Method for assisting primary frequency modulation of power system of electric energy storage virtual power plant

Abstract

The invention relates to the field of virtual power plant operation and control, in particular to a primary frequency modulation method of an electric energy storage virtual power plant auxiliary power system. According to the method, firstly, based on primary frequency modulation historical data of an electric power system, frequency modulation delay is quantified, non-delay active output response in a specific frequency modulation scene is estimated, and the vacancy of active response of a synchronous unit due to delay is made up by using active additional generation of an electric energy storage virtual power plant; and non-delay primary frequency modulation active output response is realized. If the working condition that the capacity of the electric energy storage virtual power plant is limited exists in the process, the active power output response of the electric energy storage virtual power plant is adjusted, and the response time delay of the primary frequency modulation process of the power system is shortened on the premise that the adjustable capacity of the electric energy storage virtual power plant is fully utilized. According to the technical scheme adopted by the invention, the frequency modulation response time delay of the power system can be reduced by utilizing the electric energy storage virtual power plant, so that the frequency stability of the power system in the actual operation process can reach the theoretical design level of the power system.

Description

Technical Field

[0001] The present invention relates to the field of virtual power plant operation and control, and in particular to a method for primary frequency regulation of an electric energy storage virtual power plant assisting a power system. Background Art

[0002] During operation, the power system needs to avoid excessive deviation of the system frequency from its rated value. Its frequency regulation function is mainly performed by the synchronous units in the system. The primary frequency regulation of the synchronous units is the first response measure to the system frequency deviation caused by the active power imbalance of the power system, which is completed by the speed regulator of the synchronous units. In the process of the synchronous units responding to the primary frequency regulation, the existence of the speed regulator control system and the speed regulator's own inertia will cause a certain delay when the synchronous units increase their active power to respond to the primary frequency regulation demand. This delay will cause the synchronous units to be unable to increase their active power output in time to reduce the active power imbalance of the power system, weakening the system frequency deviation suppression effect.

[0003] As an emerging flexible power generation resource within the power system, the electric energy storage virtual power plant has been widely involved in the peak and frequency regulation process of the power system. The existing technical solution mainly uses it as a backup power source for the system and introduces it as one of the main peak and frequency regulation subjects when the peak and frequency regulation pressure of the power system is high.

[0004] However, considering that the ability of the energy storage virtual power plant to continuously output active power to participate in the system frequency regulation is limited by its own capacity, it is not suitable as the main frequency regulation power source of the system. Its advantage over the synchronous units in the system lies in the relatively fast active output response speed. Its fast output response can make up for the lack of active output response of the synchronous units caused by the delay in the primary frequency regulation process, making the energy storage virtual power plant play an auxiliary role and improve the primary frequency regulation effect of the main synchronous units of the power system frequency regulation. Summary of the invention

[0005] The present invention proposes a method for assisting the primary frequency regulation of a power system with an electric energy storage virtual power plant. In view of the response delay of the synchronous unit in the primary frequency regulation process of the power system, the electric energy storage virtual power plant is used to assist the synchronous unit to make up for the shortfall of the active output response of the synchronous unit caused by the response delay compared with the primary frequency regulation setting value, so that the synchronous unit in the power system can be integrated with the electric energy storage virtual power plant to achieve a non-delayed primary frequency regulation response. In addition, under the condition that the capacity of the electric energy storage virtual power plant is limited and the non-delayed primary frequency regulation cannot be achieved, an active output scheme is provided to shorten the response delay as much as possible in the primary frequency regulation process of the power system.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] A method for assisting primary frequency regulation of a power system with an electric energy storage virtual power plant comprises the following steps:

[0008] S1: Estimate the response delay time constant of the primary frequency regulation of the power system based on the active power shortage in the initial stage of the primary frequency regulation of the power system, the unit regulation power of the synchronous units in the power system, the active output response of the primary frequency regulation of the synchronous units in the power system, and the historical data of the power system frequency;

[0009] S2: Under the condition of setting the active power shortage in the initial stage of primary frequency regulation of the power system, evaluate the ability of the internal electric energy storage virtual power plant to provide the power system with a delay-free primary frequency regulation active output response as a whole by regulating the output of the internal electric energy storage virtual power plant in the process of primary frequency regulation of the power system; if the current capacity of the internal electric energy storage virtual power plant can assist the synchronous unit in providing the power system with a delay-free primary frequency regulation active output response, then the active output response curve of the electric energy storage virtual power plant is given with the goal of providing a delay-free primary frequency regulation active output response;

[0010] S3: If the current capacity of the virtual power plant with energy storage inside the power system is insufficient to assist the synchronous units in providing the power system with a delay-free primary frequency regulation active output response, the active output response curve of the virtual power plant with energy storage is given on the premise of fully utilizing the current capacity of the virtual power plant with energy storage to achieve the maximum degree of suppression of the delay in the primary frequency regulation active output response.

[0011] Further as a preferred technical solution of the present invention, S1 comprises the following steps:

[0012] The active power shortage in the initial stage of the primary frequency regulation of the power system, the unit regulation power of the synchronous units in the power system, the active output response of the primary frequency regulation of the synchronous units in the power system, and the historical data of the power system frequency are used to estimate the response delay time constant of the primary frequency regulation of the power system through data fitting.

[0013] If the data recording time step in the recorded historical data of the primary frequency regulation process of the power system is Δt, the time period from the initial moment of the primary frequency regulation to the time when the power system frequency reaches a stable value contains N groups of data (the active output response of the primary frequency regulation of the synchronous units inside the power system, the power system frequency), considering the response delay of the primary frequency regulation of the power system, the N groups of data in the frequency regulation process should satisfy the following formula:

[0014]

[0015] Where ΔP SG,n is the active output response of the primary frequency regulation of the synchronous generator set in the power system in the nth group of data, f i-1 、f i are the power system frequencies in the i-1th and ith groups of data, respectively, and f N is the rated frequency of the power system, KSG is the unit regulation power of the synchronous units in the power system, T SG is the response delay time constant of primary frequency regulation of the power system;

[0016] The response delay time constant T of primary frequency regulation of power system is estimated by successive approximation. SG , whose estimated value is T SG,est The initial setting is 0, and the synchronous unit primary frequency regulation active output response ΔP calculated based on the estimated value of the response delay time constant of the primary frequency regulation is compared. SG,est Its actual value The size relationship, ΔP SG,est The calculation formula is,

[0017]

[0018] like Then increase the estimated value T of the response delay time constant of the frequency modulation according to the adjustment step size. SG,est ;like Then the estimated value T of the response delay time constant of the frequency modulation is reduced according to the adjustment step size. SG,est When satisfied When the condition is met, the output is the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation. SG,est ; If a frequency modulation response delay time constant estimate value T SG,est In the case of alternating between two values, the adjustment step is shortened until the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation can be output. SG,est .

[0019] Further as a preferred technical solution of the present invention, S2 comprises the following steps:

[0020] Under the condition of setting the active power shortage in the initial stage of primary frequency regulation of the power system, assuming that the current capacity of the electric energy storage virtual power plant inside the power system can assist the synchronous units in providing the power system with active power output response without delay in primary frequency regulation, the system frequency dynamics during the primary frequency regulation of the power system is evaluated;

[0021] The frequency of the power system is the rated frequency at the beginning of a frequency regulation process. The dynamic response of the frequency is solved based on the time step Δt. For the jth time step, the power system frequency at the end of the jth time step is solved based on formula (3):

[0022]

[0023] Where f j-1 、f j are the power system frequencies at the end of the j-1th and jth time steps, respectively, Pdef K is the active power shortage in the initial stage of frequency regulation. SG is the unit regulation power of the synchronous units in the power system, H SG is the inertia time constant of the synchronous units in the power system;

[0024] When |f M -f M-1 |≤0.001Hz, the power system frequency calculation process ends, that is, the frequency reaches the steady-state value after M time steps;

[0025] In these M time steps, considering the existence of the response delay of the primary frequency regulation of the power system, the active output response ΔP of the primary frequency regulation of the synchronous units in the power system in the jth time step is SG,j,est Calculate based on formula (4):

[0026]

[0027] Due to the existence of the response delay of the primary frequency regulation of the power system, in the jth time step, the active output response ΔP of the primary frequency regulation of the synchronous units in the power system SG,j,est The target value K set by the primary frequency modulation control is not reached SG (f N -f j-1 ), the shortfall is made up by the energy storage virtual power plant to achieve a non-delayed primary frequency regulation active output response. In the jth time step, the active output of the energy storage virtual power plant P ESS,j Refer to formula (5) for setting:

[0028] P ESS,j =K SG (f N -f j-1 )-ΔP SG,j,est (5);

[0029] Verify whether the active output of the energy storage virtual power plant meets its maximum active output constraint and energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value;

[0030] If the active output of the energy storage virtual power plant is less than its maximum allowable active output within M time steps (Formula (6)), it can satisfy the maximum active output constraint;

[0031]

[0032] If the total amount of active power output of the energy storage virtual power plant within M time steps is less than its allowable discharge capacity (Equation (7)), the energy storage capacity constraint can be met;

[0033]

[0034] Where S ini is the charge state of the energy storage virtual power plant at the initial time of frequency regulation, S min is the minimum charge state allowed for the energy storage virtual power plant, C ESS is the capacity of the energy storage virtual power plant, γ dis Discharge efficiency of virtual power plants for energy storage;

[0035] If the active output of the energy storage virtual power plant satisfies both its maximum active output constraint and the energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value, it indicates that the current capacity can assist the synchronous unit in providing a delay-free primary frequency regulation active output response to the power system. The active output of the energy storage virtual power plant is set with the goal of providing a delay-free primary frequency regulation active output response (Equation (5)).

[0036] Further as a preferred technical solution of the present invention, S3 comprises the following steps:

[0037] If the current capacity of the electric energy storage virtual power plant within the power system is insufficient to assist the synchronous units in providing the power system with a delay-free primary frequency regulation active output response, that is, the active output of the electric energy storage virtual power plant cannot simultaneously meet its maximum active output constraint and the electric energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value, the active output of the electric energy storage virtual power plant in the process of assisting primary frequency regulation is adjusted;

[0038] If the active output of the energy storage virtual power plant does not meet its maximum active output constraint within M time steps during the process of the frequency reaching the steady-state value, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is adjusted based on formula (8) to meet the maximum active output constraint. The adjusted active output value of the energy storage virtual power plant in the jth time step is

[0039]

[0040] The adjusted value of the active output of the energy storage virtual power plant calculated based on formula (8) is used to check whether the total amount of active output of the energy storage virtual power plant within M time steps is less than its allowable discharge amount. If it satisfies Then the active output adjustment of the energy storage virtual power plant in the auxiliary primary frequency regulation process is completed. Otherwise, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is further adjusted based on formula (9) to meet the energy storage capacity constraint;

[0041]

[0042] If the active output of the energy storage virtual power plant does not meet its energy storage capacity constraint within M time steps in the process of the frequency reaching the steady-state value, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is adjusted based on formula (10) to meet the maximum active output constraint. The adjusted active output value of the energy storage virtual power plant in the jth time step is

[0043]

[0044] The present invention proposes a method for assisting primary frequency regulation of a power system with an electric energy storage virtual power plant. Compared with the prior art, the above technical solution has the following technical effects:

[0045] (1) When the present invention uses the electric energy storage virtual power plant to assist the power system frequency regulation, it does not regard it as a backup power source that participates in the power system frequency regulation process throughout the process as in the prior art solution. Considering that the ability of the electric energy storage virtual power plant to continuously provide active output is limited by its own energy storage capacity, and its main advantage is that it can provide a relatively fast frequency regulation response, the present invention focuses on making the electric energy storage virtual power plant play the role of the main synchronous unit of the auxiliary system frequency regulation in the process of power system frequency regulation, that is, using its fast output response to make up for the insufficient active output response of the synchronous unit in the initial stage of a frequency regulation due to delay.

[0046] (2) The technical solution adopted by the present invention can be used to realize the delay-free primary frequency regulation of the power system. In the existing power system frequency stability analysis, this delay is often ignored, resulting in the actual frequency stability of the system being weaker than the theoretical analysis result based on the delay-free frequency regulation response. The technical solution adopted by the present invention can use the electric energy storage virtual power plant to reduce the delay of the power system frequency regulation response, so that the frequency stability of the power system during actual operation can reach the level of its theoretical design. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A flow chart of a method for assisting primary frequency regulation of a power system using an electric energy storage virtual power plant according to an embodiment of the present invention;

[0048] Figure 2 It is a curve diagram of active output response data of primary frequency regulation of synchronous units in the power system according to an embodiment of the present invention;

[0049] Figure 3 A curve diagram of power system frequency data during the primary frequency modulation process of a synchronous generator set within the power system according to an embodiment of the present invention;

[0050] Figure 4 Providing a comparison diagram of active output response curves corresponding to delayed and non-delayed primary frequency modulation for the synchronous unit of the embodiment of the present invention;

[0051] Figure 5 A comparison diagram of power system frequency curves corresponding to delayed and non-delayed primary frequency modulation is provided for the synchronous generator set in the embodiment of the present invention;

[0052] Figure 6 The embodiment of the present invention is to realize the electric energy storage virtual power plant output curve of the primary frequency modulation active output response without delay;

[0053] Figure 7 The curve after the active output of the electric energy storage virtual power plant is adjusted taking into account the maximum active output constraint in the embodiment of the present invention;

[0054] Figure 8 This is a comparison diagram of the power system frequency after the active output of the electric energy storage virtual power plant is adjusted according to the maximum active output constraint in an embodiment of the present invention and the power system frequency curve corresponding to the primary frequency modulation without delay. DETAILED DESCRIPTION

[0055] The present invention will be further explained below in conjunction with the detailed description of the accompanying drawings so that those skilled in the art can have a deeper understanding of the present invention and be able to implement it. However, the reference examples below are only used to explain the present invention and are not intended to limit the present invention.

[0056] Aiming at the delay of the frequency regulation actuator of the synchronous unit during the primary frequency regulation process of the power system, the present invention proposes a method for utilizing the internal electric energy storage virtual power plant of the power system to assist the power system in primary frequency regulation, thereby eliminating or shortening the response delay of the primary frequency regulation process.

[0057] See also Figure 1 , a method for assisting primary frequency regulation of a power system with an electric energy storage virtual power plant, comprising the following steps:

[0058] S1: Estimate the response delay time constant of the primary frequency regulation of the power system based on the active power shortage in the initial stage of the primary frequency regulation of the power system, the unit regulation power of the synchronous units in the power system, the active output response of the primary frequency regulation of the synchronous units in the power system, and the historical data of the power system frequency;

[0059] Specifically, the active power shortage in the initial stage of the primary frequency regulation of the power system, the unit regulation power of the synchronous units in the power system, the active output response of the primary frequency regulation of the synchronous units in the power system, and the historical data of the power system frequency are used to estimate the response delay time constant of the primary frequency regulation of the power system through data fitting.

[0060] If the data recording time step in the recorded historical data of the primary frequency regulation process of the power system is Δt, the time period from the initial moment of the primary frequency regulation to the time when the power system frequency reaches a stable value contains N groups of data (the active output response of the primary frequency regulation of the synchronous units inside the power system, the power system frequency), considering the response delay of the primary frequency regulation of the power system, the N groups of data in the frequency regulation process should satisfy the following formula:

[0061]

[0062] Where ΔP SG,n is the active output response of the primary frequency regulation of the synchronous generator set in the power system in the nth group of data, f i-1 、f i are the power system frequencies in the i-1th and ith groups of data, respectively, and f N is the rated frequency of the power system, K SG is the unit regulation power of the synchronous units in the power system, T SG is the response delay time constant of primary frequency regulation of the power system;

[0063] Specifically, in the embodiment of the present invention, the primary frequency modulation active output response of the synchronous unit in the power system and the power system frequency data are respectively as follows: Figure 2 and Figure 3 As shown, based on Figure 2 and Figure 3 The data shown are used to estimate the delay time constant of the subsequent power system primary frequency regulation response. The unit regulation power of the synchronous units within the power system is 25MW / Hz.

[0064] The response delay time constant T of primary frequency regulation of power system is estimated by successive approximation. SG , whose estimated value is T SG,est The initial setting is 0, and the synchronous unit primary frequency regulation active output response ΔP calculated based on the estimated value of the response delay time constant of the primary frequency regulation is compared. SG,est Its actual value The size relationship, ΔP SG,est The calculation formula is,

[0065]

[0066] like Then increase the estimated value T of the response delay time constant of the frequency modulation according to the adjustment step size. SG,est ;like Then the estimated value T of the response delay time constant of the frequency modulation is reduced according to the adjustment step size. SG,est When satisfied When the condition is met, the output is the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation. SG,est; If a frequency modulation response delay time constant estimate value T SG,est In the case of alternating between two values, the adjustment step is shortened until the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation can be output. SG,est .

[0067] Specifically in the embodiment of the present invention, the estimated value of the response delay time constant of the primary frequency regulation of the power system is initially taken as 0s, and is adjusted according to the above steps in steps of 0.05s. Under different estimated values ​​of the response delay time constant of the primary frequency regulation of the power system, the corresponding calculation results are shown in Table 1.

[0068] Table 1 Calculation results corresponding to the estimated values ​​of the response delay time constants of primary frequency regulation in different power systems

[0069]

[0070] From the calculation results in Table 1, it can be seen that when the estimated value of the response delay time constant of the primary frequency regulation of the power system increases to 0.6s, Condition, that is, the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation SG,est It is 0.6s.

[0071] S2: Under the condition of setting the active power shortage in the initial stage of primary frequency regulation of the power system, evaluate the ability of the internal electric energy storage virtual power plant to provide the power system with a delay-free primary frequency regulation active output response as a whole by regulating the output of the internal electric energy storage virtual power plant in the process of primary frequency regulation of the power system; if the current capacity of the internal electric energy storage virtual power plant can assist the synchronous unit in providing the power system with a delay-free primary frequency regulation active output response, then the active output response curve of the electric energy storage virtual power plant is given with the goal of providing a delay-free primary frequency regulation active output response;

[0072] Specifically, under the condition of setting the active power shortage in the initial stage of primary frequency regulation of the power system, assuming that the current capacity of the electric energy storage virtual power plant inside the power system can assist the synchronous units in providing the power system with active power output response of primary frequency regulation without delay, the system frequency dynamics during the primary frequency regulation of the power system is evaluated;

[0073] The frequency of the power system is the rated frequency at the beginning of a frequency regulation process. The dynamic response of the frequency is solved based on the time step Δt. For the jth time step, the power system frequency at the end of the jth time step is solved based on formula (3):

[0074]

[0075] Where f j-1 、f jare the power system frequencies at the end of the j-1th and jth time steps, respectively, P def K is the active power shortage in the initial stage of frequency regulation. SG is the unit regulation power of the synchronous units in the power system, H SG is the inertia time constant of the synchronous units in the power system;

[0076] When |f M -f M-1 |≤0.001Hz, the power system frequency calculation process ends, that is, the frequency reaches the steady-state value after M time steps;

[0077] Specifically, in the embodiment of the present invention, the active power shortage in the initial stage of the primary frequency regulation of the power system is set to 10MW, and the inertia time constant of the synchronous unit in the power system is 60s. Under this condition, the synchronous unit provides a comparison diagram of the active power output response curve corresponding to the delayed and non-delayed primary frequency regulation and a comparison diagram of the power system frequency curve, respectively, as shown in FIG. Figure 4 and Figure 5 It can be seen that the delay in the active output response of the synchronous unit in the primary frequency regulation leads to a reduction in its active output, which aggravates the transient frequency deviation of the power system during the primary frequency regulation process.

[0078] In these M time steps, considering the existence of the response delay of the primary frequency regulation of the power system, the active output response ΔP of the primary frequency regulation of the synchronous units in the power system in the jth time step is SG,j,est Calculate based on formula (4):

[0079]

[0080] Due to the existence of the response delay of the primary frequency regulation of the power system, in the jth time step, the active output response ΔP of the primary frequency regulation of the synchronous units in the power system SG,j,est The target value K set by the primary frequency modulation control is not reached SG (f N -f j-1 ), the shortfall is made up by the energy storage virtual power plant to achieve a non-delayed primary frequency regulation active output response. In the jth time step, the active output of the energy storage virtual power plant P ESS,j Refer to formula (5) for setting:

[0081] P ESS,j =K SG (f N -f j-1 )-ΔP SG,j,est (5);

[0082] Specifically, in the embodiment of the present invention, in order to achieve a delay-free primary frequency modulation active output response, the active output curve of the electric energy storage virtual power plant calculated based on formula (5) is as follows: Figure 6 shown.

[0083] Verify whether the active output of the energy storage virtual power plant meets its maximum active output constraint and energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value;

[0084] If the active output of the energy storage virtual power plant is less than its maximum allowable active output within M time steps (Formula (6)), it can satisfy the maximum active output constraint;

[0085]

[0086] If the total amount of active power output of the energy storage virtual power plant within M time steps is less than its allowable discharge capacity (Equation (7)), the energy storage capacity constraint can be met;

[0087]

[0088] Where S ini is the charge state of the energy storage virtual power plant at the initial time of frequency regulation, S min is the minimum charge state allowed for the energy storage virtual power plant, C ESS is the capacity of the energy storage virtual power plant, γ dis Discharge efficiency of virtual power plants for energy storage;

[0089] If the active output of the energy storage virtual power plant satisfies both its maximum active output constraint and the energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value, it indicates that the current capacity can assist the synchronous unit in providing a delay-free primary frequency regulation active output response to the power system. The active output of the energy storage virtual power plant is set with the goal of providing a delay-free primary frequency regulation active output response (Equation (5)).

[0090] S3: If the current capacity of the virtual power plant with energy storage inside the power system is insufficient to assist the synchronous units in providing the power system with a delay-free primary frequency regulation active output response, the active output response curve of the virtual power plant with energy storage is given on the premise of fully utilizing the current capacity of the virtual power plant with energy storage to achieve the maximum degree of suppression of the delay in the primary frequency regulation active output response.

[0091] Specifically, if the current capacity of the electric energy storage virtual power plant within the power system is insufficient to assist the synchronous units in providing the power system with a delay-free primary frequency regulation active output response, that is, the active output of the electric energy storage virtual power plant cannot simultaneously meet its maximum active output constraint and the electric energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value, the active output of the electric energy storage virtual power plant in the process of assisting the primary frequency regulation is adjusted;

[0092] If the active output of the energy storage virtual power plant does not meet its maximum active output constraint within M time steps during the process of the frequency reaching the steady-state value, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is adjusted based on formula (8) to meet the maximum active output constraint. The adjusted active output value of the energy storage virtual power plant in the jth time step is

[0093]

[0094] Specifically, in the embodiment of the present invention, if the maximum active output constraint of the energy storage virtual power plant is 1.2MW, the curve after the active output adjustment of the energy storage virtual power plant taking into account the constraint is as follows: Figure 7 shown.

[0095] The adjusted value of the active output of the energy storage virtual power plant calculated based on formula (8) is used to check whether the total amount of active output of the energy storage virtual power plant within M time steps is less than its allowable discharge amount.

[0096] If satisfied Then the active output adjustment of the energy storage virtual power plant in the auxiliary primary frequency regulation process is completed. Otherwise, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is further adjusted based on formula (9) to meet the energy storage capacity constraint;

[0097]

[0098] If the active output of the energy storage virtual power plant does not meet its energy storage capacity constraint within M time steps in the process of the frequency reaching the steady-state value, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is adjusted based on formula (10) to meet the maximum active output constraint. The adjusted active output value of the energy storage virtual power plant in the jth time step is

[0099]

[0100] Specifically, in the embodiment of the present invention, the power system frequency after adjusting the active output of the energy storage virtual power plant according to the maximum active output constraint is compared with the power system frequency corresponding to the non-delayed primary frequency regulation. Figure 8 As shown, it can be seen that due to the maximum active output constraint of the electric energy storage virtual power plant, it cannot assist the synchronous unit to achieve a completely delay-free primary frequency regulation response, and the frequency offset of the power system is slightly large, but it achieves minimization of the primary frequency regulation delay of the synchronous unit within the allowable operating range.

[0101] The present invention is aimed at the primary frequency regulation process of the power system. First, based on the historical frequency regulation data, the overall response delay of the primary frequency regulation of the power system is quantified. With the goal of achieving a delay-free primary frequency regulation response of the power system, the system frequency response under this working condition is estimated. Corresponding to the system frequency change, taking into account the overall response delay of the primary frequency regulation of the power system, the actual additional active output of the synchronous unit in the frequency regulation process is calculated, and the difference between the active output adjustment target value corresponding to the primary frequency regulation is calculated by the energy storage virtual power plant, so that the synchronous unit and the energy storage virtual power plant as a whole have the ability to provide delay-free primary frequency regulation to the power system. If in this process, the energy storage virtual power plant cannot meet its maximum active output constraints and energy storage capacity constraints, the active output of the energy storage virtual power plant in the frequency regulation process is adjusted, and the maximum degree of suppression of the primary frequency regulation response delay of the power system is achieved under the premise of fully utilizing the capacity of the energy storage virtual power plant.

[0102] The specific implementation scheme described above further describes in detail the purpose, technical scheme and beneficial effects of the present invention. It should be understood that the above is only a specific implementation scheme of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any technician in the field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for assisting primary frequency modulation of a power system with an electric energy storage virtual power plant, characterized in that: The following steps are involved: S1: Estimate the response delay time constant of the primary frequency regulation of the power system based on the active power shortage in the initial stage of the primary frequency regulation of the power system, the unit regulation power of the synchronous units in the power system, the active output response of the primary frequency regulation of the synchronous units in the power system, and the historical data of the power system frequency; S2: Under the condition of setting the active power shortage in the initial stage of primary frequency regulation of the power system, evaluate the ability of the internal electric energy storage virtual power plant to provide the power system with a delay-free primary frequency regulation active output response as a whole by regulating the output of the internal electric energy storage virtual power plant in the process of primary frequency regulation of the power system; if the current capacity of the internal electric energy storage virtual power plant can assist the synchronous unit in providing the power system with a delay-free primary frequency regulation active output response, then the active output response curve of the electric energy storage virtual power plant is given with the goal of providing a delay-free primary frequency regulation active output response; S3: If the current capacity of the virtual power plant with energy storage inside the power system is insufficient to assist the synchronous units in providing the power system with a delay-free primary frequency regulation active output response, the active output response curve of the virtual power plant with energy storage is given on the premise of fully utilizing the current capacity of the virtual power plant with energy storage to achieve the maximum degree of suppression of the delay in the primary frequency regulation active output response.

2. A method for primary frequency modulation of an electric energy storage virtual power plant assisting a power system according to claim 1, characterized in that: S1 includes the following steps: the active power shortage in the initial stage of frequency regulation during the primary frequency regulation of the power system, the unit regulation power of the internal synchronous units of the power system, the active output response of the primary frequency regulation of the internal synchronous units of the power system, and the historical data of the power system frequency, and the response delay time constant of the primary frequency regulation of the power system is estimated by data fitting; If the data recording time step in the recorded historical data of the primary frequency regulation process of the power system is Δt, the time period from the initial moment of the primary frequency regulation to the time when the power system frequency reaches a stable value contains N groups of data, including the active output response of the primary frequency regulation of the synchronous units inside the power system and the power system frequency; considering the response delay of the primary frequency regulation of the power system, the N groups of data in the frequency regulation process should satisfy the following formula: Where ΔP SG,n is the active output response of the primary frequency regulation of the synchronous generator set in the power system in the nth group of data, f i-1 、f i are the power system frequencies in the i-1th and ith groups of data, respectively, and f N is the rated frequency of the power system, K SG is the unit regulation power of the synchronous units in the power system, T SG is the response delay time constant of primary frequency regulation of the power system; The response delay time constant T of primary frequency regulation of power system is estimated by successive approximation. SG , whose estimated value is T SG,est The initial setting is 0, and the synchronous unit primary frequency regulation active output response ΔP calculated based on the estimated value of the response delay time constant of the primary frequency regulation is compared. SG,est Its actual value The size relationship, ΔP SG,est The calculation formula is, like Then increase the estimated value T of the response delay time constant of the frequency modulation according to the adjustment step size. SG,est ;like Then the estimated value T of the response delay time constant of the frequency modulation is reduced according to the adjustment step size. SG,est When satisfied When the condition is met, the output is the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation. SG,est ; If a frequency modulation response delay time constant estimate value T SG,est In the case of alternating between two values, the adjustment step is shortened until the estimated value T of the response delay time constant of the primary frequency modulation obtained by stepwise approximation can be output. SG,est .

3. The method for primary frequency modulation of an electric energy storage virtual power plant assisting a power system according to claim 2, characterized in that: In S2: Under the condition of setting the active power shortage in the initial stage of primary frequency regulation of the power system, assuming that the current capacity of the electric energy storage virtual power plant inside the power system can assist the synchronous units in providing the power system with active power output response without delay in primary frequency regulation, the system frequency dynamics during the primary frequency regulation of the power system is evaluated; The frequency of the power system is the rated frequency at the beginning of a frequency regulation process. The dynamic response of the frequency is solved based on the time step Δt. For the jth time step, the power system frequency at the end of the jth time step is solved based on formula (3): Where f j-1 、f j are the power system frequencies at the end of the j-1th and jth time steps, respectively, P def K is the active power shortage in the initial stage of frequency regulation. SG is the unit regulation power of the synchronous units in the power system, H SG is the inertia time constant of the synchronous units in the power system; When |f M -f M-1 |≤0.001Hz, the power system frequency calculation process ends, that is, the frequency reaches the steady-state value after M time steps; In these M time steps, considering the existence of the response delay of the primary frequency regulation of the power system, the active output response ΔP of the primary frequency regulation of the synchronous units in the power system in the jth time step is SG,j,est Calculate based on formula (4): Due to the existence of the response delay of the primary frequency regulation of the power system, in the jth time step, the active output response ΔP of the primary frequency regulation of the synchronous units in the power system SG,j,est The target value K set by the primary frequency modulation control is not reached SG (f N -f j-1 ), the shortfall is made up by the energy storage virtual power plant to achieve a non-delayed primary frequency regulation active output response. In the jth time step, the active output of the energy storage virtual power plant P ESS,j Refer to formula (5) for setting: P ESS,j =K SG (f N -f j-1 )-ΔP SG,j,est (5); Verify whether the active output of the energy storage virtual power plant meets its maximum active output constraint and energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value; If the active output of the energy storage virtual power plant is less than its maximum allowable active output within M time steps Then it can meet the maximum active output constraint; If the total amount of active power output of the energy storage virtual power plant within M time steps is less than its allowable discharge amount, the energy storage capacity constraint can be met; Where S ini is the charge state of the energy storage virtual power plant at the initial time of frequency regulation, S min is the minimum charge state allowed for the energy storage virtual power plant, C ESS is the capacity of the energy storage virtual power plant, γ dis Discharge efficiency of virtual power plants for electric energy storage; If the active output of the energy storage virtual power plant satisfies both its maximum active output constraint and the energy storage capacity constraint within M time steps in the process of the frequency reaching the steady-state value, it indicates that the current capacity can assist the synchronous units in providing a delay-free primary frequency regulation active output response to the power system. The active output of the energy storage virtual power plant is set with the goal of providing a delay-free primary frequency regulation active output response.

4. The method for primary frequency modulation of an electric energy storage virtual power plant assisting a power system according to claim 3, characterized in that: The S3 comprises the following steps: If the current capacity of the electric energy storage virtual power plant within the power system is insufficient to assist the synchronous units in providing the power system with a delay-free primary frequency regulation active output response, that is, the active output of the electric energy storage virtual power plant cannot simultaneously meet its maximum active output constraint and the electric energy storage capacity constraint within M time steps during the process of the frequency reaching the steady-state value, the active output of the electric energy storage virtual power plant in the process of assisting primary frequency regulation is adjusted; If the active output of the energy storage virtual power plant does not meet its maximum active output constraint within M time steps during the process of the frequency reaching the steady-state value, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is adjusted based on formula (8) to meet the maximum active output constraint. The adjusted active output value of the energy storage virtual power plant in the jth time step is The adjusted value of the active output of the energy storage virtual power plant calculated based on formula (8) is used to check whether the total amount of active output of the energy storage virtual power plant within M time steps is less than its allowable discharge amount. If satisfied Then the active output adjustment of the energy storage virtual power plant in the auxiliary primary frequency regulation process is completed. Otherwise, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is further adjusted based on formula (9) to meet the energy storage capacity constraint; If the active output of the energy storage virtual power plant does not meet its energy storage capacity constraint within M time steps in the process of the frequency reaching the steady-state value, the active output of the energy storage virtual power plant in the auxiliary primary frequency regulation process is adjusted based on formula (10) to meet the maximum active output constraint. The adjusted active output value of the energy storage virtual power plant in the jth time step is

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