A method for controlling operation of a thermal power generating unit in an isolated network with participation of an electric boiler heat storage device

Abstract

The application discloses a thermal power generating unit isolated network operation control method under participation of an electric boiler heat storage device, belongs to the technical field of thermal power generating unit isolated network operation control of an electric network, and judges whether the thermal power generating unit is in an isolated network operation state; after the thermal power generating unit triggers the isolated network, DEH load switching and electric boiler heat storage device load switching control adopt the thermal power generating unit isolated network operation control method under participation of the electric boiler heat storage device, real-time monitoring of the electric network and the unit operation state can be realized, when the thermal power generating unit is in the isolated network operation due to extreme weather, system disturbance and other complex faults, the system timely makes a decision, and according to boundary conditions, the electric boiler is switched in or out, the deviation of the thermal power generating unit output and the plant load is reduced, the disturbance of the isolated network to the boiler and the steam turbine is reduced, the thermal power generating unit can stably transit into the isolated network operation, and under participation of the electric boiler heat storage device, the residential heating is effectively ensured.

Description

Technical Field

[0001] This invention relates to the field of isolated grid operation control technology for thermal power units, and more specifically, to a method for isolated grid operation control of thermal power units with the participation of an electric boiler thermal storage device. Background Technology

[0002] With the advancement of the construction of new power systems, the proportion of new energy installed capacity is gradually increasing while the proportion of thermal power units is gradually decreasing. Faced with the strong uncertainty of high-proportion new energy power generation, the power system's regulation capacity is significantly insufficient, and the power system's operational stability mechanism is more complex, making it difficult to guarantee the safe operation of the power grid under complex fault conditions such as extreme weather and system disturbances. Electric boilers and other thermal energy storage devices, due to their rapid regulation and strong energy storage capacity, are widely used in the research and application of thermal power plant flexibility retrofitting. Since the pilot project for thermal power unit flexibility retrofitting was launched in 2016, more than 30 power plants in northern China have installed electric boiler thermal energy storage devices. However, the value of electric boiler thermal energy storage devices as a highly flexible electrical load in quickly participating in coordinated regulation during grid line faults to maintain the power and load balance of boilers and turbines, enabling the unit to operate on an isolated grid with electric thermal load, avoiding unit shutdowns, and improving the value of rapid grid connection and heating economy has not been fully recognized. Research and application of using thermal energy storage devices to quickly participate in coordinated regulation during grid faults, enabling the unit to operate on an isolated grid with electric thermal load and ensuring residential heating, and ensuring rapid grid connection after the fault is resolved, have not yet been carried out. Summary of the Invention

[0003] The purpose of this invention is to provide a method for controlling the isolated operation of thermal power units with the participation of an electric boiler thermal storage device. This method enables the unit to stably switch to isolated operation when the power grid fails, and automatically matches the operation mode of the electric boiler thermal storage device according to the unit's output before the isolated grid, effectively ensuring the function of residential heating.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a method for controlling the isolated grid operation of a thermal power unit with the participation of an electric boiler thermal storage device, characterized by comprising the following steps:

[0005] The first step is to determine whether the thermal power unit is operating in an isolated grid state;

[0006] The second step involves DEH load switching and electric boiler thermal storage device load switching control.

[0007] (1) DEH load switching

[0008] After the thermal power unit is triggered by the isolated grid, the DEH disconnects the remote DCS control, and the steam turbine generator immediately switches to speed control mode to ensure that the speed change during the entire transition process is within the allowable range and to maintain speed stability after the transition process ends. When the thermal power unit enters isolated grid operation, the primary frequency regulation of the thermal power unit automatically switches to a mode without speed dead zone.

[0009] (2) Switching on and off of electric boiler heat storage device

[0010] The deviation between the output of the thermal power unit before the isolated grid and the sum of the electric boiler thermal storage device and other plant power loads is calculated. Let Pn be the output of the thermal power unit before the isolated grid, Pz be the sum of the electric boiler thermal storage device and other plant power loads, and Py be the allowable deviation of the unit load.

[0011] After the isolated network is triggered, when Pn-Pz≤Py, the electric boiler thermal storage device continues to operate in the original mode;

[0012] When Pn-Pz>Py, start a set of electric boiler thermal storage device load to balance the unit output;

[0013] When Pn-Pz < -Py, it is necessary to stop the load of one electric boiler thermal storage device to balance the unit output.

[0014] In the first step, the islanding trigger criterion for determining whether a thermal power unit is in islanded operation is as follows:

[0015] There are two busbars between the power plant and the substation, namely busbar A and busbar B. The following two lines refer to busbar A and busbar B. Each busbar has three-phase current. The three-phase currents of busbar A are IAa, IAb and IAc, and the three-phase currents of busbar B are IBa, IBb and IBc.

[0016] (1) The power surge of both lines is greater than the starting setpoint P0;

[0017] Power mutation trigger criterion: ΔP = P t-0.2s -P t ΔP≥P0

[0018] Among them, P t P is the current effective power value. t-0.2s ΔP is the effective power value before tripping, ΔP is the power mutation value, and P0 is the starting set value of the power mutation before the accident.

[0019] (2) The current surge of both lines is greater than the starting set value I0;

[0020] Current surge trigger criterion: ΔI = I t-20ms -I t ΔI≥I0;

[0021] Among them, I t I is the current effective value of the current. t-20ms The effective value of the current before one cycle, ΔI is the current mutation, and I0 is the current mutation start-up setpoint;

[0022] (3) 0.2 seconds before the line fault, the sum of the power of the two lines is greater than or equal to the set value P. s1 P t-0.2s ≥P s1 , where P s1 The power setting before the fault;

[0023] (4) After a line fault, the sum of the power of the two lines is less than or equal to the power setting value P. s2 P t ≤P s2 , where P s2 Power setpoint after fault;

[0024] (5) Both lines have two or three phase currents that are less than the operating current I. s I t ≤I s , where I s Commissioning current setting;

[0025] (6) Both lines have two or three phase current mutations that are greater than the set value I0.

[0026] When conditions (1)-(6) above are met simultaneously, the isolated network operation signal is triggered.

[0027] In the first step, after the unit is triggered by the isolated grid, the DEH disconnects the remote DCS control, and the turbine generator immediately switches to speed control mode to ensure that the speed is less than 3090 r / min throughout the entire transition process.

[0028] Through the above design scheme, the present invention can bring the following beneficial effects: the method of controlling the isolated operation of thermal power units with the participation of electric boiler thermal storage device can monitor the grid and unit operation status in real time. When the thermal power unit is in isolated operation due to complex faults such as extreme weather and system disturbance, the system makes timely decisions and switches the electric boiler according to the boundary conditions, which reduces the deviation of unit output and plant load, reduces the disturbance of isolated grid to boiler and turbine, and the unit can stably switch to isolated operation. At the same time, with the participation of electric boiler thermal storage device, the heating supply to residents is effectively guaranteed. Attached Figure Description

[0029] The accompanying drawings are provided to further illustrate the invention and form part of this application. The illustrative embodiments and descriptions thereof are used to understand the invention and do not constitute an undue limitation thereof. In the drawings:

[0030] Figure 1A power system structure diagram on which the control method for isolated grid operation of thermal power units with the participation of electric boiler thermal storage devices is based.

[0031] Figure 2 A flowchart of the control method for isolated grid operation of thermal power units with the participation of electric boiler thermal storage devices.

[0032] Figure 3 The logic diagram for triggering criteria for isolated networks. Detailed Implementation

[0033] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, this invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions of this invention and actual circumstances. To avoid obscuring the essence of this invention, well-known methods, processes, flows, components, and circuits are not described in detail.

[0034] like Figure 1 As shown, the isolated grid operation control system of a thermal power unit with the participation of an electric boiler thermal storage device uses Hollysys K-series controllers to acquire, process, and control data from the turbine DEH control system (i.e., the turbine digital electro-hydraulic control system), the electric boiler thermal storage device control system, and the electrical ECS control system (i.e., the electrical control system). The Hollysys K-CU03 main controller and its corresponding fast I / O modules can achieve a total processing time of ≤40ms from signal acquisition and processing to the output of action commands, meeting the rapid response requirements of the electric boiler thermal storage device to operation on an isolated grid after a grid fault.

[0035] The isolated grid operation control system for thermal power units, involving electric boiler thermal storage devices, monitors the operating conditions of two 220kV incoming lines through data interaction with the ECS system. When both 220kV incoming lines trip simultaneously, it automatically determines whether the power plant is in an isolated grid state based on isolated grid triggering criteria and triggers an isolated grid operation signal. Through data interaction with the electric boiler thermal storage device control system, it automatically matches the operating mode of the electric boiler thermal storage device to the output of the thermal power unit before the isolated grid, based on the device's operating status. Finally, through data interaction with the turbine DEH control system, it achieves smooth turbine control after the thermal power unit is isolated from the grid.

[0036] The specific implementation process is as follows: Figure 2 Where Pn is the power output of the thermal power unit before the isolated grid, Pz is the sum of the electric boiler thermal storage device and other plant power loads, and Py is the allowable load deviation of the unit.

[0037] The first step is to determine whether the thermal power unit is in an isolated grid operation state. The isolated grid triggering criteria are as follows: Figure 3 As shown.

[0038] To ensure reliable power supply, two busbars, designated A busbar and B busbar, are typically designed between power plants and substations. The following two lines refer to busbar A and busbar B. Each busbar carries three-phase currents: the three-phase currents of busbar A are IAa, IAb, and IAc, and the three-phase currents of busbar B are IBa, IBb, and IBc.

[0039] (1) The power surge of both lines is greater than the starting setpoint P0.

[0040] Power mutation trigger criterion: ΔP = P t-0.2s -P t ΔP≥P0

[0041] Among them, P t P is the current effective power value. t-0.2s ΔP is the effective power value before tripping, ΔP is the power mutation value, and P0 is the starting set value of the power mutation before the accident.

[0042] (2) The current surge of both lines is greater than the starting set value I0.

[0043] Current surge trigger criterion: ΔI = I t-20ms -I t ΔI≥I0

[0044] Among them, I t I is the current effective value of the current. t-20ms ΔI is the effective value of the current one cycle in advance, I0 is the current mutation amount, and I0 is the starting set value of the current mutation amount.

[0045] (3) 0.2 seconds before the line fault, the sum of the power of the two lines is greater than or equal to the set value P. s1 P t-0.2s ≥P s1 , where P s1 The power setting before the fault;

[0046] (4) After a line fault, the sum of the power of the two lines is less than or equal to the power setting value P. s2 P t ≤P s2 , where P s2 The power setting after a fault.

[0047] (5) Both busbar A and busbar B have two or three phase currents that are less than the operating current I. s I t ≤I s , where I s Commissioning current setting.

[0048] (6) Both busbar A and busbar B have two or three phase current mutations that are greater than the set value I0.

[0049] Once all of the above conditions are met, the isolated network operation signal is triggered.

[0050] The second step involves DEH load switching and electric boiler thermal storage device load switching control.

[0051] (1) DEH load switching

[0052] After the thermal power unit is isolated, the DEH disconnects the remote DCS control, and the turbine generator immediately switches to speed control mode to ensure that the speed change during the entire transition process is within the allowable range (less than 3090 r / min), and maintains speed stability after the transition process ends. When the thermal power unit enters isolated operation, the primary frequency regulation of the thermal power unit automatically switches to a mode without speed dead zone.

[0053] (2) Switching on the electric cooker heat storage device

[0054] The deviation between the output of the thermal power unit before the isolated grid and the sum of the electric boiler thermal storage device and other plant power loads is calculated. Let Pn be the output of the thermal power unit before the isolated grid, Pz be the sum of the electric boiler thermal storage device and other plant power loads, and Py be the allowable load deviation of the thermal power unit.

[0055] After the isolated network is triggered, if Pn-Pz≤Py, it means that the deviation between the output of the thermal power unit and the sum of the electric boiler thermal storage device and other plant power loads is within a controllable range, and the electric boiler thermal storage device continues to operate in the original mode.

[0056] If Pn-Pz>Py, it means that the sum of the output of the thermal power unit, the electric boiler thermal storage device, and other plant power loads is not within the controllable range. At this time, the output of the thermal power unit is greater than the sum of the electric boiler thermal storage device and other plant power loads, and it is necessary to start a set of electric boiler thermal storage device loads to balance the unit output.

[0057] If Pn-Pz<-Py, it means that the sum of the output of the thermal power unit and the electric boiler thermal storage device and other plant power loads is not within the controllable range. At this time, the output of the thermal power unit is less than the sum of the electric boiler thermal storage device and other plant power loads, and it is necessary to stop the load of one electric boiler thermal storage device to balance the output of the unit.

[0058] Compared with the prior art, the advantages of the technical solution of this invention are as follows:

[0059] When thermal power units are isolated due to complex faults such as extreme weather or system disturbances, the units will instantly shed their electrical load, leading to an imbalance between boiler and turbine output and load. This can cause a series of problems, including turbine overspeed, boiler steam pressure overpressure, and steam temperature overheating. The thermal power units will struggle to maintain zero output and will have to shut down, failing to provide effective power support. A thermal power unit isolated operation control system with the participation of electric boiler thermal storage devices can monitor the power grid and the operating status of the thermal power units in real time. When isolated operation is caused by complex faults such as extreme weather or system disturbances, the system makes timely decisions and switches the electric boiler on or off according to boundary conditions. This reduces the deviation between the thermal power unit output and the sum of the electric boiler thermal storage device and other plant power loads, minimizing the disturbance of the isolated grid to the boiler and turbine. The thermal power units can then stably transition to isolated operation. Simultaneously, with the participation of the electric boiler thermal storage device, residential heating is effectively guaranteed.

Claims

1. A method for controlling the isolated grid operation of a thermal power unit with the participation of an electric boiler thermal storage device, characterized in that, Includes the following steps: The first step is to determine whether the thermal power unit is operating in an isolated grid state; The second step involves DEH load switching and electric boiler thermal storage device load switching control. (1) DEH load switching After the thermal power unit is triggered by the isolated grid, the DEH disconnects the remote DCS control, and the steam turbine generator immediately switches to speed control mode to ensure that the speed change during the entire transition process is within the allowable range and to maintain speed stability after the transition process ends. When the thermal power unit enters isolated grid operation, the primary frequency regulation of the thermal power unit automatically switches to a mode without speed dead zone. (2) Switching on and off of electric boiler heat storage device The deviation between the output of the thermal power unit before the isolated grid and the sum of the electric boiler thermal storage device and other plant power loads is calculated. Let Pn be the output of the thermal power unit before the isolated grid, Pz be the sum of the electric boiler thermal storage device and other plant power loads, and Py be the allowable deviation of the unit load. After the isolated network is triggered, when Pn-Pz≤Py, the electric boiler thermal storage device continues to operate in the original mode; When Pn-Pz>Py, start a set of electric boiler thermal storage device load to balance the unit output; When Pn-Pz < -Py, it is necessary to stop the load of one electric boiler thermal storage device to balance the unit output; In the first step, the islanding trigger criterion for determining whether a thermal power unit is in islanded operation is as follows: There are two busbars between the power plant and the substation, namely busbar A and busbar B. The following two lines refer to busbar A and busbar B. Each busbar has three-phase current. The three-phase currents of busbar A are IAa, IAb and IAc, and the three-phase currents of busbar B are IBa, IBb and IBc. (1) The power surge of both lines is greater than the starting setpoint P0; Power mutation trigger criterion: ΔP = P t-0.2s -P t ΔP≥P0; Among them, P t P is the current effective power value. t-0.2s ΔP is the effective power value before tripping, ΔP is the power mutation value, and P0 is the starting set value of the power mutation before the accident. (2) The current surge of both lines is greater than the starting set value I0; Current surge trigger criterion: ΔI = I t-20ms -I t ΔI≥I0; Among them, I t I is the current effective value of the current. t-20ms The effective value of the current before one cycle, ΔI is the current mutation, and I0 is the current mutation start-up setpoint; (3) 0.2 seconds before the line fault, the sum of the power of the two lines is greater than or equal to the set value P. s1 P t-0.2s ≥P s1 , where P s1 The power setpoint before the fault; (4) After a line fault, the sum of the power of the two lines is less than or equal to the power setting value P. s2 P t ≤P s2 , where P s2 Power setpoint after fault; (5) Both lines have two or three phase currents that are less than the operating current I. s I t ≤I s , where I s Commissioning current setting; (6) Both lines have two or three phase current mutations that are greater than the set value I0. When conditions (1)-(6) above are met simultaneously, the isolated network operation signal is triggered.

2. The method for controlling isolated grid operation of thermal power units with the participation of an electric boiler thermal storage device according to claim 1, characterized in that: In the first step, after the unit is triggered by the isolated grid, the DEH disconnects the remote DCS control, and the turbine generator immediately switches to speed control mode to ensure that the speed is less than 3090 r / min throughout the entire transition process.

Images