Comprehensive design method for unit regulation power and damping coefficient of energy storage-containing grid-connected power generation system

Abstract

The invention discloses a unit regulation power and damping coefficient comprehensive design method of an energy storage-containing grid-connected power generation system. The method comprises the following steps: step 1, constructing a frequency dynamic response model of an energy storage grid-connected power generation system containing a second-order differential damping link; 2, a second-order differential damping link is additionally arranged, and decoupling control over the energy storage unit adjusting power and the damping coefficient is achieved; 3, according to the frequency steady state deviation constraint of the energy storage grid-connected power generation system containing the second-order differential damping link, designing energy storage unit regulation power based on a primary frequency modulation demand; 4, according to the oscillation suppression requirement of the energy storage grid-connected power generation system containing the second-order differential damping link, the energy storage damping coefficient is designed based on the optimal damping ratio constraint; and 5, putting forward an energy storage unit regulation power and damping coefficient comprehensive design method in combination with the frequency stability constraint and oscillation suppression requirements of the energy storage grid-connected power generation system containing the second-order differential damping link. According to the comprehensive design method for the energy storage unit regulation power and the damping coefficient, the primary frequency modulation performance and the virtual damping support of energy storage can be brought into full play, and the frequency stability and the power oscillation suppression capability of an energy storage support system can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency support and oscillation suppression of a new type of power system with high penetration of new energy, and in particular to a comprehensive design method of unit regulation power and damping coefficient of a grid-connected power generation system including energy storage. Background Art

[0002] Theoretically, energy storage devices under virtual synchronous control have both frequency support and oscillation suppression potential, but there are always design contradictions in multi-objective integrated control. When designing the unit regulation power and virtual damping parameters of virtual synchronous machines, droop control is adopted, which results in mutual constraints between the unit regulation power of virtual synchronous machines and the damping vibration suppression control target. It is difficult to ensure the steady-state frequency safety of the system by adjusting the damping coefficient according to the optimal damping ratio. It is also difficult to maintain the system damping ratio within a reasonable range by designing the primary frequency regulation coefficient according to the expected droop ratio, which is not conducive to oscillation suppression. To this end, existing literature has proposed a decoupling control scheme that realizes the dual control targets of unit regulation power and virtual damping parameters of energy storage by introducing a multi-objective autonomous collaborative control link for energy storage grid-connected power generation systems. However, after introducing a multi-objective autonomous collaborative control link for energy storage grid-connected power generation systems, how to coordinate the design of the unit regulation power and damping coefficient of the controller, give full play to the unit regulation power and damping support of energy storage, and effectively ensure the frequency stability and power oscillation suppression capability of new power systems under high penetration of new energy is still an urgent problem to be solved. Summary of the invention

[0003] The present invention provides a comprehensive design method for unit regulation power and damping coefficient of a grid-connected power generation system containing energy storage, which is conducive to giving full play to the unit regulation power and damping support of the grid-connected power generation system containing energy storage, and can significantly improve the frequency stability and power oscillation suppression capability of the support system of the grid-connected power generation system containing energy storage.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system including energy storage comprises the following steps:

[0006] Step 1: Construct a frequency dynamic response model of the energy storage grid-connected power generation system with a second-order differential damping link;

[0007] Step 2: Add a second-order differential damping link to achieve decoupling control of energy storage unit regulation power and damping coefficient;

[0008] Step 3: Design the energy storage unit regulation power based on the primary frequency regulation demand according to the frequency steady-state deviation constraint of the energy storage grid-connected power generation system containing the second-order differential damping link;

[0009] Step 4: Design the energy storage damping coefficient based on the optimal damping ratio constraint according to the oscillation suppression demand of the energy storage grid-connected power generation system containing the second-order differential damping link;

[0010] Step 5: In combination with the frequency stability constraints and oscillation suppression requirements of the energy storage grid-connected power generation system containing a second-order differential damping link, a comprehensive design method for the energy storage unit regulation power and damping coefficient is proposed.

[0011] Optionally, the step 1: constructing a frequency dynamic response model of an energy storage grid-connected power generation system including a second-order differential damping link specifically includes:

[0012] After the introduction of the unit regulation power and damping integrated controller, the motion equation of the virtual synchronous machine is:

[0013]

[0014] In the formula, H v , D v , K f are the inertia time constant, virtual damping coefficient and unit regulation power of the virtual synchronous machine respectively; P ref With P B are the output active power setting value and actual output electromagnetic power of the virtual synchronous machine respectively; ω v and ω0 are the virtual angular velocity of the virtual synchronous machine and the angular velocity of the power grid.

[0015] When the energy storage is connected to the grid through the unit power regulation and damping integrated controller, the frequency response dynamic equation of the grid-connected power generation system taking into account the penetration rate of new energy is:

[0016] (1-k)ΔP G +ηkΔP B +ΔP L =ΔP d

[0017] Where k is the penetration rate of new energy, η represents the proportion of energy storage to new energy capacity; ΔP d is the load disturbance power; ΔP G , ΔP B With ΔP L The power responses of synchronous machine, energy storage and load are expressed as

[0018]

[0019] In the formula, H G , D G and σ are the inertia time constant, damping coefficient and adjustment coefficient of the synchronous machine respectively; K L is the load regulation factor;

[0020] From the above analysis, the system frequency response model expression can be obtained as follows:

[0021]

[0022] Where H is the equivalent inertia time constant after system capacity reduction, which can be expressed as

[0023] H=(1-k)H G +ηkH V

[0024] Taking the pull-type change of the system frequency response model expression, the frequency domain expression of the system frequency response can be obtained as follows:

[0025]

[0026] In the formula, ω n is the undamped natural oscillation frequency of the synchronous power generation system, ξ is the damping ratio of the synchronous power generation system, which are expressed as

[0027]

[0028] In order to conservatively evaluate the frequency stability requirements of the system, the present invention takes the load disturbance as a step response, and quantitatively calculates the frequency dynamic response characteristics of the grid-connected power generation system containing energy storage after being disturbed; the frequency domain expression of the system frequency response is subjected to the inverse transformation of the Lapland type, and the time domain expression of the system frequency response taking into account the new energy penetration rate can be obtained as follows:

[0029]

[0030] In the formula, each parameter is expressed as

[0031]

[0032] Optionally, the step 2: adding a second-order differential damping link to achieve decoupling control of the energy storage unit regulation power and the damping coefficient, specifically includes:

[0033] The system equivalent unit regulation power coefficient of the grid-connected power generation system containing energy storage can be obtained from the frequency domain expression of the system frequency response:

[0034]

[0035] In the formula, K s is the system equivalent unit adjustment power coefficient of the energy storage grid-connected power generation system, expressed as

[0036] K S =(1-k)D G +(1-k) / σ+ηkK f +K L

[0037] From the above formula, it can be seen that when the energy storage grid-connected power generation system introduces a comprehensive controller of unit adjustment power and damping coefficient, K f With D v Decoupling control, only increase the energy storage K f Without considering D v This can enhance the unit regulation power of the grid-connected power generation system, thereby reducing the steady-state frequency deviation Δf s The damping coefficient and the adjustment coefficient of the synchronous machine are limited by the stability constraint and have a small adjustable range, so they are regarded as fixed values. f Improve the unit regulation power of the grid-connected power generation system.

[0038] Optionally, the step 3: implementing the design of the energy storage unit regulation power based on the primary frequency regulation demand according to the frequency steady-state deviation constraint of the energy storage grid-connected power generation system including the second-order differential damping link, specifically includes:

[0039] At present, the national standard GB / T15945-2008 stipulates that the allowable range of frequency deviation in my country is ±0.2Hz to ±0.5Hz; therefore, the present invention takes the steady-state frequency deviation value not higher than ±0.2Hz as a constraint condition. The unit regulation power requirement of energy storage under the steady-state frequency deviation constraint can be obtained from the system equivalent unit regulation power coefficient Ks of the grid-connected power generation system containing energy storage:

[0040]

[0041] Optionally, the step 4: implementing the design of the energy storage damping coefficient based on the optimal damping ratio constraint according to the oscillation suppression requirement of the energy storage grid-connected power generation system including the second-order differential damping link, specifically includes:

[0042] The grid-connected power generation system with energy storage should also have the ability to suppress power oscillations. Its oscillation suppression ability can be expressed by the damping ratio. The larger the damping ratio, the better the oscillation suppression effect. However, it cannot be ignored that the power generation system with too large a damping ratio has a slower power response speed. In order to take into account both the fast response speed and oscillation suppression ability of the new power system, in engineering design, it is generally hoped that the damping ratio is between 0.5 and 1. At the optimal damping ratio ξ opt The constraint is near the best, at which point the grid-connected power generation system has good dynamic performance and oscillation suppression capabilities. In practical applications, this constraint can be adjusted according to the actual grid operation requirements to design the damping coefficient of the grid-connected power generation system with energy storage.

[0043] Optionally, the step 5: combining the frequency stability constraint and oscillation suppression requirement of the energy storage grid-connected power generation system containing the second-order differential damping link, proposes a comprehensive design method for energy storage unit regulation power and damping coefficient, specifically including:

[0044] Considering that the disturbance power of the load is random, impactful and intermittent in the actual operation of the power grid, the method of adaptively adjusting the controller parameters by real-time detection of the disturbance power will cause the controller to start and stop frequently, and it is difficult to ensure the safety of the system under complex faults. Therefore, in the demand assessment, the present invention uses the historical maximum disturbance power ΔP encountered by the power grid as the dmax Conservatively evaluate the frequency regulation demand of the system, combine the actual operation data of the regional power grid, and take ΔP dmax =0.1P N , the parameter setting can be adjusted according to the actual grid operation status; the demand assessment of the present invention comprehensively considers the steady-state frequency deviation and oscillation suppression requirements of the grid-connected power generation system containing energy storage, and has two evaluation functions of unit regulation power and damping coefficient. The parameter evaluation process is as follows:

[0045] Since the integrated control module of unit regulation power and damping coefficient has both unit regulation power and virtual damping support capabilities, the unit regulation power of the controller is improved, which has the ability to enhance system stability; therefore, the present invention is based on the steady-state frequency deviation constraint and the possible maximum disturbance power ΔP dmax and system parameters, conservatively estimate the unit regulation power K of energy storage f need.

[0046] In order to ensure the system's oscillation suppression capability and rapid response speed, the present invention needs to substitute the unit regulation power of the energy storage device into the optimal damping ratio constraint expression to solve the damping coefficient of the energy storage, taking into account the rapid response characteristics and oscillation suppression capability of the new power system.

[0047] In order to prevent the low-frequency load shedding device of the power system from being triggered under large load disturbances, my country's "State Grid Corporation Power Supply Service Quality Standard" stipulates that the maximum transient frequency deviation of the power grid shall not exceed 1Hz; therefore, the present invention sets the first round action value of the low-frequency load shedding device as the maximum transient frequency deviation constraint of the system;

[0048] After the load disturbance, the time t when the system output power and load power first reach a balance again fm It is the extreme point of the frequency response equation. At this time, df / dt=0. The corresponding extreme value is the maximum transient frequency deviation of the system. By differentiating the time domain expression of the system frequency response, we can get

[0049]

[0050] Substituting the above formula into the system frequency response time domain expression, the maximum frequency deviation equation of the system after load disturbance can be calculated.

[0051]

[0052] In order to ensure the frequency safety of the system, the present invention can use the above formula as an evaluation function to verify the reliability of the unit regulation power and damping coefficient design results of the above energy storage; the maximum frequency change Δf of the system under the condition of meeting the steady-state frequency deviation constraint and oscillation suppression requirements can be obtained. max , and judge whether it meets the frequency transient deviation constraint; when Δf max When ≤1Hz, it is considered that the frequency safety requirement can be met; when Δf max ≥1Hz, the controller's unit adjustment power K needs to be updated f and the damping coefficient D V Until the frequency transient deviation constraint is met, a better unit regulation power and damping coefficient are calculated; at this point, all the frequency safety constraints proposed in the present invention are met.

[0053] Compared with the existing technology, this technology has the following beneficial effects:

[0054] The present invention provides a comprehensive design method for unit regulating power and damping coefficient of a grid-connected power generation system containing energy storage. Compared with the traditional method, a frequency dynamic response model of the energy storage grid-connected power generation system containing a second-order differential damping link is first constructed; secondly, a second-order differential damping link is added to realize the decoupling control of the energy storage unit regulating power and the damping coefficient; thirdly, the energy storage unit regulating power is designed based on the primary frequency regulation demand according to the frequency steady-state deviation constraint of the energy storage grid-connected power generation system containing the second-order differential damping link; thirdly, the energy storage damping coefficient is designed based on the optimal damping ratio constraint according to the oscillation suppression demand of the energy storage grid-connected power generation system containing the second-order differential damping link; finally, combined with the frequency stability constraint and oscillation suppression demand of the energy storage grid-connected power generation system containing the second-order differential damping link, a comprehensive design method for unit regulating power and damping coefficient of energy storage is proposed. The comprehensive design method for unit regulating power and damping coefficient provided by the present invention is conducive to giving full play to the primary frequency regulation performance and damping support of energy storage, and can significantly improve the frequency stability and power oscillation suppression ability of the energy storage support system.

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0056] Figure 1 It is a flow chart of designing unit regulating power and virtual damping parameters of energy storage under comprehensive control of unit regulating power and damping coefficient in an embodiment of the present invention;

[0057] Figure 2It is a diagram of a control structure of an energy storage grid-connected power generation system and an embodiment of the present invention based on the introduction of comprehensive control of unit adjustment power and damping coefficient;

[0058] Figure 3 It is a flow chart of coordinated design of unit regulation power and damping coefficient of energy storage grid-connected power generation system based on the introduction of comprehensive control of unit regulation power and damping coefficient in an embodiment of the present invention;

[0059] Figure 4 is a topology diagram of a simulation system according to an embodiment of the present invention;

[0060] Figure 5 is a dynamic response curve of the system when the disturbance suddenly increases in the embodiment of the present invention;

[0061] Figure 6 is a dynamic response curve of the system during free oscillation in the embodiment of the present invention; DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] The comprehensive design method of unit regulation power and damping coefficient provided by the present invention is conducive to giving full play to the primary frequency regulation performance and damping support of energy storage, and can significantly improve the frequency stability and power oscillation suppression capabilities of the energy storage support system.

[0064] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Figure 1 : is a flow chart of the design of unit regulating power and virtual damping parameters of energy storage under the comprehensive control of unit regulating power and damping coefficient in an embodiment of the present invention, such as Figure 1 As shown, the following steps are included:

[0066] Step 1: Construct a frequency dynamic response model of the energy storage grid-connected power generation system with a second-order differential damping link;

[0067] Step 2: Add a second-order differential damping link to achieve decoupling control of energy storage unit regulation power and damping coefficient;

[0068] Step 3: Design the energy storage unit regulation power based on the primary frequency regulation demand according to the frequency steady-state deviation constraint of the energy storage grid-connected power generation system containing the second-order differential damping link;

[0069] Step 4: Design the energy storage damping coefficient based on the optimal damping ratio constraint according to the oscillation suppression demand of the energy storage grid-connected power generation system containing the second-order differential damping link;

[0070] Step 5: In combination with the frequency stability constraints and oscillation suppression requirements of the energy storage grid-connected power generation system containing a second-order differential damping link, a comprehensive design method for the energy storage unit regulation power and damping coefficient is proposed.

[0071] Theoretically, energy storage devices under virtual synchronous control have both frequency support and oscillation suppression potential, but there are always design contradictions in multi-objective integrated control. When designing the unit regulation power and virtual damping parameters of virtual synchronous machines, droop control is adopted, which results in mutual constraints between the unit regulation power of virtual synchronous machines and the damping vibration suppression control target. It is difficult to ensure the steady-state frequency safety of the system by adjusting the damping coefficient according to the optimal damping ratio. It is also difficult to maintain the system damping ratio within a reasonable range by designing the primary frequency regulation coefficient according to the expected droop ratio, which is not conducive to oscillation suppression. To this end, existing literature has proposed a decoupling control scheme that realizes the dual control targets of unit regulation power and virtual damping parameters of energy storage by introducing a multi-objective autonomous collaborative control link for energy storage grid-connected power generation systems. However, after introducing a multi-objective autonomous collaborative control link for energy storage grid-connected power generation systems, how to coordinate the design of the unit regulation power and damping coefficient of the controller, give full play to the unit regulation power and damping support of energy storage, and effectively ensure the frequency stability and power oscillation suppression capability of new power systems under high penetration of new energy is still an urgent problem to be solved.

[0072] The energy storage grid-connected power generation system and control structure diagram based on the introduction of unit regulation power and damping coefficient comprehensive control are as follows: Figure 2 shown.

[0073] Depend on Figure 2 The motion equation of the virtual synchronous machine after introducing the integrated controller of unit regulation power and damping coefficient is obtained as follows:

[0074]

[0075] In the formula, H v , D v , K f are the inertia time constant, virtual damping coefficient and unit regulation power of the virtual synchronous machine respectively; P ref With P B are the output active power setting value and actual output electromagnetic power of the virtual synchronous machine respectively; ω v and ω0 are the virtual angular velocity of the virtual synchronous machine and the angular velocity of the power grid.

[0076] When the energy storage is connected to the grid through a unit-adjusted power and damping coefficient integrated controller, the frequency response dynamic equation of the grid-connected power generation system taking into account the penetration rate of new energy is:

[0077] (1-k)ΔP G +ηkΔP B +ΔP L =ΔP d (2)

[0078] Where k is the penetration rate of new energy, η represents the proportion of energy storage to new energy capacity; ΔP d is the load disturbance power; ΔP G , ΔP B With ΔP L The power responses of synchronous machine, energy storage and load are expressed as

[0079]

[0080] In the formula, H G , D G and σ are the inertia time constant, damping coefficient and adjustment coefficient of the synchronous machine respectively; K L is the load regulation factor;

[0081] Substituting equation (3) into equation (2), the system frequency response model expression is:

[0082]

[0083] Where H is the equivalent inertia time constant after system capacity reduction, which can be expressed as

[0084] H=(1-k)H G +ηkH V (5)

[0085] By taking the pull-type change from equation (4), the frequency domain expression of the system frequency response can be obtained as

[0086]

[0087] In the formula, ω n is the undamped natural oscillation frequency of the synchronous power generation system, ξ is the damping ratio of the synchronous power generation system, which are expressed as

[0088]

[0089] In order to conservatively evaluate the frequency stability requirements of the system, the present invention takes the load disturbance as a step response and quantitatively calculates the frequency dynamic response characteristics of the grid-connected power generation system containing energy storage after being disturbed. By taking the inverse transformation of the Lapland formula (6), the time domain expression of the system frequency response taking into account the penetration rate of new energy can be obtained as follows:

[0090]

[0091] In the formula, each parameter is expressed as

[0092]

[0093] At present, the national standard GB / T15945-2008 stipulates that the allowable range of frequency deviation in my country is ±0.2Hz to ±0.5Hz; therefore, the present invention takes the steady-state frequency deviation value not higher than ±0.2Hz as the constraint condition to evaluate the control parameter requirements of the unit regulation power and damping ratio integrated controller; the equivalent unit regulation power coefficient of the grid-connected power generation system can be obtained from formula (8):

[0094]

[0095] In the formula, K s is the equivalent unit adjustment power factor of the grid-connected power generation system, expressed as

[0096] K S =(1-k)D G +(1-k) / σ+ηkK f +K L (11)

[0097] From formula (11), it can be seen that when the energy storage grid-connected power generation system introduces the integrated controller of unit regulation power and damping coefficient, K f With D v Decoupling control, only increase the energy storage K f Without considering D v This can enhance the unit regulation power of the grid-connected power generation system, thereby reducing the steady-state frequency deviation Δf s The damping coefficient and the adjustment coefficient of the synchronous machine are limited by the stability constraint and have a small adjustable range, so they are regarded as fixed values. f Improve the unit regulation power of the grid-connected power generation system.

[0098] Combining equations (10) and (11), we can obtain the unit regulation power requirement of energy storage under the constraint of steady-state frequency deviation:

[0099]

[0100] The grid-connected power generation system with energy storage should also have the ability to suppress power oscillations. Its oscillation suppression ability can be expressed by the damping ratio. The larger the damping ratio, the better the oscillation suppression effect. However, it cannot be ignored that the power generation system with too large a damping ratio has a slower power response speed. In order to take into account both the fast response speed and oscillation suppression ability of the new power system, in engineering design, it is generally hoped that the damping ratio is between 0.5 and 1. At the optimal damping ratio ξ opt The constraint is near the best, at which point the grid-connected power generation system has good dynamic performance and oscillation suppression capabilities. In practical applications, this constraint can be adjusted according to the actual grid operation requirements to design the damping coefficient of the grid-connected power generation system with energy storage.

[0101] The grid-connected power generation system damping ratio ξ is set to 0.707, and K fmin Substituting into equation (7) we can design the energy storage damping coefficient D that satisfies the optimal damping ratio constraint: V :

[0102]

[0103] In order to prevent the low-frequency load shedding device of the power system from being triggered under large load disturbances, my country's "State Grid Corporation Power Supply Service Quality Standard" stipulates that the maximum transient frequency deviation of the power grid shall not exceed 1Hz. Therefore, the present invention sets the first round action value of the low-frequency load shedding device as the maximum transient frequency deviation constraint of the system.

[0104] After the load disturbance, the time t when the system output power and load power first reach a balance again fm is the extreme point of the frequency response equation. At this time, df / dt=0. The corresponding extreme value is the maximum transient frequency deviation of the system. By taking the derivative of equation (8), we can get

[0105]

[0106] Substituting equation (14) into equation (8) can calculate the maximum frequency deviation equation of the system after load disturbance:

[0107]

[0108] From the above analysis, it can be seen that in order to ensure the frequency safety of the system, the present invention designs the unit regulation power and damping coefficient of the energy storage controller according to formula (12) and formula (13), and uses formula (15) as the evaluation function to update and calculate the unit regulation power and damping coefficient of the energy storage controller, thereby ensuring that the grid-connected power generation system satisfies both the frequency steady-state deviation constraint and the frequency transient deviation constraint.

[0109] Figure 3 This is a flowchart of the coordinated design of unit regulation power and damping coefficient of the energy storage grid-connected power generation system based on the introduction of comprehensive control of unit regulation power and damping coefficient in the embodiment of the present invention. Considering that in the actual operation of the power grid, the disturbance power of the load is random, impactful and intermittent, the method of adaptively adjusting the controller parameters by real-time detection of the disturbance power will cause the controller to start and stop frequently, and it is difficult to ensure the safety of the system under complex faults; for this reason, in the demand assessment, the present invention uses the historical maximum disturbance power ΔP encountered by the power grid dmax Conservatively evaluate the frequency regulation demand of the system, combine the actual operation data of the regional power grid, and take ΔP dmax =0.1P N, the parameter setting can be adjusted according to the actual grid operation status; the demand assessment of the present invention comprehensively considers the steady-state frequency deviation and oscillation suppression requirements of the grid-connected power generation system containing energy storage, and has two evaluation functions of unit regulation power and damping coefficient. The parameter evaluation process is as follows:

[0110] Since the integrated control module of unit regulating power and damping coefficient has both unit regulating power and virtual damping support capabilities, the unit regulating power of the controller is improved, which has the ability to enhance system stability; therefore, the present invention is based on the steady-state frequency deviation constraint and the possible maximum disturbance power ΔP by formula (12). dmax and system parameters, conservatively estimate the unit regulation power K of energy storage f need.

[0111] In order to ensure the system's oscillation suppression capability and rapid response speed, the present invention needs to substitute the unit regulation power of the energy storage device into the optimal damping ratio constraint (13) expression to solve the damping coefficient of the energy storage, taking into account the rapid response characteristics and oscillation suppression capability of the new power system.

[0112] In order to ensure the frequency safety of the system, the present invention can use formula (15) as an evaluation function to verify the reliability of the unit regulation power and damping coefficient design results of the above energy storage; the maximum frequency change Δf of the system under the condition of meeting the steady-state frequency deviation constraint and oscillation suppression requirements can be obtained. max , and judge whether it meets the frequency transient deviation constraint; when Δf max When ≤1Hz, it is considered that the frequency safety requirement can be met; when Δf max ≥1Hz, the controller's unit adjustment power K needs to be updated f and the damping coefficient D V Until the frequency transient deviation constraint is met, a better unit regulation power and damping coefficient are calculated; at this point, all the frequency safety constraints proposed in the present invention are met.

[0113] Figure 4 This is a topology diagram of the simulation system of the embodiment of the present invention. The present invention is based on the DIGSILENT / Power Factory simulation environment to build Figure 4 The basic parameters of the IEEE three-machine nine-node simulation model are shown in Table 1.

[0114] Table 1 Basic parameters of IEEE three-machine nine-section power grid with high proportion of wind farms

[0115]

[0116]

[0117] The simulation sets the fan penetration rates to 20%, 40%, and 60%, respectively, and the controller parameters are designed based on the demand assessment results.

[0118] Example 1: Under different wind power penetration rates, the load L1 active power suddenly increases to the maximum disturbance power in history when the simulation is set at 2s to verify the controller performance under the proposed parameter design method. The system dynamic response is as follows: Figure 5 shown.

[0119] like Figure 5 As shown, when the grid-connected power generation system including energy storage adopts the unit regulation power and virtual damping parameter design method of energy storage under the comprehensive control of unit regulation power and damping ratio provided by the present invention, the energy storage controller conservatively evaluates the virtual damping and unit regulation power requirements of the grid-connected power generation system including energy storage based on the new energy penetration rate and the historical maximum load disturbance power, and the energy storage device dynamically responds to frequency changes.

[0120] Example 2: To verify the suppression effect of the energy storage power generation system on the free oscillation of the system power using the proposed parameter design method. When the simulation is set to 2s, the line L 6-9 The three phases are short-circuited and the fault is cleared after 0.1s. The test results are as follows Figure 6 shown.

[0121] Depend on Figure 6 It can be seen that when the energy storage equipment has no additional control, it does not respond to changes in system frequency and does not have damping support capabilities. After the system short-circuit fault, continuous power oscillation occurs. After the short-circuit fault is removed, the system frequency and the power of the synchronous machine G2 continue to oscillate, and the oscillation time exceeds 15s, which seriously threatens the safety of the system.

[0122] After adopting the parameter design method proposed in the present invention, the energy storage has a good damping support effect, which greatly improves the oscillation suppression ability of the system.

[0123] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0124] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. The present invention discloses a method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system including energy storage, characterized in that: The following steps are involved: Step 1: Construct a frequency dynamic response model of the energy storage grid-connected power generation system with a second-order differential damping link; Step 2: Add a second-order differential damping link to achieve decoupling control of energy storage unit regulation power and damping coefficient; Step 3: Design the energy storage unit regulation power based on the primary frequency regulation demand according to the frequency steady-state deviation constraint of the energy storage grid-connected power generation system containing the second-order differential damping link; Step 4: Design the energy storage damping coefficient based on the optimal damping ratio constraint according to the oscillation suppression demand of the energy storage grid-connected power generation system containing the second-order differential damping link; Step 5: Based on the frequency stability constraints and oscillation suppression requirements of the energy storage grid-connected power generation system containing the second-order differential damping link, a comprehensive design method for the energy storage unit regulation power and damping coefficient is proposed.

2. The method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system with energy storage according to claim 1, characterized in that: The step 1: constructing a frequency dynamic response model of an energy storage grid-connected power generation system including a second-order differential damping link, specifically comprising: After the introduction of the unit regulation power and damping integrated controller, the motion equation of the virtual synchronous machine is: In the formula, H v , D v , K f are the inertia time constant, virtual damping coefficient and unit regulation power of the virtual synchronous machine respectively; P ref With P B are the output active power setting value and actual output electromagnetic power of the virtual synchronous machine respectively; ω v and ω0 are the virtual angular velocity of the virtual synchronous machine and the angular velocity of the power grid. When the energy storage is connected to the grid through the unit power regulation and damping integrated controller, the frequency response dynamic equation of the grid-connected power generation system taking into account the penetration rate of new energy is: (1-k)ΔP G +ηkΔP B +ΔP L =ΔP d Where k is the penetration rate of new energy, η represents the proportion of energy storage to new energy capacity; ΔP d is the load disturbance power; ΔP G , ΔP B With ΔP L The power responses of synchronous machine, energy storage and load are expressed as In the formula, H G , D G and σ are the inertia time constant, damping coefficient and adjustment coefficient of the synchronous machine respectively; K L is the load regulation factor; From the above analysis, the system frequency response model expression can be obtained as follows: Where H is the equivalent inertia time constant after system capacity reduction, which can be expressed as H=(1-k)H G +ηkH V Taking the pull-type change of the system frequency response model expression, the frequency domain expression of the system frequency response can be obtained as follows: In the formula, ω n is the undamped natural oscillation frequency of the synchronous power generation system, ξ is the damping ratio of the synchronous power generation system, which are expressed as In order to conservatively evaluate the frequency stability requirements of the system, the present invention takes the load disturbance as a step response, and quantitatively calculates the frequency dynamic response characteristics of the grid-connected power generation system containing energy storage after being disturbed; the frequency domain expression of the system frequency response is subjected to the inverse transformation of the Lapland type, and the time domain expression of the system frequency response taking into account the new energy penetration rate can be obtained as follows: In the formula, each parameter is expressed as 3. The method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system with energy storage according to claim 1, characterized in that: The step 2: adding a second-order differential damping link to realize the decoupling control of the energy storage unit regulation power and the damping coefficient, specifically includes: The equivalent unit regulation power coefficient of the system including energy storage grid-connected power generation system can be obtained from the frequency domain expression of the system frequency response: In the formula, K s is the system equivalent unit adjustment power coefficient of the energy storage grid-connected power generation system, expressed as K S =(1-k)D G +(1-k) / σ+ηkK f +K L From the above formula, it can be seen that when the energy storage grid-connected power generation system introduces a comprehensive controller of unit adjustment power and damping coefficient, K f With D v Decoupling control, only increase the energy storage K f Without considering D v This can enhance the unit regulation power of the grid-connected power generation system, thereby reducing the steady-state frequency deviation Δf s The damping coefficient and the adjustment coefficient of the synchronous machine are limited by the stability constraint and have a small adjustable range, so they are regarded as fixed values. f Improve the unit regulation power of the grid-connected power generation system.

4. The method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system with energy storage according to claim 1, characterized in that: The step 3: designing the energy storage unit regulation power based on the primary frequency regulation demand according to the frequency steady-state deviation constraint of the energy storage grid-connected power generation system including the second-order differential damping link, specifically includes: At present, the national standard GB / T15945-2008 stipulates that the allowable range of frequency deviation in my country is ±0.2Hz to ±0.5Hz; therefore, the present invention takes the steady-state frequency deviation value not higher than ±0.2Hz as a constraint condition. The unit regulation power requirement of energy storage under the steady-state frequency deviation constraint can be obtained from the system equivalent unit regulation power coefficient Ks of the grid-connected power generation system containing energy storage:

5. The method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system with energy storage according to claim 1, characterized in that: The step 4: designing the energy storage damping coefficient based on the optimal damping ratio constraint according to the oscillation suppression demand of the energy storage grid-connected power generation system including the second-order differential damping link, specifically includes: The grid-connected power generation system with energy storage should also have the ability to suppress power oscillations. Its oscillation suppression ability can be expressed by the damping ratio. The larger the damping ratio, the better the oscillation suppression effect. However, it cannot be ignored that the power generation system with too large a damping ratio has a slower power response speed. In order to take into account both the fast response speed and oscillation suppression ability of the new power system, in engineering design, it is generally hoped that the damping ratio is between 0.5 and 1. At the optimal damping ratio ξ opt The constraint is optimal near the grid, at which point the grid-connected power generation system has good dynamic performance and oscillation suppression capability. In practical applications, this constraint can be adjusted according to the actual grid operation requirements to design the damping coefficient of the grid-connected power generation system with energy storage.

6. The method for comprehensive design of unit regulation power and damping coefficient of a grid-connected power generation system with energy storage according to claim 1, characterized in that: The step 5: combining the frequency stability constraint and oscillation suppression requirement of the energy storage grid-connected power generation system with the second-order differential damping link, a comprehensive design method of energy storage unit regulation power and damping coefficient is proposed, which specifically includes: Considering that the disturbance power of the load is random, impactful and intermittent in the actual operation of the power grid, the method of adaptively adjusting the controller parameters by real-time detection of the disturbance power will cause the controller to start and stop frequently, and it is difficult to ensure the safety of the system under complex faults. Therefore, in the demand assessment, the present invention uses the historical maximum disturbance power ΔP encountered by the power grid as the dmax Conservatively evaluate the frequency regulation demand of the system, combine the actual operation data of the regional power grid, and take ΔP dmax =0.1P N , the parameter setting can be adjusted according to the actual grid operation status; the demand assessment of the present invention comprehensively considers the steady-state frequency deviation and oscillation suppression requirements of the grid-connected power generation system containing energy storage, and has two evaluation functions of unit regulation power and damping coefficient. The parameter evaluation process is as follows: Since the integrated control module of unit regulation power and damping coefficient has both unit regulation power and virtual damping support capabilities, the unit regulation power of the controller is improved, which has the ability to enhance system stability; therefore, the present invention is based on the steady-state frequency deviation constraint and the possible maximum disturbance power ΔP dmax and system parameters, conservatively estimate the unit regulation power K of energy storage f need. In order to ensure the system's oscillation suppression capability and rapid response speed, the present invention needs to substitute the unit regulation power of the energy storage device into the optimal damping ratio constraint expression to solve the damping coefficient of the energy storage, taking into account the rapid response characteristics and oscillation suppression capability of the new power system. In order to prevent the low-frequency load shedding device of the power system from being triggered under large load disturbances, my country's "State Grid Corporation Power Supply Service Quality Standard" stipulates that the maximum transient frequency deviation of the power grid shall not exceed 1Hz; therefore, the present invention sets the first round action value of the low-frequency load shedding device as the maximum transient frequency deviation constraint of the system; After the load disturbance, the time t when the system output power and load power first reach a balance again fm It is the extreme point of the frequency response equation. At this time, df / dt=0. The corresponding extreme value is the maximum transient frequency deviation of the system. By differentiating the time domain expression of the system frequency response, we can get Substituting the above formula into the system frequency response time domain expression, the maximum frequency deviation equation of the system after load disturbance can be calculated. In order to ensure the frequency safety of the system, the present invention can use the above formula as an evaluation function to verify the reliability of the unit regulation power and damping coefficient design results of the above energy storage; the maximum frequency change Δf of the system under the condition of meeting the steady-state frequency deviation constraint and oscillation suppression requirements can be obtained. max , and judge whether it meets the frequency transient deviation constraint; when Δf max When ≤1Hz, it is considered that the frequency safety requirement can be met; when Δf max ≥1Hz, the controller's unit adjustment power K needs to be updated f and the damping coefficient D V Until the frequency transient deviation constraint is met, a better unit regulation power and damping coefficient are calculated; at this point, all the frequency safety constraints proposed in the present invention are met.

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