CN114123239A - Flywheel-battery hybrid energy storage frequency regulation system, method, device and medium - Google Patents
Flywheel-battery hybrid energy storage frequency regulation system, method, device and medium Download PDFInfo
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
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Abstract
The application discloses a flywheel-battery hybrid energy storage frequency adjusting system, a method, equipment and a medium, wherein the system comprises a flywheel energy storage system and a battery energy storage system, in a starting stage, the rotating speed of a flywheel is increased from zero to a rated rotating speed, and the battery energy storage system enters a standby state; when the frequency of the power grid is in a normal state, the flywheel energy storage system enters into rotation speed control to keep the rotation speed of the flywheel at a rated rotation speed, and the battery energy storage system works in a standby state; the power grid frequency is in an abnormal state, an inertia response adjusting stage is started, and the flywheel energy storage system adopts a virtual inertia control strategy based on the self inertia of the flywheel and the power grid frequency state; entering a primary frequency modulation stage, wherein a droop control strategy is adopted by a battery energy storage system, and a virtual inertia control strategy is kept by a flywheel energy storage system; in the flywheel energy storage charge state recovery stage, the flywheel energy storage system enters a charge state recovery state, the battery energy storage system participates in primary frequency modulation of the power grid, and meanwhile, the extra output power is matched with the energy absorbed when the flywheel energy storage charge state is recovered.
Description
Technical Field
The present application relates to the field of energy storage and grid system inertia and frequency response technologies, and in particular, to a flywheel-battery hybrid energy storage frequency adjusting system, method, device, and medium.
Background
From the aspect of power grid stability, the dynamics and stability of the frequency are important indexes indicating the power grid strength and the balance of the power consumption of the generated energy. In a new energy power grid, inertia of a power grid system is reduced due to access of a large number of power electronic converters, which also means that when a frequency event (such as disconnection of a generator, access of a load and fluctuation of wind power photovoltaic processing) occurs in the system, the power grid system is easy to have faster frequency change and larger frequency deviation under load disturbance, and the introduction of an energy storage system can effectively control the frequency change frequency and the frequency deviation of the system when the frequency event occurs, so that the energy storage system plays an important role in stabilizing the frequency fluctuation and stabilizing the voltage of the power grid.
According to the power grid frequency change stage, the frequency modulation control strategy can be divided into an inertia response stage and a primary frequency modulation response stage. The inertial response stage is that a frequency event generally occurs within tens of milliseconds to several seconds, the system bears a large frequency change rate at the moment and is in a frequency deterioration period, and the frequency fluctuation at the moment presents a high-frequency characteristic; the primary frequency modulation response stage is usually within tens of seconds to one minute of the frequency event of the power grid, and is in a frequency recovery period, and the primary frequency modulation response stage needs the energy storage system to provide long-time energy support.
The grid frequency response puts power and energy demands on the energy storage system at different time scales, so the energy storage system must have both good power output characteristics and certain capacity. The single type of energy storage form hardly meets the above requirements, so that a power type energy storage system with higher power density and an energy type energy storage system with high capacity and long-time energy storage capacity can be combined to form a hybrid energy storage system. The flywheel energy storage system is used as a power type energy storage system, has the advantages of high power density, high response speed and long service life, can participate in frequency modulation of a power grid at high frequency, has self inertia, and can reasonably set a control strategy, so that the flywheel energy storage system provides damping and inertia for the power grid, and the inertia frequency adjustment of the power grid is realized; the lithium ion battery energy storage system is used as an energy type energy storage system, can provide long-time power support for a power grid, and achieves primary frequency modulation response of the power grid. The hybrid energy storage system combining the flywheel energy storage system and the lithium ion battery system can exert the advantages of the energy storage system to the maximum extent and control the frequency change of a power grid within a reasonable range.
In the related art, most energy storage systems adopting a single form participate in grid frequency response. In the power type energy storage system participating power grid inertia response control strategy, a virtual inertia control strategy based on a fixed inertia constant is mostly adopted, and the strategy cannot determine the depth of energy storage participating power grid frequency modulation by utilizing the self parameters of energy storage and the power grid frequency condition to the maximum extent. In the research of the related hybrid energy storage system, the power type energy storage system and the energy type energy storage system are mostly controlled and operated respectively and independently, and the output control strategy of the power type energy storage system at different stages of frequency response and the charge state recovery of the power type energy storage system are not researched, so that the frequency recovery time of a power grid is prolonged, the energy storage capacity configuration is increased, the system cost is increased, and urgent solution is needed.
Content of application
The present application is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, a first objective of the present application is to provide a flywheel-battery hybrid energy storage frequency adjusting system, which can implement an inertial response and a primary frequency adjustment after a power grid frequency event occurs, implement a state of charge recovery of a flywheel energy storage system, and improve utilization efficiency of the energy storage system.
A second objective of the present application is to provide a flywheel-battery hybrid energy storage frequency adjustment method.
A third object of the present application is to provide an electronic device.
A fourth object of the present application is to propose a computer readable storage medium.
In order to achieve the above object, a flywheel-battery hybrid energy storage frequency adjusting system is provided in an embodiment of the present application, which includes a flywheel energy storage system connected to a power grid and a lithium ion battery energy storage system, wherein,
when the lithium ion battery is in a starting stage, the rotating speed of the flywheel is gradually increased from zero to a rated rotating speed, and the lithium ion battery energy storage system is controlled to enter a standby state;
if the power grid frequency is in a preset normal state, the flywheel energy storage system enters a rotating speed control working condition, the rotating speed of the flywheel is kept at the rated rotating speed, and the battery energy storage system works in a standby state; and
if the power grid frequency is in a preset abnormal state, the system enters an inertia response adjustment stage, the flywheel energy storage system adopts a virtual inertia control strategy based on the self inertia of the flywheel and the power grid frequency state, the system enters a primary frequency adjustment stage, the battery energy storage system adopts a droop control strategy, and the flywheel energy storage system keeps the virtual inertia control strategy; and
when the energy storage system is in a flywheel energy storage charge state recovery stage, the flywheel energy storage system enters a charge state recovery state, so that the battery energy storage system participates in primary frequency modulation of a power grid, and meanwhile, extra output power is matched with energy absorbed when the flywheel energy storage charge state is recovered.
According to the flywheel-battery hybrid energy storage frequency adjusting system, inertia and frequency response control strategies of flywheel-battery system coordination considering the inertia of the flywheel and the frequency state of a power grid are adopted, inertia is provided for the power grid through flywheel energy storage at the initial stage of frequency event occurrence, frequency support is provided for the power grid through the combination of the battery energy storage system and the flywheel energy storage system during primary frequency modulation, and the charge state recovery of the flywheel energy storage system is realized, so that the inertia response and the primary frequency adjustment after the frequency event of the power grid occurs are realized, the charge state recovery of the flywheel energy storage system is realized, and the utilization efficiency of the energy storage system is improved.
In addition, the flywheel-battery hybrid energy storage frequency adjusting system according to the above embodiment of the present application may further have the following additional technical features:
optionally, when the power grid frequency is in the secondary frequency modulation stage, the adjusting system waits for other units to enter the secondary frequency modulation while maintaining the current output level, so that the power grid frequency is restored to the preset normal state.
Optionally, the flywheel energy storage system and the lithium ion battery energy storage system are connected in parallel through a direct current bus unit, and are connected to the power grid through a grid-side converter, an LCL filter, a grid-connected converter and a transformer.
Optionally, wherein,
the power grid is connected with the direct current bus unit sequentially through the transformer, the LCL filter circuit and the grid-side converter, wherein the grid-side converter is used for maintaining the voltage of the direct current bus to be stable, and therefore power can flow between the power grid and the energy storage system in a two-way mode.
Optionally, in the flywheel energy storage system, each three-phase of the stator side of the dual three-phase permanent magnet synchronous motor forms a bridge arm, each bridge arm is provided with a machine side filter and a machine side converter, the two bridge arms are connected in parallel and then connected with the dc bus unit through a flywheel energy storage grid-connected circuit breaker, the machine side converter regulates the voltage input to the rotor of the flywheel energy storage motor to control the physical quantity, and the rotor of the dual three-phase permanent magnet synchronous motor and the large inertia flywheel rotor are connected through a rotating shaft to transmit the mechanical power.
Optionally, the lithium ion battery energy storage system is sequentially connected with a battery energy storage side DC/DC converter and a battery energy storage system grid-connected breaker, the DC bus capacitor is connected, and the DC/DC converter adjusts a lithium ion battery side voltage to perform power exchange between the lithium ion battery energy storage system and the power grid.
In order to achieve the above object, a second aspect of the present application provides a flywheel-battery hybrid energy storage frequency adjustment method, which employs the above flywheel-battery hybrid energy storage frequency adjustment system, where the method includes the following steps:
when the lithium ion battery is in a starting stage, the rotating speed of the flywheel is gradually increased from zero to a rated rotating speed, and the lithium ion battery energy storage system is controlled to enter a standby state;
if the power grid frequency is in a preset normal state, controlling the flywheel energy storage system to enter a rotating speed control working condition, keeping the rotating speed of the flywheel at the rated rotating speed, and controlling the battery energy storage system to work in a standby state; and
if the power grid frequency is in a preset abnormal state, controlling the system to enter an inertia response adjustment stage, enabling the flywheel energy storage system to adopt a virtual inertia control strategy based on the inertia of the flywheel and the power grid frequency state, and enabling the battery energy storage system to adopt a droop control strategy to control the flywheel energy storage system to keep the virtual inertia control strategy, wherein the system enters a primary frequency modulation stage; and
and when the energy storage state of charge of the flywheel is recovered, controlling the energy storage system of the flywheel to enter the state of charge recovery, so that the energy storage system of the battery participates in primary frequency modulation of a power grid, and simultaneously, additionally outputting power to match the energy absorbed when the energy storage state of charge of the flywheel is recovered.
According to the flywheel-battery hybrid energy storage frequency adjusting method, the inertia and frequency response control strategy of flywheel-battery system coordination considering the self inertia of the flywheel and the frequency state of the power grid is adopted, the inertia is provided for the power grid through flywheel energy storage at the initial stage of the frequency event, the battery energy storage system and the flywheel energy storage system are combined to provide frequency support for the power grid during the primary frequency modulation period, and the charge state recovery of the flywheel energy storage system is realized, so that the inertia response and the primary frequency adjustment after the frequency event of the power grid is realized, the charge state recovery of the flywheel energy storage system is realized, and the utilization efficiency of the energy storage system is improved.
Optionally, the flywheel-battery hybrid energy storage frequency adjusting method according to the embodiment of the present application further includes:
and when the power grid frequency is in the secondary frequency modulation stage, controlling the adjusting system to maintain the current output level, and waiting for other units to enter secondary frequency modulation to recover the power grid frequency to the preset normal state.
To achieve the above object, an embodiment of a third aspect of the present application provides an electronic device, including: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being configured to perform a flywheel-battery hybrid energy storage frequency adjustment method as described in the above embodiments.
In order to achieve the above object, a fourth aspect of the present application provides a computer-readable storage medium storing computer instructions for causing a computer to execute the flywheel-battery hybrid energy storage frequency adjusting method according to the above embodiment.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a flowchart of a flywheel-battery hybrid energy storage frequency adjustment method according to an embodiment of the present application;
FIG. 2 is a block diagram of a topology of a flywheel-battery hybrid energy storage frequency regulation system according to an embodiment of the present application;
FIG. 3 is a control block diagram of a flywheel-battery hybrid energy storage frequency regulation system according to an embodiment of the present application;
FIG. 4 is a control flow diagram of a flywheel-battery hybrid energy storage frequency regulation system according to an embodiment of the present application;
FIG. 5 is a waveform diagram of a grid frequency and a rate of change of the grid frequency according to an embodiment of the present application;
FIG. 6 is a waveform diagram of flywheel energy storage power, flywheel energy storage virtual inertia, flywheel energy storage state of charge, and battery energy storage power according to one embodiment of the present application;
fig. 7 is a flowchart of a flywheel-battery hybrid energy storage frequency adjustment method according to an embodiment of the present application;
fig. 8 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application.
The flywheel-battery hybrid energy storage frequency regulation system, method, apparatus, and medium proposed according to an embodiment of the present application will be described below with reference to the accompanying drawings, and first, the flywheel-battery hybrid energy storage frequency regulation system proposed according to an embodiment of the present application will be described with reference to the accompanying drawings.
Specifically, fig. 1 is a block diagram illustrating a flywheel-battery hybrid energy storage frequency adjustment system according to an embodiment of the present disclosure.
As shown in fig. 1, the flywheel-battery hybrid energy storage frequency adjusting system 100 includes a flywheel energy storage system 101 and a lithium ion battery energy storage system 102, which are connected to a power grid, wherein, in a starting phase, a flywheel rotation speed gradually increases from zero to a rated rotation speed, and the lithium ion battery energy storage system 102 is controlled to enter a standby state; if the power grid frequency is in a preset normal state, the flywheel energy storage system 101 enters a rotation speed control working condition, the rotation speed of the flywheel is kept at a rated rotation speed, and the battery energy storage system works in a standby state; if the power grid frequency is in a preset abnormal state, the system enters an inertia response adjustment stage, the flywheel energy storage system 101 adopts a virtual inertia control strategy based on the self inertia of the flywheel and the power grid frequency state, the system enters a primary frequency adjustment stage, the battery energy storage system adopts a droop control strategy, and the flywheel energy storage system 101 keeps the virtual inertia control strategy; and when the energy storage state of charge of the flywheel is in a recovery stage, the energy storage system 101 of the flywheel enters the state of charge recovery stage, so that the energy storage system of the battery participates in primary frequency modulation of the power grid, and meanwhile, the extra output power is matched with the energy absorbed when the energy storage state of charge of the flywheel is recovered.
Specifically, when the flywheel-battery hybrid energy storage frequency adjusting system 100 is in a starting stage (i.e., enters a power-on starting stage), the flywheel energy storage system 101 is closed in a grid-connected circuit breaker, the flywheel energy storage system 101 absorbs power of a power grid through a side converter of the flywheel energy storage machine, and the rotating speed of the flywheel gradually rises from zero to a rated rotating speed; the lithium ion battery energy storage system 102 is closed when the grid-connected circuit breaker is closed, and the lithium ion battery energy storage system 102 enters a standby state.
Further, when the grid frequency is in a preset normal state, the flywheel-battery hybrid energy storage frequency adjusting system 100 does not participate in grid frequency modulation; the flywheel energy storage system 101 enters into the rotation speed control, keeps the rotation speed of the flywheel at the rated rotation speed and does not emit and absorb power to the outside; the lithium ion battery energy storage system 102 does not emit and absorb power to the outside when operating in a standby state.
Further, when the grid frequency is in a preset abnormal state (for example, a generator is disconnected, a load is connected, and wind power photovoltaic processing fluctuates), the flywheel-battery hybrid energy storage frequency adjusting system 100 participates in the grid frequency adjustment, and is divided into an inertial response adjustment stage, a primary frequency adjustment stage, a flywheel energy storage charge state recovery stage, and a secondary frequency modulation stage according to different stages of the grid frequency fluctuation. When the power grid frequency modulation is in an inertia response adjustment stage, the control unit of the flywheel energy storage system 101 detects the frequency change rate of the power grid, at the moment, the flywheel energy storage system 101 quickly responds, and provides inertia power for the power grid to support and participate in the power grid frequency modulation by adopting a virtual inertia control strategy based on the inertia of the flywheel and the power grid frequency state; the control unit of the lithium ion battery energy storage system 102 detects the frequency deviation of the power grid, at the moment, the frequency deviation of the system does not exceed a control dead zone (50 +/-0.033 Hz), and the lithium ion battery energy storage system 102 does not emit and absorb power outwards and is in a standby state; when the frequency modulation stage is in a primary frequency modulation stage, the control unit of the lithium ion battery energy storage system 102 detects that the frequency deviation of the power grid exceeds a control dead zone (50 +/-0.033 Hz), the lithium ion battery energy storage system 102 adopts a droop control strategy, and the droop coefficient depends on the frequency deviation of the power grid and the rated capacity of the lithium ion battery energy storage system 102; the flywheel energy storage system 101 control unit detects the grid frequency change rate and keeps a virtual inertia control strategy based on the inertia of the flywheel and the grid frequency state.
Further, in the flywheel energy storage state of charge recovery phase, the flywheel energy storage system 101 detects that the flywheel state of charge SOC is lower than the set rating: SOCminWhen the power is not equal to 0.25, the flywheel energy storage system 101 stops sending power to the outside, and starts a flywheel energy storage charge state recovery stage, and the PI controller is used for realizing flyingThe energy storage charge state of the wheel is recovered, and the energy storage charge state of the flywheel is recovered to a set value SOCn0.75; in the process of recovering the energy storage state of charge of the flywheel, the lithium ion battery energy storage system 102 continuously participates in primary frequency modulation of the power grid on one hand, and additionally outputs power to match the energy absorbed when the energy storage state of charge of the flywheel is recovered on the other hand, so that secondary falling of the frequency of the power grid is avoided.
Further, in some embodiments, in the secondary frequency modulation stage, the adjustment system waits for other units to enter the secondary frequency modulation while maintaining the current output level, so that the power grid frequency is restored to the preset normal state.
Therefore, compared with the method of the related art, the method has the following characteristics and beneficial effects:
(1) in the phase of adjusting the inertia response of the power grid, a virtual inertia control strategy based on the inertia of the flywheel and the frequency state of the power grid is adopted, inertia power support is provided for the power grid to participate in frequency modulation of the power grid, the characteristics of large inertia and high power density of a flywheel energy storage system can be reflected to the maximum degree, the system frequency deterioration is prevented in a short time, and the frequency change rate and the maximum frequency deviation of the power grid are reduced.
(2) The coordination control and complementation of the power type energy storage system and the energy type energy storage system in the power grid frequency regulation are realized, the advantages of the two energy storage systems are maximized, and the power grid frequency regulation response speed and the regulation effect are improved.
(3) The control strategy of the recovery of the SOC (state of charge) of the flywheel energy storage system is considered, so that the cycle number of the system can be ensured, the efficiency of the system is improved, the energy storage capacity configuration is reduced, and the cost is saved.
For ease of understanding, the components of the flywheel-battery hybrid storage frequency adjustment system 100 will be described in detail below.
Specifically, in some embodiments, the flywheel energy storage system 101 and the lithium ion battery energy storage system 102 are connected in parallel through a dc bus unit, and are connected to the grid through a grid-side converter, an LCL filter, a grid-connected converter, and a transformer.
The flywheel energy storage system 101 comprises a flywheel energy storage grid-connected circuit breaker, two sets of flywheel energy storage machine side converters, a flywheel energy storage machine side LC filter, a double three-phase permanent magnet synchronous motor and a large-inertia flywheel rotor; the lithium ion battery energy storage system 102 comprises a battery energy storage system grid-connected circuit breaker, a battery energy storage side DC/DC converter and a lithium ion battery pack. The connection relationship of each device is as follows:
in some embodiments, the grid is connected to the dc bus unit sequentially through a transformer, an LCL filter circuit, and a grid-side converter, wherein the grid-side converter is configured to maintain the dc bus voltage stable, so that power flows bidirectionally between the grid and the energy storage system.
Optionally, in some embodiments, in the flywheel energy storage system 101, each three-phase of the stator side of the dual three-phase permanent magnet synchronous motor forms a bridge arm, and each bridge arm is provided with a machine side filter and a machine side converter, after the two bridge arms are connected in parallel, the two bridge arms are connected with the dc bus unit through the flywheel energy storage grid-connected circuit breaker, the machine side converter adjusts the voltage input to the rotor of the flywheel energy storage motor to control physical quantities such as the electromagnetic torque and the rotation speed of the motor, and the rotor of the dual three-phase permanent magnet synchronous motor and the large inertia flywheel rotor are connected through a rotating shaft to transmit mechanical power.
Optionally, in some embodiments, the lithium ion battery energy storage system 102 is sequentially connected to a battery energy storage side DC/DC converter and a battery energy storage system grid-connected breaker, and the DC bus capacitor is connected, and the DC/DC converter adjusts a voltage at the lithium ion battery side to perform power exchange between the lithium ion battery energy storage system 102 and a power grid.
In order to further understand the flywheel-battery hybrid energy storage frequency adjustment system according to the embodiment of the present application, the following detailed description is provided with reference to specific embodiments.
Specifically, as shown in fig. 2, the topology of the flywheel-battery hybrid energy storage frequency adjustment system of the embodiment of the present application includes: the system comprises a power grid model 1, a transformer 2, an LCL filter 3, a grid-side converter 4, a direct-current bus capacitor 5, a flywheel energy storage grid-connected circuit breaker 6, a flywheel energy storage machine-side converter 7, a flywheel energy storage machine-side LC filter 8, a double three-phase permanent magnet synchronous motor 9, a large-inertia flywheel rotor 10, a battery energy storage grid-connected circuit breaker 11, a battery energy storage side DC/DC converter 12 and a lithium ion battery energy storage system 102.
Specifically, the power grid 1 is connected with the direct-current bus capacitor 5 through the transformer 2, the LCL filter circuit 3 and the grid-side converter 4, and the grid-side converter 4 maintains the voltage stability of the direct-current bus capacitor 5, so that the power can flow between the power grid and the hybrid energy storage system in a two-way mode.
In the flywheel energy storage system, a stator side of a double three-phase permanent magnet synchronous motor 9 forms two bridge arms, a machine side converter 7 and a machine side filter 8 are arranged on the two bridge arms and are connected with a direct current bus capacitor 5 through a flywheel energy storage grid-connected circuit breaker 6, the machine side converter 7 regulates the voltage input to a rotor of the flywheel energy storage motor and realizes the control of physical quantities such as electromagnetic torque, rotating speed and the like of the motor, and the rotor of the double three-phase permanent magnet synchronous motor 9 is connected with a large inertia flywheel rotor 10 through a rotating shaft to realize the transmission of mechanical power; the converters in the flywheel energy storage system all adopt bidirectional AC/DC converters.
The lithium ion battery energy storage system 102 is sequentially connected with the battery energy storage side DC/DC converter 12, the battery energy storage system grid-connected breaker 11 and the direct current bus capacitor 5, the battery energy storage side DC/DC converter 12 regulates the voltage of the lithium ion battery side, and power exchange between the lithium ion battery energy storage system and a power grid is realized.
Further, as shown in fig. 3 and fig. 4, where fig. 3 is a schematic control block diagram of a flywheel-battery hybrid energy storage frequency adjusting system according to an embodiment of the present application, and fig. 4 is a control flowchart of the flywheel-battery hybrid energy storage frequency adjusting system, and as can be seen from fig. 2 to fig. 4, the flywheel-battery hybrid energy storage frequency adjusting method according to the embodiment of the present application includes the following steps:
and S1, a system power-on starting stage. After power-on starting, the flywheel-battery hybrid energy storage frequency adjusting system enters a power-on starting stage; the fly wheel energy storage system is closed by the grid-connected circuit breaker 6, the fly wheel energy storage system absorbs the power of the power grid through the side converter 7 of the fly wheel energy storage system, and the rotating speed of the fly wheel motor is gradually increased from 0 to the rated rotating speed omegan(ii) a The battery energy storage system grid-connected circuit breaker 11 is closed, and the lithium ion battery system enters a standby state.
S2, monitoring the frequency of the power grid, judging whether the power grid has a frequency event, if not, the flywheel-battery hybrid energy storage frequency adjusting system does not participate in frequency modulation, and the flywheel motor is kept at the rated rotating speed omeganThe power is not sent out to the outside, and the battery energy storage system does not send out power to the outside when working in a standby state; if the frequency event is detected (the grid frequency fluctuates), the process proceeds to step S3.
S3, detecting the change rate of the power grid frequency, and if the change rate of the power grid frequency is not detected, returning to the step S2; and if the frequency change rate is detected, performing low-pass filtering on the frequency change rate to filter out high-frequency components. When the product of the frequency variation frequency and the frequency deviation is judged to be a positive value, the system is in a frequency deterioration period at the time, and a frequency control mark K flag1, when the energy storage SOC state of the flywheel is in a normal state, a mark K SOC1, when the system enters an inertia response stage, the flywheel energy storage system is started to adopt a virtual inertia control strategy based on the frequency state of a flywheel inertia power grid, the frequency change rate of the power grid is reduced to the maximum extent, and the power output of the flywheel energy storage system can be calculated as follows:
in the formula, PFESS_refRepresenting the reference active power output H of the flywheel energy storage system participating in the grid frequency modulation in the inertial response stagefIndicating the flywheel stored energy self-inertia, KfwIndicating the grid frequency deviation adjustment factor, KflagRepresenting a grid frequency control mark with a value of 0 or 1, KSOCRepresenting the flywheel energy storage SOC state mark, the value is 0 or 1,
expressing the per unit value of the change rate of the grid frequency, PnIndicating the rated output power of the flywheel energy storage system.
Wherein:
where J is the flywheel's own inertia, ωeIs the electrical angular velocity, omega, of the flywheelenFor rating the angular speed, p, of the flywheelnIs the number of pole pairs, S, of the flywheel motorbaseFor flywheel energy storage system rated capacity, fd+For the forward dead zone of the grid frequency, the frequency is generally set to 50+0.033Hz, f according to the grid requirementd-The frequency negative dead zone of the power grid is generally set to be 50-0.033Hz, the inertial frequency support provided by the flywheel energy storage system to the power grid under different power grid frequency conditions and flywheel rotating speeds can be obtained through calculation, the calculated value comprehensively considers the factors such as the power grid frequency change rate, the frequency deviation, the flywheel SOC and the like, and the output of the flywheel energy storage system can be optimized to the maximum extent.
S4, detecting the frequency deviation of the power grid, wherein if the frequency deviation of the power grid does not exceed the dead zone, the lithium ion battery system does not emit or absorb power outwards and is in a standby state; if the frequency deviation of the power grid exceeds the dead zone, the flywheel energy storage system keeps a virtual inertia control strategy, the battery energy storage system adopts a droop control strategy, and the power reference of the battery energy storage system can be calculated as follows:
wherein D isLIBFor the maximum battery energy storage droop coefficient, after the battery energy storage starts droop control, and the grid frequency reaches the lowest point, the grid is startedAnd starting a frequency recovery phase.
S5, detecting whether the SOC of the flywheel energy storage exceeds a safety range, if not, continuously keeping the virtual inertia control strategy by the flywheel energy storage, and continuously keeping the primary frequency modulation control strategy by the battery energy storage; and if the energy storage SOC of the flywheel is lower than the lower limit of the safety range, starting a flywheel energy storage state of charge recovery stage. At the moment, the flywheel energy storage machine side converter 7 adopts double closed-loop control, the outer ring adopts SOC reference, and the Q-axis current reference of the inner ring is given through PI control
Therein, SOCFESSStoring the current SOC and SOC for the acquired flywheelrefIs a reference SOC, kpsocAnd kisocRespectively, set PI parameters. At this time, the battery energy storage system needs to compensate the flywheel energy storage SOC recovery power except that the battery energy storage system continues to keep the primary frequency modulation power output, and the output of the battery energy storage at this time can be expressed as:
wherein the content of the first and second substances,
is KSOCMarking the result after negation, PFESSThe actual output of the flywheel energy storage system is obtained.
When the flywheel energy storage charge state is detected to be recovered to the allowable range, the system is recovered to a primary frequency modulation stage, and the battery energy storage output reference is recovered to be PLIB_ref1。
And S5, when the frequency deviation value of the system is detected to be stabilized at a constant deviation value, the flywheel energy storage system and the battery energy storage system are maintained at the current output level, and the other units are waited to carry out secondary frequency modulation, so that the frequency of the power grid is recovered to the normal level.
The following is a verification of the flywheel-battery hybrid energy storage frequency regulation system of the embodiment of the present application.
Specifically, a digital simulation system of a flywheel-battery hybrid energy storage participating power grid inertia and frequency response device is built in an MATLAB/Simulink platform, and the process that a flywheel energy storage system and a battery energy storage system participate in power grid frequency modulation is simulated. And when the time is 0s, the system is electrified and started, the rotating speed of the flywheel motor is gradually increased from 0 to the rated rotating speed, and when the time is 0.08s, the rotating speed of the flywheel motor reaches the rated rotating speed, and the system finishes the starting process. And 0.08s-0.1s, the power grid frequency is in a normal state, the flywheel stores energy and maintains a rated rotating speed, and does not emit or absorb power outwards, and the battery stores energy and is in a standby state, and does not emit or absorb power outwards. And at 0.1s, based on the rated capacity of the power grid, a load of 0.1p.u is suddenly added, so that the frequency of the power grid is suddenly reduced, and the frequency modulation of the flywheel-battery hybrid energy storage frequency regulation system is started.
As shown in fig. 5, fig. 5 is a waveform diagram of the grid frequency and the grid frequency change rate in an embodiment of the present application, in an initial stage of a frequency event, the frequency change rate changes faster, and the flywheel energy storage system outputs high power quickly and in a short time through inertial response, so as to suppress an increasing trend of the frequency change rate and reduce a maximum deviation of the grid frequency; when the frequency deviation of the power grid exceeds a primary frequency modulation dead zone, the battery energy storage system and the flywheel energy storage system jointly participate in primary frequency modulation, and the steady-state error of the power grid frequency is reduced.
Fig. 6 is a waveform diagram of the flywheel energy storage power, the flywheel energy storage virtual inertia, the flywheel energy storage state of charge, and the battery energy storage power according to an embodiment of the present application. In the inertial response stage, the output of the flywheel energy storage system quickly reaches the maximum value, the characteristic of high flywheel energy storage power density can be fully exerted, and inertial power support is provided for a power grid; in the primary frequency modulation stage, the flywheel and the battery participate in frequency modulation together, so that continuous energy is provided for a power grid, and the steady-state frequency deviation of the primary frequency modulation is reduced; when the flywheel energy storage SOC is lower than the lower limit, a flywheel energy storage SOC recovery stage is started, and the battery energy storage can be matched with the flywheel energy storage power in real time to recover absorbed energy through reasonably setting a control strategy, so that the secondary drop of the power grid frequency is avoided.
According to the flywheel-battery hybrid energy storage frequency adjusting system provided by the embodiment of the application, inertia and frequency response control strategies of flywheel-battery system coordination considering the inertia of the flywheel and the frequency state of a power grid are adopted, the inertia is provided for the power grid through flywheel energy storage at the initial stage of the frequency event, the battery energy storage system and the flywheel energy storage system are combined to provide frequency support for the power grid during the primary frequency modulation period, and the charge state recovery of the flywheel energy storage system is realized, so that the inertia response and the primary frequency adjustment after the frequency event of the power grid are realized, the charge state recovery of the flywheel energy storage system is realized, and the utilization efficiency of the energy storage system is improved.
Next, a flywheel-battery hybrid energy storage frequency adjusting method proposed according to an embodiment of the present application is described with reference to the drawings.
Fig. 7 is a flowchart of a flywheel-battery hybrid energy storage frequency adjustment method according to an embodiment of the present application.
As shown in fig. 7, the flywheel-battery hybrid energy storage frequency adjusting method adopts the flywheel-battery hybrid energy storage frequency adjusting system, wherein the method includes the following steps:
s701, when the lithium ion battery is in a starting stage, the rotating speed of a flywheel is gradually increased from zero to a rated rotating speed, and the lithium ion battery energy storage system is controlled to enter a standby state;
s702, if the power grid frequency is in a preset normal state, controlling the flywheel energy storage system to enter a rotating speed control working condition, keeping the rotating speed of the flywheel at a rated rotating speed, and controlling the battery energy storage system to work in a standby state; and
s703, if the power grid frequency is in a preset abnormal state, the control system enters an inertia response adjustment stage, so that the flywheel energy storage system adopts a virtual inertia control strategy based on the self inertia of the flywheel and the power grid frequency state, and the system enters a primary frequency adjustment stage, so that the battery energy storage system adopts a droop control strategy, and the flywheel energy storage system is controlled to keep the virtual inertia control strategy; and
and S704, when the energy storage state of charge of the flywheel is in a recovery stage, controlling the energy storage system of the flywheel to enter the state of charge recovery, enabling the energy storage system of the battery to participate in primary frequency modulation of a power grid, and simultaneously outputting extra power to match the energy absorbed when the energy storage state of charge of the flywheel is recovered.
Optionally, the flywheel-battery hybrid energy storage frequency adjusting method according to the embodiment of the present application further includes:
and when the power grid frequency is in the secondary frequency modulation stage, the control and regulation system maintains the current output level, and waits for other units to enter secondary frequency modulation so as to recover the power grid frequency to a preset normal state.
It should be noted that the foregoing explanation of the embodiment of the flywheel-battery hybrid energy storage frequency adjusting system also applies to the flywheel-battery hybrid energy storage frequency adjusting method of the embodiment, and details are not repeated here.
According to the flywheel-battery hybrid energy storage frequency adjusting method provided by the embodiment of the application, the inertia and frequency response control strategy of flywheel-battery system coordination considering the inertia of the flywheel and the frequency state of a power grid is adopted, the inertia is provided for the power grid through flywheel energy storage at the initial stage of the frequency event, the battery energy storage system and the flywheel energy storage system are combined to provide frequency support for the power grid during the primary frequency modulation period, and the charge state recovery of the flywheel energy storage system is realized, so that the inertia response and the primary frequency adjustment after the frequency event of the power grid are realized, the charge state recovery of the flywheel energy storage system is realized, and the utilization efficiency of the energy storage system is improved.
Fig. 8 is a schematic structural diagram of an electronic device according to an embodiment of the present application. The electronic device may include:
a memory 801, a processor 802, and a computer program stored on the memory 801 and executable on the processor 802.
The processor 802, when executing the program, implements the flywheel-battery hybrid energy storage frequency adjustment method provided in the above embodiments.
Further, the electronic device further includes:
a communication interface 803 for communicating between the memory 801 and the processor 802.
A memory 801 for storing computer programs operable on the processor 802.
The memory 801 may comprise high-speed RAM memory, and may also include non-volatile memory (non-volatile memory), such as at least one disk memory.
If the memory 801, the processor 802 and the communication interface 803 are implemented independently, the communication interface 803, the memory 801 and the processor 802 may be connected to each other via a bus and communicate with each other. The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended ISA (EISA) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 8, but this is not intended to represent only one bus or type of bus.
Optionally, in a specific implementation, if the memory 801, the processor 802, and the communication interface 803 are integrated on one chip, the memory 801, the processor 802, and the communication interface 803 may complete communication with each other through an internal interface.
The processor 802 may be a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits configured to implement embodiments of the present Application.
The present embodiment also provides a computer-readable storage medium storing computer instructions for causing a computer to execute the flywheel-battery hybrid energy storage frequency adjustment method according to the above embodiment.
In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or N embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "N" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more N executable instructions for implementing steps of a custom logic function or process, and alternate implementations are included within the scope of the preferred embodiment of the present application in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of implementing the embodiments of the present application.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or N wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.
In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.
The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc. Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.
Claims (10)
1. A flywheel-battery hybrid energy storage frequency adjusting system is characterized by comprising a flywheel energy storage system and a lithium ion battery energy storage system which are connected to a power grid, wherein,
when the lithium ion battery is in a starting stage, the rotating speed of the flywheel is gradually increased from zero to a rated rotating speed, and the lithium ion battery energy storage system is controlled to enter a standby state;
if the power grid frequency is in a preset normal state, the flywheel energy storage system enters a rotating speed control working condition, the rotating speed of the flywheel is kept at the rated rotating speed, and the battery energy storage system works in a standby state; and
if the power grid frequency is in a preset abnormal state, the system enters an inertia response adjustment stage, the flywheel energy storage system adopts a virtual inertia control strategy based on the self inertia of the flywheel and the power grid frequency state, the system enters a primary frequency adjustment stage, the battery energy storage system adopts a droop control strategy, and the flywheel energy storage system keeps the virtual inertia control strategy; and
when the energy storage system is in a flywheel energy storage charge state recovery stage, the flywheel energy storage system enters a charge state recovery state, so that the battery energy storage system participates in primary frequency modulation of a power grid, and meanwhile, extra output power is matched with energy absorbed when the flywheel energy storage charge state is recovered.
2. The system of claim 1, wherein in the secondary frequency modulation stage, the regulating system waits for other units to enter secondary frequency modulation while maintaining the current output level, so as to recover the grid frequency to the preset normal state.
3. The system of claim 1, wherein the flywheel energy storage system and the lithium ion battery energy storage system are connected in parallel through a direct current bus unit and are connected to the power grid through a grid-side converter, an LCL filter, a grid-connected converter and a transformer.
4. The system of claim 3, wherein,
the power grid is connected with the direct current bus unit sequentially through the transformer, the LCL filter circuit and the grid-side converter, wherein the grid-side converter is used for maintaining the voltage of the direct current bus to be stable, and therefore power can flow between the power grid and the energy storage system in a two-way mode.
5. The system as claimed in claim 3 or 4, wherein in the flywheel energy storage system, a bridge arm is formed by each three-phase of the stator side of the double three-phase permanent magnet synchronous motor, a machine side filter and a machine side converter are respectively arranged on each bridge arm, the two bridge arms are connected in parallel and then connected with the direct current bus unit through a flywheel energy storage grid-connected circuit breaker, the machine side converter regulates the voltage input to the rotor of the flywheel energy storage motor to control the physical quantity, and the rotor of the double three-phase permanent magnet synchronous motor and the large inertia flywheel rotor are connected through a rotating shaft to transmit the mechanical power.
6. The system according to claim 3 or 4, wherein the lithium ion battery energy storage system is connected with a battery energy storage side DC/DC converter, a battery energy storage system grid-connected breaker and a direct current bus capacitor in sequence, and the DC/DC converter regulates the voltage at the lithium ion battery side so as to exchange power between the lithium ion battery energy storage system and the power grid.
7. A flywheel-battery hybrid energy storage frequency regulation method, characterized in that the flywheel-battery hybrid energy storage frequency regulation system of any one of claims 1-6 is adopted, wherein the method comprises the following steps:
when the lithium ion battery is in a starting stage, the rotating speed of the flywheel is gradually increased from zero to a rated rotating speed, and the lithium ion battery energy storage system is controlled to enter a standby state;
if the power grid frequency is in a preset normal state, controlling the flywheel energy storage system to enter a rotating speed control working condition, keeping the rotating speed of the flywheel at the rated rotating speed, and controlling the battery energy storage system to work in a standby state; and
if the power grid frequency is in a preset abnormal state, controlling the system to enter an inertia response adjustment stage, enabling the flywheel energy storage system to adopt a virtual inertia control strategy based on the inertia of the flywheel and the power grid frequency state, and enabling the battery energy storage system to adopt a droop control strategy to control the flywheel energy storage system to keep the virtual inertia control strategy, wherein the system enters a primary frequency modulation stage; and
and when the energy storage state of charge of the flywheel is recovered, controlling the energy storage system of the flywheel to enter the state of charge recovery, so that the energy storage system of the battery participates in primary frequency modulation of a power grid, and simultaneously, additionally outputting power to match the energy absorbed when the energy storage state of charge of the flywheel is recovered.
8. The method of claim 7, further comprising:
and when the power grid frequency is in the secondary frequency modulation stage, controlling the adjusting system to maintain the current output level, and waiting for other units to enter secondary frequency modulation to recover the power grid frequency to the preset normal state.
9. An electronic device, comprising: a memory, a processor and a computer program stored on the memory and executable on the processor, the processor executing the program to implement the flywheel-battery hybrid energy storage frequency adjustment method according to any one of claims 7 to 8.
10. A computer-readable storage medium, on which a computer program is stored, the program being executable by a processor for implementing the flywheel-battery hybrid energy storage frequency adjustment method as claimed in any one of claims 7 to 8.
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