Active power coordination control method for photovoltaic station containing distributed phase modifier and hybrid energy storage

Abstract

The invention relates to the technical field of power system automation control, in particular to an active power coordination control method for a photovoltaic station containing a distributed phase modifier and hybrid energy storage. According to the technical scheme, the active power coordination control method for the photovoltaic station containing the distributed phase modifier and the hybrid energy storage comprises the steps that S1, data of the photovoltaic station, the distributed phase modifier, a super capacitor and a lithium battery are collected in real time; s2, inertia response control is carried out; s3, primary frequency modulation response control; s4, power smooth control is carried out; and S5, superposing the active instructions of the inertia response, the primary frequency modulation response and the power smooth control. The hybrid energy storage system comprising the distributed phase modifier, the super capacitor and the lithium battery is constructed, the response characteristics of different energy storage units are fully played, and the control requirements of multiple time scales such as station inertia, primary frequency modulation and power smoothness can be met at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of power system automation control, and particularly to an active power coordination control method for a photovoltaic power station with distributed synchronous condensers and hybrid energy storage. Background Art

[0002] With the continuous increase in the proportion of new energy (such as wind power and photovoltaic power) in the power system, the grid-connected operation stability of new energy power stations has become an important research topic in the field of power systems. Photovoltaic power generation has intermittency, volatility, and uncontrollability, and its power output is significantly affected by natural conditions, which easily leads to problems such as grid frequency fluctuations and voltage instability.

[0003] To address these challenges, energy storage systems and synchronous condenser technologies have been widely applied in new energy power stations to improve their grid-friendly performance and system stability. Energy storage systems (such as battery energy storage and supercapacitors) have fast response capabilities and can suppress new energy power fluctuations, but their capacity is limited and the cost is high, and frequent charge and discharge will shorten the equipment life.

[0004] As a dynamic reactive power compensation device, a distributed synchronous condenser can provide fast reactive power support and enhance grid voltage stability. However, its traditional application scenarios are mainly limited to reactive power regulation, and its rotor kinetic energy regulation ability has not been fully utilized. In recent years, domestic and foreign scholars have begun to explore the coordinated control strategies of energy storage and synchronous condensers to further improve the operating performance of new energy power stations.

[0005] However, existing technologies usually control energy storage and synchronous condensers separately, and the synchronous condenser is only used as a reactive power compensation device, without using its rotor kinetic energy for active power regulation, resulting in frequent operation of the energy storage system, shortened life, and failure to fully explore the coordinated potential of synchronous condensers and energy storage, especially in the multi-source and multi-time-scale power regulation of synchronous condensers, energy storage, and new energy, there are obvious deficiencies.

[0006] Existing photovoltaic power stations have significant deficiencies in active power flexible regulation. Without energy storage, they cannot respond to inertia and primary frequency modulation in real time, and the output power fluctuates, causing great operating pressure on the power grid.

[0007] Configuring energy storage can improve the inertia and frequency modulation ability of the power station, but due to the limited cycle life of lithium battery energy storage, it is not suitable for scenarios with frequent responses.

[0008] There is an urgent need for a new method that can fully explore the coordinated potential of synchronous condensers and energy storage, solve the multi-time-scale power distribution problem, and optimize the operating state of equipment.

[0009] A patent with the publication number CN109256786B, a method for active power coordinated control of a photovoltaic energy storage power station. The method includes: calculating the reference value of the active power of the photovoltaic energy storage power station according to the grid connection point frequency, the rate of change of frequency of the photovoltaic energy storage power station, and the active power control command of the automatic generation control of the power grid; determining the active power coordinated control mode of the photovoltaic energy storage power station according to the grid connection point frequency of the photovoltaic energy storage power station; based on the reference value of the active power and the active power coordinated control mode of the photovoltaic energy storage power station, obtaining the active power control commands of the photovoltaic unit and the energy storage unit, and adjusting the active power of the photovoltaic energy storage power station according to the active power control commands of the photovoltaic unit and the energy storage unit;

[0010] A patent with the publication number CN115411787A, a method for active power coordinated control of a wind-solar hybrid power generation system based on the ideal point method, which is applied to the grid-connected operation of the wind-solar hybrid power generation system. It includes applying the ideal point method to the design of the coordinated controller, establishing an objective function to be optimized with the grid connection benefit and power fluctuation of the wind-solar hybrid power generation system as indicators, using the multi-objective optimization results for the setting of the wind power generation subsystem and the photovoltaic power generation subsystem, and respectively adopting power closed-loop control for the two subsystems to achieve the coordinated control of the wind-solar hybrid power generation system; the above two patents do not make improvements to the problem that the output power is prone to fluctuation in the case of not configuring energy storage. Summary of the Invention

[0011] The present invention proposes an active power coordinated control method for a photovoltaic power station with distributed synchronous condensers and hybrid energy storage, which solves the problems in the prior art that there are significant deficiencies in the active power flexible regulation of photovoltaic power stations, and in the case of not configuring energy storage, it is impossible to respond to inertia and primary frequency modulation in real time, and the output power fluctuates, causing a large operating pressure on the power grid.

[0012] To solve the above technical problems, the technical solution adopted by the present invention is:

[0013] An active power coordinated control method for a photovoltaic power station with distributed synchronous condensers and hybrid energy storage, including:

[0014] Step S1: Real-time collect data of the photovoltaic power station, distributed synchronous condenser, supercapacitor and lithium battery;

[0015] Step S2: Inertia response control;

[0016] Step S3: Primary frequency modulation response control;

[0017] Step S4: Power smoothing control;

[0018] Step S5: Superimpose the active power commands of the three parts of inertia response, primary frequency modulation response and power smoothing control;

[0019] Step S6: Send the real-time active power control commands of the distributed synchronous condenser, supercapacitor and lithium battery to their respective power controllers for execution;

[0020] Step S7: When there is no inertia and primary frequency regulation response control requirement in the system, charge and discharge each energy storage unit according to a preset time period.

[0021] Furthermore, in step S1, data of the photovoltaic power station, distributed synchronous condenser, super capacitor and lithium battery are collected in real time, including the grid dispatching instruction P ref , predicted photovoltaic power generation P pre , actual active power P of the photovoltaic power station solar , active power P output by the distributed synchronous condenser sync , reactive power Q output by the distributed synchronous condenser sync , active power P of the super capacitor sc , active power P of the lithium battery bat , grid connection point voltage frequency f grid .

[0022] Furthermore, in step S2, the inertia response is jointly responded by the distributed synchronous condenser and the super capacitor, and the control process is as follows:

[0023] Calculate the inertia response demand P of the photovoltaic power station in real time inertia , and the calculation formula is:

[0024]

[0025] Δf = f grid - f N

[0026] where P inertia represents the inertia response demand of the photovoltaic power station; H represents the equivalent inertia constant of the photovoltaic power station; f N represents the grid reference frequency of 50 Hz; represents the rate of change of the grid connection point voltage frequency; P N represents the rated active power of the photovoltaic power station; P solar represents the actual active power of the photovoltaic power station; ε inertia represents the inertia response dead zone of the photovoltaic power station;

[0027] Decompose the inertia control instruction, and let the super capacitor respond to the high-frequency component first, and the distributed synchronous condenser supplement the medium- and low-frequency component requirements;

[0028]

[0029] where P sc_inertia represents the inertia response power of the super capacitor; P sync_inertia represents the inertia response power of the distributed synchronous condenser; T r_sc represents the active response time of the super capacitor; T r_syncIndicates the active response time of the distributed synchronous condenser; SOC sc Indicates the remaining power of the supercapacitor; SOC sync Indicates the remaining power converted by the distributed synchronous condenser.

[0030] Furthermore, the primary frequency regulation response control in step S3 is completed by the supercapacitor, the distributed synchronous condenser, and the lithium battery. The primary frequency regulation response is second-level control. When the frequency fluctuation exceeds the dead zone of primary frequency regulation action, the supercapacitor and the distributed synchronous condenser act quickly; in the middle and late stages of the primary frequency regulation action process, the supercapacitor and the distributed synchronous condenser withdraw from primary frequency regulation, and the lithium battery undertakes all the primary frequency regulation power;

[0031] Real-time calculate the primary frequency regulation response demand P of the photovoltaic power station primary , and the calculation formula is as follows:

[0032]

[0033] Where P primary Indicates the primary frequency regulation of the photovoltaic power station; P primary_max Indicates the active power limit value of the primary frequency regulation of the photovoltaic power station; K primary Indicates the droop rate of the primary frequency regulation of the photovoltaic power station;

[0034] Perform dynamic decomposition of the primary frequency regulation control command.

[0035] Furthermore, the process of performing dynamic decomposition of the primary frequency regulation control command is specifically as follows:

[0036] Decompose the primary frequency regulation action process into three parts. The first part is from the moment T0 when the frequency fluctuation exceeds the dead zone to a certain moment T1 after the frequency fluctuation gradually decreases and tends to be stable. The second part is from the moment T1 to the moment T2 when the primary frequency regulation response is completely switched to the lithium battery response. The third part is from the moment T2 to the end moment T3 of the primary frequency regulation response.

[0037] Furthermore, in the process of T0 - T1, the supercapacitor and the distributed synchronous condenser respond to the primary frequency regulation preferentially. When the two cannot meet the primary frequency regulation response requirements during this period, the lithium battery supplements the shortage of active power output;

[0038] In the process of T1 - T2, the lithium battery responds to the primary frequency regulation. Since the moment T1, the lithium battery increases the active power output at a certain rate. At the same time, the supercapacitor and the distributed synchronous condenser reduce the active output. This dynamic switching process keeps the total power output following the primary frequency regulation control demand of the power station;

[0039] In the process of T2 - T3, all the primary frequency regulation is responded by the lithium battery.

[0040] Further, at the moment of T1, a fixed moment is preset according to statistical data, and T1 is dynamically calculated according to the remaining energy of the supercapacitor and the distributed synchronous condenser, and real-time measurement is carried out;

[0041]

[0042] wherein, P sc_primary represents the primary frequency regulation response power of the supercapacitor; P sync_primary represents the primary frequency regulation response power of the distributed synchronous condenser; P bat_primary represents the primary frequency regulation response power of the lithium battery energy storage; T0 represents the moment when the frequency fluctuation exceeds the dead zone; T1 represents the starting moment of the dynamic process when the primary frequency regulation response switches to the lithium battery; T2 represents the moment when the primary frequency regulation response completely switches to the lithium battery; T3 represents the ending moment of the primary frequency regulation response; t represents time; K bat represents the active power regulation rate set by the lithium battery in response to primary frequency regulation; P bat_max represents the maximum output power of the lithium battery.

[0043] Further, during the power smoothing control process of step S4, the power fluctuations of the photovoltaic output are suppressed by the supercapacitor, the distributed synchronous condenser and the lithium battery, and the energy of each energy storage unit is supplemented or released, and the priority of the power fluctuation suppression control belongs to the lowest level.

[0044] Further, the control strategy for suppressing power fluctuations is as follows:

[0045] Calculate the deviation P smooth between the photovoltaic power generation and the dispatching AGC command, P smooth =P solar -P ref ;

[0046] Use the low-pass filter algorithm LowPassFilter to perform frequency-domain decomposition on P smooth to obtain the low-frequency component P smooth_low and the high-frequency component P smooth_high , and the decomposition method is as follows:

[0047] P smooth_low =LowPassFilter(P smooth , f c )

[0048] P smooth_high =P smooth -P smooth_low

[0049] wherein, f c represents the cut-off frequency; P smooth_low represents the low-frequency component of power smoothing; P smooth_highRepresents the high-frequency component of power smoothing;

[0050] Calculate the power commands of each energy storage unit during power smoothing. The decomposed high-frequency component is borne by the distributed synchronous condenser and the supercapacitor, and the power is automatically allocated according to the deviation between the current SOC values of the two and the preset SOC values. The low-frequency component is borne by the lithium battery;

[0051] When P smooth_high > 0, the energy storage unit absorbs the excess power generated by the photovoltaic, and the energy storage unit is charged; when P smooth_high < 0, the energy storage unit releases electrical energy to supplement the shortfall of photovoltaic power generation, and the energy storage unit discharges;

[0052]

[0053] P sync_smooth = P smooth_high - P sc_smooth

[0054] P bat_smooth = P smooth_low

[0055] ΔSOC sc_ch = SOC sc_highlimit - SOC sc

[0056] ΔSOC sc_disch = SOC sc - SOC sc_lowlimit

[0057] ΔSOC sync_ch = SOC sync_highlimit - SOC sync

[0058] ΔSOC sync_disch = SOC sync - SOC sync_lowlimit

[0059] Among them, P sc_smooth represents the power smoothing output power of the supercapacitor; P sync_smooth represents the power smoothing output power of the distributed synchronous condenser; P bat_smooth represents the power smoothing output power of the lithium battery; ΔSOC sc_ch represents the deviation between the SOC of the supercapacitor and the upper SOC limit; ΔSOC sc_disch represents the deviation between the SOC of the supercapacitor and the lower SOC limit; ΔSOC sync_ch represents the deviation between the SOC of the distributed synchronous condenser and the upper SOC limit; ΔSOC sync_disch represents the deviation between the SOC of the distributed synchronous condenser and the lower SOC limit; SOC sc_highlimitIndicates the upper limit of the supercapacitor SOC operation; SOC sc_lowlimit Indicates the lower limit of the supercapacitor SOC operation; SOC sync_highlimit Indicates the upper limit of the distributed synchronous condenser SOC operation; SOC sync_lowlimit Indicates the lower limit of the distributed synchronous condenser SOC operation.

[0060] Furthermore, in step S5, the active power commands of the inertia response, primary frequency regulation response, and power smoothing control are superimposed, and the overall control commands for the real-time active power of the distributed synchronous condenser, supercapacitor, and lithium battery are calculated respectively:

[0061]

[0062] ΔSOC bat_ch = SOC bat_highlimit - SOC bat

[0063] ΔSOC bat_disch = SOC bat - SOC bat_lowlimit

[0064] Among them, P sc_total Indicates the active power control command of the supercapacitor; P sync_total Indicates the active power control command of the distributed synchronous condenser; P bat_total Indicates the active power control command of the lithium battery; ΔSOC bat_ch Indicates the deviation between the lithium battery SOC and the upper limit of SOC; ΔSOC bat_disch Indicates the deviation between the lithium battery SOC and the lower limit of SOC; SOC bat_highlimit Indicates the upper limit of the lithium battery SOC operation; SOC bat_lowlimit Indicates the lower limit of the lithium battery SOC operation.

[0065] The positive effects of the present invention are as follows:

[0066] A hybrid energy storage architecture including a supercapacitor, a distributed synchronous condenser, and a lithium battery is designed, and by combining different energy storage units to respond to the active power fast regulation requirements of millisecond, second, and minute multi-time scales, the inertia, frequency response ability, and photovoltaic smooth power generation output ability of the photovoltaic power station are greatly improved, and the friendly grid connection level of the photovoltaic power station is improved.

[0067] The proposed hierarchical collaborative optimization control strategy at millisecond, second, and minute levels can simultaneously ensure the rapidity and action effect of inertia, primary frequency regulation, and power smoothing control, and ensure that the overall operation cost of the system is at a low level, avoiding the problem of rapid decline in the life caused by high-frequency over-response to inertia and primary frequency regulation in traditional energy storage control methods.

[0068] The designed hybrid energy storage system architecture with a distributed synchronous condenser adjusts the active output power by controlling the speed of the distributed synchronous condenser. While improving the active flexible regulation ability of the power station, it can also provide reactive power support for the power station and increase the short-circuit ratio of the power station.

[0069] Starting from improving the active flexible regulation ability of the photovoltaic power station, the flexible speed regulation characteristic of the doubly-fed distributed synchronous condenser is applied to the active power response of the power station. A hybrid energy storage system including a distributed synchronous condenser, supercapacitors and lithium batteries is constructed, and the response characteristics of different energy storage units are fully utilized, which can simultaneously meet the control requirements of multiple time scales such as inertia, primary frequency modulation and power smoothing of the power station. By designing hierarchical collaborative optimization control of multiple time scales, the contradiction between the response effect and operation cost of the hybrid energy storage system is balanced. In addition to being able to output active power by adjusting the speed, the most important function of the distributed synchronous condenser can also provide reactive voltage support for the power station, and at the same time can significantly increase the short-circuit ratio of the power station and improve the safe and reliable operation level of the power station.

[0070] Through the hierarchical collaborative control of the distributed synchronous condenser and the energy storage system, the problems in the prior art that the photovoltaic power station does not have the ability of rapid active regulation of multiple time scales, does not have the inertia response ability, the primary frequency modulation ability is insufficient, and the operation effect of energy storage assisted frequency modulation is poor are solved. Brief Description of the Drawings

[0071] Figure 1 is the system architecture in the specific embodiment of the present invention Figure 1 ;

[0072] Figure 2 is the system architecture in the specific embodiment of the present invention Figure 2 ;

[0073] Figure 3 is the system architecture in the specific embodiment of the present invention Figure 3 ;

[0074] Figure 4 is the system control architecture diagram in the specific embodiment of the present invention;

[0075] Figure 5 is the active power coordination control flowchart in the specific embodiment of the present invention;

[0076] Figure 6 is the global optimization flowchart in the specific embodiment of the present invention. Specific Embodiment

[0077] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0078] Embodiment 1

[0079] System architecture:

[0080] As Figures 1-5 shown, the present invention is applicable to a photovoltaic power station including a distributed synchronous condenser and an energy storage system, and its system architecture includes the following main parts:

[0081] Photovoltaic power generation unit: responsible for converting solar energy into electrical energy;

[0082] Distributed synchronous condenser: Deployed in the photovoltaic power station, it provides dynamic reactive power support and participates in inertia control, primary frequency modulation, and power smoothing control. The distributed synchronous condenser has a doubly-fed structure. While ensuring a specific reactive power output, it can change the active power of the synchronous condenser by adjusting the speed of the distributed synchronous condenser, so as to provide fast active power regulation ability for the power station. However, its active power regulation ability is affected by the capacity of the synchronous condenser and the current reactive power output size, so its active power regulation ability is variable;

[0083] Supercapacitor: Due to its fast response speed and many cycle times, the supercapacitor can provide a more stable and fast active power output in addition to the fast active power support provided by the distributed synchronous condenser. However, due to its small energy density, it cannot provide long-term active power support;

[0084] Lithium battery: The lithium battery has a large energy density but a limited cycle life. Therefore, it mainly undertakes the low-frequency output demand in primary frequency modulation and power smoothing requirements to ensure the minimum life consumption of the lithium battery. In addition, the lithium battery also undertakes the task of photovoltaic power consumption. When the power grid cannot fully consume photovoltaic power, the lithium battery stores the excess photovoltaic power and releases it when the power grid needs to peak;

[0085] Coordination controller: used to coordinate and control the active powers of the distributed synchronous condenser, supercapacitor, and lithium battery, and based on the hierarchical cooperative global optimization control algorithm, calculate and issue the active power distribution instructions of each energy storage unit in real time;

[0086] Communication and monitoring system: Real-time collection of data such as photovoltaic power output, grid dispatching instructions, synchronous condenser speed, energy storage SOC, grid frequency, etc.

[0087] Hierarchical cooperative control architecture:

[0088] The present invention adopts a hierarchical collaborative control architecture, including three layers: millisecond-level control, second-level control, and minute-level optimization:

[0089] (1) Millisecond-level control layer

[0090] The millisecond-level control layer is used to implement the inertia response function of the photovoltaic power station. In this system architecture, both the supercapacitor and the distributed synchronous condenser have a millisecond-level response speed, and they have a large number of response times and a long service life, making them suitable for scenarios with high real-time requirements and frequent responses such as inertia response. Therefore, the main bodies of active power response in the millisecond-level control layer include the supercapacitor and the distributed synchronous condenser. The main function of the control layer is to calculate the requirements of inertia response, decompose the requirements into active power control instructions, and coordinate the control of the supercapacitor and the distributed synchronous condenser to perform inertia response.

[0091] (2) Second-level control layer

[0092] The second-level control layer is used to implement the primary frequency regulation control function of the photovoltaic power station. In this system architecture, the distributed synchronous condenser, the supercapacitor, and the lithium battery all have the ability to respond to primary frequency regulation. The main function of the second-level control layer is to calculate the primary frequency regulation response requirements of the photovoltaic power station, decompose the requirements into active power control instructions, and coordinate the control of the distributed synchronous condenser, the supercapacitor, and the lithium battery to perform primary frequency regulation response.

[0093] (3) Minute-level optimization layer

[0094] The minute-level optimization layer is used to continuously optimize multiple objectives such as the effect and cost of the active power coordination control of the distributed synchronous condenser, the supercapacitor, and the lithium battery. The main optimization objectives are to achieve the best overall operation effect of the system, and to minimize the system life and cost losses.

[0095] Embodiment 2

[0096] As Figures 1-5 shown, on the basis of Embodiment 1, the active power coordination control method for a photovoltaic power station with a distributed synchronous condenser and hybrid energy storage. The active power coordination control process of the distributed synchronous condenser, the supercapacitor, and the lithium battery cooperating with the photovoltaic power station includes the inertia response of the photovoltaic power station, the primary frequency regulation response of the photovoltaic power station, the suppression of the power fluctuation of the power station, and the energy management of each energy storage unit, etc. The flow steps of the control implementation are as follows:

[0097] Step S1: Real-time collect the data of the photovoltaic power station, the distributed synchronous condenser, the supercapacitor, and the lithium battery;

[0098] In step S1, to achieve the active power coordination control of the distributed synchronous condenser, the supercapacitor, the lithium battery, and the photovoltaic power station, it is necessary to real-time collect the relevant data of the photovoltaic power station, the distributed synchronous condenser, the supercapacitor, and the lithium battery, including the grid dispatching instruction P ref , the predicted power of photovoltaic power generation P pre, the actual active power P of the photovoltaic power station solar , the active power P output by the distributed synchronous condenser sync , the reactive power Q output by the distributed synchronous condenser sync , the active power P of the supercapacitor sc , the active power P of the lithium battery bat , the grid-connected point voltage frequency f grid .

[0099] Step S2, inertia response control, is a millisecond-level control;

[0100] In step S2, the inertia response is jointly responded by the distributed synchronous condenser and the supercapacitor, and the control process is as follows:

[0101] Calculate the inertia response demand P of the photovoltaic power station in real time inertia , and the calculation formula is:

[0102]

[0103] Δf = f grid - f N

[0104] Among them, P inertia represents the inertia response demand of the photovoltaic power station; H represents the equivalent inertia constant of the photovoltaic power station; f N represents the grid reference frequency of 50 Hz; represents the change rate of the grid-connected point voltage frequency; P N represents the rated active power of the photovoltaic power station; P solar represents the actual active power of the photovoltaic power station; ε inertia represents the inertia response dead zone of the photovoltaic power station;

[0105] Perform inertia control instruction decomposition. According to the different response speeds of the supercapacitor and the distributed synchronous condenser, an adaptive weight collaborative response control strategy is designed, where the supercapacitor responds to the high-frequency component first, and the distributed synchronous condenser supplements the medium- and low-frequency component demands;

[0106]

[0107] Among them, P sc_inertia represents the inertia response power of the supercapacitor; P sync_inertia represents the inertia response power of the distributed synchronous condenser; T r_sc represents the active response time of the supercapacitor; T r_sync represents the active response time of the distributed synchronous condenser; SOC sc represents the remaining power of the supercapacitor; SOC sync represents the converted remaining power of the distributed synchronous condenser.

[0108] Step S3, primary frequency regulation response control, which is second-level control;

[0109] The primary frequency regulation response control in Step S3 is jointly completed by the supercapacitor, distributed synchronous condenser, and lithium battery. Therefore, it is necessary to design a coordinated control strategy for the three. The primary frequency regulation response is second-level control. And because there is an overlap in the process of primary frequency regulation and inertia response, the inertia output of the current supercapacitor and distributed synchronous condenser needs to be considered simultaneously when decomposing the primary frequency regulation control command;

[0110] Since the active energy stored in the supercapacitor and distributed synchronous condenser is limited and it is difficult to meet the full-process response of the substation for primary frequency regulation, when the frequency fluctuation exceeds the dead zone of primary frequency regulation action, the supercapacitor and distributed synchronous condenser need to act quickly to ensure the rapidity of the response;

[0111] In the middle and later stages of the primary frequency regulation action process, the supercapacitor and distributed synchronous condenser withdraw from primary frequency regulation, and the lithium battery undertakes all the primary frequency regulation power;

[0112] Real-time calculate the primary frequency regulation response demand P of the photovoltaic power station primary , and the calculation formula is as follows:

[0113]

[0114] Where P primary represents the primary frequency regulation of the photovoltaic power station; P primary_max represents the limit value of the active power of the primary frequency regulation of the photovoltaic power station; K primary represents the droop rate of the primary frequency regulation of the photovoltaic power station;

[0115] Conduct dynamic decomposition of the primary frequency regulation control command.

[0116] The process of dynamically decomposing the primary frequency regulation control command is as follows:

[0117] Decompose the primary frequency regulation action process into three parts. The first part is from the moment T0 when the frequency fluctuation exceeds the dead zone to a certain moment T1 after the frequency fluctuation gradually decreases and tends to be stable. The second part is from moment T1 to moment T2 when the primary frequency regulation response is completely switched to the lithium battery response. The third part is from moment T2 to moment T3 when the primary frequency regulation response ends.

[0118] In the process of T0 - T1, the supercapacitor and distributed synchronous condenser are given priority to respond to the primary frequency regulation. When the two cannot meet the primary frequency regulation response requirements during this period, the lithium battery supplements the deficit of the active power output;

[0119] During the process of T1 - T2, the lithium battery responds to primary frequency regulation. Since the moment of T1, the lithium battery increases the active power output at a certain rate. At the same time, the supercapacitor and the distributed synchronous condenser reduce the active output. This dynamic switching process keeps the total power output following the primary frequency regulation control requirements of the power station.

[0120] During the process of T2 - T3, the lithium battery responds to primary frequency regulation entirely.

[0121] The determination of the moment of T1 can preset a fixed moment according to statistical data. For example, it is agreed that T1 = T0 + 5.

[0122] It can also dynamically calculate T1 according to the remaining energy of the supercapacitor and the distributed synchronous condenser. For example, it is calculated in real time according to ;

[0123]

[0124]

[0125] Among them, P sc_primary represents the primary frequency regulation response power of the supercapacitor; P sync_primary represents the primary frequency regulation response power of the distributed synchronous condenser; P bat_primary represents the primary frequency regulation response power of the lithium battery energy storage; T0 represents the moment when the frequency fluctuation exceeds the dead zone; T1 represents the start moment of the dynamic process in which the primary frequency regulation response switches to the lithium battery; T2 represents the moment when the primary frequency regulation response completely switches to the lithium battery; T3 represents the end moment of the primary frequency regulation response; t represents time; K bat represents the set active power regulation rate for the lithium battery to respond to primary frequency regulation; P bat_max represents the maximum value of the lithium battery output power.

[0126] Step S4, power smoothing control, is a second - level control.

[0127] During the power smoothing control process of step S4, the volatility, randomness, and intermittency of photovoltaic power generation result in a deviation between its output active power and the dispatching AGC control instruction. Through the supercapacitor, the distributed synchronous condenser, and the lithium battery, the power fluctuation of the photovoltaic output can be effectively suppressed. At the same time, the energy of each energy storage unit can be supplemented or released to keep it at an appropriate level to meet various active power response scenarios to the greatest extent.

[0128] Compared with inertia control and primary frequency regulation response, the priority of power fluctuation suppression control belongs to the lowest level. The control strategy for power fluctuation suppression is as follows:

[0129] Calculate the deviation P smooth between the photovoltaic power generation power and the dispatching AGC instruction, P smooth = Psolar -P ref ;

[0130] Perform frequency-domain decomposition on P using the low-pass filtering algorithm LowPassFilter smooth to obtain the low-frequency component P smooth_low and the high-frequency component P smooth_high . The low-pass filtering algorithm can use algorithms such as the fast Fourier transform (FFT) and wavelet transform.

[0131] The decomposition method is as follows:

[0132] P smooth_low = LowPassFilter(P smooth , f c )

[0133] P smooth_high = P smooth - P smooth_low

[0134] where f c represents the cut-off frequency; P smooth_low represents the power-smoothed low-frequency component; P smooth_high represents the power-smoothed high-frequency component;

[0135] Calculate the power commands of each energy storage unit during power smoothing. The decomposed high-frequency component is borne by the distributed synchronous condenser and the super capacitor, and the power is automatically allocated according to the deviation between the current SOC values of the two and the preset SOC value. The low-frequency component is borne by the lithium battery;

[0136] When P smooth_high > 0, the energy storage unit absorbs the excess power generated by the photovoltaic, and the energy storage unit charges; when P smooth_high < 0, the energy storage unit releases electrical energy to supplement the shortage of photovoltaic power generation, and the energy storage unit discharges;

[0137]

[0138] P sync_smooth = P smooth_high - P sc_smooth

[0139] P bat_smooth = P smooth_low

[0140] ΔSOC sc_ch = SOC sc_highlimit - SOC sc

[0141] ΔSOC sc_disch = SOC sc - SOC sc_lowlimit

[0142] ΔSOC sync_ch = SOC sync_highlimit - SOC sync

[0143] ΔSOC sync_disch = SOC sync - SOC sync_lowlimit

[0144] Among them, P sc_smooth represents the power smoothing output power of the supercapacitor; P sync_smooth represents the power smoothing output power of the distributed synchronous condenser; P bat_smooth represents the power smoothing output power of the lithium battery; ΔSOC sc_ch represents the deviation between the supercapacitor SOC and the upper limit of SOC; ΔSOC sc_disch represents the deviation between the supercapacitor SOC and the lower limit of SOC; ΔSOC sync_ch represents the deviation between the distributed synchronous condenser SOC and the upper limit of SOC; ΔSOC sync_disch represents the deviation between the distributed synchronous condenser SOC and the lower limit of SOC; SOC sc_highlimit represents the upper operating limit of the supercapacitor SOC; SOC sc_lowlimit represents the lower operating limit of the supercapacitor SOC; SOC sync_highlimit represents the upper operating limit of the distributed synchronous condenser SOC; SOC sync_lowlimit represents the lower operating limit of the distributed synchronous condenser SOC.

[0145] Step S5: Superimpose the active power commands of the inertia response, primary frequency regulation response, and power smoothing control;

[0146] In step S5, superimpose the active power commands of the inertia response, primary frequency regulation response, and power smoothing control, and calculate the overall control commands for the real-time active power of the distributed synchronous condenser, supercapacitor, and lithium battery respectively:

[0147]

[0148] ΔSOC bat_ch = SOC bat_highlimit - SOC bat

[0149] ΔSOC bat_disch = SOC bat - SOC bat_lowlimit

[0150] Among them, P sc_total represents the active power control command of the supercapacitor; P sync_total represents the active power control command of the distributed synchronous condenser; Pbat_total Represents the active power control instruction of the lithium battery; ΔSOC bat_ch Represents the deviation between the SOC of the lithium battery and the upper limit of SOC; ΔSOC bat_disch Represents the deviation between the SOC of the lithium battery and the lower limit of SOC; SOC bat_highlimit Represents the upper operating limit of the SOC of the lithium battery; SOC bat_lowlimit Represents the lower operating limit of the SOC of the lithium battery.

[0151] Step S6: Send the real-time active power control instructions of the distributed synchronous condenser, supercapacitor, and lithium battery to their respective power controllers for execution, and change their output powers to achieve inertia response, primary frequency modulation response, and power smoothing control functions.

[0152] Step S7: When there is no demand for inertia and primary frequency modulation response control in the system, charge and discharge each energy storage unit according to a preset time period to keep the energies of the distributed synchronous condenser, supercapacitor, and lithium battery near the preset SOC values, so as to ensure that the system always maintains the optimal flexible regulation and frequency response capabilities.

[0153] Furthermore, perform global optimization, which is minute-level optimization;

[0154] Perform global optimization calculations according to a certain time period, calculate the optimal values of the preset SOC values of the supercapacitor, lithium battery, and distributed synchronous condenser, and update the optimized results to the active power coordination control algorithm to achieve global optimal control.

[0155] (1) Construct a global optimization objective function

[0156]

[0157] Eff = ω 11 ·(P inertia - P inertia_real ) 2 + ω 12 ·(P primary - P primary_real ) 2 + ω 13 ·(P solar - P ref ) 2

[0158]

[0159] The constraint conditions are:

[0160]

[0161] SOC i,min ≤ SOC i,ref ≤ SOCi,max

[0162] |P i (t)| ≤ P i,max

[0163] SOC i,ref ∈ [SOC i,min , SOC i,max (pre - set SOC target values of supercapacitor, flywheel, and lithium - battery)

[0164] ω1, ω2, ω3 can be dynamically adjusted, such as adjusted according to the frequency deviation level.

[0165] Eff: Action deviation, comprehensive deviation of inertia, primary frequency regulation, and power smoothing response.

[0166] ω1, ω2, ω3 are the action deviation weight, energy storage unit SOC deviation weight, and life loss and operation cost weight respectively. The three weights can be adjusted separately to change the optimization goal.

[0167] ω 11 、ω 12 、ω 13 are the deviation weights of inertia, primary frequency regulation, and power smoothing respectively.

[0168] i: Serial number of energy storage unit, i = 1 represents supercapacitor, i = 2 represents distributed synchronous condenser, i = 3 represents lithium - battery.

[0169] C i : Life loss and operation cost of energy storage unit i

[0170] SOC i (t): SOC value of energy storage unit i

[0171] SOC i,ref : Preset SOC value of energy storage unit i

[0172] P i (t): Real - time active power of energy storage unit i

[0173] η i : Charge - discharge efficiency

[0174] Δt: Charge / discharge duration

[0175] E i,max : Maximum value of electrical energy that energy storage unit i can store

[0176] P i,max : Maximum value of electrical energy output power that energy storage unit i can store

[0177] N cycle,i: Equivalent cycle times of energy storage unit i, equivalent full cycle times converted under the current SOC fluctuation (related to the depth of SOC change)

[0178] N total,i : Total cycle life of energy storage unit i, the maximum full cycle times that can be tolerated under standard test conditions

[0179] λ i,cycle : Economic weight of cycle loss, economic cost corresponding to unit cycle loss

[0180] λ i,calendar : Calendar aging coefficient, loss cost caused by chemical / mechanical aging per unit time

[0181] ΔDOD k : Depth of the kth charge and discharge

[0182] Use the global optimization algorithm to perform operation optimization calculation

[0183] Use the particle swarm optimization algorithm (PSO) to optimize the objective function constructed in the above step (1), and establish the variables to be optimized as:

[0184] x = [SOC sc,ref , SOC sync,ref , SOC bat,ref

[0185] The implementation steps and methods are as follows:

[0186] Initialize the particle swarm. Randomly generate a particle population, each particle contains three preset SOC target values of energy storage (supercapacitor, distributed synchronous condenser, lithium battery), the particle positions randomly initialize three preset SOC values of energy storage, and the particle velocities are initialized to a small random value.

[0187] Define the fitness function. Define the comprehensive cost f(x) of each particle according to the objective function constructed in step (1).

[0188]

[0189] Iteratively update the particles. Update the positions and velocities of the particles, adjust the velocities by combining the individual historical optimal and global optimal positions, and calculate the cost with the new positions to update the individual / global optimal solutions.

[0190] Convergence judgment. Judge whether the convergence condition is reached. One condition is to reach the maximum number of iterations (such as 100 times), and the other condition is that the fitness tends to be stable, and the change of the optimal solution in continuous multiple iterations < threshold (such as 1%).

[0191] Output the result. Select the globally optimal preset SOC combination as the optimization result. ​

[0192] (3) Parameter update. The preset SOC value of the energy storage unit after particle swarm optimization calculation is sent to the controller of each energy storage unit as the new SOC preset target, so as to achieve the multi-objective global optimization of the multi-energy storage system to simultaneously meet the response effect and operation cost.

[0193] Embodiment 3

[0194] Based on Embodiment 2, assume that the rated power of a certain photovoltaic power station is 50 MW, and the configuration of the distributed synchronous condenser and energy storage scale is as follows:

[0195] Distributed synchronous condenser: 30 MVA

[0196] Supercapacitor: 5 MW·30 s

[0197] Lithium battery: 5 MW / 10 MWh

[0198] Their functions are as follows:

[0199] Distributed synchronous condenser: Deployed in the photovoltaic power station, it provides dynamic reactive power support and participates in inertia control, primary frequency modulation and power smoothing control. The distributed synchronous condenser has a doubly-fed structure. While ensuring a specific reactive power output, it can change the active power of the synchronous condenser by adjusting the speed of the distributed synchronous condenser, so as to provide fast active power regulation ability for the power station. However, its active power regulation ability is affected by the capacity of the synchronous condenser and the current reactive power output size, so its active power regulation ability is variable.

[0200] Supercapacitor: Due to its fast response speed and many cycle times, the supercapacitor can provide a more stable and fast active power output in addition to the fast active power support provided by the distributed synchronous condenser. However, due to its small energy density, it cannot provide long-term active power support.

[0201] Lithium battery: The lithium battery has a large energy density but a limited cycle life. Therefore, it mainly undertakes the low-frequency output demand in primary frequency modulation and power smoothing requirements to ensure the minimum life consumption of the lithium battery. In addition, the lithium battery also undertakes the task of photovoltaic power consumption. When the power grid cannot fully consume photovoltaic power, the lithium battery stores the excess photovoltaic power and releases it when the power grid needs to peak.

[0202] Coordination controller: Used to coordinate and control the active power of the distributed synchronous condenser, supercapacitor and lithium battery, and based on the hierarchical collaborative global optimization control algorithm, it calculates and sends the active power distribution instructions of each energy storage unit in real time.

[0203] Communication and monitoring system: It collects data such as photovoltaic power output, grid dispatching instructions, synchronous condenser speed, energy storage SOC, grid frequency, etc. in real time.

[0204] Real-time active power control process:

[0205] The active power coordination control process of the distributed synchronous condenser, supercapacitor, lithium battery and photovoltaic power station includes the inertia response of the photovoltaic power station, the primary frequency modulation response of the photovoltaic power station, the suppression of the power fluctuation of the power station, and the energy management of each energy storage unit. The process steps for control implementation are as follows:

[0206] (1) Real-time data acquisition

[0207] To achieve the active power coordination control of the distributed synchronous condenser, supercapacitor, lithium battery and photovoltaic power station, relevant data of the photovoltaic power station, distributed synchronous condenser, supercapacitor and lithium battery need to be collected in real time, including the grid dispatching instruction P ref , the predicted photovoltaic power P pre , the actual active power P of the photovoltaic power station solar , the active power P output by the distributed synchronous condenser sync , the reactive power Q output by the distributed synchronous condenser sync , the active power P of the supercapacitor sc , the active power P of the lithium battery bat , and the grid-connected voltage frequency f grid .

[0208] (2) Inertia response control, millisecond-level control

[0209] The inertia response is jointly responded by the distributed synchronous condenser and the supercapacitor. The control process is as follows:

[0210] Calculate the inertia response demand P of the photovoltaic power station in real time inertia , and the calculation formula is as follows:

[0211]

[0212] Δf = f grid - f N

[0213] The equivalent inertia constant H of the photovoltaic power station is taken as 10 s, the grid reference frequency f N is taken as 50 Hz, the inertia response dead zone of the photovoltaic power station is taken as 0.03 Hz, and the time calculation window of

[0214] 2) Decompose the inertia control instruction

[0215] According to the different response speeds of the supercapacitor and the distributed synchronous condenser, a cooperative response control strategy with adaptive weights is designed. The supercapacitor responds to the high-frequency component first, and the distributed synchronous condenser supplements the medium- and low-frequency component requirements.

[0216]

[0217] Among them, the active response time T of the supercapacitor r_sc is 10 ms, and the active response time T of the distributed synchronous condenser r_sync is 100 ms.

[0218] (3) Primary frequency regulation response control, second-level control

[0219] The primary frequency regulation response is jointly completed by the supercapacitor, the distributed synchronous condenser, and the lithium battery. Therefore, it is necessary to design a coordinated control strategy for the three. The primary frequency regulation response is second-level control. Since there is an overlap in the processes of primary frequency regulation and inertia response, the current inertia output of the supercapacitor and the distributed synchronous condenser needs to be considered simultaneously when decomposing the primary frequency regulation control command.

[0220] Since the active energy stored in the supercapacitor and the distributed synchronous condenser is limited and it is difficult to meet the full-process response of the primary frequency regulation of the substation, when the frequency fluctuation exceeds the dead zone of the primary frequency regulation action, the supercapacitor and the distributed synchronous condenser need to act quickly to ensure the rapidity of the response. In the middle and late stages of the primary frequency regulation action process, the supercapacitor and the distributed synchronous condenser withdraw from the primary frequency regulation, and the lithium battery undertakes all the primary frequency regulation power.

[0221] 1) Real-time calculate the primary frequency regulation response demand P of the PV power station primary , and the calculation formula is as follows:

[0222]

[0223] Among them, the limited value P of the active power of the primary frequency regulation of the PV power station primary_max is 10% of the rated power, that is, 5 MW. The primary frequency regulation droop rate K of the PV power station primary is taken as 5%

[0224] 2) Dynamically decompose the primary frequency regulation control command

[0225] The primary frequency regulation action process is decomposed into three parts. The first part is from the moment T0 when the frequency fluctuation exceeds the dead zone to a certain moment T1 after the frequency fluctuation gradually decreases and tends to be stable. The second part is from the moment T1 to the moment T2 when the primary frequency regulation response is completely switched to the lithium battery response. The third part is from the moment T2 to the end moment T3 of the primary frequency regulation response. During the process of T0 - T1, the supercapacitor and the distributed synchronous condenser respond to the primary frequency regulation preferentially. When the two cannot meet the primary frequency regulation response requirements during this period, the lithium battery supplements the shortage of active power output. During the process of T1 - T2, the lithium battery responds to the primary frequency regulation. Since the moment T1, the lithium battery increases the output of active power at a certain rate, while the supercapacitor and the distributed synchronous condenser reduce the active output. This dynamic switching process keeps the total power output following the primary frequency regulation control demand of the substation. During the process of T2 - T3, all the primary frequency regulation is responded by the lithium battery. Among them, T1 = T0 + 5.

[0226]

[0227]

[0228] Among them

[0229] The active power regulation rate K set for the lithium battery to respond to primary frequency modulation bat is 5 MW / s, and the maximum output power P of the lithium battery bat_max is 5 MW.

[0230] (3) Power smoothing control, second-level control

[0231] The volatility, randomness, and intermittency of photovoltaic power generation result in a deviation between its output active power and the dispatching AGC control instruction. Through supercapacitors, distributed synchronous condensers, and lithium batteries, the power fluctuations of photovoltaic output can be effectively suppressed. At the same time, the energy of each energy storage unit can be supplemented / released to keep it at an appropriate level to meet various active power response scenarios to the greatest extent. Compared with inertia control and primary frequency modulation response, the priority of power fluctuation suppression control belongs to the lowest level. The control strategy for suppressing power fluctuations is as follows:

[0232] 1) Calculate the deviation P between the photovoltaic power generation power and the dispatching AGC instruction smooth

[0233] P smooth = P solar - P ref

[0234] 2) Use the fast Fourier transform (FFT) to perform frequency-domain decomposition on P smooth to obtain the low-frequency component P smooth_low and the high-frequency component P smooth_high , and the decomposition method is as follows:

[0235] P smooth_low = FFT(P smooth , f c )

[0236] P smooth_high = P smooth - P smooth_low

[0237] Among them, the cut-off frequency f c is taken as 1 Hz

[0238] 3) Calculate the power commands of each energy storage unit during power smoothing

[0239] The decomposed high-frequency component is borne by the distributed synchronous condenser and the supercapacitor, and the power is automatically distributed according to the deviation between the current SOC values of the two and the preset SOC values. The low-frequency component is borne by the lithium battery. When Psmooth_high >0, energy storage is needed to absorb the excess electricity generated by photovoltaics, and the energy storage unit is charged at this time; when P smooth_high <0, energy storage is needed to release electric energy to supplement the shortfall of photovoltaic power generation, and the energy storage unit discharges at this time.

[0240]

[0241] P sync_smooth =P smooth_high -P sc_smooth

[0242] P bat_smooth =P smooth_low

[0243] ΔSOC sc_ch =SOC sc_highlimit -SOC sc

[0244] ΔSOC sc_disch =SOC sc -SOC sc_lowlimit

[0245] ΔSOC sync_ch =SOC sync_highlimit -SOC sync

[0246] ΔSOC sync_disch =SOC sync -SOC sync_lowlimit

[0247] Supercapacitor SOC operating upper limit SOC sc_highlimit Set to 0.9, the supercapacitor SOC lower limit SOC sc_lowlimit Set to 0.3, the SOC upper limit of the distributed phase condenser SOC sync_highlimit Set to 0.8, the distributed phase regulator SOC operating lower limit SOC sync_lowlimit Set to 0.3; Lithium battery SOC upper limit SOC bat_highlimit Set to 0.3, the lithium battery SOC lower limit SOC bat_lowlimit Set to 0.9.

[0248] Perform power superposition, superimpose the active power instructions of the three parts of inertia response, primary frequency modulation response and power smoothing control, and calculate the overall real-time active power control instructions of the distributed phase regulator, supercapacitor and lithium battery respectively:

[0249]

[0250] ΔSOC bat_ch =SOC bat_highlimit -SOCbat

[0251] ΔSOC bat_disch = SOC bat - SOC bat_lowlimit

[0252] Send the real-time active power control instructions of the distributed synchronous condenser, supercapacitor, and lithium battery to their respective power controllers for execution, and change their output powers to achieve inertia response, primary frequency regulation response, and power smoothing control functions.

[0253] When there is no demand for inertia and primary frequency regulation response control in the system, charge and discharge each energy storage unit according to a preset time period to keep the energies of the distributed synchronous condenser, supercapacitor, and lithium battery near the preset SOC values, so as to ensure that the system always maintains the optimal flexible regulation and frequency response capabilities.

[0254] Global optimization, minute-level optimization

[0255] Perform global optimization calculations with a period of every 15 minutes, calculate the optimal values of the preset SOC values of the supercapacitor, lithium battery, and distributed synchronous condenser, and update the optimized results to the active power coordination control algorithm to achieve global optimal control.

[0256] (1) Construct an optimization objective function

[0257]

[0258] Eff = ω 11 ·(P inertia - P inertia_real ) 2 + ω 12 ·(P primary - P primary_real ) 2 + ω 13 ·(P solar - P ref ) 2

[0259]

[0260] The constraint conditions are:

[0261]

[0262] SOC i,min ≤ SOC i,ref ≤ SOC i,max

[0263] |P i (t)| ≤ P i,max

[0264] ω1, ω2, and ω3 are set to 0.3, 0.3, and 0.4 respectively; ω 11 , ω 12 , ω 13 are taken as 0.4, 0.4, and 0.2 respectively.

[0265] The economic weights λ of the cycle losses of the supercapacitor, distributed synchronous condenser, and lithium battery i,cycle are taken as 0.007 yuan / time, 0.08 yuan / time, and 0.14 yuan / time respectively; the calendar aging coefficients λ of the supercapacitor, distributed synchronous condenser, and lithium battery i,calendar are taken as 0.0007 yuan / h, 0.002 yuan / h, and 0.014 yuan / h respectively.

[0266] Operation optimization

[0267] The particle swarm optimization (PSO) algorithm is used to optimize the objective function constructed in the above step (1), and the variables to be optimized are established as:

[0268] x = [SOC sc,ref , SOC sync,ref , SOC bat,ref

[0269] The implementation steps and methods are as follows:

[0270] Initialize the particle swarm. Randomly generate a particle swarm, and each particle contains three preset SOC target values of the energy storage devices (supercapacitor, distributed synchronous condenser, and lithium battery). The particle positions are randomly initialized with three preset SOC values of the energy storage devices, which are 0.5 respectively, and the particle velocities are initialized to a small random value of 0.1.

[0271] Define the fitness function. Define the comprehensive cost f(x) of each particle according to the objective function constructed in step (1).

[0272]

[0273] Iteratively update the particles. Update the positions and velocities of the particles, adjust the velocities by combining the individual historical optimal and global optimal positions, calculate the cost with the new positions, and update the individual / global optimal solutions.

[0274] Convergence judgment. Judge whether the convergence condition is reached. One of the conditions is that the maximum number of iterations reaches 100 times, and the other condition is that the fitness tends to be stable, and the change in the optimal solution for consecutive multiple iterations is <1%. When either of the two conditions is met, it is considered that the optimization process has converged.

[0275] Output the results. Select the globally optimal preset SOC combination x as the optimization result.

[0276] ​(3) Parameter update. The preset SOC value of the energy storage unit after particle swarm optimization calculation is sent to the controllers of each energy storage unit as the new SOC preset target, so as to realize the multi-objective global optimization of the multi-energy storage system to simultaneously meet the response effect and operation cost.

[0277] The above-described embodiments are described in detail and specifically, expressing the preferred embodiments of the present invention. They are only used to illustrate the technical ideas and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, it is not limited to the present invention only. The patent scope of the present invention cannot be limited only by this embodiment. That is, any equivalent changes or modifications made in accordance with the spirit disclosed by the present invention, for those researchers or technicians in the field, within the structure of the present invention, local improvements within the system and changes and transformations between subsystems are still within the patent scope of the present invention.

Claims

1. A method for coordinated control of active power of a photovoltaic station including distributed phase-converters and hybrid energy storage, characterized in that: include: Step S1, real-time data collection of photovoltaic stations, distributed phase regulators, supercapacitors and lithium batteries; Step S2, inertia response control, calculating the inertia response demand of the photovoltaic station and performing inertia control instruction decomposition; Step S3, primary frequency modulation response control, calculating primary frequency modulation response requirements, and primary frequency modulation control instruction decomposition; Step S4: power smoothing control, calculating the deviation between photovoltaic power generation and dispatching, and performing frequency domain decomposition; Step S5, superimposing the active power instructions of the three parts of inertia response, primary frequency modulation response and power smoothing control; Step S6: Send the real-time active power control instructions of the distributed phase regulator, supercapacitor, and lithium battery to their respective power controllers for execution; Step S7: When the system has no inertia and primary frequency modulation response control requirements, each energy storage unit is charged and discharged according to a preset time period.

2. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 1 is characterized in that: In step S1, data of photovoltaic stations, distributed phase regulators, supercapacitors and lithium batteries are collected in real time, including the grid dispatching instruction P ref , photovoltaic power generation predicted power P pre , the actual active power P of the photovoltaic station solar 、Distributed phase regulator output active power P sync , Distributed phase regulator output reactive power Q sync , supercapacitor active power P sc , Lithium battery active power P bat , grid connection point voltage frequency f grid .

3. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 1 is characterized in that: In step S2, the inertia response is jointly responded by the distributed phase regulator and the supercapacitor, and the control process is as follows: Real-time calculation of photovoltaic station inertia response demand P inertia , the calculation formula is: Among them, P inertia represents the inertia response requirement of the photovoltaic station; H represents the equivalent inertia constant of the photovoltaic station; f N Indicates the grid reference frequency 50Hz; Indicates the rate of change of the voltage frequency at the grid connection point; P N Indicates the rated active power of the photovoltaic station; P solar Indicates the actual active power of the photovoltaic station; ε inertia Indicates the dead zone of inertia response of photovoltaic stations; Decompose the inertia control command, with the supercapacitor responding to the high-frequency component first, and the distributed phase regulator supplementing the medium and low-frequency component demand; Among them, P sc_inertia Indicates the supercapacitor inertia response power; P sync_inertia represents the inertia response power of the distributed phase regulator; T r_sc Indicates the active response time of the supercapacitor; T r_sync Indicates the active response time of distributed phase regulator; SOC sc Indicates the remaining power of the supercapacitor; SOC sync Indicates the remaining power converted by the distributed phase regulator.

4. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 1 is characterized in that: In step S3, the primary frequency modulation response control is completed by the supercapacitor, the distributed phase condenser, and the lithium battery. The primary frequency modulation response is controlled in seconds. When the frequency fluctuation exceeds the primary frequency modulation action dead zone, the supercapacitor and the distributed phase condenser act quickly. In the middle and late stages of the primary frequency modulation action process, the supercapacitor and the distributed phase condenser exit the primary frequency modulation, and the lithium battery bears all the primary frequency modulation power. Real-time calculation of the primary frequency regulation response demand P of the photovoltaic station primary , the calculation formula is as follows: Where P primary Indicates the primary frequency regulation of the photovoltaic station; P primary_max Indicates the primary frequency regulation active power limit value of the photovoltaic station; K primary Indicates the primary frequency regulation rate of the photovoltaic station; Perform a dynamic decomposition of the frequency modulation control instruction.

5. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 4 is characterized in that: The process of dynamic decomposition of a frequency modulation control instruction is as follows: The primary frequency modulation action process is decomposed into three parts. The first part is from the moment T0 when the frequency fluctuation exceeds the dead zone to a certain moment T1 after the frequency fluctuation gradually decreases and stabilizes. The second part is from moment T1 to the moment T2 when the primary frequency modulation response is completely switched to the lithium battery response. The third part is from moment T2 to the moment T3 when the primary frequency modulation response ends.

6. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 5 is characterized in that: In the T0-T1 process, supercapacitors and distributed phase regulators respond to primary frequency modulation first. When the two cannot meet the primary frequency modulation response requirements during this period, lithium batteries will supplement the output of the missing active power. In the process of T1-T2, the lithium battery responds to the primary frequency modulation. Since T1, the lithium battery increases the active power output at a certain rate, while the supercapacitor and distributed phase regulator reduce the active power output. This dynamic switching process keeps the total power output in line with the primary frequency modulation control requirements of the station. During the T2-T3 process, the lithium battery responds to the frequency modulation once.

7. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 6 is characterized in that: At the time T1, a fixed time is preset according to statistical data, and T1 is dynamically calculated according to the remaining energy of the supercapacitor and the distributed phase regulator. Conduct real-time calculations; Among them, P sc_primary Indicates the primary frequency modulation response power of the supercapacitor; P sync_primary P represents the primary frequency modulation response power of the distributed phase regulator; bat_primary Indicates the power of the primary frequency modulation response of the lithium battery energy storage; T0 indicates the moment when the frequency fluctuation exceeds the dead zone; T1 indicates the moment when the primary frequency modulation response switches to the lithium battery; T2 indicates the moment when the primary frequency modulation response is completely switched to the lithium battery; T3 indicates the moment when the primary frequency modulation response ends; t indicates time; K bat Indicates the active power regulation rate of the lithium battery in response to the primary frequency modulation setting; P bat_max Indicates the maximum output power of the lithium battery.

8. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 1 is characterized in that: In the power smoothing control process of step S4, the power fluctuation of photovoltaic output is smoothed by supercapacitors, distributed phase regulators and lithium batteries, and the energy of each energy storage unit is supplemented or released. The priority of power fluctuation smoothing control belongs to the lowest level.

9. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 8 is characterized in that: The control strategy for smoothing power fluctuations is as follows: Calculate the deviation P between the photovoltaic power generation and the dispatch AGC instruction smooth , P smooth =P solar -P ref ; The low-pass filter algorithm LowPassFilter is used to filter P smooth Perform frequency domain decomposition to obtain the low-frequency component P smooth_low and high frequency component P smooth_high , decomposed as follows: P smooth_low =LowPassFilter(P smooth ,f c ) P smooth_high =P smooth -P smooth_low Among them, f c represents the cut-off frequency; P smooth_low Represents the power smoothing low-frequency component; P smooth_high Indicates the power smoothing high frequency component; When calculating power smoothing, the power instructions of each energy storage unit are decomposed, and the high-frequency components are borne by the distributed phase regulator and supercapacitor, and the power is automatically distributed according to the deviation between the current SOC value of the two and the preset SOC value, and the low-frequency components are borne by the lithium battery; When P smooth_high >0, the energy storage unit absorbs the excess electricity generated by photovoltaics and charges; when P smooth_high <0, the energy storage unit releases electric energy to supplement the insufficient photovoltaic power generation, and the energy storage unit discharges; P sync_smooth =P smooth_high -P sc_smooth P bat_smooth =P smooth_low ΔSOC sc_ch =SOC sc_highlimit -SOC sc ΔSOC sc_disch =SOC sc -SOC sc_lowlimit ΔSOC sync_ch =SOC sync_highlimit -SOC sync ΔSOC sync_disch =SOC sync -SOC sync_lowlimit Among them, P sc_smooth Indicates the supercapacitor power smoothing output power; P sync_smooth P represents the smoothed output power of the distributed phase regulator; bat_smooth Indicates the smoothed output power of the lithium battery; ΔSOC sc_ch Indicates the deviation between the supercapacitor SOC and the upper limit of SOC; ΔSOC sc_disch Indicates the deviation between the supercapacitor SOC and the lower limit of SOC; ΔSOC sync_ch Indicates the deviation between the SOC of the distributed phase regulator and the upper limit of SOC; ΔSOC sync_disch Indicates the deviation between the SOC of the distributed phase regulator and the lower limit of SOC; SOC sc_highlimit Indicates the upper limit of supercapacitor SOC operation; SOC sc_lowlimit Indicates the lower limit of supercapacitor SOC operation; SOC sync_highlimit Indicates the upper limit of SOC operation of distributed phase regulator; SOC sync_lowlimit Indicates the lower limit of SOC operation of distributed phase regulator.

10. The active power coordinated control method of a photovoltaic station containing a distributed phase regulator and hybrid energy storage according to claim 1, characterized in that: In step S5, the active power instructions of the three parts of inertia response, primary frequency modulation response and power smoothing control are superimposed to calculate the overall real-time active power control instructions of the distributed phase regulator, supercapacitor and lithium battery respectively: ΔSOC bat_ch =SOC bat_highlimit -SOC bat ΔSOC bat_disch =SOC bat -SOC bat_lowlimit Among them, P sc_total Indicates the supercapacitor active power control instruction; P sync_total Indicates the active power control instruction of the distributed phase regulator; P bat_total Indicates the active power control instruction of the lithium battery; ΔSOC bat_ch Indicates the deviation between the lithium battery SOC and the SOC upper limit; ΔSOC bat_disch Indicates the deviation between the lithium battery SOC and the SOC lower limit; SOC bat_highlimit Indicates the upper limit of SOC operation of lithium battery; SOC bat_lowlimit Indicates the lower limit of lithium battery SOC operation.

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