a complex frequency observation loop. The CFLL is used to monitor the rate of change of voltage amplitude at the grid connection point, the voltage frequency at the grid connection point, and the rate of change of voltage frequency at the grid connection point in real time.

[0010] The aforementioned photovoltaic-storage coordinated transient voltage control method includes, in step 2: The voltage amplitude change rate, voltage frequency change rate, voltage frequency deviation, and voltage amplitude deviation at the grid connection point are monitored in real time and compared with the corresponding preset thresholds. The judgment conditions are as follows: The rate of change of voltage amplitude exceeds the threshold:

[0011] Voltage frequency change rate exceeds threshold:

[0012] Voltage frequency deviation exceeds threshold:

[0013] Voltage amplitude deviation exceeds threshold:

[0014] , , , These are, respectively, voltage amplitude, voltage frequency, voltage frequency deviation, and voltage amplitude deviation. , , , These are, respectively, the rate of change of voltage amplitude, the rate of change of voltage frequency, the voltage frequency deviation, and the voltage amplitude deviation threshold; When one or more parameters exceed the preset threshold, the fault detection module outputs a fault start control signal with a value of 1 to each inverter, thereby triggering additional transient support control.

[0015] The aforementioned photovoltaic-storage coordinated transient voltage control method includes, in step 3: When the grid-connected and network-structured devices detect a fault start control signal of 1, additional reactive power reference values ​​are applied.

[0016] The aforementioned photovoltaic-storage coordinated transient voltage control method, for grid-connected equipment with voltage droop, expresses reactive power control before fault control is initiated as follows: (9) In the formula, This is a reference value for reactive power. This is the voltage droop factor. This is the inverter output voltage. This is the voltage reference value; When transient voltage control is initiated, an additional term for the rate of change of voltage amplitude is added. The reactive power reference value at this time is expressed as: (10) In the formula, The voltage amplitude change rate droop coefficient is one. The voltage change rate is obtained from the equation. (11) The transient reactive power support range is set according to the equipment capacity and overload capacity, when the reactive power reference value is... If the device capacity is exceeded, the corresponding upper or lower limit value will be output. (12) Subsequently, the voltage amplitude change rate droop coefficient was... The value of satisfies the set condition, which is to enable the inverter to provide additional rate of change droop support based on the continuously decreasing voltage for a period of time after the fault occurs. At the moment of the fault, due to the rapid voltage drop, the transient voltage control will output the upper limit value.

[0017] The aforementioned photovoltaic-storage collaborative transient voltage control method, for droop control grid-type equipment containing low-pass filtering stages, expresses reactive power control before fault control is initiated as follows: (13) In the formula, This is a reference value for reactive power. To output reactive power, and These are parameters one and two of the low-pass filter, respectively. This is the inverter output voltage. This is the voltage reference value; When transient voltage control is initiated, an additional voltage change rate droop term is added. The reactive power control loop at this time is represented as follows: (14) In the formula, The voltage amplitude change rate droop coefficient is 2.

[0018] A computer system includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the photoelectric storage coordinated transient voltage control method as described above.

[0019] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a photoelectric storage-coordinated transient voltage control method as described above.

[0020] The beneficial effects achieved by this invention are as follows: This invention utilizes CFLL to detect the voltage frequency and amplitude change rate of grid-connected nodes, avoiding the measurement noise amplification caused by directly using digital differentiators, thus achieving accurate observation of grid-connected node voltage information. The fault detection module of this invention, which integrates four types of voltage parameters, ensures rapid and accurate perception of voltage fault conditions, and then, in conjunction with transient voltage control, achieves faster fault response. The transient voltage control method based on voltage amplitude change rate and voltage amplitude deviation can achieve high-performance dynamic support for system voltage under disturbance scenarios, improving voltage stability under transient scenarios. Attached Figure Description

[0021] Figure 1 This is a block diagram of the complex frequency locking loop in Embodiment 1 of the present invention; Figure 2 This is a block diagram of the multi-parameter fault detection module in Embodiment 1 of the present invention; Figure 3 This is a block diagram of the photovoltaic-storage cooperative transient voltage control in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the mixed droop curve of transient voltage amplitude change rate and deviation in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the transient voltage amplitude deviation droop curve used in current technology. Figure 6 This is a schematic diagram comparing the voltage dynamic local magnification of Embodiment 1 of the present invention and the prior art. Detailed Implementation Example 1

[0022] This embodiment provides a method for controlling transient voltage in a photovoltaic-storage coordinated manner, including: Step 1: Observe the rate of change of the voltage amplitude at the grid connection point, the voltage frequency at the grid connection point, and the rate of change of the voltage frequency at the grid connection point using a complex frequency locked loop (CFLL), including: 1) Define the complex phase angle and complex frequency as follows: (1) (2) in Voltage amplitude, The voltage phase angle, It is the voltage angular frequency. The normalized rate of change of voltage amplitude, superscript Denotes the derivative. It is a complex unit.

[0023] 2) In Fundamental positive sequence voltage in coordinate system Represented as: (3) At this time, the fundamental positive sequence voltage The derivative satisfies the following relationship (4) To estimate the fundamental positive sequence voltage First, a complex frequency reduced-order generalized integrator (CF-ROGI) is designed to achieve voltage observation: (5) In the formula, For voltage observations, The normalized voltage change rate observation, These are frequency observations. These are complex frequency observations. For voltage observation error, This is the gain coefficient.

[0024] Transfer function of complex frequency reduced-order generalized integrator for: (6) In the formula, For Laplace variables.

[0025] At this point, the voltage observation error is dynamically expressed as: (7) In the formula, This represents the observation error of complex frequencies.

[0026] From the above formula, it can be seen that when = 0 and gain coefficient If the voltage is large enough, the voltage observation error will decay to 0.

[0027] At this point, design a complex frequency observation loop: (8) Where * denotes the conjugate operation. As an auxiliary variable, For complex frequency observation gain, and >0.

[0028] Using the CF-ROGI voltage observer and complex frequency observation loop, the following can be obtained: Figure 1 The complex frequency locking loop (CFLL) shown is used to monitor the rate of change of the grid connection point voltage amplitude, the grid connection point voltage frequency, and the rate of change of the grid connection point voltage frequency in real time.

[0029] Step 2. In the fault detection module, a fault control signal is generated using the rate of change of grid connection point voltage amplitude, the deviation of grid connection point voltage amplitude, the rate of change of grid connection point voltage frequency, and the deviation of grid connection point voltage frequency from the reference value (the reference value is 50Hz). This signal includes: Fault detection and control signal generation: Real-time observation of the voltage amplitude change rate, voltage frequency change rate, voltage frequency deviation, and voltage amplitude deviation at the grid connection point, and comparison with corresponding preset thresholds. The judgment conditions are as follows: The rate of change of voltage amplitude exceeds the threshold:

[0030] Voltage frequency change rate exceeds threshold:

[0031] Voltage frequency deviation exceeds threshold:

[0032] Voltage amplitude deviation exceeds threshold:

[0033] , , , These are, respectively, voltage amplitude, voltage frequency, voltage frequency deviation, and voltage amplitude deviation. , , , These are the voltage amplitude change rate, voltage frequency change rate, voltage frequency deviation, and voltage amplitude deviation threshold, respectively.

[0034] The fault detection module block diagram is as follows: Figure 2 As shown, when one or more parameters exceed the preset threshold, the fault detection module outputs a fault start control signal with a value of 1 to each inverter, thereby triggering additional transient support control.

[0035] Step 3. Based on the fault control signal output by the fault detection module, perform photovoltaic-storage coordinated transient voltage control, including: When the grid-connected and network-structured devices detect a fault start control signal of 1, additional reactive power reference values ​​are applied.

[0036] For grid-connected equipment with voltage droop, reactive power control before fault control is initiated is as follows: (9) In the formula, This is a reference value for reactive power. This is the voltage droop factor. This is the inverter output voltage. This is the voltage reference value.

[0037] When transient voltage control is initiated, an additional term for the rate of change of voltage amplitude is added. The reactive power reference value at this time is expressed as: (10) In the formula, The voltage amplitude change rate droop coefficient is one. The voltage change rate is obtained from the equation. (11) Considering the significant difference in the system voltage change rate between the instantaneous and subsequent time phases after a fault occurs, the transient reactive power support range is first set based on equipment capacity and overload capacity. When the reactive power reference value... If the device capacity is exceeded, the corresponding upper or lower limit value will be output. (12) Subsequently, the voltage amplitude change rate droop coefficient was... The value of satisfies the set condition, which is to enable the inverter to provide additional rate of change droop support based on the continuously decreasing voltage for a period of time after the fault occurs. At the moment of the fault, due to the rapid voltage drop, the transient voltage control will output the upper limit value.

[0038] For droop-controlled network equipment containing low-pass filters, reactive power control before fault control is initiated is as follows: (13) In the formula, This is a reference value for reactive power. To output reactive power, and These are parameters one and two of the low-pass filter, respectively. This is the inverter output voltage. This is the voltage reference value.

[0039] When transient voltage control is initiated, an additional voltage change rate droop term is added. The reactive power control loop at this time is represented as follows: (14) In the formula, The voltage amplitude change rate droop coefficient is 2.

[0040] Due to the voltage amplitude change rate droop coefficient two With voltage amplitude change rate droop coefficient one Since all values ​​are negative, for grid-connected equipment with low-pass filtering in reactive power control, the droop of the starting voltage amplitude change rate in transient scenarios is equivalent to increasing the voltage inertia, thereby mitigating the drop and oscillation of the output voltage.

[0041] This embodiment constructs a grid-connected scenario involving three units: grid-connected energy storage, grid-connected photovoltaic, and grid-connected SVG. The steady-state power control uses the same parameters, while the fault detection module and transient voltage control utilize the method of this invention and a conventional transient voltage support control method, respectively. When a 15000Var reactive power disturbance occurs at the grid connection point, the result is as follows: Figure 4 As shown. Figure 5 As shown, existing transient support control methods can only output a certain amount of reactive power support when the voltage at the grid-connected node drops to a certain level. However, the voltage amplitude change rate and deviation hybrid droop of the present invention can provide additional dynamic support based on its amplitude change rate during the instant of voltage drop caused by disturbance and during the subsequent continuous voltage drop, thus exhibiting a voltage support performance that is significantly better than the voltage deviation transient control currently used.

[0042] Figure 6 This is a partial comparison diagram of simulation results between the method of this invention and existing technologies under the same system and control parameters. Figure 6 As can be seen, because the method of this invention has an additional voltage amplitude change rate droop stage, the grid-connected converter outputs additional reactive power support at the instant of reactive power disturbance, thus making the voltage drop at the grid connection point significantly less than that of existing transient voltage control technologies. Furthermore, after the voltage drop, the method of this invention continuously provides dynamic reactive power support by relying on the voltage drop rate, thereby enabling the voltage amplitude of the grid connection point to recover quickly and always remain higher than that of grid connection points using existing technologies. Example 2

[0043] A computer system includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to perform the steps of the method as described in Embodiment 1. Example 3

[0044] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the method as described in Example 1.

[0045] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0046] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0047] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling transient voltage in a photovoltaic-storage coordinated manner, characterized in that, include: Step 1: Use a complex frequency-locked loop (CFLL) to observe the rate of change of voltage amplitude at the grid connection point, the voltage frequency at the grid connection point, and the rate of change of voltage frequency at the grid connection point. Step 2. In the fault detection module, a fault control signal is generated using the rate of change of the grid connection point voltage amplitude, the deviation of the grid connection point voltage amplitude, the rate of change of the grid connection point voltage frequency, and the deviation of the grid connection point voltage frequency from the reference value. Step 3. Perform photovoltaic-storage collaborative transient voltage control based on the fault control signal output by the fault detection module.

2. The photovoltaic-storage coordinated transient voltage control method according to claim 1, characterized in that, Step 1 includes: 1) Define the complex phase angle and complex frequency : （1） （2） in Voltage amplitude, The voltage phase angle, It is the voltage angular frequency. The normalized rate of change of voltage amplitude, superscript Denotes the derivative. For complex units; 2) In Fundamental positive sequence voltage in coordinate system Represented as: （3） At this time, the fundamental positive sequence voltage The derivative satisfies the following relationship: （4） To estimate the fundamental positive sequence voltage A complex frequency reduced-order generalized integrator CF-ROGI is designed to achieve voltage observation: （5） In the formula, For voltage observations, The normalized voltage change rate observation, These are frequency observations. These are complex frequency observations. For voltage observation error, This is the gain coefficient; Transfer function of complex frequency reduced-order generalized integrator for: （6） In the formula, For Laplace variables; At this point, the voltage observation error is dynamically expressed as: （7） In the formula, This indicates the error in complex frequency observation; From the above formula, it can be seen that when = 0 and gain coefficient If the voltage is large enough, the voltage observation error will decay to 0; Design a complex frequency observation loop: （8） Where * denotes the conjugate operation. As an auxiliary variable, For complex frequency observation gain; A complex frequency locking loop (CFLL) is constructed by a CF-ROGI voltage observer and a complex frequency observation loop. The CFLL is used to monitor the rate of change of voltage amplitude at the grid connection point, the voltage frequency at the grid connection point, and the rate of change of voltage frequency at the grid connection point in real time.

3. The photovoltaic-storage coordinated transient voltage control method according to claim 2, characterized in that, Step 2 includes: The voltage amplitude change rate, voltage frequency change rate, voltage frequency deviation, and voltage amplitude deviation at the grid connection point are monitored in real time and compared with the corresponding preset thresholds. The judgment conditions are as follows: Voltage amplitude change rate exceeds threshold: Voltage frequency change rate exceeds threshold: Voltage frequency deviation exceeds threshold: Voltage amplitude deviation exceeds threshold: , , , These are, respectively, voltage amplitude, voltage frequency, voltage frequency deviation, and voltage amplitude deviation. , , , These are, respectively, the rate of change of voltage amplitude, the rate of change of voltage frequency, the voltage frequency deviation, and the voltage amplitude deviation threshold; When one or more parameters exceed the preset threshold, the fault detection module outputs a fault start control signal with a value of 1 to each inverter, thereby triggering additional transient support control.

4. The photovoltaic-storage coordinated transient voltage control method according to claim 3, characterized in that, Step 3 includes: When the grid-connected and network-structured devices detect a fault start control signal of 1, additional reactive power reference values ​​are applied.

5. The photovoltaic-storage coordinated transient voltage control method according to claim 4, characterized in that, For grid-connected equipment with voltage droop, reactive power control before fault control is initiated is as follows: （9） In the formula, This is a reference value for reactive power. This is the voltage droop factor. This is the inverter output voltage. This is the voltage reference value; When transient voltage control is initiated, an additional term for the rate of change of voltage amplitude is added. The reactive power reference value at this time is expressed as: （10） In the formula, The voltage amplitude change rate droop coefficient is one. The voltage change rate is obtained from equation (11). （11） The transient reactive power support range is set according to the equipment capacity and overload capacity, when the reactive power reference value is... If the device capacity is exceeded, the corresponding upper or lower limit value will be output. （12） Subsequently, the voltage amplitude change rate droop coefficient was... The value of satisfies the set condition, which is to enable the inverter to provide additional rate of change droop support based on the continuously decreasing voltage for a period of time after the fault occurs. At the moment of the fault, due to the rapid voltage drop, the transient voltage control will output the upper limit value.

6. The photovoltaic-storage coordinated transient voltage control method according to claim 5, characterized in that, For droop-controlled network equipment containing low-pass filters, reactive power control before fault control is initiated is as follows: （13) In the formula, This is a reference value for reactive power. To output reactive power, and These are parameters one and two of the low-pass filter, respectively. This is the inverter output voltage. This is the voltage reference value; When transient voltage control is initiated, an additional voltage change rate droop term is added. The reactive power control loop at this time is represented as follows: (14) In the formula, The voltage amplitude change rate droop coefficient is 2.

7. A computer system comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the photovoltaic-storage coordinated transient voltage control method as described in any one of claims 1-6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of a photoelectric storage-coordinated transient voltage control method as described in any one of claims 1-6.

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