Grid-based energy storage coupled with thermal power black start method

Abstract

This disclosure provides a method for black start of grid-connected energy storage coupled with thermal power, belonging to the technical field of black start technology for grid-connected energy storage coupled with thermal power. The method includes: setting up a virtual synchronous machine for energy storage connected to the power grid; constructing a coordinated frequency response model of the grid-connected energy storage and the thermal power unit based on the frequency response models of the grid-connected energy storage and the thermal power unit; adjusting the virtual inertia and droop coefficient of the energy storage based on the coordinated frequency response model to ensure the system frequency meets stability indicators; generating a black start recovery path based on power balance constraints, equivalent inertia constraints, and voltage constraints; and gradually starting the thermal power unit and grid nodes according to the recovery path. This disclosure, through the coordinated operation of grid-connected energy storage and thermal power, optimizes coordinated control and path planning, compensates for the shortcomings of traditional black start power sources, improves recovery efficiency, enhances system frequency stability and inertia support, and is suitable for areas with scarce hydropower resources. It is flexible in adaptation and has good economic benefits.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the field of grid-type energy storage coupled with thermal power black start technology, specifically relating to a grid-type energy storage coupled with thermal power black start method. Background Technology

[0002] Traditional black start methods for power systems rely on large hydropower units or external power sources. However, in areas with scarce hydropower resources, these methods suffer from large restoration zones, limited pathways, and a lack of flexibility. With the large-scale grid connection of new energy sources, system inertia decreases, significantly reducing the adaptability of traditional black start schemes.

[0003] In existing technologies, distributed power sources (such as small hydropower and wind storage systems) are difficult to support black starts independently due to their small capacity and low inertia, and recovery path planning often uses fixed algorithms, which cannot efficiently aggregate multiple types of power sources.

[0004] Existing black start technologies have the following shortcomings: they rely on large hydropower units or external power sources, making them unsuitable for grid structures dominated by new energy sources; distributed power sources have insufficient capacity and poor frequency stability when operating alone; and the recovery path planning algorithm is inefficient, making it difficult to achieve multi-power source collaborative aggregation. Summary of the Invention

[0005] The embodiments of this disclosure aim to at least solve one of the technical problems existing in the prior art, and provide a grid-connected energy storage coupled thermal power black start method, the method comprising:

[0006] Configure an energy storage virtual synchronizer to connect to the power grid;

[0007] Based on the frequency response models of grid-type energy storage and thermal power units, a coordinated frequency response model of grid-type energy storage and thermal power units is constructed.

[0008] Based on the aforementioned collaborative frequency response model, the virtual inertia and droop coefficient of the energy storage are adjusted to ensure that the system frequency meets the stability index.

[0009] A black start recovery path is generated based on power balance constraints, equivalent inertia constraints, and voltage constraints.

[0010] Thermal power units and grid nodes will be gradually restarted according to the recovery path described above.

[0011] Furthermore, the cooperative frequency response model is expressed as:

[0012]

[0013] In the formula, G (·) represents the cooperative frequency response model. s For the Laplace operator, R v The droop coefficient is...T v The response time constant of the energy storage converter. K g For speed controller gain, T g The governor response time constant is , , H v For energy storage virtual inertia, S v For energy storage capacity, H j For the inertia of the thermal power unit, S j For the capacity of thermal power units, D v This is the energy storage load damping coefficient. D j This represents the damping coefficient of thermal power load.

[0014] Furthermore, the frequency response model of the grid-type energy storage satisfies:

[0015]

[0016] In the formula, Δ P v ( s () represents the change in energy storage output power. s For the Laplace operator, R v The droop coefficient is... T v Let Δ be the response time constant of the energy storage converter. f ( s ) represents the change in system frequency.

[0017] Furthermore, the frequency response model of the thermal power unit satisfies:

[0018]

[0019] In the formula, Δ P m ( s () represents the change in thermal power output. s For the Laplace operator, K g For speed controller gain, T g Δ is the governor response time constant. ω ( s ) represents the Laplace transform of the rotational speed deviation.

[0020] Optionally, the stability metrics include:

[0021] The rate of change of frequency is less than or equal to 0.5 Hz.

[0022] Optionally, the stability metrics include:

[0023] The lowest point frequency is greater than or equal to -0.5Hz.

[0024] Optionally, the stability metrics include:

[0025] The steady-state error is less than or equal to 0.2 Hz.

[0026] Furthermore, the power balance constraint is expressed as follows:

[0027]

[0028] In the formula, P i For aggregated power supply, N The total number of power sources for aggregation. P a This refers to the starting power of auxiliary equipment in thermal power units. P m This represents the power margin.

[0029] Furthermore, the equivalent inertia constraint is expressed by the following formula:

[0030]

[0031] In the formula, H v For energy storage virtual inertia, S v For energy storage capacity, S j For the capacity of thermal power units, H min This is the minimum equivalent inertia threshold.

[0032] Furthermore, the voltage constraint is expressed by the following formula:

[0033]

[0034] In the formula, U i To restore the voltage at the path nodes, U min The minimum voltage safety threshold, U max This is the maximum voltage safety threshold.

[0035] This disclosure discloses a black-start method for grid-connected energy storage coupled with thermal power. By cooperating with thermal power, the grid-connected energy storage optimizes collaborative control and path planning, overcoming the shortcomings of traditional black-start power sources, improving recovery efficiency, and enhancing system frequency stability and inertia support. Through multi-source aggregation and path optimization, the start-up time of auxiliary equipment in thermal power units is shortened, and recovery efficiency is improved. Simulations show that the recovery efficiency is improved by more than 20%. The virtual inertia compensation system of the grid-connected energy storage has inertia deficiency, frequency stability, and maximum frequency deviation controlled within ±0.5Hz. It is suitable for areas with scarce hydropower resources, supports various combination modes of distributed power sources and thermal power, and is flexible in adaptation. It reduces power outage losses by approximately 18%, lowers the start-up cost of thermal power units, and has good economic benefits. Attached Figure Description

[0036] Figure 1 This is a schematic flowchart of a grid-type energy storage coupled thermal power black start method according to an embodiment of the present disclosure;

[0037] Figure 2 This is a schematic diagram of an IEEE 10 machine 39-node topology according to another embodiment of this disclosure. Detailed Implementation

[0038] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0039] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0040] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0041] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this disclosure. As used in this disclosure, the term "and / or" includes all combinations of any and more of the associated listed items.

[0042] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this disclosure, and therefore cannot be used to limit the scope of protection of this disclosure.

[0043] To study the collaborative participation of grid-connected energy storage and thermal power in power system black start, it is first necessary to analyze the feasibility of aggregating grid-connected energy storage and thermal power units as a black start power source to drive the auxiliary load of thermal power units and thus restore the thermal power units to be started. During the power restoration process, there are various voltage control methods, but due to the virtual inertia characteristics of grid-connected energy storage and the dynamic characteristics of the thermal power unit speed governor, frequency stability during the restoration process needs to be a key focus. Based on this, the embodiments of this disclosure propose frequency response models for the grid-connected energy storage cluster and the thermal power units under virtual synchronous control, and propose a dynamic frequency control model for the grid-connected energy storage and thermal power units, thereby analyzing the system frequency response characteristics and establishing constraints for the aggregated black start power source.

[0044] like Figure 1 As shown, one embodiment of this disclosure provides a grid-connected energy storage coupled thermal power black start method, including:

[0045] Step S1: Configure the energy storage virtual synchronous machine to connect to the power grid.

[0046] Specifically, energy storage is connected to the power grid through power electronic devices, and virtual synchronization control technology leverages the flexibility of power electronics to provide frequency support for the power system. The frequency dynamics of energy storage virtual synchronization machine control can be expressed as:

[0047]

[0048] In the formula, H v The virtual inertia Δ set for the virtual synchronous unit f ( t Let t be the change in the system's frequency at time t. D Let Δ be the load damping constant. P e ( t ) represents the increase in system load at time t.

[0049] Taking the Laplace transform of the above equation, we get:

[0050]

[0051] in, s For the Laplace operator.

[0052] Step S2: Construct a coordinated frequency response model of grid-type energy storage and thermal power units based on the frequency response model of grid-type energy storage and the frequency response model of thermal power units.

[0053] Specifically, firstly, based on virtual synchronous control technology, a frequency response model of grid-type energy storage is established to analyze the impact of parameters such as virtual inertia and droop coefficient on the system frequency. s In the domain, the frequency response model of grid-type energy storage should satisfy the relationship between the change in energy storage output power and the change in system frequency, as shown in the following equation:

[0054]

[0055] Where, Δ P v ( s () represents the change in energy storage output power. R v The droop coefficient is... T v Let Δ be the response time constant of the energy storage converter. f ( s ) represents the change in system frequency.

[0056] In the frequency domain, the transfer function of the energy storage system is also known as the frequency response model. G ESS ( s )for:

[0057]

[0058] Subsequently, considering the governor response characteristics and mechanical power variations of the thermal power unit, a frequency response model for the thermal power unit is established. The frequency response model of the thermal power unit should satisfy the following equation regarding the relationship between the mechanical output power variation and the speed deviation of the thermal power unit:

[0059]

[0060] Where, Δ P m ( s () represents the change in thermal power output. K g For speed controller gain, T g Δ is the governor response time constant. ω ( s ) represents the Laplace transform of the rotational speed deviation.

[0061] Considering the unit's inertia and load damping, the equation for the rate of change of rotational speed is expressed as:

[0062]

[0063] in, H j For the inertia of the thermal power unit, D j Δ is the damping coefficient of thermal power load. P L This represents the change in load.

[0064] During black start, when working in conjunction with grid-type energy storage, the overall frequency response model of the thermal power unit. G j ( s )for:

[0065]

[0066] Finally, a dynamic frequency response model of the coordinated operation of grid-type energy storage and thermal power units is constructed. The system frequency change rate, minimum frequency, and steady-state error are analyzed to determine the system frequency stability constraints. Combining the above frequency response models of energy storage and thermal power, the overall system transfer function, i.e., the coordinated frequency response model, is as follows:

[0067]

[0068] In the formula, G (·) represents the cooperative frequency response model. s For the Laplace operator, R v The droop coefficient is... T v The response time constant of the energy storage converter. K g For speed controller gain, T g The governor response time constant is , , H v For energy storage virtual inertia, S v Energy storage capacity (MW), H j For the inertia of the thermal power unit, S j For thermal power unit capacity (MW), D v This is the energy storage load damping coefficient. D j This represents the damping coefficient of thermal power load.

[0069] Step S3: Adjust the energy storage virtual inertia and droop coefficient based on the cooperative frequency response model to ensure that the system frequency meets the stability index.

[0070] Specifically, frequency stability is a key safety indicator during the black start process of a power system. The frequency response characteristics of a grid-connected energy storage and thermal power co-generation system are quantitatively evaluated using the following core indicators:

[0071] The frequency change rate reflects the severity of the instantaneous frequency change after the system is subjected to power disturbance. An excessively high frequency change rate may trigger the low-frequency load shedding device to malfunction, resulting in unplanned power outages. The frequency change rate must be ≤0.5Hz.

[0072] The minimum frequency is the lowest frequency drop in the system after a power deficit, which directly affects the safe operation of generator sets and load equipment. The minimum frequency must be ≥-0.5Hz.

[0073] Steady-state error is the deviation of the system frequency from the rated value after the system frequency stabilizes. It reflects the accuracy of coordinated control. The steady-state error must be ≤0.2Hz.

[0074] Step S4: Generate a black start recovery path based on power balance constraints, equivalent inertia constraints, and voltage constraints.

[0075] Specifically, in black boot path planning, the following constraints must be met to ensure the safety and feasibility of the recovery process:

[0076] 1. Power balance constraints

[0077]

[0078] In the formula, P i For aggregated power supply, N The total number of power sources for aggregation. P a This refers to the starting power of auxiliary equipment in thermal power units. P m This is for power margin. The total power of the polymer power source must cover the starting power of the auxiliary equipment of the thermal power unit. P a and power margin P m To avoid overload that could damage the equipment or cause startup failure.

[0079] 2. Equivalent inertia constraint

[0080]

[0081] In the formula, H v For energy storage virtual inertia, S v For energy storage capacity,S j For the capacity of thermal power units, H min This is the minimum equivalent inertia threshold. The equivalent inertia must reach the minimum safe threshold. H min To maintain system frequency stability. Virtual inertia of grid-type energy storage. H v It can increase the equivalent inertia and make up for the insufficient inertia of thermal power plants.

[0082] 3. Voltage constraint

[0083]

[0084] In the formula, U i To restore the voltage at the path nodes, U min The minimum voltage safety threshold, U max The maximum voltage safety threshold. Node voltages on the recovery path. U i It is necessary to keep the voltage within a safe range to avoid equipment shutdown due to excessively low voltage or insulation breakdown due to excessively high voltage. U min It can be set to 0.95 pu. U max It can be set to 1.5 pu.

[0085] Step S5: Start the thermal power units and grid nodes step by step according to the recovery path.

[0086] Specifically, through the above model and constraints, it is possible to achieve black start-up of grid-connected energy storage and thermal power in synergy. For example... Figure 2 The IEEE 10-unit 39-node topology shown is a specific embodiment, which includes one large thermal power unit node, three energy storage nodes, three thermal power units to be started, and two conventional photovoltaic power generation units. First, the feasibility of grid-connected energy storage co-located with thermal power for black start is analyzed, followed by an analysis of the improvement in recovery efficiency by the black start power supply. Detailed parameters for each unit are shown in Table 1 below.

[0087] Table 1:

[0088]

[0089] The recovery time for each line in the system is shown in Table 2 below, where each unit takes 15 minutes.

[0090] Table 2:

[0091]

[0092] This disclosure discloses a black-start method for grid-connected energy storage coupled with thermal power. By cooperating with thermal power, the grid-connected energy storage optimizes collaborative control and path planning, overcoming the shortcomings of traditional black-start power sources, improving recovery efficiency, and enhancing system frequency stability and inertia support. Through multi-source aggregation and path optimization, the start-up time of auxiliary equipment in thermal power units is shortened, and recovery efficiency is improved. Simulations show that the recovery efficiency is improved by more than 20%. The virtual inertia compensation system of the grid-connected energy storage has inertia deficiency, frequency stability, and maximum frequency deviation controlled within ±0.5Hz. It is suitable for areas with scarce hydropower resources, supports various combination modes of distributed power sources and thermal power, and is flexible in adaptation. It reduces power outage losses by approximately 18%, lowers the start-up cost of thermal power units, and has good economic benefits.

[0093] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A black start method for grid-connected energy storage coupled with thermal power, characterized in that, The method includes: Configure an energy storage virtual synchronizer to connect to the power grid; Based on the frequency response models of grid-type energy storage and thermal power units, a coordinated frequency response model of grid-type energy storage and thermal power units is constructed. Based on the aforementioned collaborative frequency response model, the virtual inertia and droop coefficient of the energy storage are adjusted to ensure that the system frequency meets the stability index. A black start recovery path is generated based on power balance constraints, equivalent inertia constraints, and voltage constraints. Thermal power units and grid nodes will be gradually restarted according to the recovery path described above; The cooperative frequency response model is expressed as follows: In the formula, G (·) represents the cooperative frequency response model. s For the Laplace operator, R v The droop coefficient is... T v The response time constant of the energy storage converter. K g For speed controller gain, T g The governor response time constant is , , H v For energy storage virtual inertia, S v For energy storage capacity, H j For the inertia of the thermal power unit, S j For thermal power unit capacity, D v This is the energy storage load damping coefficient. D j This represents the damping coefficient of thermal power load.

2. The method according to claim 1, characterized in that, The frequency response model of the grid-type energy storage satisfies: In the formula, Δ P v ( s () represents the change in energy storage output power. s For the Laplace operator, R v The droop coefficient is... T v Let Δ be the response time constant of the energy storage converter. f ( s ) represents the change in system frequency.

3. The method according to claim 1, characterized in that, The frequency response model of the thermal power unit satisfies: In the formula, Δ P m ( s () represents the change in thermal power output. s For the Laplace operator, K g For speed controller gain, T g Δ is the governor response time constant. ω ( s ) represents the Laplace transform of the rotational speed deviation.

4. The method according to claim 1, characterized in that, The stability indicators include: The rate of change of frequency is less than or equal to 0.5 Hz.

5. The method according to claim 1, characterized in that, The stability indicators include: The lowest point frequency is greater than or equal to -0.5Hz.

6. The method according to claim 1, characterized in that, The stability indicators include: The steady-state error is less than or equal to 0.2 Hz.

7. The method according to any one of claims 1 to 6, characterized in that, The power balance constraint is expressed by the following formula: In the formula, P i For aggregated power supply, N The total number of power sources for aggregation. P a This refers to the starting power of auxiliary equipment in thermal power units. P m This represents the power margin.

8. The method according to any one of claims 1 to 6, characterized in that, The equivalent inertia constraint is expressed by the following formula: In the formula, H v For energy storage virtual inertia, S v For energy storage capacity, S j For thermal power unit capacity, H min This is the minimum equivalent inertia threshold.

9. The method according to any one of claims 1 to 6, characterized in that, The voltage constraint is expressed by the following formula: In the formula, U i To restore the voltage at the path nodes, U min The minimum voltage safety threshold, U max This is the maximum voltage safety threshold.

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