Power type gravity energy storage system and control method

Abstract

The invention provides a power type gravity energy storage system and a control method, and belongs to the technical field of energy stock. The power type gravity energy storage system is composed of a weight, a mechanical transmission system, a first motor, a machine side converter, a grid side converter and a power quick response device; the first motor rotor is connected with the weight through the transmission system, the machine-side converter is connected with the motor stator, the machine-side converter, the grid-side converter and the direct-current side of the power quick response device are connected in parallel, and the grid-side converter is connected with a power grid. The control method comprises the steps that during hot standby, the grid-side converter stabilizes voltage, the machine-side converter is locked, a brake is locked to keep a weight static, and the power quick response device adjusts stored energy; during power response, the grid-side converter tracks an active instruction, the power quick response device stabilizes voltage, the brake is released, and the machine-side converter controls the motor to drive the weight to ascend and descend to track power and maintain energy storage balance. Millisecond-level power tracking is realized by combining a small-capacity power quick response device, and the device has the advantages of long service life, hot standby zero loss and the like, and is suitable for frequency modulation of a power system and traffic energy recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and more specifically, to a power-type gravity energy storage system and a control method. Background Art

[0002] In new power systems with a high proportion of renewable energy and power electronic equipment, power-type energy storage systems play an important role in smoothing frequency fluctuations. Currently, power-type energy storage technologies include flywheel energy storage and supercapacitor energy storage, which are used in situations where frequent charging and discharging occur over a sustained period of time. Flywheel energy storage technology is highly difficult, as it contains harsh conditions such as ultra-high speed, ultra-high vacuum, and ultra-strong magnetic field, resulting in problems such as heat dissipation difficulties, manufacturing difficulties, and high costs. Supercapacitor energy storage also has the problems of high cost and capacity attenuation, which restricts its large-scale development.

[0003] Gravity energy storage is a new type of energy storage technology. The current research direction is mainly concentrated in the field of energy-type energy storage for long-term energy storage. It is used for peak regulation of power systems, compensation of fluctuations in wind power, photovoltaics and power loads, and maintenance of energy balance in power systems.

[0004] In new power systems with a high proportion of renewable energy and power electronic equipment, power-type energy storage needs to take on the task of smoothing millisecond-level frequency fluctuations. Current mainstream technologies have significant drawbacks:

[0005] 1. Flywheel energy storage: Relying on ultra-high speed (>100,000 rpm), ultra-high vacuum, and superconducting magnetic fields, it leads to high manufacturing costs, heat dissipation difficulties, and high technical risks.

[0006] 2. Supercapacitor energy storage: Problems such as rapid capacity decay and high cost restrict large-scale application;

[0007] 3. Traditional gravity energy storage: It focuses on energy-based scenarios (such as peak load regulation). Due to the inertia of heavy objects, the power response speed is slow (seconds) and cannot meet frequency regulation requirements.

[0008] Existing patents attempt to combine gravity energy storage with power-based energy storage (such as flywheels). Patent CN202210318924.0 uses a gravity-flywheel hybrid system to suppress power fluctuations during weight switching through electrical coupling. Patent CN202311360559.0 mechanically couples the flywheel to increase the system's rotational inertia, suppressing the disturbance caused by weight switching. The common drawback of these technologies is that they only use power-based energy storage as an auxiliary means, without changing the energy-based properties of gravity energy storage. This fails to address the power delay problem caused by the inherent inertia of gravity energy storage, and the system is complex and the cost has not been significantly reduced.

[0009] Currently, there is an urgent need for a low-cost, high-response, and long-life power-type gravity energy storage solution to fill the following technical gaps:

[0010] Directly use gravity energy storage for power-based scenarios (such as millisecond-level frequency modulation);

[0011] Break through the limitation of heavy object inertia on power response speed;

[0012] Achieve zero self-discharge and zero standby loss in hot standby state. Summary of the Invention

[0013] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a power-type gravity energy storage system and a control method to solve the problems raised in the above-mentioned background technology.

[0014] To achieve the above objectives, the present invention provides the following technical solution: a power-type gravity energy storage system, characterized in that it includes:

[0015] heavy objects;

[0016] Mechanical transmission system, including brakes;

[0017] a first motor, the rotor of which is connected to a weight via the mechanical transmission system;

[0018] a machine-side converter, the AC side of which is connected to the stator of the first motor;

[0019] Grid-side converter, whose AC side is connected to the grid;

[0020] The power fast response device includes an energy storage element and a power control device and has two combination modes;

[0021] The generator-side converter, the grid-side converter, and the DC side of the power rapid response device are connected in parallel to form a DC bus.

[0022] Preferably, the rapid power response device is a combination of a supercapacitor and a power control device; or the rapid power response device is a combination of a flywheel, a second motor and a power control device.

[0023] A control method for a power-type gravity energy storage system, comprising:

[0024] (a) Hot standby status control:

[0025] The grid-side converter performs constant DC voltage control; the generator-side converter is locked; the brake device is in a locked state, providing braking force for the mechanical transmission system to maintain the position of the heavy object unchanged;

[0026] The power control device inside the power fast response device maintains the energy of the energy storage element at a reasonable state of 20% to 80% by controlling its DC side voltage and current;

[0027] (b) Power response state control:

[0028] After receiving the power command, the power-type gravity energy storage system enters the power response state from the hot standby state, and the grid-side converter switches to the fixed active power mode within 10 milliseconds to track the power command; the power fast response device switches to the fixed DC voltage control; the brake device is released, and at the same time, the machine-side converter adjusts the rotor speed and direction of the first motor to drive the weight to rise and fall, dynamically adjusting the lifting speed of the weight to make the DC power of the machine-side converter match the grid-side converter in real time; and maintain the energy of the energy storage element at a reasonable state of 20% to 80%;

[0029] (c) Return to step (a) after the response is completed.

[0030] Preferably, the power dynamic matching implementation method of step (b) is: based on the DC power setting value of the grid-side converter, a motor torque command is generated through a proportional-integral regulator, and then the lifting acceleration of the heavy object is controlled according to the linear mapping relationship between the torque command and the potential energy of the heavy object.

[0031] Preferably, the zero-power maintenance mechanism in the hot standby state specifically includes: the mechanical locking structure of the brake device cuts off the power transmission path; the power device drive signal is turned off when the machine-side converter is locked; the power fast response device only outputs the maintenance current, and the system standby power consumption is <0.1% of the rated power.

[0032] Preferably, the energy state of the energy storage element is maintained in the following manner: when the state of charge is greater than 80%, the power control device actively discharges energy to the braking resistor; when the state of charge is less than 20%, it absorbs energy from the DC bus for charging.

[0033] The technical effects and advantages of the present invention are as follows:

[0034] 1. Compared with flywheel energy storage and supercapacitor energy storage, the present invention uses the potential energy of the weight to store energy. By quickly changing the rising or falling speed of the weight, its charge and discharge state and power size are controlled. A small-capacity power fast response device is used to achieve a fast power response. Its cost is low and the technical difficulty is small.

[0035] 2. The structure of the present invention is relatively simple. Through system optimization, the power response speed of the power-type gravity energy storage system can reach millisecond level, which is on par with flywheel energy storage and supercapacitor energy storage;

[0036] 3. The present invention is a mechanical energy storage device with a long lifespan. The number of charge and discharge cycles can reach millions without the problem of capacity attenuation.

[0037] 4. Compared with flywheel energy storage and supercapacitor energy storage, the present invention has almost zero power loss in hot standby state. The heavy object maintains its position under the braking action of the brake device and there is no self-discharge phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the power-type gravity energy storage system and control method of the present invention.

[0039] Figure 2 This is a fast power response device based on supercapacitor energy storage in the present invention.

[0040] Figure 3 It is a power rapid response device based on flywheel energy storage in the present invention.

[0041] Figure 4 Schematic diagram of the workflow of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] Example 1

[0044] As attached Figure 1-4 As shown, a power-type gravity energy storage system is disclosed, comprising:

[0045] The weight, the core energy storage medium, realizes the conversion of potential energy into electrical energy through lifting;

[0046] The mechanical transmission system includes a brake device that transmits mechanical power. The brake device locks the transmission shaft to lock the weight in place during hot standby.

[0047] The first motor has a rotor connected to the weight through the mechanical transmission system, the rotor is directly connected to the transmission system, and the stator is connected to the machine-side converter; when discharging, it acts as a generator (the weight descends and drives the rotor to generate electricity), and when charging, it acts as a motor (absorbing electrical energy to lift the weight);

[0048] The AC side of the machine-side converter is connected to the stator of the first motor to control the torque / speed of the first motor and realize the power regulation of the lifting of heavy objects;

[0049] The grid-side converter has its AC side connected to the grid, a grid-connected interface, voltage stabilization during hot standby, and tracking of active power instructions during response;

[0050] A fast power response device, including energy storage elements such as a flywheel and its controller, is connected in parallel to the busbar on the DC side to instantly compensate for power differences;

[0051] The generator-side converter, the grid-side converter, and the DC side of the power rapid response device are connected in parallel to form a DC bus, thereby achieving bidirectional power flow and dynamic balance.

[0052] In this embodiment, the power rapid response device is a combination of a supercapacitor and a power control device; or the power rapid response device is a combination of a flywheel, a second motor and a power control device, wherein the supercapacitor serves as an energy storage element and is connected to the DC bus through a power control device (such as a bidirectional DC / DC converter). When the power suddenly changes, the supercapacitor charges and discharges in milliseconds to absorb / release the difference in power; the power control device adjusts the charging and discharging current to maintain the capacitor charge state (20%-80%); the flywheel + second motor (motor / generator integrated unit) serves as an energy storage unit, and the power control device drives the second motor. When the power fluctuates, the second motor controls the acceleration / deceleration of the flywheel to convert kinetic energy into electrical energy and inject / absorb the DC bus power.

[0053] In this embodiment, a control method for a power-type gravity energy storage system is provided, including:

[0054] (a) Hot standby status control:

[0055] The grid-side converter performs constant DC voltage control; the generator-side converter is locked; the brake device is in a locked state, providing braking force for the mechanical transmission system to maintain the position of the heavy object unchanged;

[0056] The power control device inside the power rapid response device maintains the energy of the energy storage element at a reasonable state of 20% to 80% by controlling its DC side voltage and current; among them, the grid-side converter is controlled by a fixed DC voltage to maintain a constant bus voltage and isolate grid disturbances; the machine-side converter is locked, shutting down the power devices and cutting off the motor electrical circuit; the brake locking mechanism locks the heavy objects to eliminate position drift; the power control device of the power rapid response device actively adjusts charging and discharging (such as small current circulation) to maintain the energy of the energy storage element in the optimal range of 20%-80%.

[0057] (b) Power response state control:

[0058] Upon receiving a power command, the power-type gravity energy storage system enters a power response state from a hot standby state. The grid-side converter switches to a constant active power mode within 10 milliseconds to track the power command. The power rapid response device switches to a constant DC voltage control mode. The brake device releases, and the generator-side converter adjusts the rotor speed and direction of the first motor to drive the weight up and down, dynamically adjusting the lifting speed of the weight so that the DC power of the generator-side converter matches the grid-side converter in real time. The energy storage element maintains a reasonable energy level of 20% to 80%. The grid-side converter switches to a constant active power mode within 10 milliseconds to accurately track the external command (e.g., ±1% error). The power rapid response device switches to a constant DC voltage control mode to assume the bus voltage stabilization task. The brake release removes mechanical constraints, allowing the weight to move. The generator-side converter adjusts the motor speed / torque to drive the weight up and down, so that the generator-side DC power matches the grid-side power command in real time (dynamic hysteresis ≤ 0.5 seconds). The energy storage maintenance power control device limits the depth of charge and discharge to ensure that the energy is always within the 20%-80% safety window.

[0059] (c) After the response is completed, return to step (a).

[0060] In this embodiment, the dynamic power matching of step (b) is implemented as follows: based on the DC power setting value of the grid-side converter, a motor torque command is generated through a proportional-integral regulator, and then the lifting acceleration of the heavy object is controlled according to the linear mapping relationship between the torque command and the potential energy of the heavy object.

[0061] In this embodiment, the zero-power maintenance mechanism in the hot standby state specifically includes: the mechanical locking structure of the brake device cuts off the power transmission path; the power device drive signal is turned off when the machine-side converter is locked; the power fast response device only outputs the maintenance current, and the system standby power consumption is less than 0.1% of the rated power. Among them, the triple isolation design, the mechanical isolation is: the brake device adopts a normally closed electromagnetic brake, and the friction plate presses the drive shaft in hot standby to cut off the power transmission path (mechanical efficiency loss ≈ 0); the electrical isolation is to turn off the IGBT drive signal when the machine-side converter is locked, and the DC side is disconnected from the motor winding (leakage current <1mA); in micro-power standby, the power fast response device only outputs the maintenance current (such as supercapacitor self-discharge compensation), and the total standby power consumption of the system is controlled within 0.1% of the rated power (such as 10kW system standby <10W).

[0062] In this embodiment, the energy state of the energy storage element is maintained in the following manner: when the state of charge is greater than 80%, the power control device actively discharges energy to the braking resistor; when the state of charge is less than 20%, energy is absorbed from the DC bus for charging. Among them, for overcharge protection, when the state of charge is greater than 80%, the power control device triggers the discharge circuit to dissipate excess energy into the braking resistor (such as through voltage reduction and heat generation through the Buck circuit); when the state of charge is less than 20%, the power control device draws power from the DC bus and charges the energy storage element through the Boost circuit. In the range of 20%-80%, charging and discharging are adjusted according to the power instruction priority (response instruction>energy maintenance).

[0063] The working process of the present invention is as follows:

[0064] First, in hot standby mode, the grid-side converter implements constant DC voltage control to stabilize the DC bus. Simultaneously, the generator-side converter remains locked, disconnecting motor control. The brake device locks the mechanical transmission system to immobilize the load. Meanwhile, the rapid power response device continuously regulates the charge and discharge of its internal energy storage element (supercapacitor or flywheel) to maintain stored energy within a reasonable range, achieving zero system standby loss. Upon receiving an external power command, the system immediately switches to power response mode: the grid-side converter first switches to constant active power mode, tracking the grid power command within milliseconds. Simultaneously, the rapid power response device takes over DC bus voltage regulation, switching to constant DC voltage control to compensate for instantaneous power fluctuations. The brake device then releases the mechanical brake. At the same time, the machine-side converter is unlocked and drives the weight up and down by controlling the speed and direction of the first motor rotor: if discharge is required (such as grid frequency regulation shortage), the weight is driven down to make the motor generate electricity, and the electric energy is injected into the DC bus through the machine-side converter for grid-side output; if charging is required (such as energy recovery), the grid-side electric energy is absorbed to drive the motor to lift the weight to store potential energy. During the dynamic adjustment process, the machine-side converter continuously adjusts the lifting speed of the weight so that the machine-side power gradually approaches the grid-side power, and the power fast response device absorbs or fills the power difference between the two in real time to ensure the energy stability of the energy storage element, and finally forms After the response is complete, the system returns to hot standby mode: the generator-side converter decelerates the load to a stop and relocks it, the brake device locks the load in place, and the grid-side converter and power rapid response device switch back to their initial control mode. The key collaborative advantage lies in the fact that the power rapid response device instantly compensates for the mechanical inertia delay of the load (seconds to milliseconds), while the dual mechanisms of mechanical braking and electrical locking ensure zero loss in hot standby mode, ultimately achieving long-life, self-attenuating, and low-cost power-based energy storage.

[0065] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense, and may refer to mechanical or electrical connections, internal communication between two components, or direct connection. "Up," "down," "left," and "right" are only used to indicate relative positional relationships. When the absolute positions of the objects being described change, the relative positional relationships may also change.

[0066] Secondly: The drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention. Other structures may refer to conventional designs. The same embodiment and different embodiments of the present invention may be combined with each other without conflict.

[0067] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A power-type gravity energy storage system, characterized in that: include: heavy objects; Mechanical transmission system, including brakes; a first motor, the rotor of which is connected to a weight via the mechanical transmission system; a machine-side converter, the AC side of which is connected to the stator of the first motor; Grid-side converter, whose AC side is connected to the grid; The power fast response device includes an energy storage element and a power control device and has two combination modes; The generator-side converter, the grid-side converter, and the DC side of the power rapid response device are connected in parallel to form a DC bus.

2. A power-type gravity energy storage system according to claim 1, characterized in that: The rapid power response device is a combination of a supercapacitor and a power control device; or the rapid power response device is a combination of a flywheel, a second motor and a power control device.

3. A control method for a power-type gravity energy storage system according to any one of claims 1 to 2, characterized in that: include: (a) Hot standby status control: The grid-side converter performs constant DC voltage control; the generator-side converter is locked; the brake device is in a locked state, providing braking force for the mechanical transmission system to maintain the position of the heavy object; the power control device inside the power rapid response device controls its DC side voltage and current to maintain the energy of the energy storage element at a reasonable state of 20% to 80%; (b) Power response state control: After receiving the power command, the power-type gravity energy storage system enters the power response state from the hot standby state, and the grid-side converter switches to the fixed active power mode within 10 milliseconds to track the power command; the power fast response device switches to the fixed DC voltage control; the brake device is released, and at the same time, the machine-side converter adjusts the rotor speed and direction of the first motor to drive the weight to rise and fall, dynamically adjusting the lifting speed of the weight to make the DC power of the machine-side converter match the grid-side converter in real time; and maintain the energy of the energy storage element at a reasonable state of 20% to 80%; (c) Return to step (a) after the response is completed.

4. The control method of a power-type gravity energy storage system according to claim 3, characterized in that: The dynamic power matching implementation method of step (b) is as follows: based on the DC power setting value of the grid-side converter, the motor torque command is generated through the proportional-integral regulator, and then the lifting acceleration of the heavy object is controlled according to the linear mapping relationship between the torque command and the potential energy of the heavy object.

5. The control method of a power-type gravity energy storage system according to claim 3, characterized in that: The zero-power maintenance mechanism in the hot standby state specifically includes: the mechanical locking structure of the brake device cuts off the power transmission path; the power device drive signal is turned off when the machine-side converter is locked; the power fast response device only outputs the maintenance current, and the system standby power consumption is less than 0.1% of the rated power.

6. The control method of a power-type gravity energy storage system according to claim 3, characterized in that: Energy state maintenance method of energy storage element: when the state of charge is greater than 80%, the power control device actively discharges energy to the braking resistor; when the state of charge is less than 20%, it absorbs energy from the DC bus to charge.

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