A method for primary frequency regulation of an electric energy storage virtual power plant assisting a power system

Abstract

The present invention relates to the field of virtual power plant operation and control, and in particular to a method for assisting primary frequency regulation of a power system with an electric energy storage virtual power plant. The method of the present invention first quantifies the frequency regulation delay based on the historical data of the primary frequency regulation of the power system, estimates the delay-free active output response under a specific frequency regulation scenario, and uses the additional active power of the electric energy storage virtual power plant to make up for the shortfall in the active power response of the synchronous unit due to the delay, thereby achieving a delay-free primary frequency regulation active output response. If there is a working condition in which the capacity of the electric energy storage virtual power plant is limited during this process, the active output response of the electric energy storage virtual power plant is adjusted, and the response delay of the primary frequency regulation process of the power system is shortened while fully utilizing its adjustable capacity. The technical solution adopted by the present invention can utilize the electric energy storage virtual power plant to reduce the frequency regulation response delay of the power system, so that the frequency stability of the power system during actual operation can reach the level of its theoretical design.

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 auxiliary power system of an electric energy storage virtual power plant. Background Art

[0002] During operation, power systems must prevent excessive deviations of their frequency from their rated values. This frequency regulation function is primarily handled by the synchronous generators within the system. Primary frequency regulation of synchronous generators is a preemptive measure to address system frequency deviations caused by active power imbalances in the power system, and is performed by the synchronous generator's speed regulator. When a synchronous generator responds to primary frequency regulation, the inertia of the speed regulator control system and the speed regulator itself can cause a delay in the generator's increased active power output to respond to the primary frequency regulation request. This delay prevents the synchronous generator from increasing its active power output in a timely manner to reduce the power system's active power imbalance, weakening the effectiveness of suppressing system frequency deviations.

[0003] As an emerging flexible power generation resource within the power system, virtual power plants (VPPs) with energy storage have become widely used in peak and frequency regulation. Existing technical solutions primarily utilize them as a backup power source, integrating them into peak and frequency regulation when the pressure on the system is high.

[0004] However, given that the ability of a VPP with energy storage to continuously output active power to participate in system frequency regulation is limited by its own capacity, it is not suitable as the primary frequency regulation power source. Its advantage over the synchronous units within the system lies in its relatively fast active power output response. This rapid output response can compensate for the shortfall in active power output response of the synchronous units caused by delays during the primary frequency regulation process. This allows the VPP to play a supporting role, improving the primary frequency regulation of the synchronous units that are the primary frequency regulator of the power system. Summary of the Invention

[0005] This invention proposes a method for using an energy storage virtual power plant to assist in the primary frequency regulation of a power system. This method addresses the response delay of synchronous generators during the primary frequency regulation process. The energy storage virtual power plant assists the synchronous generators, compensating for the shortfall in their active output response compared to the primary frequency regulation setpoint caused by the response delay. This allows the synchronous generators in the power system and the energy storage virtual power plant to function as a whole, achieving zero-delay primary frequency regulation. Furthermore, under conditions where zero-delay primary frequency regulation is impossible due to limited capacity of the energy storage virtual power plant, a method for minimizing the response delay during the primary frequency regulation process is proposed.

[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 power system primary frequency regulation based on the active power shortage in the initial stage of the frequency regulation, the unit regulation power of the synchronous units within the power system, the active power output response of the synchronous units within the power system during the primary frequency regulation, and the historical data of the power system frequency.

[0009] S2: Under the assumption of an active power shortage in the initial stage of the power system's primary frequency regulation, evaluate the ability of the internal energy storage virtual power plant to regulate the output of the power system's internal primary frequency regulation process, so that the internal synchronous units and the virtual power plant, as a whole, can provide a non-delayed primary frequency regulation active power output response to the power system. If the current capacity of the internal energy storage virtual power plant can assist the synchronous units in providing a non-delayed primary frequency regulation active power output response to the power system, then the active power output response curve of the energy storage virtual power plant is developed with the goal of providing a non-delayed primary frequency regulation active power output response.

[0010] S3: 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, the active output response curve of the electric energy storage virtual power plant is given on the premise of fully utilizing the current capacity of the electric energy storage virtual power plant to achieve the maximum degree of suppression of the primary frequency regulation active output response delay.

[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 power system primary frequency regulation process, the unit regulation power of the internal synchronous units in the power system, the active output response of the internal synchronous units in the power system primary frequency regulation, and the historical data of the power system frequency are used to estimate the response delay time constant of the power system primary frequency regulation through data fitting.

[0013] If the recorded historical data of the primary frequency regulation process of the power system has a data recording time step of Δt, and 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 sets of data (the active output response of the primary frequency regulation of the synchronous units within the power system, and the power system frequency), considering the response delay of the primary frequency regulation of the power system, the N sets 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 The unit power regulation of the synchronous units in the power system, T SG is the response delay time constant of the primary frequency regulation of the power system;

[0016] The response delay time constant T of the primary frequency regulation of the power system is estimated by using the successive approximation method. SG , its estimated value T SG,est The initial setting is 0, and the response delay time constant of the synchronous unit primary frequency regulation is calculated based on the estimated value of the response delay time constant of the primary frequency regulation. 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 by the adjustment step size. SG,est ;like Then reduce the estimated value of the response delay time constant T of the frequency modulation by one adjustment step. 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 successive 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 successive 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 assumption that there is an active power shortage in the initial stage of primary frequency regulation in the power system, the system frequency dynamics during the primary frequency regulation process are evaluated, assuming that the current capacity of the electric energy storage virtual power plant within the power system can assist the synchronous units in providing active power output response to the power system without delay.

[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 j-th time step, the power system frequency at the end of the j-th 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 The unit power regulation 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 unit in the power system in the jth time step is SG,j,est Calculation is 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 of the primary frequency regulation of the synchronous unit in the power system is ΔP 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 delay-free 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 when the frequency reaches 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 (Equation (6)), it can satisfy the maximum active output constraint;

[0031]

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

[0033]

[0034] Where S ini is the state of charge of the energy storage virtual power plant at the initial time of frequency regulation, S min is the minimum state of charge 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 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 (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 energy storage virtual power plant within the power system is insufficient to assist the synchronous generators in providing the power system with a delay-free primary frequency regulation active output response, that is, if the active output of the energy storage virtual power plant cannot simultaneously meet 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, the active output of the 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 when the frequency reaches 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 capacity. If it satisfies Then the active output adjustment of the electric energy storage virtual power plant in the auxiliary primary frequency regulation process is completed. Otherwise, the active output of the electric energy storage virtual power plant in the auxiliary primary frequency regulation process is further adjusted based on formula (9) to meet the electric 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 when the frequency reaches 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 utilizing the electric energy storage virtual power plant to assist in the frequency regulation of the power system, the present invention does not treat it as a backup power source that fully participates in the frequency regulation process of the power system as in the prior art solutions. 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 during the power system frequency regulation process, that is, using its fast output response to compensate 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 achieve zero-delay primary frequency regulation in power systems. This delay is often ignored in existing power system frequency stability analyses, resulting in the actual frequency stability of the system being weaker than the theoretical analysis results based on zero-delay frequency regulation response. The technical solution adopted by the present invention can utilize an electric energy storage virtual power plant to reduce the delay in 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 This is 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 This is a graph showing the active output response data of the primary frequency regulation of the synchronous generator sets in the power system according to an embodiment of the present invention;

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

[0050] Figure 4 A comparison chart of active output response curves corresponding to delayed and non-delayed primary frequency modulation is provided for the synchronous generator set according to an embodiment of the present invention;

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

[0052] Figure 6 The embodiment of the present invention is to achieve a non-delayed primary frequency modulation active output response of the electric energy storage virtual power plant output curve;

[0053] Figure 7 The curve of the active output of the energy storage virtual power plant after adjustment 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 regulation without delay. DETAILED DESCRIPTION

[0055] The present invention will be further explained below with reference to 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 following reference examples are only used to explain the present invention and are not intended to limit the present invention.

[0056] Aiming at the delay of the synchronous unit frequency regulation actuator 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 comprises the following steps:

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

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

[0060] If the recorded historical data of the primary frequency regulation process of the power system has a data recording time step of Δt, and 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 sets of data (the active output response of the primary frequency regulation of the synchronous units within the power system, and the power system frequency), considering the response delay of the primary frequency regulation of the power system, the N sets 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 The unit power regulation of the synchronous units in the power system, T SG is the response delay time constant of the primary frequency regulation of the power system;

[0063] Specifically, in the embodiment of the present invention, the active output response of the primary frequency regulation of the synchronous generator set 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 the primary frequency regulation of the power system is estimated by using the successive approximation method. SG , its estimated value T SG,est The initial setting is 0, and the response delay time constant of the synchronous unit primary frequency regulation is calculated based on the estimated value of the response delay time constant of the primary frequency regulation. 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 by the adjustment step size. SG,est ;like Then reduce the estimated value of the response delay time constant T of the frequency modulation by one adjustment step. 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 successive 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 successive 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 set to 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 of the estimated response delay time constants for 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 power system primary frequency regulation increases to 0.6s, Condition, that is, the estimated value T of the response delay time constant of the primary frequency modulation obtained by successive approximation SG,est 0.6s.

[0071] S2: Under the assumption of an active power shortage in the initial stage of the power system's primary frequency regulation, evaluate the ability of the internal energy storage virtual power plant to regulate the output of the power system's internal primary frequency regulation process, so that the internal synchronous units and the virtual power plant, as a whole, can provide a non-delayed primary frequency regulation active power output response to the power system. If the current capacity of the internal energy storage virtual power plant can assist the synchronous units in providing a non-delayed primary frequency regulation active power output response to the power system, then the active power output response curve of the energy storage virtual power plant is developed with the goal of providing a non-delayed primary frequency regulation active power output response.

[0072] Specifically, under the condition that there is an active power shortage in the initial stage of the power system's primary frequency regulation, it is assumed that the current capacity of the electric energy storage virtual power plant within the power system can assist the synchronous units in providing the power system with a delay-free active power output response for primary frequency regulation. The system frequency dynamics during the power system's primary frequency regulation process are 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 j-th time step, the power system frequency at the end of the j-th 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 The unit power regulation 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 units in the power system is 60s. Under this condition, the synchronous units provide active power output response curve comparison diagram corresponding to the delayed and non-delayed primary frequency regulation and the power system frequency curve comparison diagram are 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 offset 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 unit in the power system in the jth time step is SG,j,est Calculation is 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 of the primary frequency regulation of the synchronous unit in the power system is ΔP 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 delay-free 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 when the frequency reaches 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 (Equation (6)), it can satisfy the maximum active output constraint;

[0085]

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

[0087]

[0088] Where S ini is the state of charge of the energy storage virtual power plant at the initial time of frequency regulation, S min is the minimum state of charge 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 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 (Equation (5)).

[0090] S3: 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, the active output response curve of the electric energy storage virtual power plant is given on the premise of fully utilizing the current capacity of the electric energy storage virtual power plant to achieve the maximum degree of suppression of the primary frequency regulation active output response delay.

[0091] Specifically, if the current capacity of the energy storage virtual power plant within the power system is insufficient to assist the synchronous generators in providing the power system with a delay-free primary frequency regulation active output response, that is, if the active output of the energy storage virtual power plant cannot simultaneously meet 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, the active output of the energy storage virtual power plant in the process of assisting 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 when the frequency reaches 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 adjusting the active output 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 capacity.

[0096] If satisfied Then the active output adjustment of the electric energy storage virtual power plant in the auxiliary primary frequency regulation process is completed. Otherwise, the active output of the electric energy storage virtual power plant in the auxiliary primary frequency regulation process is further adjusted based on formula (9) to meet the electric 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 when the frequency reaches 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 power system frequency offset 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 response delay of the primary frequency regulation of the power system as a whole 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 power output of the synchronous unit in the frequency regulation process is calculated. The difference between the actual additional active power output and the active power output adjustment target value corresponding to the primary frequency regulation is the responsibility of 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, during this process, the energy storage virtual power plant cannot meet its maximum active power output constraint and energy storage capacity constraint, the active output of the energy storage virtual power plant in the frequency regulation process is adjusted, and the maximum 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 illustrates in detail the purpose, technical solutions 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 this 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 regulation of a power system using an electric energy storage virtual power plant, characterized in that: The following steps are involved: S1: Estimate the response delay time constant of the power system primary frequency regulation based on the active power shortage in the initial stage of the frequency regulation, the unit regulation power of the synchronous units within the power system, the active power output response of the synchronous units within the power system during the primary frequency regulation, and the historical data of the power system frequency. S2: Under the assumption of an active power shortage in the initial stage of the power system's primary frequency regulation, evaluate the ability of the internal energy storage virtual power plant to regulate the output of the power system's internal primary frequency regulation process, so that the internal synchronous units and the virtual power plant, as a whole, can provide a non-delayed primary frequency regulation active power output response to the power system. If the current capacity of the internal energy storage virtual power plant can assist the synchronous units in providing a non-delayed primary frequency regulation active power output response to the power system, then the active power output response curve of the energy storage virtual power plant is developed with the goal of providing a non-delayed primary frequency regulation active power output response. S3: If the current capacity of the electric energy storage virtual power plant within the power system is insufficient to assist the synchronous generators in providing the power system with a delay-free primary frequency regulation active output response, then, while fully utilizing the current capacity of the electric energy storage virtual power plant, an active output response curve of the electric energy storage virtual power plant is provided to minimize the delay in the primary frequency regulation active output response. Said S1 comprises the following steps: estimating the response delay time constant of the primary frequency regulation of the power system by fitting the active power shortage in the initial stage of the frequency regulation process of the power system primary frequency regulation, the unit regulation power of the synchronous units within the power system, the active output response of the synchronous units within the power system primary frequency regulation, and the historical data of the power system frequency; If the recorded historical data of the primary frequency regulation process of the power system has a data recording time step of 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 sets of data, including the active output response of the primary frequency regulation of the synchronous units within the power system and the power system frequency; considering the response delay of the primary frequency regulation of the power system, the N sets of data during the frequency regulation process should satisfy the following formula: （1）； In the formula 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, 、 Respectively The power system frequency in the group and the i-th group of data, is the rated frequency of the power system, Adjust the power of the synchronous units within the power system, is the response delay time constant of the primary frequency regulation of the power system; Estimation of the response delay time constant of primary frequency regulation in power system using successive approximation method , its estimated value The initial setting is 0, and the response delay time constant of the synchronous unit primary frequency regulation is calculated based on the estimated value of the response delay time constant of the primary frequency regulation. Its actual value The size relationship, The calculation formula is, （2）； like , then increase the estimated value of the response delay time constant of the frequency modulation by the adjustment step size. ;like , then reduce the estimated value of the response delay time constant of the frequency modulation by one adjustment step When satisfied When the condition is met, the estimated value of the response delay time constant of the primary frequency modulation obtained by successive approximation is output. ; If a frequency modulation response delay time constant estimate occurs In the case of alternating between two values, the adjustment step is shortened until the estimated value of the response delay time constant of the primary frequency modulation obtained by successive approximation can be output. .

2. The method for assisting primary frequency modulation of a power system with an electric energy storage virtual power plant according to claim 1, characterized in that: In S2: Under the assumption that there is an active power shortage in the initial stage of primary frequency regulation in the power system, the system frequency dynamics during the primary frequency regulation process are evaluated, assuming that the current capacity of the electric energy storage virtual power plant within the power system can assist the synchronous units in providing active power output response to the power system without delay. 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 j-th time step, the power system frequency at the end of the j-th time step is solved based on formula (3): （3）； In the formula 、 Respectively The power system frequency at the end of the j-th time step, It is the active power shortage in the initial stage of frequency regulation. Adjust the power of the synchronous units within the power system, is the inertia time constant of the synchronous units in the power system; When satisfied After the condition is met, the power system frequency calculation process ends, that is, after M time steps, the frequency reaches the steady-state value; 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 of the primary frequency regulation of the synchronous units in the power system in the jth time step is Calculation based on formula (4): （4）； Due to the existence of the response delay of the primary frequency regulation of the power system, the active output response of the primary frequency regulation of the synchronous units in the power system in the jth time step is The target value set by its primary frequency modulation control is not reached , the shortfall is made up by the energy storage virtual power plant to achieve a non-delayed primary frequency regulation active output response. The active output of the energy storage virtual power plant in the jth time step is Refer to formula (5) for setting: （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 when the frequency reaches 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; （6）； If the total active power output of the energy storage virtual power plant within M time steps is less than its allowed discharge capacity, the energy storage capacity constraint can be met; （7）； In the formula is the state of charge of the energy storage virtual power plant at the initial moment of frequency regulation, is the minimum state of charge allowed for the energy storage virtual power plant, For the capacity of the energy storage virtual power plant, Discharge efficiency of virtual power plants for 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 during 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.

3. The method for assisting primary frequency regulation of a power system with an electric energy storage virtual power plant according to claim 2, characterized in that: The S3 includes the following steps: If the current capacity of the energy storage virtual power plant within the power system is insufficient to assist the synchronous generators in providing the power system with a delay-free primary frequency regulation active output response, that is, if the active output of the energy storage virtual power plant cannot simultaneously meet 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, the active output of the 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 when the frequency reaches 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 ; （8）； 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 capacity. If satisfied , then the active output adjustment of the electric energy storage virtual power plant in the auxiliary primary frequency regulation process is completed; otherwise, based on formula (9), the active output of the electric energy storage virtual power plant in the auxiliary primary frequency regulation process is further adjusted to meet the electric energy storage capacity constraint; （9）； If the active output of the energy storage virtual power plant does not meet its energy storage capacity constraint within M time steps when the frequency reaches 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 ; （10）。

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