An AGC control method for a virtual power plant containing a high proportion of isomerically distributed photovoltaics

Abstract

The application discloses an AGC control method for a virtual power plant containing a high-proportion isomer distributed photovoltaic. The method comprises the following steps: according to the minimum shutdown time of a photovoltaic switching unit, a controller design is carried out on the side of a grid-connected inverter to realize shutdown self-locking, and subsequent AGC instruction distribution is carried out under the constraint of meeting the minimum shutdown time; according to the starting operation load of the switching unit, the minimum shutdown time, the maximum operation load, the minimum operation load and the regulation dead zone of the continuously adjustable unit and other known information, a mixed integer programming model is designed, the optimization target of which is flexibility, the constraints of which are power, the regulation dead zone and the minimum shutdown time, the received total active instruction is decomposed, and the photovoltaic switching unit and the continuously adjustable unit in the jurisdiction are controlled to complete the power generation task.

Description

Technical Field

[0001] This invention belongs to the field of automatic power generation control of virtual power plants, and specifically relates to an AGC control method for virtual power plants with a high proportion of heterogeneous distributed photovoltaics. Background Technology

[0002] With global energy shortages and increasing electricity demand, power generation has gradually shifted from large-scale centralized generation to distributed generation, with power systems now primarily relying on clean, decentralized renewable energy sources. Virtual power plant technology aggregates multiple distributed generation (DG) units into a virtual power generation cluster, enabling flexible and adjustable load aggregation and internal coordinated optimization management, providing a new solution for effectively addressing system balance and renewable energy consumption. In typical virtual power plant designs, photovoltaic (PV) generators are indispensable. PV generators exhibit heterogeneous characteristics and typically operate in two modes: on-off units, which directly influence system load through grid connection and shutdown, with power output not adjustable in real-time during operation; and continuously adjustable units, which achieve continuous power adjustment through the controller design of the PV grid-connected inverter. Currently, photovoltaic generator units in virtual power plants mainly rely on continuously adjustable units responding to Automatic Generation Control (AGC) commands. The issue of coordinated scheduling has not been considered from the perspective of simultaneously involving switching units and continuously adjustable units in the allocation of power generation commands. The efficiency improvement and overall system flexibility enhancement brought about by the participation of switching units in regulation have been ignored.

[0003] Furthermore, according to national regulations, photovoltaic power generation systems can only be restored to grid connection after a certain delay time after shutdown, also known as the minimum downtime, which must not be less than 60 seconds. However, current control schemes for switching photovoltaic units rarely consider this characteristic in their algorithms and controllers. Therefore, even if switching units participate in coordinated scheduling, they cannot reasonably participate in completing the power generation tasks assigned to the virtual power plant by the actual AGC. Summary of the Invention

[0004] This invention addresses the problems of the existing technology by providing an AGC control method for virtual power plants with a high proportion of heterogeneous distributed photovoltaics. For systems with heterogeneous photovoltaic generator sets that have both switching and continuously adjustable modes, the invention designs a controller at the hardware level to determine the minimum downtime of the switching action. Based on this, it designs a hybrid integer programming control instruction that involves both switching and continuously adjustable modes, thereby improving the system's flexibility in AGC instruction allocation.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] An AGC control method for a virtual power plant with a high proportion of heterogeneous distributed photovoltaic (PV) power generation includes heterogeneous PV generator sets with both switching and continuously adjustable modes. The switching-operated generator sets are controlled by a self-locking controller, which controls their switching actions and thus their operating state. The self-locking controller includes a timer that outputs high and low level signals. A high-level signal is output when no timing is available; when the self-locking controller detects the switching action, it indicates the actual switching state of the unit. If the generator is in a shutdown and not generating power state, a timer is triggered, outputting a low-level signal during the timing period and automatically resuming a high-level signal after the timing ends. This method, based on known information such as the operating load and minimum downtime of the switching unit, and the maximum operating load, minimum operating load, and regulation dead zone of the continuously adjustable unit, designs a mixed-integer programming model with flexibility as the optimization objective and power, regulation dead zone, and minimum downtime as constraints. The received total active power command is decomposed into an AGC command allocation algorithm, including:

[0007] Obtain the total power to be allocated And initialize the control command switching action matrix S of the switching action unit, and initialize the switching action unit capacity, continuously adjustable unit capacity and continuously adjustable unit adjustment dead zone;

[0008] Detect the adjustable status of the unit currently in operation: And the current generating capacity of the continuously adjustable generating unit: Where n is the number of switching units and m is the number of continuously adjustable units;

[0009] With the goal of maximizing the flexibility of the virtual power plant photovoltaic system, a mixed-integer programming model is constructed to solve for the control command switching action matrix S of the on / off operating units and the rated power matrix of the continuously adjustable units allocated by AGC. The mixed-integer programming model includes:

[0010] Optimization goal: flex

[0011] A feasible solution should meet the total power generation requirement:

[0012] In a feasible solution, continuously adjustable generating units should meet the upper and lower limits of power generation:

[0013] In the feasible solution, the power variation allocated to the continuously adjustable unit should also be greater than the regulation dead zone.

[0014] In the formula, This represents the control command for the i-th switching unit. This represents the capacity of the unit whose switch is activated (i). This represents the rated power of the j-th continuously adjustable unit allocated by AGC; This represents the capacity of the j-th continuously adjustable generating unit; This represents the current generating capacity of the j-th continuously adjustable generating unit. This represents the adjustment dead zone of the j-th continuously adjustable unit;

[0015] Based on the obtained control command switching action matrix of the switching action unit , Rated power matrix of continuously adjustable units allocated by AGC The operation of the switch-operated unit and the continuously adjustable unit are controlled separately.

[0016] Furthermore, the timing duration T of the timer is 60s to 300s.

[0017] Furthermore, the specific steps for obtaining the control command switching action matrix S of the switching unit and the rated power matrix of the continuously adjustable unit allocated by AGC are as follows:

[0018] Initialize the upper bound Ub and lower bound Lb of feasible solutions;

[0019] calculate Under the condition of satisfying the optimization objective of total power generation requirements, if the feasible solution is not empty, then the control command switching action matrix S of the switching unit and the rated power matrix of the continuously adjustable unit allocated by AGC are obtained.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) The minimum downtime constraint was achieved at the hardware level, ensuring the accuracy of the system and enabling the photovoltaic generator set with switching action to correctly execute the system power generation command, thus providing a basis for participating in coordinated scheduling.

[0022] (2) In response to the photovoltaic power generation problem of both switching action and continuously adjustable heterogeneous photovoltaic generator sets, a hybrid integer programming optimization method is proposed to ensure that the total power generation of the system meets the power generation task and improves the system flexibility. When the photovoltaic generator sets participate in the virtual power plant system scheduling, it provides higher flexibility, coordinates scheduling, realizes peak shaving and valley filling, and copes with the situation of large fluctuations in the system power generation task. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0024] Figure 1 Diagram of a photovoltaic generator set actively participating in the AGC power regulation and control scheme of a virtual power plant.

[0025] Figure 2 This is a schematic diagram of the grid connection control method for photovoltaic power generation switch-operated units.

[0026] Figure 3 This is the initialization step of the method of the present invention.

[0027] Figure 4 A flowchart for solving AGC instruction allocation based on mixed integer programming.

[0028] Figure 5 The simulation waveform is shown under a given load, with the horizontal axis representing time (s). Detailed Implementation

[0029] This invention addresses the heterogeneous characteristics of existing photovoltaic generator sets in virtual power plants. Based on two unit operation modes—switching operation and continuously adjustable mode—it enables both switching operation units and continuously adjustable units to participate in coordinated scheduling through a reasonable AGC command allocation method and internal unit control methods. This effectively improves the flexibility of photovoltaic generator sets within the virtual power plant's jurisdiction.

[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.

[0031] This application will use terminology commonly employed by those skilled in the art to describe various aspects of the illustrative embodiments in order to convey the essence of their work to others skilled in the art. However, it will be apparent to those skilled in the art that alternative embodiments can be practiced using portions of the described aspects. For purposes of explanation, specific figures, materials, and configurations are set forth to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to those skilled in the art that alternative embodiments can be implemented without specific details. In other instances, some well-known features have been omitted or simplified in order not to obscure the illustrative embodiments.

[0032] This embodiment uses Taiwan switch operation photovoltaic generator set and This article will take a virtual power plant system with a continuously adjustable photovoltaic generator set as an example. Figure 1 The diagram illustrates a scheme for photovoltaic (PV) generator units actively participating in the AGC (Automatic Generation Control) power regulation and control of a virtual power plant. As shown, the PV generator unit monitoring center in the virtual power plant interacts with the switching-operated units and continuously adjustable units via a communication module. The communication module sends the power generation operation information of the switching-operated units and continuously adjustable units to the PV generator unit monitoring center. Based on the acquired power generation operation information, the PV generator unit monitoring center uses the AGC control method of this invention to issue control commands, which are transmitted through the communication module to each switching-operated unit and continuously adjustable unit. Each switching-operated unit and continuously adjustable unit operates according to the control commands.

[0033] The AGC control method of the present invention first limits the minimum downtime of the photovoltaic power generation switching control unit at the hardware level, and then designs a hybrid integer programming algorithm at the software level to implement AGC instruction allocation.

[0034] First, based on the minimum downtime of the photovoltaic switching unit, a shutdown self-locking controller (function) is designed on the grid-connected inverter side to ensure that subsequent AGC command allocation is performed under the constraint of meeting the minimum downtime; specifically:

[0035] 1.1) The grid-connected control schematic diagram of the photovoltaic switch-operated unit is as follows: Figure 2 As shown, both the switch-operated and continuously adjustable units are connected to the grid according to the following two-stage structure. The first stage ensures the maximum output power of the photovoltaic power generation unit through boost circuit and maximum power point tracking (MPPT) control. The second stage locks the phase of the AC signal during grid connection through a phase-locked loop (PLL), and then controls the inverter through three-phase coordinate transformation and active-reactive power control. The difference is that the switch-operated unit only receives "start" and "stop" commands issued by the virtual power plant control layer through the AGC control method of this invention, and controls them through the controlled switch on the grid connection side. (where n is the number of units with switching operations) to start and stop the units. Once a unit with switching operations is started, the rated power generation will not change. The switching operation command is filtered by the communication module into a 0 / 1 signal that can be received by the unit. As a controlled switch The control signals are 0 for unit shutdown and 1 for unit startup.

[0036] 1.2) For photovoltaic switching units, according to national regulations, after the photovoltaic inverter receives a shutdown command, the inverter should wait for an adjustable delay time. Grid connection can only be restored after the shutdown delay time, which can range from 60s to 300s. Therefore, after a photovoltaic switch is shut down, it cannot be immediately controlled to resume power generation. Start-up commands received during this period should be filtered out by the system; only commands received after the shutdown delay time has elapsed can be accepted.

[0037] 1.3) To address the above problems, this application proposes a method to detect the unit shutdown command and start timing the delay time from that moment. s, a self-locking controller that is not affected by the virtual power plant start-up command during the timing period, thereby meeting the minimum downtime requirement of the system at the hardware level.

[0038] This indicates the actual switching state of the generator unit, represented by a high or low level signal. A value of 1 indicates the system is in power-on state, while 0 indicates the system is in power-off state. The signal is detected on the falling edge. This proves that the controller detected the unit's shutdown action and triggered the timer.

[0039] Timer outputs high and low level signals When the timer is not in operation, it outputs a signal of 1. Upon receiving the trigger signal, the timer starts timing from the stop time as the starting point 0. s, in Output within s (Low level signal) automatically returns to output signal 1 (high level signal) after the timing ends. This output signal is a flag indicating whether the system can receive virtual power plant dispatch instructions (adjustable state). 0 means uncontrollable and 1 means controllable.

[0040] Therefore, we can conclude that:

[0041] ;

[0042] The power-on command can only be accepted when the power-on signal given by the virtual power plant is under the condition that it can be powered on. Therefore, this invention provides a control method from a hardware perspective to meet the minimum downtime of the system.

[0043] Based on the aforementioned hardware improvements, this invention provides an AGC control method for virtual power plants with a high proportion of heterogeneous distributed photovoltaic power. Using known information such as the start-up load and minimum downtime of the switching units, and the maximum operating load, minimum operating load, and regulation dead zone of the continuously adjustable units, a mixed integer programming model is designed with flexibility as the optimization objective and power, regulation dead zone, and minimum downtime as constraints. This model decomposes the received total active power command and controls each photovoltaic switching unit and continuously adjustable unit within the jurisdiction to complete its power generation task.

[0044] Specifically, the following steps are included:

[0045] Step 1: As Figure 3 As shown, the control command switching action matrix S of the switching action unit is initialized. , ; Initialize the switching capacity of each photovoltaic generator unit according to the work manual of each unit in the virtual power plant system: Initialize continuously adjustable unit capacity: Initialize the dead zone of the continuously adjustable unit: .

[0046] Step 2: Input the total power that AGC needs to allocate based on the power generation instructions received by the virtual power plant. Then check the adjustable status of the unit's switch operation: And the current generating capacity of the continuously adjustable generating unit: .

[0047] Step 3: Since the command for switching action is an integer of 0 (stop) or 1 (start), the command for continuously adjustable units is a real number, such as... Figure 4 The diagram shows the optimization objective and constraints for solving the system, as well as the solution process. Therefore, a mixed-integer programming model can be used to solve it.

[0048] Step 3.1: Using the highest instantaneous upward flexibility of the system as the optimization objective, plan the switching control unit and the continuously adjustable unit to determine the flexibility of the switching action unit. and the flexibility of continuously adjustable units Specifically:

[0049] For continuously adjustable units, the formula for describing their instantaneous upward flexibility is:

[0050]

[0051] in, This indicates the instantaneous upward flexibility of a continuously adjustable generator unit. Indicates the current moment. Indicates a time scale. wait; This represents the rated power of the j-th continuously adjustable unit allocated by AGC. express The capacity (maximum power) of the j-th continuously adjustable unit at time j.

[0052] For a switching unit, the formula for describing its instantaneous upward flexibility is:

[0053]

[0054] in This indicates the instantaneous upward flexibility of a continuously adjustable generator unit. Indicates the unit Maximum power; n represents the number of switching units;

[0055] Due to the capacity of the continuously adjustable unit in this embodiment It does not change over time, that is = Therefore, the current time can be... The variable is omitted, and even if it changes, it is not a variable controlled by AGC; therefore, it is abbreviated as:

[0056]

[0057] The objective function obtained based on maximizing system flexibility is:

[0058] flex

[0059] Substituting the above formulas and simplifying, we can obtain the equivalent system objective function being minimized:

[0060] flex

[0061] Step 3.2: In addition, the system also needs to meet the following constraints: First, it must meet the minimum downtime requirement. When the switching unit i is within the minimum downtime, the system cannot control the unit to start; otherwise, the portion of the load allocated to the switching unit i will not be able to be output by the switching unit i. Therefore, the system should meet the accuracy constraint: detected in Step 1. When the timer changes from 1 to 0, it starts. The AGC control method determines whether it is adjustable. If it is adjustable, the accuracy condition is met.

[0062] 1) A feasible solution should meet the total power generation requirement:

[0063]

[0064] To facilitate subsequent solution using mixed-integer programming algorithms, this formula should be written as follows: Therefore, the total power generation requirement is written in matrix form, i.e. , ;

[0065] 2) In feasible solutions, continuously adjustable generating units should meet the upper and lower limits of power generation:

[0066]

[0067] 3) In the feasible solution, the power variation allocated to the continuously adjustable unit should also be greater than the regulation dead zone:

[0068]

[0069] Combining the above formulas, mixed integer programming can be used to find the solution of the mixed integer programming model that satisfies the three constraints of minimum downtime (system accuracy), total system power generation, and regulation dead zone—the objective function matrix (composed of the control command switching action matrix S of the switching units and the rated power matrix of the continuously adjustable units allocated by AGC). ,in Determine if a feasible solution has been found. Specifically: Initialize the upper bound Ub and lower bound Lb of feasible solutions;

[0070] calculate Under the given conditions, a feasible solution is found that satisfies the optimization objective of total power generation requirements. If the feasible solution is not empty, then the control command switching action matrix S of the switching units and the rated power matrix of the continuously adjustable units allocated by AGC are obtained. During the absolute value processing, case-by-case discussions will occur. and This will affect continuously adjustable units. The upper and lower limits, such as Figure 4 As shown, there are two cases:

[0071] Scenario 1: When When the upper limit of feasible solutions Ub remains unchanged, The lower bound is no longer 0, therefore the lower bound of feasible solutions is modified: ;

[0072] calculate Mixed integer programming algorithm in the case of: C = intlinprog(C, A, b, Lb, Ub), where intlinprog() is the mixed integer programming function;

[0073] Scenario 2: When When the lower limit of the feasible solution Lb remains unchanged, The upper limit is no longer , but Therefore, the upper limit of feasible solutions is modified as follows: ;in

[0074] calculate Mixed integer programming algorithm in the case of: C = intlinprog(C, A, b, Lb, Ub), where intlinprog() is the mixed integer programming function;

[0075] If the feasible solution is not empty, then the objective function matrix is ​​obtained by solving the control command switching action matrix S of the switching unit and the rated power matrix of the continuously adjustable unit allocated by AGC. .

[0076] Step 4: Further, if a feasible solution is found, the solution is complete, and the switching action matrix can be obtained. ; Adjustable power of continuously adjustable units: The data is then transmitted to the generating units in the virtual power plant system to complete the power generation.

[0077] like Figure 5 The figure shows the electricity load curve of a certain unit and the actual power generation of the system obtained by the method of the present invention. It can be seen that the method of the present invention can ensure that the total power generation of the system meets the power generation task and ensure the improvement of system flexibility. When the photovoltaic generator sets participate in the virtual power plant system scheduling, it provides higher flexibility, coordinated scheduling, peak shaving and valley filling, and copes with the situation of large fluctuations in the system power generation task.

[0078] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An AGC control method for a virtual power plant containing a high proportion of heterogeneous distributed photovoltaic power, characterized in that, The high-proportion heterogeneous distributed photovoltaic system includes heterogeneous photovoltaic generator sets with both switching and continuously adjustable modes. The switching-operated units control the switching action and thus the operating state of the switching-operated units through a self-locking controller. The self-locking controller includes a timer that outputs high and low level signals. A high-level signal is output when no timing is available; when the self-locking controller detects the actual switching state of the unit during the switching action, a high-level signal is output. If the generator is in a shutdown and not generating power state, a timer is triggered, outputting a low-level signal during the timing period, and automatically resuming the output of a high-level signal after the timing ends; this method includes: Obtain the total power to be allocated And initialize the control command switching action matrix S of the switching action unit, and initialize the switching action unit capacity, continuously adjustable unit capacity and continuously adjustable unit adjustment dead zone; Detect the adjustable status of the unit currently in operation: And the current generating capacity of the continuously adjustable generating unit: Where n is the number of switching units and m is the number of continuously adjustable units; With the goal of maximizing the flexibility of the virtual power plant photovoltaic system, a mixed-integer programming model is constructed to solve for the control command switching action matrix S of the on / off operating units and the rated power matrix of the continuously adjustable units allocated by AGC. The mixed-integer programming model includes: Optimization goal: A feasible solution should meet the total power generation requirement: In a feasible solution, continuously adjustable generating units should meet the upper and lower limits of power generation: In the feasible solution, the power variation allocated to the continuously adjustable unit should also be greater than the regulation dead zone. In the formula, This represents the control command for the i-th switching unit. This represents the capacity of the unit whose switch is activated (i). This represents the rated power of the j-th continuously adjustable unit allocated by AGC; This represents the capacity of the j-th continuously adjustable generating unit; This represents the current generating capacity of the j-th continuously adjustable generating unit. This represents the adjustment dead zone of the j-th continuously adjustable unit; Based on the control command switching action matrix S of the switch-operated unit obtained from the solution and the rated power matrix of the continuously adjustable unit allocated by AGC, the operation of the switch-operated unit and the continuously adjustable unit are controlled respectively.

2. The method according to claim 1, characterized in that, The timing timer's timing duration T is 60s to 300s.

3. The method according to claim 1, characterized in that, The solution obtains the control command switching action matrix S of the switching unit and the rated power matrix of the continuously adjustable unit allocated by AGC, specifically as follows: Initialize the upper bound Ub and lower bound Lb of feasible solutions; calculate Under the condition of satisfying the optimization objective of total power generation requirements, if the feasible solution is not empty, then the control command switching action matrix S of the switching unit and the rated power matrix of the continuously adjustable unit allocated by AGC are obtained.

Images