Combined control method and system for gravity energy storage hybrid electrochemical energy storage system

Abstract

The invention discloses a combined control method and system of a gravity energy storage hybrid electrochemical energy storage system. The combined control system of the gravity energy storage hybrid electrochemical energy storage system comprises a gravity energy storage system with a storage block and an electrochemical energy storage system with a storage battery and a super capacitor. The method comprises the following steps of: obtaining a power difference of a power instruction required by the gravity energy storage system according to different moments of acceleration, constant-speed and deceleration motion of a storage block; and carrying out power optimization distribution control on the power difference according to the frequency, respectively obtaining the charging and discharging power of the storage battery and the super capacitor, and carrying out charging / discharging supplement by utilizing the electrochemical energy storage system to realize the combined control on the gravity energy storage hybrid electrochemical energy storage system. According to the scheme, the gravity energy storage, the storage battery and the super capacitor can be subjected to power distribution at different time scales, cooperative control over the electricity-gravity hybrid energy storage system is achieved, and the overall performance of the system is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hybrid energy storage control, and specifically relates to a combined control method and system of a gravity energy storage hybrid electrochemical energy storage system. Background Art

[0002] As the proportion of wind power, photovoltaic and other new energy sources in the power grid continues to increase, the safe and reliable operation of the power system has been severely tested. In the power system, energy storage technology can be used to balance the imbalance between the load and power supply of the power system. Since there is a time mismatch between the load and power supply in the power system, and at the same time, it is necessary to ensure the safe and stable operation of the power system after the access of various types of fluctuating power sources, energy storage technology is needed to adjust the difference between the load and power supply of the power system.

[0003] Gravity energy storage is a recently emerging physical energy storage technology that has attracted much attention. It can be used to replace the energy storage medium with solid heavy objects such as sand, rocks, concrete blocks and other materials for a large number of abandoned mines and abandoned idle industrial land in suburban areas. By changing the height of the storage blocks, the abundant electrical energy in the power grid can be stored as the potential energy of the storage blocks. However, due to the limitations of the energy storage principle, the storage blocks, as solids, are non-flowable and non-continuous. The size, weight and height difference of each storage block are fixed. In addition, there must be a certain time and space interval for each storage block to descend and rise. Therefore, a single gravity energy storage system cannot continuously, efficiently and reliably match and respond to the needs of the power grid.

[0004] Different types of energy storage devices have different charging and discharging powers, response speeds, and costs. Power-type energy storage systems have high energy storage efficiency, fast response speed, but limited capacity, while energy-type energy storage systems have large energy storage capacity, long energy storage time, and low output power. The complementary characteristics of energy-type energy storage and power-type energy storage devices can be used to establish a hybrid energy storage system (HESS) with multiple types of energy storage working in coordination. Its ability to migrate energy and power in time can be used to isolate power generation and power consumption in time and space. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a joint control method and system for a gravity energy storage hybrid electrochemical energy storage system, so as to solve the problems of non-flowability and discontinuity of storage blocks in a single gravity energy storage system, and the inability to continuously, efficiently and reliably match and respond to grid-side demand, so as to achieve continuous, efficient and rapid transmission of multiple objects, and reduce the impact of the start-stop and switching process of heavy objects on mechanical transmission and grid systems.

[0006] According to the technical solution of the present invention, the present invention provides a combined control method of a gravity energy storage hybrid electrochemical energy storage system, wherein the combined control system of the gravity energy storage hybrid electrochemical energy storage system comprises a gravity energy storage system having a storage block, and an electrochemical energy storage system having a battery and a supercapacitor; the combined control system comprises the following steps:

[0007] According to the different moments of acceleration, uniform speed and deceleration of the storage block, the power difference of the power command required by the gravity energy storage system is obtained;

[0008] The power difference is controlled by optimizing power distribution according to the frequency, and the charging and discharging power of the battery and supercapacitor are obtained respectively. The electrochemical energy storage system is used for charging / discharging supplement to realize the joint control of the gravity energy storage hybrid electrochemical energy storage system.

[0009] Furthermore, in the process of setting up the gravity energy storage system, the power and capacity of the gravity energy storage system are obtained according to the unit parameters of the gravity energy storage system; the unit parameters of the gravity energy storage system include the mass of the storage block, the rated speed of the motor and the height difference.

[0010] Furthermore, the capacity of the gravity energy storage system is expressed as:

[0011]

[0012] Where n is the total number of storage blocks used in the gravity energy storage system, m i is the mass of the i-th storage block, h 上 is the total height of the gravity energy storage system, h 下 It is the height of the descending area of ​​the gravity energy storage system.

[0013] Furthermore, the upper-level power command controls the battery and the supercapacitor respectively under the power division control strategy; the gravity energy storage system is connected to the power grid system through the permanent magnet synchronous motor, and then through the machine-side converter and the grid-side converter in sequence; the permanent magnet synchronous motor is controlled by the upper-level power command, and the machine-side converter and the grid-side converter are controlled by the machine-side controller and the grid-side controller respectively.

[0014] Furthermore, in the process of obtaining the power difference of the power command required by the gravity energy storage system, the process of the storage block descending is the process of the gravity energy storage system releasing energy and generating electricity, which is divided into three stages, including the descent start acceleration stage, the uniform falling stage, and the descent deceleration braking stage;

[0015] The lifting process of the storage block is the energy storage and charging process of the gravity energy storage system, which is divided into three stages, including the lifting start acceleration stage, the uniform rising stage, and the lifting deceleration braking stage;

[0016] Based on the different moments of acceleration, uniform speed and deceleration of the storage block, the grid-connected power value of the gravity energy storage system in each stage is obtained, and the difference between the total power command value of the upper load at time t and the output power of the gravity energy storage system is used as the power difference.

[0017] Furthermore, in the process of power optimization distribution control, the pre-output of the electrochemical hybrid energy storage system is obtained based on the power difference, and the pre-output is decomposed into high-frequency components and low-frequency components according to the deterministic rule control strategy, which are provided by supercapacitors and batteries respectively.

[0018] Furthermore, in the process of charging / discharging supplementation using the electrochemical energy storage system, power optimization distribution control is performed according to the different intervals of the SOC of the electrochemical energy storage system, the charging and discharging power of the battery and the supercapacitor is changed, and the instantaneous power fluctuation is smoothed by the supercapacitor to reduce the overshoot of the energy storage system regulation.

[0019] Furthermore, in the process of optimizing power distribution control according to the different SOC intervals of the electrochemical energy storage system, the SOC of the battery and the supercapacitor are i :

[0020] Set the SOC discharge dead zone threshold to SOC min , that is, when SOC i <SOC min When the battery and supercapacitor are in the state of being charged, they cannot be discharged.

[0021] Set the SOC discharge slowdown zone threshold to SOC low , that is, when SOC min <SOC i <SOC low When the battery and supercapacitor are charged normally, the discharge power is reduced;

[0022] Set the SOC charging dead zone threshold to SOC max , that is, when SOC max <SOC i When the battery and supercapacitor cannot be charged, they can only be discharged;

[0023] Set the SOC charging slowdown zone threshold to SOC high , that is, when SOC high <SOC i <SOC max When the battery and supercapacitor charge power decreases, they discharge normally;

[0024] When SOC low <SOC i <SOC highWhen the battery and supercapacitor are charged and discharged normally.

[0025] Furthermore, the discharge dead zone threshold SOC mi The discharge slowdown zone threshold SOC is 10%. low The SOC threshold of the charging slowdown zone is 20%. high The charging dead zone threshold SOC is 80%. max is 90%.

[0026] According to the technical solution of the present invention, the present invention also provides a combined control system of a gravity energy storage hybrid electrochemical energy storage system, which is used for the combined control method of the gravity energy storage hybrid electrochemical energy storage system of the present invention; it includes a data calculation module and a combined control module connected to each other, and the combined control module is respectively connected to the battery, the supercapacitor and the permanent magnet synchronous motor of the gravity energy storage system;

[0027] The battery is connected to a battery bidirectional DC / DC converter and a battery bidirectional DC / DC controller, and the battery bidirectional DC / DC controller is connected to the battery bidirectional DC / DC converter; the supercapacitor is connected to a supercapacitor bidirectional DC / DC converter and a supercapacitor bidirectional DC / DC controller, and the supercapacitor bidirectional DC / DC controller is connected to the supercapacitor bidirectional DC / DC converter; the battery bidirectional DC / DC converter and the supercapacitor bidirectional DC / DC converter are connected in parallel with an electrochemical energy storage voltage stabilizing filter capacitor, and are connected to the power grid system through a bidirectional DC / AC converter;

[0028] The permanent magnet synchronous motor is connected to a machine-side converter and a machine-side controller, the machine-side controller is connected to the machine-side converter, the machine-side converter is connected to the grid-side converter, a gravity energy storage voltage stabilizing filter capacitor is connected in parallel between the machine-side converter and the grid-side converter, the grid-side converter is connected to the grid-side controller, and both the grid-side converter and the grid-side controller are connected to the power grid system.

[0029] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0030] The present invention solves the problem of non-flowability and discontinuity of storage blocks in a single gravity energy storage system by combining different types of energy storage technologies, and can realize continuous, efficient and rapid transmission of multiple objects, and reduce the impact of heavy object start-stop and switching processes on mechanical transmission and power grid systems; battery energy storage can achieve continuous and uninterrupted power generation and storage, and the technology is relatively mature. In the process where the gravity energy storage block cannot be continuously transmitted, it can serve as a power supplement to provide energy requirements to meet upper-level power instructions; at the same time, in the process of starting and stopping the gravity energy storage system and switching the motion state of the storage block, the large impact current and other problems are generated. Supercapacitors have a faster charging and discharging speed than batteries, can quickly provide or absorb a large amount of electrical energy, and smooth power fluctuations; control based on the method disclosed in the present invention can realize the reasonable allocation of upper-level power instructions, meet the requirements of larger-scale energy storage, and be configured and adjusted according to different application scenarios and needs to adapt to various energy storage needs and improve the overall performance of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural diagram of the combined control system of the gravity energy storage hybrid electrochemical energy storage system described in the present invention.

[0032] Figure 2 This is the waveform diagram of the electromagnetic torque of the permanent magnet motor described in the present invention.

[0033] Figure 3 This is a waveform diagram of the DC bus side voltage Udc described in the present invention.

[0034] Figure 4 It is a waveform diagram of the change in speed n of the permanent magnet synchronous motor described in the present invention.

[0035] Figure 5a , Figure 5b is a schematic diagram of the operation process of the gravity energy storage system of the present invention, wherein Figure 5a The schematic diagram of the energy storage process is shown in Figure 2. Figure 5b Schematic diagram showing the operation process of power generation.

[0036] Figure 6 It is a power distribution control principle diagram of the electrochemical hybrid energy storage system described in the present invention.

[0037] Figure 7 It is a flow chart of power distribution of the battery and supercapacitor described in the present invention.

[0038] Figures 8a to 8c is a schematic diagram of system power distribution according to the present invention, wherein Figure 8a The power distribution waveform of the electrochemical energy storage system without peak power fluctuation is shown. Figure 8b It shows the power distribution waveform of each energy storage system when there is no peak power fluctuation. Figure 8cIt shows the power distribution waveform of each energy storage system when there is peak power fluctuation.

[0039] Description of reference numerals in the accompanying drawings:

[0040] 1. Data calculation module; 2. Joint control module; 3. Battery; 4. Supercapacitor; 5. Permanent magnet synchronous motor; 6. Battery bidirectional DC / DC converter; 7. Battery bidirectional DC / DC controller; 8. Supercapacitor bidirectional DC / DC converter; 9. Supercapacitor bidirectional DC / DC controller; 10. Electrochemical energy storage voltage stabilizing filter capacitor; 11. Bidirectional DC / AC converter; 12. Power grid system; 13. Machine-side converter; 14. Machine-side controller; 15. Grid-side converter; 16. Gravity energy storage voltage stabilizing filter capacitor; 17. Grid-side controller. DETAILED DESCRIPTION

[0041] The present invention provides a joint control technology of a gravity energy storage hybrid electrochemical energy storage system, specifically a joint control method and system of a gravity energy storage hybrid electrochemical energy storage system, which belongs to the field of hybrid energy storage control technology, and its main purpose is to solve the non-flowability and discontinuity of storage blocks existing in a single gravity energy storage system, realize continuous, efficient and rapid transmission of multiple objects, and reduce the impact of heavy object start-stop and switching processes on mechanical transmission and power grid systems. The gravity energy storage hybrid electrochemical energy storage system consists of a gravity energy storage system with a storage block and an electrochemical energy storage system with a battery and a supercapacitor, including: according to the different moments of acceleration, uniform speed and deceleration of the storage block, the power difference of the power instruction required by the gravity energy storage system is obtained; according to the power demand characteristics of the battery and the supercapacitor, and the power of the SOC state of charge of the two, the power difference is distributed, and the charging and discharging power of the battery and the supercapacitor are obtained respectively, and finally the joint control of the gravity energy storage hybrid electrochemical energy storage system is realized. The present invention can realize power distribution among gravity energy storage, batteries and supercapacitors at different time scales, realize coordinated control of the electric-gravity hybrid energy storage system, and effectively improve the overall performance of the system.

[0042] See also Figure 1 A combined control system of a gravity energy storage hybrid electrochemical energy storage system according to an embodiment of the present invention is used to implement the combined control method of the present invention, including a gravity energy storage system having a storage block and a gravity energy storage unit (permanent magnet synchronous motor 5), and an electrochemical energy storage system having a battery 3 and a super capacitor 4, and also including a connected data calculation module 1 and a combined control module 2, the combined control module 2 is respectively connected to the battery 3, the super capacitor 4 and the permanent magnet synchronous motor 5 of the gravity energy storage system.

[0043] In the electrochemical energy storage system part, the battery 3 is connected to the battery bidirectional DC / DC converter 6 and the battery bidirectional DC / DC controller 7, and the battery bidirectional DC / DC controller 7 is connected to the battery bidirectional DC / DC converter 6; the supercapacitor 4 is connected to the supercapacitor bidirectional DC / DC converter 8 and the supercapacitor bidirectional DC / DC controller 9, and the supercapacitor bidirectional DC / DC controller 9 is connected to the supercapacitor bidirectional DC / DC converter 8; the battery bidirectional DC / DC converter 6 and the supercapacitor bidirectional DC / DC converter 8 are connected in parallel with the electrochemical energy storage voltage stabilizing filter capacitor 10, and are connected to the power grid system 12 through the bidirectional DC / AC converter 11.

[0044] In the gravity energy storage system, the permanent magnet synchronous motor 5 (PMSM) is connected to the machine-side converter 13 and the machine-side controller 14, the machine-side controller 14 is connected to the machine-side converter 13, the machine-side converter 13 is connected to the grid-side converter 15, a gravity energy storage voltage stabilizing filter capacitor 16 is connected in parallel between the machine-side converter 13 and the grid-side converter 15, the grid-side converter 15 is connected to the grid-side controller 17, and the grid-side converter 15 and the grid-side controller 17 are both connected to the power grid system 12. The permanent magnet synchronous motor 5 is connected to the storage block through a transmission system, for example, to form a vertical shaft hoisting gravity energy storage system.

[0045] The data calculation module is used to obtain the power difference of the power command required by the gravity energy storage system according to the different moments of acceleration, uniform speed and deceleration of the storage block. The joint control module is used to optimize the power distribution control of the power difference according to the frequency, obtain the charging and discharging power of the battery and supercapacitor respectively, and use the electrochemical energy storage system for charging / discharging supplement to realize the joint control of the gravity energy storage hybrid electrochemical energy storage system.

[0046] by Figure 1 Taking the illustrated embodiment as an example, a combined control method of a gravity energy storage hybrid electrochemical energy storage system according to an embodiment of the present invention generally includes the following steps:

[0047] According to the different moments of acceleration, uniform speed and deceleration of the storage block, the power difference of the power command required by the gravity energy storage system is obtained;

[0048] The power difference is controlled by optimizing power distribution according to the frequency, and the charging and discharging power of the battery and supercapacitor are obtained respectively. The electrochemical energy storage system is used for charging / discharging supplement to realize the joint control of the gravity energy storage hybrid electrochemical energy storage system.

[0049] Among them, one end of the battery and the supercapacitor are respectively connected to a bidirectional DC / DC converter. At the same time, the upper power command controls the battery and the supercapacitor respectively under the power division control strategy; the other side of the bidirectional DC / DC converter is connected in parallel with a voltage stabilizing filter capacitor, and is connected to the simulated power grid through a bidirectional DC / AC converter; the gravity energy storage system is connected to the simulated power grid system through a permanent magnet synchronous motor, a machine-side converter and a grid-side converter in turn; the permanent magnet synchronous motor is controlled by the upper power command, and the machine-side converter and the grid-side converter are controlled by the machine-side controller and the grid-side controller respectively, and a voltage stabilizing filter capacitor is connected in parallel between the machine-side converter and the grid-side converter.

[0050] More specifically, first, in the process of setting up the gravity energy storage system (i.e., before performing joint control), the power and capacity of the gravity energy storage system are obtained according to the set unit parameters of the gravity energy storage system; the unit parameters of the gravity energy storage system include the mass of the storage block, the rated speed of the motor and the height difference, etc.

[0051] The heavy load model needs to consider various practical factors, including air resistance, motor reversal caused by dragging the heavy object to start, and large impact current. The real-time air resistance is:

[0052] f=1 / 2*CρSv 2 ,

[0053] Among them, f is air resistance, C is air resistance coefficient, ρ is air density, S is windward area of ​​the heavy object, and v is instantaneous speed of the storage block.

[0054] The capacity of the gravity energy storage system is expressed as:

[0055]

[0056] Where n is the total number of storage blocks used in the gravity energy storage system, m i is the mass of the i-th storage block, h 上 is the total height of the gravity energy storage system, h 下 It is the height of the descending area of ​​the gravity energy storage system.

[0057] When the transmission ratio of the transmission system is taken into consideration:

[0058] The starting torque is:

[0059] T 启 =m i gR,

[0060] The load torque is:

[0061] T L =(m i gf i )R,

[0062] Where R is the pulley radius in the transmission system, m i is the mass of the i-th storage block, g is the acceleration due to gravity, and f i is the air resistance experienced by the i-th storage block at a certain moment.

[0063] The gravity energy storage system is modeled according to the set parameters and can be represented by six basic modules: lifting system (weight model), mechanical system (mechanical transmission model), motor and machine-side / grid-side converter model, speed control system, machine-side control system, and grid-side control system.

[0064] The lifting system, mechanical system, motor and machine-side control system and converter model together constitute the electrical transmission system. The power and speed of the motor are controlled by the speed control system of the heavy object to achieve coordinated power control and heavy object lifting speed control. The machine-side control system performs vector control through the double closed loop of the speed outer loop and the current inner loop. The grid-side control system performs vector control through the double closed loop of the voltage outer loop and the current inner loop, and finally realizes the following given of the system state quantity. The waveform of the electromagnetic torque of the permanent magnet motor, the waveform of the voltage Udc on the DC bus side and the waveform of the speed n change of the permanent magnet synchronous motor are shown as follows respectively. Figure 2 , Figure 3 and Figure 4 shown.

[0065] In the process of obtaining the power difference of the power instruction required by the gravity energy storage system, based on the storage block at different times of acceleration, uniform speed and deceleration, the grid-connected power value of the gravity energy storage system in each stage is obtained, and the difference between the total power instruction value of the upper load (from the upper power instruction) at time t and the output power of the gravity energy storage system is used as the power difference.

[0066] Specifically, see Figure 5a and Figure 5b The schematic diagram of the energy storage process and power generation process of the gravity energy storage system is shown:

[0067] During the descent of the storage block, the gravity energy storage system releases energy and generates electricity, which is divided into three stages: the descent start acceleration stage, the uniform falling stage, and the descent deceleration braking stage.

[0068] The lifting process of the storage block is the energy storage and charging process of the gravity energy storage system, which is divided into three stages, including the lifting start-up acceleration stage, the uniform rising stage, and the lifting deceleration braking stage.

[0069] The gravity energy storage system obtains the grid-connected power value of gravity energy storage at different stages in real time at different times such as acceleration, uniform speed, and deceleration of the storage block, and uses the formula:

[0070] P load,t -PG,t =P bat,t +P SC,t ,

[0071] Calculate the sum of the power instructions of the battery and supercapacitor at each moment in the preset period, where P load,t is the total power command value of the upper load at time t, P G,t is the output power of the gravity energy storage system at time t, P bat,t and P SC,t They represent the power instructions of the battery and supercapacitor at time t respectively; for the comprehensive energy storage system, the two parts are independent of each other, and the power allocation of the gravity energy storage system and the electrochemical hybrid energy storage system is carried out through control strategy.

[0072] In the process of power optimization and distribution control, the pre-output of the electrochemical hybrid energy storage system is obtained based on the power difference, and the pre-output is decomposed into high-frequency components and low-frequency components according to the deterministic rule control strategy, which are provided by supercapacitors and batteries respectively. More specifically, Figure 6 As shown, according to the upper power instruction P load,t and P emitted by the gravity energy storage system G,t The power shortage required by the power acquisition system is the pre-output power of the electrochemical hybrid energy storage system. The required power is divided by a high-frequency filter, and its output is decomposed into high-frequency and low-frequency components according to its deterministic rule control strategy. The low-frequency power is controlled by the SOC of the battery to obtain the power command P of the battery. bat,t , while the remaining power and high-frequency components with large fluctuation frequency are provided by supercapacitors, which is P SC,t .

[0073] like Figure 7 As shown, the power distribution of the electrochemical hybrid energy storage system is further controlled, and the energy management setting is set to, for example, the following five ranges according to the SOC of the battery and the supercapacitor in the electrochemical energy storage unit:

[0074]

[0075] In other words, in the process of optimizing power distribution control according to the different SOC intervals of the electrochemical energy storage system, the SOC of the battery and the supercapacitor i :

[0076] Set the SOC discharge dead zone threshold to SOC min , that is, when SOC i <SOC min When the discharge temperature is too low, it is the over-discharge zone, or discharge dead zone, where the battery and supercapacitor can only be charged but not discharged;

[0077] Set the SOC discharge slowdown zone threshold to SOC low , that is, when SOC min <SOC i <SOC low When the discharge power is low, it is a slow discharge area, or discharge slowdown area, the battery and supercapacitor are charged normally, and the discharge power is reduced (relative to the normal discharge power);

[0078] Set the SOC charging dead zone threshold to SOC max , that is, when SOC max <SOC i When the battery is at overcharge, it is also called the charging dead zone. The battery and supercapacitor cannot be charged but can only be discharged.

[0079] Set the SOC charging slowdown zone threshold to SOC high , that is, when SOC high <SOC i <SOC max When the battery is in the slow charging zone, or the charging slowing zone, the charging power of the battery and supercapacitor is reduced (relative to the normal charging power), and the discharge is normal;

[0080] When SOC low <SOC i <SOC high It is the normal working area, and the battery and supercapacitor are charged and discharged normally.

[0081] In the process of charging / discharging supplementation using the electrochemical energy storage system, power optimization distribution control is performed according to the different SOC intervals of the electrochemical energy storage system, the charging and discharging power of the battery and supercapacitor is changed, and the instantaneous power fluctuation is smoothed by the supercapacitor to reduce the overshoot of the energy storage system regulation.

[0082] In a preferred embodiment, the discharge dead zone threshold SOC mi The discharge slowdown zone threshold SOC is 10%. low The SOC threshold of the charging slowdown zone is 20%. high The charging dead zone threshold SOC is 80%. max is 90%.

[0083] This part focuses on studying whether the control strategy is feasible and whether the joint control system operates normally. The simulation time is set to 6s, with the power emitted by the energy storage unit (grid-connected discharge) as the positive direction. The attached figure shows that the power waveform is on the positive half axis. When the power command is positive, the energy storage system works in the grid-connected discharge state, and power flows from the energy storage unit to the grid; when the power command is negative, the energy storage system works in the grid-connected charging state, and power flows from the grid to the energy storage unit; when the power command is 0, the energy storage system works in the standby state, and there is no power exchange. Set the power command required for the initial grid to 8kW, as shown in Figure 8:

[0084] The time range of 0 to 2.5s is the start-up and grid-connected discharge stage of the energy storage unit; the time range of 0 to 0.5s is the start-up stage of the gravity energy storage system. During the gravity energy storage start-up stage, the electrochemical hybrid energy storage system uses batteries and supercapacitors to supplement the power shortage in real time. When t = 0.5s, the gravity energy storage motor reaches the set speed of 100rad / s. The gravity energy storage system stably outputs 6kW of power, and the battery provides the remaining 2kW of system power shortage. The supercapacitor enters the standby state. At t = 2s, the speed of the gravity energy storage motor begins to decrease, the power output decreases, and at t = 2.5s, the final speed is reduced to 0, and no power is output. In 1.5 to 2.5s, the battery mainly compensates for the reduced power of the gravity energy storage system.

[0085] In the time range of 2.5 to 3.5 s, it is mainly the standby stage of the energy storage unit; at t = 2.5 s and t = 3.5 s, the upper power command changes, and the command output changes from 8 kW to 0 and from 0 to -8 kW respectively. Figure 3 As shown, in the initial stage, the DC bus voltage is stabilized at the set value of 600V after a short period of adjustment. At t=2.5s and t=3.5s, it is also stabilized at the set value, meeting the grid-connected control requirements.

[0086] In the time range of 3.5 to 6 seconds, it is the grid-connected charging stage of the energy storage unit; at this time, the upper power command is -8kW, and the gravity energy storage motor changes from generator mode to motor mode. In the reverse start-up stage of the gravity energy storage system, the electrochemical hybrid energy storage system uses batteries and supercapacitors to supplement the power shortage in real time during the gravity energy storage reverse start-up stage. When t = 4 seconds, the gravity energy storage motor reaches the set speed of -100rad / s. The gravity energy storage system stably absorbs 6kW of power, and the battery absorbs the remaining 2kW of the system power. The supercapacitor enters the standby state. At t = 5.5 seconds, the reverse speed of the gravity energy storage motor begins to decrease, and the absorbed power decreases. At t = 6 seconds, the final speed is reduced to 0, and no longer absorbs power. In 5.5 to 6 seconds, the power reduced by the gravity energy storage system is mainly absorbed by the battery, completing a power generation and storage cycle.

[0087] Supercapacitors have a faster charge and discharge speed than batteries and can quickly provide or absorb large amounts of electrical energy, such as Figure 8a As shown in the enlarged part, at t=0s, 2.5s and 3.5s, the gravity energy storage system starts or the power command changes. The supercapacitor can provide microsecond response to the instantaneous impact speed, timely meet the upper power demand, and then the battery and gravity energy storage gradually provide or supplement in turn to ensure the output active power and voltage and current stability. Figure 8c In the setting shown, instantaneous power spike fluctuations occurred at t=1.5s and t=4.5s. At this time, the gravity energy storage system still maintained a stable supply / output power, which was jointly smoothed by the electrochemical hybrid energy storage system. The supercapacitor first responded quickly to smooth the power spike, and then the battery supplemented the low-frequency component of the peak power fluctuation. Since supercapacitors are relatively expensive, the combined effect of the two can reduce system costs and further improve the overall system performance.

[0088] The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present invention. The present invention is not limited to the aforementioned specific embodiments, and those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0089] In summary, the present invention solves the problems of non-flowability and discontinuity of storage blocks in a single gravity energy storage system by combining different types of energy storage technologies, and can realize continuous, efficient and rapid transmission of multiple objects, and reduce the impact of heavy object start-stop and switching processes on mechanical transmission and power grid systems; battery energy storage can achieve continuous and uninterrupted power generation and storage, and the technology is relatively mature. In the process where the gravity energy storage block cannot be continuously transmitted, it can serve as a power supplement to provide energy requirements to meet the upper power instructions; at the same time, in the process of starting, stopping and switching the motion state of the gravity energy storage system, the large impact current generated, etc., the supercapacitor has a faster charging and discharging speed than the battery, can quickly provide or absorb a large amount of electrical energy, and smooth the power fluctuations; the control based on the method disclosed in the present invention can realize the reasonable allocation of upper power instructions, meet the requirements of larger-scale energy storage, and be configured and adjusted according to different application scenarios and needs to adapt to various energy storage needs and improve the overall performance of the energy storage system.

Claims

1. A combined control method for a gravity energy storage hybrid electrochemical energy storage system, characterized in that: The combined control system of the gravity energy storage hybrid electrochemical energy storage system includes a gravity energy storage system with a storage block, and an electrochemical energy storage system with a battery and a supercapacitor; It includes the following steps: According to the different moments of acceleration, uniform speed and deceleration of the storage block, the power difference of the power command required by the gravity energy storage system is obtained; The power difference is controlled by optimizing power distribution according to the frequency, and the charging and discharging power of the battery and supercapacitor are obtained respectively. The electrochemical energy storage system is used for charging / discharging supplement to realize the joint control of the gravity energy storage hybrid electrochemical energy storage system.

2. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 1 is characterized in that: In the process of setting up the gravity energy storage system, the power and capacity of the gravity energy storage system are obtained according to the unit parameters of the gravity energy storage system; the unit parameters of the gravity energy storage system include the mass of the storage block, the rated speed of the motor and the height difference.

3. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 2 is characterized in that: The capacity of the gravity energy storage system is expressed as: Where n is the total number of storage blocks used in the gravity energy storage system, m i is the mass of the i-th storage block, h 上 is the total height of the gravity energy storage system, h 下 It is the height of the descending area of ​​the gravity energy storage system.

4. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 1 is characterized in that: The upper power command controls the battery and supercapacitor respectively under the power division control strategy; the gravity energy storage system is connected to the power grid system through the permanent magnet synchronous motor, the machine-side converter and the grid-side converter in turn; the permanent magnet synchronous motor is controlled by the upper power command, and the machine-side converter and the grid-side converter are controlled by the machine-side controller and the grid-side controller respectively.

5. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 1 is characterized in that: In the process of obtaining the power difference of the power command required by the gravity energy storage system, the process of the storage block descending is the process of the gravity energy storage system releasing energy and generating electricity, which is divided into three stages, including the descent start acceleration stage, the uniform falling stage, and the descent deceleration braking stage; The lifting process of the storage block is the energy storage and charging process of the gravity energy storage system, which is divided into three stages, including the lifting start acceleration stage, the uniform rising stage, and the lifting deceleration braking stage; Based on the different moments of acceleration, uniform speed and deceleration of the storage block, the grid-connected power value of the gravity energy storage system in each stage is obtained, and the difference between the total power command value of the upper load at time t and the output power of the gravity energy storage system is used as the power difference.

6. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 1 is characterized in that: In the process of power optimization distribution control, the pre-output of the electrochemical hybrid energy storage system is obtained based on the power difference, and the pre-output is decomposed into high-frequency and low-frequency components according to the deterministic rule control strategy, which are provided by supercapacitors and batteries respectively.

7. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 1 is characterized in that: In the process of charging / discharging supplementation using the electrochemical energy storage system, power optimization distribution control is performed according to the different SOC intervals of the electrochemical energy storage system, the charging and discharging power of the battery and supercapacitor is changed, and the instantaneous power fluctuation is smoothed by the supercapacitor to reduce the overshoot of the energy storage system regulation.

8. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 7 is characterized in that: In the process of optimizing power distribution control according to the different SOC intervals of the electrochemical energy storage system, the SOC of the battery and supercapacitor i : Set the SOC discharge dead zone threshold to SOC min , that is, when SOC i <SOC min When the battery and supercapacitor are in the state of being charged, they cannot be discharged. Set the SOC discharge slowdown zone threshold to SOC low , that is, when SOC min <SOC i <SOC low When the battery and supercapacitor are charged normally, the discharge power is reduced; Set the SOC charging dead zone threshold to SOC max , that is, when SOC max <SOC i When the battery and supercapacitor cannot be charged, they can only be discharged; Set the SOC charging slowdown zone threshold to SOC high , that is, when SOC high <SOC i <SOC max When the battery and supercapacitor charge power decreases, they discharge normally; When SOC low <SOC i <SOC high When the battery and supercapacitor are charged and discharged normally.

9. The combined control method of the gravity energy storage hybrid electrochemical energy storage system according to claim 8, characterized in that: Discharge dead zone threshold SOC mi The discharge slowdown zone threshold SOC is 10%. low The SOC threshold of the charging slowdown zone is 20%. high The charging dead zone threshold SOC is 80%. max is 90%.

10. A combined control system for a gravity energy storage hybrid electrochemical energy storage system, characterized in that: A combined control method for a gravity energy storage hybrid electrochemical energy storage system according to any one of claims 1 to 9; comprising a data calculation module and a combined control module connected to each other, wherein the combined control module is respectively connected to a battery, a supercapacitor and a permanent magnet synchronous motor of the gravity energy storage system; The battery is connected to a battery bidirectional DC / DC converter and a battery bidirectional DC / DC controller, and the battery bidirectional DC / DC controller is connected to the battery bidirectional DC / DC converter; the supercapacitor is connected to a supercapacitor bidirectional DC / DC converter and a supercapacitor bidirectional DC / DC controller, and the supercapacitor bidirectional DC / DC controller is connected to the supercapacitor bidirectional DC / DC converter; the battery bidirectional DC / DC converter and the supercapacitor bidirectional DC / DC converter are connected in parallel with an electrochemical energy storage voltage stabilizing filter capacitor, and are connected to the power grid system through a bidirectional DC / AC converter; The permanent magnet synchronous motor is connected to a machine-side converter and a machine-side controller, the machine-side controller is connected to the machine-side converter, the machine-side converter is connected to the grid-side converter, a gravity energy storage voltage stabilizing filter capacitor is connected in parallel between the machine-side converter and the grid-side converter, the grid-side converter is connected to the grid-side controller, and both the grid-side converter and the grid-side controller are connected to the power grid system.

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