A power system, power control method and related devices

Abstract

The application provides a power system, a power control method and related devices, and relates to the field of power supply. A first controller determines active power of a first inverter based on a first grid active power reference value, and determines active power of the first inverter and reactive power of a second inverter based on a grid reactive power reference value. A second controller determines active power of the second inverter based on a second grid active power reference value, so that the first inverter and the second inverter output power according to the respective active power and reactive power. The reactive power of the second inverter is in a proportional relationship with the reactive power of the first inverter, so that the two inverters can each bear the part of the reactive power that they need to bear, avoiding the problem that a certain inverter cannot output enough reactive power due to insufficient reactive power output capability, or the problem of insufficient active power output capability in order to output enough reactive power.

Description

Technical Field

[0001] This application relates to the field of power supply, and more specifically, to a power system, a power control method, and related devices. Background Technology

[0002] In recent years, in order to improve the stability of renewable energy power generation systems such as photovoltaics, reduce the impact of renewable power generation systems on the power grid, and enhance the inertia and active adjustment capabilities of renewable power generation systems, grid-connected energy storage systems are integrated with grid-connected systems to form hybrid power generation systems.

[0003] In hybrid power generation systems, grid-connected energy storage systems include photovoltaic inverters, while grid-connected systems include energy storage inverters. The dynamic characteristics and output curves of photovoltaic inverters and energy storage inverters differ greatly. Therefore, an accurate power control method is needed to coordinate the output of different inverters so that the output signal at the grid connection point meets the grid connection requirements. Summary of the Invention

[0004] In view of this, this application provides a power system, a power control method, and related apparatus to address the urgent need to improve the accuracy of power control methods used to control the output of different inverters.

[0005] To solve the above-mentioned technical problems, this application adopts the following technical solution:

[0006] In a first aspect, this application discloses an electric power system, comprising:

[0007] The first controller is used to determine the active power of the first inverter based on a first grid active power reference value, and to determine the reactive power of the first inverter and the reactive power of the second inverter based on a grid reactive power reference value, wherein the reactive power of the second inverter is proportional to the reactive power of the first inverter; the first grid active power reference value is the grid active power reference value corresponding to the first inverter.

[0008] The second controller is used to determine the active power of the second inverter based on the second grid active power reference value, wherein the second grid active power reference value is the grid active power reference value corresponding to the second inverter.

[0009] Optionally, the first controller determines the active power of the first inverter based on a first grid active power reference value, including:

[0010] The active power reference value of the first power grid is used as the active power of the first inverter, so that the first inverter outputs active power according to the active power of the first inverter.

[0011] Obtain the actual active power at the grid connection point;

[0012] Based on the actual active power of the grid connection point, the first grid active power reference value, and the second grid active power reference value, the updated active power of the first inverter is determined so that the first inverter outputs active power according to the updated active power of the first inverter.

[0013] Optionally, based on the actual active power at the grid connection point, the first grid active power reference value, and the second grid active power reference value, the updated active power of the first inverter is determined, including:

[0014] The total active power reference value is obtained by summing the active power reference values ​​of the first power grid and the second power grid.

[0015] Obtain the difference between the total active power reference value and the actual active power at the grid connection point;

[0016] The difference is subjected to active power closed-loop control to obtain the updated active power of the first inverter.

[0017] Optionally, the first controller determines the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value, including:

[0018] The reactive power reference value of the power grid is used as the reactive power of the first inverter, and a specified multiple of the reactive power of the first inverter is used as the reactive power of the second inverter, so that the first inverter outputs reactive power according to the reactive power of the first inverter, and the second inverter outputs reactive power according to the reactive power of the second inverter.

[0019] Obtain the actual reactive power at the grid connection point;

[0020] Based on the actual reactive power of the grid connection point and the reference value of the grid reactive power, the updated reactive power of the first inverter and the updated reactive power of the second inverter are determined, so that the first inverter outputs reactive power according to the updated reactive power of the first inverter, and the second inverter outputs reactive power according to the updated reactive power of the second inverter.

[0021] Return to the step of obtaining the actual reactive power of the grid connection point until the actual reactive power of the grid connection point is the same as the reference value of the reactive power of the power grid.

[0022] Optionally, based on the actual reactive power at the grid connection point and the reference value of the grid reactive power, the updated reactive power of the first inverter and the updated reactive power of the second inverter are determined, including:

[0023] Obtain the difference between the reference value of reactive power of the power grid and the actual reactive power of the grid connection point;

[0024] The difference is subjected to reactive power closed-loop control to obtain the updated reactive power of the first inverter;

[0025] The updated reactive power of the first inverter is taken as a specified multiple of the updated reactive power of the second inverter.

[0026] Optionally, the process of determining the specified multiple includes:

[0027] Determine the ratio of the reference value of reactive power of the power grid to the active power of the first inverter;

[0028] The difference between the ratio and the preset value is used as the specified multiple.

[0029] Optionally, the specified multiple is a value that changes over time;

[0030] Alternatively, the specified multiple is the value of the target constant after passing through the filter; the parameters of the filter are fixed or adjustable.

[0031] Optionally, the second controller determines the active power of the second inverter based on a second grid active power reference value, including:

[0032] The active power reference value of the second power grid is used as the active power of the second inverter, so that the second inverter outputs active power according to the active power of the second inverter.

[0033] Obtain the actual active power of the target sampling point set between the second inverter and the first AC bus connected to the second inverter;

[0034] Based on the actual active power of the target sampling point and the reference value of the active power of the second power grid, the updated active power of the second inverter is determined so that the second inverter outputs active power according to the updated active power of the second inverter.

[0035] Optionally, based on the actual active power of the target sampling point and the reference value of the active power of the second power grid, the updated active power of the second inverter is determined, including:

[0036] Obtain the difference between the second power grid active power reference value and the actual active power at the target sampling point;

[0037] The difference is subjected to active power closed-loop control to obtain the updated active power of the second inverter.

[0038] Optionally, when the first controller determines the frequency change of the power system, it calculates the change in active power of the first inverter based on the frequency change of the power system and the droop coefficient of the first inverter, and adjusts the active power of the first inverter based on the change in active power.

[0039] Optionally, when the second controller determines the frequency change of the power system, it calculates the change in active power of the second inverter based on the frequency change of the power system and the droop coefficient of the second inverter, and adjusts the active power of the second inverter based on the change in active power of the second inverter.

[0040] Secondly, this application discloses an energy system, including the aforementioned power system, and further including a first inverter and a second inverter;

[0041] The first inverter outputs power according to its reactive power and active power.

[0042] The second inverter outputs power according to its reactive power and active power.

[0043] Optionally, the first inverter is connected to the first AC bus via a first step-up transformer; the second inverter is connected to the first AC bus via a second step-up transformer; the first AC bus is connected to the second AC bus via a third step-up transformer, and the second AC bus is connected to the power grid.

[0044] Thirdly, this application discloses a power control method, including:

[0045] The first controller determines the active power of the first inverter based on the first grid active power reference value, and determines the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value. The reactive power of the second inverter is proportional to the reactive power of the first inverter. The first grid active power reference value is the grid active power reference value corresponding to the first inverter.

[0046] The second controller determines the active power of the second inverter based on the second grid active power reference value, where the second grid active power reference value is the grid active power reference value corresponding to the second inverter.

[0047] This application provides a power system, a power control method, and related devices. In this application, a first controller determines the active power of a first inverter based on a first grid active power reference value, and determines the reactive power of the first inverter and the second inverter based on a grid reactive power reference value. This ensures that the first inverter outputs power according to its active and reactive power, and the second inverter outputs reactive power according to its reactive power. A second controller determines the active power of the second inverter based on a second grid active power reference value, ensuring that the second inverter outputs active power according to its active power. Since the reactive power of the second inverter is proportional to that of the first inverter, each inverter can bear its own required portion of reactive power, avoiding the problem of insufficient reactive power output capacity leading to insufficient reactive power output when one inverter bears all the reactive power, or insufficient active power output capacity due to the effort to output sufficient reactive power. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0049] Figure 1 A schematic diagram of the structure of a power system provided for related technologies;

[0050] Figure 2 A schematic diagram of the structure of a power system provided in this application embodiment;

[0051] Figure 3 This application provides a schematic diagram of another power system structure.

[0052] Figure 4 A power control flowchart is provided for an embodiment of this application;

[0053] Figure 5 Another power control flowchart provided in this application embodiment;

[0054] Figure 6 A comparison chart of grid connection point voltage and output reactive power provided for related technologies;

[0055] Figure 7 A comparison diagram of grid connection point voltage and output reactive power provided for an embodiment of this application;

[0056] Figure 8 A comparison chart of grid connection point voltage and output active power provided for related technologies;

[0057] Figure 9 A comparison diagram of grid connection point voltage and output active power provided for an embodiment of this application;

[0058] Figure 10 This is a flowchart of a power control method provided in an embodiment of this application. Detailed Implementation

[0059] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0060] In recent years, in order to improve the stability of renewable energy power generation systems such as photovoltaics, reduce the impact of renewable power generation systems on the power grid, and enhance the inertia and active adjustment capabilities of renewable power generation systems, grid-connected energy storage systems are integrated with grid-connected systems to form hybrid power generation systems.

[0061] In hybrid power generation systems, grid-connected energy storage systems include photovoltaic inverters, while grid-connected systems include energy storage inverters. The dynamic characteristics and output curves of photovoltaic inverters and energy storage inverters differ greatly. Therefore, an accurate power control method is needed to coordinate the output of different inverters so that the output signal at the grid connection point meets the grid connection requirements.

[0062] In one implementation, with Figure 1 Taking a twin-station hybrid power plant as an example, a twin-station hybrid power plant is equipped with three controllers, namely:

[0063] Master PPC (PPC: Power Plant Controller).

[0064] BESS PPC (BESS: Battery Energy Storage System) energy storage controller.

[0065] Photovoltaic controller PV PPC (PV: Photovoltaic, photovoltaic system).

[0066] The three controllers can communicate with each other. The main controller sends the corresponding active and reactive power to the energy storage controller and the photovoltaic controller in the form of instructions.

[0067] In addition, the twin-station hybrid power plant is equipped with two inverters: a BESS inverter (Best Energy Storage Inverter) and a PV inverter.

[0068] The energy storage inverter communicates with the energy storage controller, which can adjust the active and reactive power of the energy storage inverter.

[0069] The photovoltaic inverter communicates with the photovoltaic controller, which can adjust the active and reactive power of the photovoltaic inverter.

[0070] The energy storage inverter and the photovoltaic inverter are connected to the same 33kV AC bus via a step-up transformer (0.69 / 33kV). The 33kV AC bus is connected to the 132kV AC bus via a step-up transformer (33 / 132kV), and the 132kV AC bus is connected to the power grid. Appropriate electronic components can be installed between the 132kV AC bus and the power grid.

[0071] In practice, the power grid company issues corresponding active power commands to both the energy storage inverter and the photovoltaic inverter. The active power command for the energy storage inverter uses... The table indicates that the active power in the active power command of the photovoltaic inverter adopts... This indicates that a reactive power command is issued simultaneously, and the reactive power in the reactive power command adopts... express.

[0072] like Figure 1 As shown, the response of the hybrid power plant is measured at the POC (Point of Connection). For example, a meter is installed at the POC to sample the output signal of the grid connection point. This output signal can represent the active power of the grid connection point. Reactive power at grid connection point Frequency of grid connection points Voltage, current, etc.

[0073] The main controller receives the sent message. , as well as After that, a power allocation operation will be performed to obtain the active power of the energy storage inverter and the active power of the photovoltaic inverter. At the same time, the reactive power in the reactive power command issued by the grid will be allocated to a single power source, such as the photovoltaic inverter or the energy storage inverter. In this embodiment, the allocation to the photovoltaic inverter will be taken as an example.

[0074] To ensure the overall power response at the point of origin (POC) meets the grid company's requirements, the energy storage controller and photovoltaic controller adjust the power of their respective connected inverters, thereby jointly controlling the power and voltage of the 33kV bus. To compensate for power losses on the line, the measured active power output from the POC is optimized. and To be equal, we need to... and The difference is calculated, and after passing through the PI (Proportional-Integral Control) regulator in the active power control loop of the main controller, it is distributed to the energy storage inverter and the photovoltaic inverter. The energy storage inverter and the photovoltaic inverter provide active power compensation according to the capacity ratio of the two. and .

[0075] Assuming the installed capacities of energy storage inverters and photovoltaic inverters are respectively and In steady state, Figure 1 The signal relationship can be represented as follows:

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084] in, and The active power of the energy storage inverter;

[0085] and The reactive power of the energy storage inverter;

[0086] and This refers to the active power of the photovoltaic inverter.

[0087] and The reactive power of a photovoltaic inverter;

[0088] The active power in the issued active power command for the energy storage inverter;

[0089] The active power in the issued active power command for the photovoltaic inverter;

[0090] The reactive power in the issued reactive power command;

[0091] S For the installed capacity of energy storage inverters, This refers to the installed capacity of photovoltaic inverters;

[0092] For active power compensation of energy storage inverters. For active power compensation of photovoltaic inverters;

[0093] This is the proportionality coefficient. The integral coefficient is... As a control factor, The active power at the grid connection point;

[0094] It should be noted that the energy storage controller and the photovoltaic controller adopt a direct connection method, which only transmits signals and does not perform calculations.

[0095] While the above methods can allocate power, when allocating reactive power, the reactive power in the reactive power command issued by the power grid is allocated to a single power source. This can lead to problems such as the single power source being unable to generate sufficient reactive power due to its limited reactive power capacity, or the output capacity of active power being insufficient in order to generate sufficient reactive power.

[0096] Therefore, in this embodiment of the application, the distributed reactive power is allocated to both the energy storage inverter and the photovoltaic inverter. That is, the reactive power output task is undertaken by two inverters, avoiding the problem that a single inverter may not be able to output enough reactive power due to its limited reactive power capacity, or that the output capacity of active power may be insufficient due to the need to output enough reactive power.

[0097] Based on the above, one embodiment of this application provides a power system including a first controller 11 and a second controller 12.

[0098] In one implementation, the first controller 11 can be the photovoltaic controller (PV PPC) described above, and the second controller 12 can be the energy storage controller (BESS PPC) described above. In another implementation, the first controller 11 can be the energy storage controller described above, and the second controller 12 can be the photovoltaic controller described above. In subsequent embodiments, the example of the first controller 11 being the photovoltaic controller described above and the second controller 12 being the energy storage controller described above will be used for illustration.

[0099] like Figure 3 As shown, the power system has two controllers, namely the first controller ( Figure 3 The photovoltaic controller and the second controller (in the middle) Figure 3 The system comprises two inverters: a first controller (comprising a second inverter, such as an energy storage inverter) and a second inverter (comprising a first inverter, such as a photovoltaic inverter). The first controller communicates with both the second inverter (e.g., an energy storage inverter) and the first inverter (e.g., a photovoltaic inverter). The first controller controls the active and reactive power of the photovoltaic inverter, as well as the reactive power of the energy storage inverter. The second controller communicates with the energy storage inverter and controls its active power. The energy storage inverter is a grid-connected inverter, a type of inverter that is a voltage-oriented current source inverter. The photovoltaic inverter is a grid-connected inverter, a type of inverter that is a power-oriented voltage source inverter.

[0100] It should be noted that in this embodiment... Figure 3 The communication architecture of the two controllers compared to Figure 1 The master-slave controller communication architecture (with the master controller as the first layer and the energy storage controller and photovoltaic controller as the second layer) reduces the number of master controllers, which can avoid the communication and control delay problems caused by the master-slave controller communication architecture. In addition, it will directly reduce hardware costs, increase control bandwidth and control flexibility, and reserve more bandwidth margin for other active control functions (such as active power damping control).

[0101] Figure 3 In this configuration, the energy storage inverter and the photovoltaic inverter are connected to the same 33kV AC bus via a step-up transformer (0.69 / 33kV). The 33kV AC bus is then connected to the 132kV AC bus via a step-up transformer (33 / 132kV), and the 132kV AC bus is connected to the power grid. Appropriate electronic components can be installed between the 132kV AC bus and the power grid.

[0102] In this embodiment, a target sampling point is set between the 0.69 / 33kV step-up transformer and the 33kV AC bus on the energy storage inverter side. The target sampling point is equipped with a meter, which can collect information such as active power, reactive power, frequency, voltage, and current of the target sampling point.

[0103] In addition, a meter is still installed at the grid connection point to collect the output signal of the grid connection point. This output signal can be the active power of the grid connection point. Reactive power at grid connection point Frequency of grid connection points Information such as voltage and current.

[0104] In addition, a sampling point is set between the 0.69 / 33kV step-up transformer and the 33kV AC bus on the photovoltaic inverter side. Control operations can be performed based on data such as active power, reactive power, frequency, voltage, and current from this sampling point. It should be noted that the data from this sampling point will not be used for power allocation in this embodiment; therefore, it is acceptable not to set up this sampling point. If other power requires the data from this sampling point, then this sampling point can be set up.

[0105] exist Figure 3 Based on this, the first controller determines the active power of the first inverter based on the first grid active power reference value, and determines the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value.

[0106] Wherein, the first grid active power reference value is the grid active power reference value corresponding to the first inverter, specifically referring to the aforementioned... In addition, along with the first grid active power reference value, the second grid active power reference value and the grid reactive power reference value were also issued. The second grid active power reference value is the grid active power reference value corresponding to the second inverter, specifically referring to the aforementioned... The reference value for reactive power in the power grid refers to the above-mentioned... .

[0107] The first controller receives After that, it will be based on Determine the active power of the first inverter . It is used only to control the first inverter. When the first controller is a photovoltaic controller, the first inverter is a photovoltaic inverter. When the second controller is an energy storage controller, the second inverter is an energy storage inverter.

[0108] The first controller will also be based on Determine the reactive power of the first inverter and the reactive power of the second inverter . Used to control the first inverter. Used to control the second inverter.

[0109] The reactive power of the second inverter is proportional to the reactive power of the first inverter; for example, the reactive power of the second inverter is equal to the reactive power of the first inverter. times, of which, It is a positive number.

[0110] The first controller will determine the active power of the first inverter. and reactive power The data is sent to the first inverter so that the first inverter can operate according to... Output active power, and according to Output reactive power.

[0111] The first controller will determine the reactive power of the second inverter. The command is sent to the second inverter so that the second inverter can operate according to... Output reactive power.

[0112] The second controller is based on the active power reference value of the second power grid, that is Determine the active power of the second inverter. ,Will The data is sent to the second inverter so that the output of the second inverter is connected to... The active power is matched. Simultaneously, the second inverter also receives the reactive power from the first controller. ,according to Output the corresponding reactive power.

[0113] In this embodiment, the first controller determines the active power of the first inverter based on a first grid active power reference value, and determines the reactive power of both the first and second inverters based on a grid reactive power reference value. This ensures that the first inverter outputs power according to its active and reactive power, and the second inverter outputs reactive power according to its reactive power. The second controller determines the active power of the second inverter based on a second grid active power reference value, ensuring that the second inverter outputs active power according to its active power. Since the reactive power of the second inverter is proportional to that of the first inverter, each inverter can bear its own required portion of reactive power. This avoids the problem of insufficient reactive power output due to insufficient reactive power output capacity when one inverter bears all the reactive power, or insufficient active power output capacity due to the effort to output sufficient reactive power.

[0114] In addition, this application is compared to Figure 1This application's embodiment employs a master-slave control structure consisting of a main controller, an energy storage controller, and a photovoltaic controller for power regulation. Instead of a main controller, it only includes a first controller and a second controller, reducing one controller module and lowering hardware costs. Furthermore, by utilizing the first and second controllers for independent power control and calculation, direct control of the inverter can be achieved. This reduces the communication process between the main controller and the energy storage and photovoltaic controllers, lowering control latency, increasing control bandwidth and flexibility, and reserving more bandwidth margin for other active control functions.

[0115] Based on any of the above embodiments, refer to Figure 4 The first controller determines the active power of the first inverter based on a first grid active power reference value, including:

[0116] S11. Use the first grid active power reference value as the active power of the first inverter, so that the first inverter outputs active power according to the active power of the first inverter.

[0117] In practice, the active power reference value of the first power grid is directly used. As the active power of the first inverter, at this time The first controller will The message is sent to the first inverter, and the first inverter responds. Adjust its own output power to After the first inverter adjusts its output power, the active power at the grid connection point will also change accordingly.

[0118] S12. Obtain the actual active power at the grid connection point.

[0119] In practical scenarios, theoretically, the power supplied by a photovoltaic inverter to the grid is... The energy storage inverter provides power to the grid as follows: Active power of grid connection point Should with The two systems are similar, but there are line losses in the line between the photovoltaic inverter and the grid connection point, which reduces the active power at the grid connection point. and They are not the same. Therefore, line loss compensation should be performed so that the active power at the grid connection point is increased after line loss compensation. and same.

[0120] Therefore, in this embodiment, the actual active power at the grid connection point is collected by an electricity meter, and this actual active power adopts the above-mentioned... This indicates that, in addition, information such as reactive power, voltage, current, and frequency at the grid connection point can also be collected.

[0121] S13. Based on the actual active power of the grid connection point, the first grid active power reference value, and the second grid active power reference value, determine the updated active power of the first inverter so that the first inverter outputs active power according to the updated active power of the first inverter.

[0122] In this embodiment, the actual active power at the grid connection point and the reference value of the active power of the first power grid are known. and the reference value of active power of the second power grid Subsequently, since PI control offers high adjustment accuracy, in this embodiment, PI control within the active power closed-loop control (also known as the active power control loop) can be used to... , and The calculation is performed to obtain the updated active power of the first inverter.

[0123] In one implementation, when performing PI control, a reference value for the active power of the first power grid is determined. and the reference value of active power of the second power grid The sum of these values ​​yields the total active power reference value, which is the total active power reference value. .

[0124] Then, the difference between the total active power reference value and the actual active power at the grid connection point is obtained, specifically, .

[0125] Finally, active power closed-loop control is performed on the difference to obtain the updated active power of the first inverter.

[0126] The specific calculation formula is as follows:

[0127]

[0128] in, This is the active power compensation amount for the first inverter. This is the proportionality coefficient. The integral coefficient is... As a control factor, This refers to the active power reference value of the first power grid, specifically the active power in the active power command issued to the photovoltaic inverter. This refers to the active power reference value for the second power grid, specifically the active power in the active power command issued to the energy storage inverter. The active power of the grid connection point refers specifically to the actual active power of the grid connection point.

[0129] In the calculation Subsequently, the updated formula for calculating the active power of the first inverter is as follows:

[0130]

[0131] That is, at this time ,Will The first inverter is sent to the first inverter so that it can operate according to... Adjust its own output power so that its output power is .

[0132] It should be noted that after the adjustments in steps S12 and S13, the active power at the grid connection point is increased. and If the two are close or the same, then repeat steps S12 and S13 until the active power at the grid connection point is reached. and Same. Generally, one or more PI controls are sufficient to guarantee the active power at the grid connection point. and The same applies. For example, in one implementation, the active power at the grid connection point is achieved through four or five PI controls. and same.

[0133] In this embodiment, the first grid active power reference value is directly sent to the first inverter, so that the first inverter outputs active power in accordance with the grid's active power demand. In the process of active power output, the impact of line loss on active power output is considered to ensure that the active power at the grid connection point is the same as the sum of the active power output of the energy storage inverter and the photovoltaic inverter, thus meeting the grid's active power demand.

[0134] Based on any of the above embodiments, in another implementation of this application, refer to Figure 5 The first controller determines the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value, including:

[0135] S21. The reactive power reference value of the power grid is used as the reactive power of the first inverter, and a specified multiple of the reactive power of the first inverter is used as the reactive power of the second inverter, so that the first inverter outputs reactive power according to the reactive power of the first inverter, and the second inverter outputs reactive power according to the reactive power of the second inverter.

[0136] In this embodiment, based on the above discussion, the reactive power of the second inverter is proportional to the reactive power of the first inverter; for example, the reactive power of the second inverter is equal to the reactive power of the first inverter. Therefore, in this embodiment, the reactive power of the first inverter should first be determined, and then the reactive power of the second inverter should be determined based on the ratio between the two.

[0137] In one implementation method, the reference value of reactive power of the power grid can be used first, i.e. As the reactive power of the first inverter, the reactive power of the second inverter is at this time. .in, The specified multiple, also known as the reactive power factor, is a user-defined factor that can be a constant or a variable, used to adjust the reactive power output of the first and second inverters.

[0138] Then As The command is sent to the first inverter so that the first inverter adjusts its output reactive power to... .Will As The command is sent to the second inverter so that the second inverter adjusts its output reactive power to... .

[0139] In one implementation, the process of determining the specified multiple includes:

[0140] Determine the ratio of the grid reactive power reference value to the active power of the first inverter, and use the difference between the ratio and a preset value as the specified multiple.

[0141] The default value is 1.

[0142] Specifically, theoretically, the actual reactive power at the grid connection point should be: ,at this time Should equal to Then we can deduce that:

[0143] .

[0144] in, This is a reference value for reactive power in the power grid. This represents the active power of the first inverter.

[0145] In another implementation, the specified multiple It can be a value that changes over time. In one embodiment, The possible values ​​for are:

[0146] Time 1: The value is constant 1, and the time is 2: The value is a constant 2, and the time is 3. The value is a constant 3...

[0147] In real-world scenarios, the photovoltaic modules connected to the photovoltaic inverter are affected by sunlight, resulting in fluctuating output power. In this embodiment, the power output can be adjusted according to the changes in the photovoltaic module's output power. This value allows the photovoltaic inverter to generate more or less reactive power, which can be achieved while ensuring the output ratio of the energy storage inverter. The system's dynamic performance is optimized by adjusting the parameters to meet the needs of actual photovoltaic module operation scenarios.

[0148] In another implementation, the specified multiple is the value of the target constant after passing through the filter; the parameters of the filter are fixed or adjustable.

[0149] The target constant can be configured according to actual conditions.

[0150] In one embodiment, To obtain the value of a target constant after passing it through a low-pass or high-pass filter, the time constant of the filter is fixed. This method can avoid sudden changes in reactive power of the energy storage inverter and improve the dynamic performance of the system.

[0151] In another embodiment, In this embodiment, the time constant of the low-pass or high-pass filter is a variable parameter that changes with time or power, so that the value obtained after passing a certain target constant through a low-pass or high-pass filter is obtained. This implementation method can further improve the dynamic response of the system.

[0152] In another implementation, Related to the rated capacity of the first and second inverters, such as The ratio of the rated capacity of the first inverter to the rated capacity of the second inverter, or determined based on the ratio. When determining the value of , the rated capacity of the inverter is considered during reactive power distribution, making the distribution more reasonable. This avoids situations where the reactive power allocated to each inverter exceeds its rated capacity, resulting in insufficient reactive power output or reduced active power output to achieve sufficient reactive power. Furthermore, through... It can allocate reactive power more flexibly to adapt to different operating conditions.

[0153] S22. Obtain the actual reactive power at the grid connection point.

[0154] After adjusting the reactive power output of the first and second inverters according to step S21, the required power at the grid connection point is... However, at this time, the sum of the reactive power outputs of the first inverter and the second inverter is This means that the sum of the reactive power outputs of the first and second inverters is greater than the power demand at the grid connection point. Subsequent PI control will be used at least once to ensure that the actual reactive power at the grid connection point is [the required power]. Therefore, in this embodiment of the application, the actual reactive power at the grid connection point can be collected by an electricity meter, specifically referring to the aforementioned... In addition, it can also collect information such as voltage, current, and frequency at the grid connection point.

[0155] S23. Determine whether the actual reactive power at the grid connection point is the same as the reference value of the grid reactive power; if they are the same, the process ends. If they are different, proceed to step S24.

[0156] Specifically, in theory, the actual reactive power at the grid connection point should be the same as the reference value of the reactive power of the power grid. However, due to line losses, the actual reactive power at the grid connection point is different from the reference value of the reactive power of the power grid. In this case, line loss compensation should be performed to make the actual reactive power at the grid connection point the same as the reference value of the reactive power of the power grid.

[0157] S24. Based on the actual reactive power of the grid connection point and the reference value of the grid reactive power, determine the updated reactive power of the first inverter and the updated reactive power of the second inverter, so that the first inverter outputs reactive power according to the updated reactive power of the first inverter, and the second inverter outputs reactive power according to the updated reactive power of the second inverter.

[0158] In this embodiment, the implementation process of step S24 is the same as that of step S13 described above. In one implementation, the difference between the reference value of reactive power of the power grid and the actual reactive power of the grid connection point is first obtained. This difference is... .

[0159] Then, reactive power closed-loop control (also known as reactive power control loop) is performed on the difference to obtain the updated reactive power of the first inverter. The specific calculation formula is as follows:

[0160]

[0161] in, This refers to the updated reactive power of the first inverter. This is the proportionality coefficient. The integral coefficient is... As a control factor, This is the reference value for reactive power in the power grid, and can also be referred to as the reactive power in the issued reactive power command.

[0162] Finally, the updated reactive power of the first inverter is taken as a specified multiple of the updated reactive power of the second inverter.

[0163] Specifically, in the calculation Subsequently, the updated reactive power of the second inverter The calculation formula is:

[0164] .

[0165] It should be noted that after executing step S24, the process returns to step S22 and executes sequentially until the actual reactive power at the grid connection point is the same as the grid reactive power reference value. Generally, after executing step S21, the sum of the reactive power outputs of the first inverter and the second inverter is greater than the required power at the grid connection point. Subsequently, with at least one PI control operation, the sum of the reactive power outputs of the first inverter and the second inverter can be made close to the required power at the grid connection point, ultimately making the sum of the reactive power outputs of the first inverter and the second inverter equal to the required power at the grid connection point.

[0166] In this embodiment, a specified multiple of the reactive power of the first inverter is used as the reactive power of the second inverter, so that both inverters can undertake the task of reactive power and output reactive power. This avoids the problem that a single inverter may not be able to output enough reactive power due to its limited reactive power output, or that the output capacity of active power may be insufficient due to the need to output enough reactive power.

[0167] Based on any of the above embodiments, the second controller determines the active power of the second inverter based on the second grid active power reference value, including:

[0168] The active power reference value of the second power grid is used as the active power of the second inverter, so that the second inverter outputs active power according to the active power of the second inverter.

[0169] Obtain the actual active power of the target sampling point set between the second inverter and the first AC bus connected to the second inverter;

[0170] Based on the actual active power of the target sampling point and the reference value of the active power of the second power grid, the updated active power of the second inverter is determined so that the second inverter outputs active power according to the updated active power of the second inverter.

[0171] Specifically, the process by which the second controller determines the active power of the second inverter based on the second grid active power reference value is similar to the process by which the first controller determines the active power of the first inverter based on the first grid active power reference value. First, the second controller... As The command is sent to the second inverter so that the second inverter can operate according to the command. The active power output is then adjusted. After the second inverter adjusts its output power, the active power of the electricity used in the aforementioned target will also change accordingly.

[0172] The first AC bus connected to the second inverter (i.e.) is configured to... Figure 3 The active power at the target sampling point between the 33kV AC bus and the target sampling point will also change accordingly. Theoretically, the active power at the target sampling point should be... However, due to line losses, the active power at the target sampling point is lower than that of the target sampling point. The difference is that line loss compensation should be performed. At this point, the actual active power of the target sampling point can be obtained. Based on the actual active power of the target sampling point and the reference value of the active power of the second power grid, the updated active power of the second inverter is determined, so that the second inverter outputs active power according to the updated active power of the second inverter.

[0173] In practice, the difference between the second grid active power reference value and the actual active power of the target sampling point is obtained, and active power closed-loop control is performed on the difference to obtain the updated active power of the second inverter.

[0174] It should be noted that the active power closed-loop control in this embodiment has the same implementation logic as the active power closed-loop control of the first controller described above, both of which use PI control. The specific implementation method is described in the corresponding description above and will not be repeated here.

[0175] In this embodiment, the active power output of the second inverter is adjusted by sampling the active power of the target sampling point, so that the active power output of the second inverter is the active power required by the power grid in the presence of line losses.

[0176] In addition, the second controller performs active power closed-loop control at the 33kV AC bus, thus controlling the droop factor of the second inverter.

[0177] In another implementation of this application, the power grid company issues two active power commands, namely, active power commands corresponding to the first inverter and the second inverter respectively. This is intended to give the first inverter and the second inverter different droop coefficients, where the droop coefficient is the active power droop coefficient, which is the ratio of active power to frequency. However, in... Figure 1Based on the circuit, power closed-loop control at the grid connection point only yields the combined droop coefficient of the first and second inverters, making it difficult to control the droop coefficients of the first and second inverters individually. Furthermore, considering the need to provide power at loss, the actual droop coefficients of the first and second inverters are unlikely to meet grid requirements.

[0178] Therefore, in the embodiments of this application, with Figure 3 For example, two closed-loop controls are set up: one is the active power closed-loop control of the second controller based on the target sampling point, and the other is the active and reactive power closed-loop control of the first controller based on the grid connection point. Through the active power closed-loop control of the second controller at the 33kV AC bus, the droop coefficient of the second inverter can be guaranteed. Figure 1 After obtaining the combined droop coefficient of the first inverter and the second inverter, the droop coefficient of the first inverter can be guaranteed through closed-loop control at the grid connection point.

[0179] Assume the parameters of the first inverter and the second inverter are as follows:

[0180]

[0181] The formulas for calculating the active power droop factor of the first inverter and the second inverter are as follows:

[0182]

[0183]

[0184]

[0185] in, This refers to the droop factor of the second inverter, specifically the active power droop factor. This represents the change in active power of the second inverter, which is a change in active power demand. For the frequency of the power system, For the frequency variation of the power system, The rated frequency of the power system. This is the frequency dead zone of the second inverter. This refers to the active power droop rate of the second inverter. This is the rated active power of the second inverter. The droop coefficient of the grid connection point. This is the rated active power of the first inverter. The active power droop rate of the first inverter. This represents the change in active power of the first inverter, which is a change in active power demand.

[0186] Therefore, the droop coefficients of the first inverter and the second inverter can be calculated using the above formula. Under steady-state conditions, i.e., when the power system frequency does not change, the droop coefficients of both inverters are fixed values. When the power system frequency changes, in order to ensure that the droop coefficients of the two inverters remain fixed, the active power of the first and second inverters needs to be adjusted.

[0187] In one implementation, when the first controller determines the frequency change of the power system, it calculates the change in active power of the first inverter based on the frequency change of the power system and the droop coefficient of the first inverter, and adjusts the active power of the first inverter based on the change in active power.

[0188] Specifically, the frequency variation of the power system refers to The droop factor of the first inverter is the active power droop factor. At this time, the change in active power of the first inverter .

[0189] Then, the active power of the first inverter is calculated according to... Adjust the amount of change.

[0190] It should be noted that if the frequency of the power system decreases, at this time... If it is a negative value, then If the value is negative, then the active power of the first inverter is calculated according to... When adjusting for changes in the frequency of the power system, the active power of the first inverter is reduced to ensure that its droop coefficient remains constant. Similarly, if the frequency of the power system increases, the active power of the first inverter is increased to ensure that its droop coefficient remains constant.

[0191] In another implementation, the second controller can also adjust the active power of the second inverter based on the frequency variation of the power system.

[0192] Specifically, when the second controller determines the frequency change of the power system, it calculates the change in active power of the second inverter based on the frequency change of the power system and the droop coefficient of the second inverter, and adjusts the active power of the second inverter based on the change in active power of the second inverter.

[0193] To elaborate, the frequency variation of a power system refers to... The droop factor of the second inverter is At this time, the change in active power of the first inverter .

[0194] Then, the active power of the first inverter is calculated according to... Adjust the amount of change.

[0195] It should be noted that if the frequency of the power system decreases, at this time... If it is a negative value, then If the value is negative, then the active power of the second inverter will be calculated according to... When adjusting for changes in the frequency of the power system, the active power of the second inverter will be reduced to ensure that its droop factor remains constant. Conversely, if the frequency of the power system increases, the active power of the second inverter will be increased to ensure that its droop factor remains constant.

[0196] In this embodiment, the first controller and the second controller are used for corresponding power control, which enables the control of the droop coefficients of the first inverter and the second inverter respectively. Furthermore, when the power system frequency changes, the first controller and the second controller are used to adjust the power accordingly, ensuring that the droop coefficient remains constant.

[0197] In another implementation of this application, in order to enable those skilled in the art to better understand the power control effect in this application, an example is given based on the standard operating conditions of a Dynamic Model Acceptance Test (DMAT).

[0198] Operating Condition 1: Step change in reactive power reference value

[0199] In related technologies, Figure 6 In order to be in Figure 1 Based on the structure, the actual reactive power response curves of BESS, PV and POC points were tested when the reactive power reference value changed abruptly. The horizontal axis represents time and the vertical axis represents reactive power (MVar).

[0200] Figure 6 The top graph in the image shows the curve of the reactive power reference value at the grid connection point changing over time. Figure 6 The lower graph shows the actual reactive power changes over time for the photovoltaic inverter (PV), energy storage inverter (BESS), and grid connection point (POC). Figure 6 As shown in the figure below, almost all the reactive power at the grid connection point is provided by the photovoltaic inverter, and the energy storage inverter hardly participates in reactive power regulation.

[0201] In the embodiments of this application, Figure 7 In order to be in Figure 3Based on the structure, the response curves of BESS, PV and POC points were tested when the reactive power reference value changed abruptly. The horizontal axis represents time and the vertical axis represents reactive power (MVar). Figure 7 The top graph in the image shows the curve of the reactive power reference value at the grid connection point changing over time. Figure 7 The lower graph in the image shows the actual reactive power of the photovoltaic inverter (denoted by PV), energy storage inverter (denoted by BESS), and grid connection point (denoted by POC) over time. Figure 7 As shown in the figure below, this application has a stronger ability to support grid connection point voltage, and both the energy storage inverter and the photovoltaic inverter participate in reactive power regulation, and the reactive power output distribution is more reasonable.

[0202] Operating Condition 2: Step Change in Active Power Reference Value

[0203] In related technologies, Figure 8 Is Figure 1 Based on the structure, the response curves of actual reactive power at BESS, PV and POC points were tested when the active power reference value changed abruptly. The horizontal axis is time, the vertical axis of the upper graph is active power (MW) and the vertical axis of the lower graph is reactive power (MVar).

[0204] Figure 8 The top graph in the image represents the curve showing the change of the active power reference value at the grid connection point over time. Figure 8 The lower graph in the image shows the actual reactive power of the photovoltaic inverter (denoted by PV), energy storage inverter (denoted by BESS), and grid connection point (denoted by POC) over time. Figure 8 As shown in the figure below, changes in active power at the grid connection point will cause voltage changes, which in turn will lead to changes in reactive power at the grid connection point. Although the reactive power reference value is zero under this condition, the reactive power at the grid connection point under this control mode is not zero in most cases.

[0205] In the embodiments of this application, Figure 9 In order to be in Figure 3 Based on the structure, the response curves of actual reactive power at BESS, PV and POC points were tested when the active power reference value changed abruptly. The upper graph shows time on the horizontal axis and active power (MW) on the vertical axis, while the lower graph shows reactive power (MVar) on the vertical axis.

[0206] Figure 9 The top graph in the image represents the curve showing the change of the active power reference value at the grid connection point over time. Figure 9 The lower graph in the image shows the actual reactive power of the photovoltaic inverter (denoted by PV), energy storage inverter (denoted by BESS), and grid connection point (denoted by POC) over time. Figure 9 As shown in the figure below, changes in active power at the grid connection point will cause voltage changes, which in turn will lead to changes in reactive power at the grid connection point. However, by reasonably allocating the reactive power of the photovoltaic inverter and the energy storage inverter, the reactive power at the grid connection point under this operating condition can be tracked by the reference reactive power in steady state, which is zero. This indicates that the voltage stability of this technical solution is better.

[0207] Under the above two working conditions, this application ( Figure 7 and Figure 9 ) and related technologies ( Figure 6 and Figure 8 The comparison shows that when the reactive power reference value or the active power reference value changes abruptly, it causes a change in the voltage at the POC point. Since both the first and second inverters operate in reactive power-voltage droop control mode, this affects the reactive power response. Related technologies' BESS (Boiler Escalator Variable Reactive Power) hardly participates in reactive power regulation, while in this solution, both the BESS and PV (Power Generation Unit) participate in reactive power regulation, resulting in better voltage stability in terms of amplitude.

[0208] Based on the above-described power system embodiments, another embodiment of this application provides an energy system including the above-described power system, and further including a first inverter and a second inverter.

[0209] The first inverter outputs power according to its reactive power and active power.

[0210] The second inverter outputs power according to its reactive power and active power.

[0211] Furthermore, the first inverter is connected to the first AC bus via a first step-up transformer; the second inverter is connected to the first AC bus via a second step-up transformer; the first AC bus is connected to the second AC bus via a third step-up transformer, and the second AC bus is connected to the power grid.

[0212] It should be noted that the structural diagram of the energy system in the embodiments of this application can be referred to Figure 3 As shown.

[0213] Another embodiment of this application provides a power control method, referring to... Figure 10 It can include:

[0214] S101. The first controller determines the active power of the first inverter based on the first grid active power reference value, and determines the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value. The reactive power of the second inverter is proportional to the reactive power of the first inverter. The first grid active power reference value is the grid active power reference value corresponding to the first inverter.

[0215] S102. The second controller determines the active power of the second inverter based on the second grid active power reference value, wherein the second grid active power reference value is the grid active power reference value corresponding to the second inverter.

[0216] It should be noted that the specific implementation of each step in this embodiment is described in the corresponding descriptions above.

[0217] In this embodiment, the first controller determines the active power of the first inverter based on a first grid active power reference value, and determines the reactive power of both the first and second inverters based on a grid reactive power reference value. This ensures that the first inverter outputs power according to its active and reactive power, and the second inverter outputs reactive power according to its reactive power. The second controller determines the active power of the second inverter based on a second grid active power reference value, ensuring that the second inverter outputs active power according to its active power. Since the reactive power of the second inverter is proportional to that of the first inverter, each inverter can bear its own required portion of reactive power. This avoids the problem of insufficient reactive power output due to insufficient reactive power output capacity when one inverter bears all the reactive power, or insufficient active power output capacity due to the effort to output sufficient reactive power.

[0218] This application also provides a computer program product including computer-readable instructions, which, when executed on an electronic device, cause the electronic device to implement any of the power control methods provided in this application.

[0219] This application also provides a computer-readable storage medium carrying one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device can implement any of the power control methods provided in this application.

[0220] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power system, characterized in that, include: The first controller is used to determine the active power of the first inverter based on the first grid active power reference value, and to determine the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value, wherein the reactive power of the second inverter is proportional to the reactive power of the first inverter. The first grid active power reference value is the grid active power reference value corresponding to the first inverter; The second controller is used to determine the active power of the second inverter based on the second grid active power reference value, wherein the second grid active power reference value is the grid active power reference value corresponding to the second inverter.

2. The power system according to claim 1, characterized in that, The first controller determines the active power of the first inverter based on a first grid active power reference value, including: The active power reference value of the first power grid is used as the active power of the first inverter, so that the first inverter outputs active power according to the active power of the first inverter. Obtain the actual active power at the grid connection point; Based on the actual active power of the grid connection point, the first grid active power reference value, and the second grid active power reference value, the updated active power of the first inverter is determined so that the first inverter outputs active power according to the updated active power of the first inverter.

3. The power system according to claim 2, characterized in that, Based on the actual active power of the grid connection point, the first grid active power reference value, and the second grid active power reference value, the updated active power of the first inverter is determined, including: The total active power reference value is obtained by summing the active power reference values ​​of the first power grid and the second power grid. Obtain the difference between the total active power reference value and the actual active power at the grid connection point; The difference is subjected to active power closed-loop control to obtain the updated active power of the first inverter.

4. The power system according to claim 1, characterized in that, The first controller determines the reactive power of the first inverter and the reactive power of the second inverter based on the grid reactive power reference value, including: The reactive power reference value of the power grid is used as the reactive power of the first inverter, and a specified multiple of the reactive power of the first inverter is used as the reactive power of the second inverter, so that the first inverter outputs reactive power according to the reactive power of the first inverter, and the second inverter outputs reactive power according to the reactive power of the second inverter. Obtain the actual reactive power at the grid connection point; Based on the actual reactive power of the grid connection point and the reference value of the grid reactive power, the updated reactive power of the first inverter and the updated reactive power of the second inverter are determined, so that the first inverter outputs reactive power according to the updated reactive power of the first inverter, and the second inverter outputs reactive power according to the updated reactive power of the second inverter. Return to the step of obtaining the actual reactive power of the grid connection point until the actual reactive power of the grid connection point is the same as the reference value of the reactive power of the power grid.

5. The power system according to claim 4, characterized in that, Based on the actual reactive power at the grid connection point and the reference value of the grid reactive power, the updated reactive power of the first inverter and the updated reactive power of the second inverter are determined, including: Obtain the difference between the reference value of reactive power of the power grid and the actual reactive power of the grid connection point; The difference is subjected to reactive power closed-loop control to obtain the updated reactive power of the first inverter; The updated reactive power of the first inverter is taken as a specified multiple of the updated reactive power of the second inverter.

6. The power system according to claim 4 or 5, characterized in that, The process of determining the specified multiple includes: Determine the ratio of the reference value of reactive power of the power grid to the active power of the first inverter; The difference between the ratio and the preset value is used as the specified multiple.

7. The power system according to claim 4 or 5, characterized in that, The specified multiple is a value that changes over time; Alternatively, the specified multiple is the value of the target constant after passing through the filter; the parameters of the filter are fixed or adjustable.

8. The power system according to claim 1, characterized in that, The second controller determines the active power of the second inverter based on the second grid active power reference value, including: The active power reference value of the second power grid is used as the active power of the second inverter, so that the second inverter outputs active power according to the active power of the second inverter. Obtain the actual active power of the target sampling point set between the second inverter and the first AC bus connected to the second inverter; Based on the actual active power of the target sampling point and the reference value of the active power of the second power grid, the updated active power of the second inverter is determined so that the second inverter outputs active power according to the updated active power of the second inverter.

9. The power system according to claim 8, characterized in that, Based on the actual active power of the target sampling point and the reference value of the active power of the second power grid, the updated active power of the second inverter is determined, including: Obtain the difference between the second power grid active power reference value and the actual active power at the target sampling point; The difference is subjected to active power closed-loop control to obtain the updated active power of the second inverter.

10. The power system according to claim 1, characterized in that, When the first controller determines the frequency change of the power system, it calculates the change in active power of the first inverter based on the frequency change of the power system and the droop coefficient of the first inverter, and adjusts the active power of the first inverter based on the change in active power.

11. The power system according to claim 1, characterized in that, When the second controller determines the frequency change of the power system, it calculates the change in active power of the second inverter based on the frequency change of the power system and the droop coefficient of the second inverter, and adjusts the active power of the second inverter based on the change in active power of the second inverter.

12. An energy system, characterized in that, The system includes the power system as described in any one of claims 1-11, and further includes a first inverter and a second inverter; The first inverter outputs power according to its reactive power and active power. The second inverter outputs power according to its reactive power and active power.

13. The energy system according to claim 12, characterized in that, The first inverter is connected to the first AC bus via a first step-up transformer; the second inverter is connected to the first AC bus via a second step-up transformer; the first AC bus is connected to the second AC bus via a third step-up transformer, and the second AC bus is connected to the power grid.

14. A power control method, characterized in that, include: The first controller determines the active power of the first inverter based on the active power reference value of the first power grid, and determines the reactive power of the first inverter and the reactive power of the second inverter based on the reactive power reference value of the power grid. The reactive power of the second inverter is proportional to the reactive power of the first inverter. The first grid active power reference value is the grid active power reference value corresponding to the first inverter; The second controller determines the active power of the second inverter based on the second grid active power reference value, where the second grid active power reference value is the grid active power reference value corresponding to the second inverter.

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