A protection device adaptive control method for a network-constructed energy storage grid-connected system

Abstract

The application discloses a kind of protection device adaptability control methods for network type energy storage grid-connected system, comprising: when network type energy storage grid-connected system is in fault state and the short-circuit ratio of energy storage is less than the first preset short-circuit ratio threshold, start optimization process;Determine the first operating state of energy storage based on the PCS system of network type energy storage grid-connected system in energy storage;According to the bus voltage and the secondary sampling current of energy storage access interval collected by protection device, real-time calculation active power and reactive power, and determine the second operating state of energy storage according to active power and reactive power;When the first operating state and second operating state are consistent, determine the state of energy storage;According to the state of energy storage and current short-circuit ratio, adjust the braking coefficient of protection device to carry out the adaptability control of protection device.The application solves the technical problem that main protection is difficult to adapt after network type equipment is accessed to power grid system.

Description

Technical Field

[0001] This invention relates to the field of relay protection adaptability analysis technology, and more specifically, to an adaptive control method and system for protection devices in grid-connected energy storage systems. Background Technology

[0002] With the large-scale grid connection of grid-connected energy storage devices, the system exhibits a heterogeneous trend with both "grid-following" and "grid-based" control strategies coexisting. Virtual impedance control, due to its low cost and good oscillation suppression effect, has become a standard feature of grid-connected converters. However, while improving system stability, the introduction of virtual impedance also profoundly alters the current spectrum composition and attenuation characteristics during fault transients: the fault current not only contains power frequency components but also non-negligible DC attenuation components and second harmonic attenuation components, and the amplitude and attenuation time constant of each component are coupled and affected by the virtual impedance parameters.

[0003] Existing relay protection systems (such as power frequency differential protection and distance protection) are designed based on the characteristics of synchronous generator power supplies, which are difficult to adapt to the multi-component, variable attenuation, and strongly coupled fault current characteristics mentioned above. This poses a risk of decreased sensitivity, failure to operate, or false operation. Therefore, there is an urgent need for an adaptive control method for protection devices in grid-connected energy storage systems to provide technical support for the protection setting of such systems. Summary of the Invention

[0004] This invention proposes an adaptive control method and system for protection devices of grid-connected energy storage systems, in order to solve the problem of how to adaptively control the protection devices of grid-connected energy storage systems.

[0005] To address the aforementioned problems, according to one aspect of the present invention, an adaptive control method for a protection device in a grid-connected energy storage system is provided, the method comprising: When the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than the first preset short-circuit ratio threshold, the optimization process is initiated. Based on the PCS system for energy storage in a grid-connected energy storage system, determine the first operating state of energy storage; Based on the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, the active power and reactive power are calculated in real time, and the second operating state of the energy storage is determined based on the active power and reactive power. When the first operating state and the second operating state are consistent, the state of the energy storage is determined. The current short-circuit ratio of the energy storage is obtained, and the braking coefficient of the protection device is adjusted according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device.

[0006] Preferably, the first preset short-circuit ratio threshold is 10.

[0007] Preferably, the PCS system based on energy storage in the grid-connected energy storage system determines the first operating state of the energy storage, including: The energy storage PCS system outputs the first operating state through hard contact or GOOSE digital input, and the protection device determines the first operating state of the energy storage in real time from the PCS system using a hard circuit or through communication.

[0008] Preferably, determining the second operating state of energy storage based on active power and reactive power includes: If the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state. If the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharge state.

[0009] Preferably, adjusting the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio includes: When the energy storage is in a charging state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.3; if the current short-circuit ratio is greater than or equal to the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.4. When the energy storage is in the discharge state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, it is determined whether there is a differential current between any two phases of the bus. If there is a differential current, the braking coefficient of the protection device is adjusted to 0.3.

[0010] According to another aspect of the present invention, an adaptive control system for a protection device of a grid-connected energy storage system is provided, the system comprising: The optimization process initiation unit is used to initiate the optimization process when the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than the first preset short-circuit ratio threshold. The first operating status acquisition unit is used to determine the first operating status of energy storage based on the PCS system of energy storage in the grid-connected energy storage system. The second operating state determination unit is used to calculate the active power and reactive power in real time based on the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, and determine the second operating state of the energy storage based on the active power and reactive power. A state determination unit is used to determine the state of energy storage when the first operating state and the second operating state are consistent. The control unit obtains the current short-circuit ratio of the energy storage and adjusts the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device.

[0011] Preferably, the first preset short-circuit ratio threshold is 10.

[0012] Preferably, the first operating state acquisition unit determines the first operating state of the energy storage based on the PCS system of the grid-connected energy storage system, including: The energy storage PCS system outputs the first operating state through hard contact or GOOSE digital input, and the protection device determines the first operating state of the energy storage in real time from the PCS system using a hard circuit or through communication.

[0013] Preferably, the second operating state determination unit determines the second operating state of the energy storage based on active power and reactive power, including: If the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state. If the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharge state.

[0014] Preferably, the control unit adjusts the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio, including: When the energy storage is in a charging state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.3; if the current short-circuit ratio is greater than or equal to the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.4. When the energy storage is in the discharge state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, it is determined whether there is a differential current between any two phases of the bus. If there is a differential current, the braking coefficient of the protection device is adjusted to 0.3.

[0015] This invention provides an adaptive control method and system for a protection device in a grid-connected energy storage system, comprising: initiating an optimization process when the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than a first preset short-circuit ratio threshold; determining a first operating state of the energy storage based on the PCS system of the energy storage in the grid-connected energy storage system; calculating active power and reactive power in real time according to the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, and determining a second operating state of the energy storage based on the active power and reactive power; determining the state of the energy storage when the first operating state and the second operating state are consistent; obtaining the current short-circuit ratio of the energy storage, and adjusting the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device. In order to ensure the reliability of the bus differential protection operation when a grid fault occurs during the operation of the energy storage system, this invention proposes an adaptive ratio braking adjustment scheme for bus protection based on the identification of the energy storage operation mode. This scheme enables the protection device to adaptively adjust the ratio braking coefficient according to the operating status of the energy storage system, thus solving the technical problem that the main protection is difficult to adapt after the grid-connected equipment is connected to the grid system. Attached Figure Description

[0016] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 A flowchart of an adaptive control method 100 for a protection device of a grid-connected energy storage system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a typical grid-connected energy storage system. Figure 3 This is a schematic diagram of the fault point in the transmission line; Figure 4 This is a schematic diagram showing the angles between different currents at both ends when a two-phase short circuit occurs on the transmission line. Figure 5 This is a schematic diagram showing the relationship between differential current and braking current under different current angles. (a) and (b) show the differential protection operation under small current angles, and (c) and (d) show the differential protection operation under large current angles. Figure 6 This is a flowchart of the adaptive proportional braking strategy; where (a) is the differential protection optimization strategy under charging state, and (b) is the differential protection optimization strategy under discharging state. Figure 7 This is a schematic diagram illustrating the operation of the bus differential adaptive proportional braking strategy. Figure 8 This is a schematic diagram of the adaptive control system 900 for a grid-connected energy storage system according to an embodiment of the present invention. Detailed Implementation

[0017] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0018] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0019] Figure 1 This is a flowchart of an adaptive control method 100 for a protection device in a grid-connected energy storage system according to an embodiment of the present invention. Figure 1 As shown, the adaptive control method for protection devices of grid-connected energy storage systems provided by this invention proposes an adaptive ratio braking adjustment scheme for bus protection based on energy storage operation mode identification to ensure the reliability of bus differential protection when a grid fault occurs during the operation of the energy storage system. This allows the protection device to adaptively adjust the ratio braking coefficient according to the operating state of the energy storage system, solving the technical problem that the main protection is difficult to adapt after grid-connected equipment is connected to the grid system. The adaptive control method 100 for protection devices of grid-connected energy storage systems provided by this invention starts from step 101. In step 101, when the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than a first preset short-circuit ratio threshold, an optimization process is initiated.

[0020] Preferably, the first preset short-circuit ratio threshold is 10.

[0021] In step 102, the first operating state of energy storage is determined based on the PCS system of the grid-connected energy storage system.

[0022] Preferably, the PCS system based on energy storage in the grid-connected energy storage system determines the first operating state of the energy storage, including: The energy storage PCS system outputs the first operating state through hard contact or GOOSE digital input, and the protection device determines the first operating state of the energy storage in real time from the PCS system using a hard circuit or through communication.

[0023] In step 103, based on the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, the active power and reactive power are calculated in real time, and the second operating state of the energy storage is determined based on the active power and reactive power.

[0024] Preferably, determining the second operating state of energy storage based on active power and reactive power includes: If the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state. If the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharge state.

[0025] In step 104, when the first operating state and the second operating state are consistent, the state of the energy storage is determined; In step 105, the current short-circuit ratio of the energy storage is obtained, and the braking coefficient of the protection device is adjusted according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device.

[0026] Preferably, adjusting the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio includes: When the energy storage is in a charging state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.3; if the current short-circuit ratio is greater than or equal to the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.4. When the energy storage is in the discharge state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, it is determined whether there is a differential current between any two phases of the bus. If there is a differential current, the braking coefficient of the protection device is adjusted to 0.3.

[0027] The purpose of this invention is to improve the adaptability of protection in new power systems. Based on the virtual impedance control strategy of grid-connected energy storage converters, the fault characteristics of grid-connected energy storage systems are analyzed, and the adaptability boundary of the main relay protection is analyzed according to the fault characteristics. Then, an adaptive control method for the protection device of grid-connected energy storage systems is proposed to solve the technical problem that the main protection is difficult to adapt after grid-connected equipment is connected to the power grid system, and to deepen the understanding of relay protection in new power systems.

[0028] Grid-forming converters (GFCs), as an important component of new power systems, directly determine the stability and dynamic response capability of the grid-connected system through their control strategies. Figure 2In a typical new energy base topology, the grid-type converter uses active / frequency control (i.e., active loop) and reactive / voltage control (i.e., reactive loop) to form a power control loop, generating the phase angle δ and amplitude E of a virtual internal potential. Subsequently, this internal potential passes through a three-phase sinusoidal signal generator, a voltage and current dual closed-loop control system, and a coordinate transformation module, ultimately generating the sinusoidal pulse width modulation (SPWM) signal required by the power electronic converter, driving the converter to output an AC voltage with a constant frequency and stable amplitude.

[0029] The energy storage VSG control loop mainly consists of three parts: the power loop, the virtual impedance loop, and the current control loop. The functions and control equations of each part are as follows: The power loop consists of two parts: an active-frequency control loop and a reactive-voltage control loop. The virtual synchronization control loop also consists of two parts: an active-frequency control loop and a reactive-voltage control loop. The former simulates the generator rotor motion equations, providing damping and inertial support to the power grid, and outputs a virtual internal electromotive force phase angle. θ ref The latter simulates reactive power-voltage regulation characteristics by simulating the excitation of a synchronous machine, and outputs a virtual internal potential amplitude. E ref The basic governing equations for both are: (1) In the formula: , The phase and amplitude of the power loop output reference internal potential. P *、 Q *These represent reference values ​​for active and reactive power, respectively. J D K , w , w N These represent virtual inertia, damping coefficient, reactive voltage integral coefficient, reference internal potential angular frequency, and rated angular frequency, respectively. This is the base voltage value.

[0030] The virtual impedance element simulates the internal impedance of an actual synchronous generator, which can improve the operational stability of virtual synchronization control. Its basic control equation is: (2) In the formula: e d e q For reference internal potential in a two-phase rotating coordinate system d , q Axial components, u d , u q For inverter port voltage d , q Axial components,R v , L v For virtual resistance and reactance.

[0031] To achieve error-free current control, the inner current loop employs PI control, with the basic control equation being: (3) In the formula: K p , K i These are the proportional and integral coefficients for PI control.

[0032] In grid-connected energy storage and transmission systems, the analysis of fault steady-state current is fundamental to designing current-limiting strategies. Energy is transmitted directly to the grid via inverters, meaning the inverters control the output power of the energy storage power source. Fault characteristics are primarily determined by the system voltage drop, network impedance, converter output voltage, and its control strategy.

[0033] In the early stages of a fault, a virtual impedance is introduced to directly suppress the current amplitude. By modifying the reference voltage of the control loop, the converter actively reduces the output voltage, thereby suppressing the rate of current rise.

[0034] The analysis of fault transient currents involves not only abrupt changes in current amplitude but also multi-dimensional dynamic behaviors such as attenuation characteristics, frequency components, and phase jumps. Due to the presence of multiple coupling elements in its control structure, such as voltage loops, current loops, power loops, and virtual synchronization elements, grid-type converters exhibit significant nonlinearity and time-varying characteristics in their response during fault transient processes.

[0035] According to the traditional definition of current differential protection, the typical operating criteria for the main protection are as follows: (4) in: I d For differential current, I r For the braking current, respectively satisfy the following conditions: I d =| I N + I M |, I r =| I N – I M |, among which I N The current collected by the corresponding phase on the grid-type energy storage side. I MThe current measured by the same phase on the AC system side is shown in the positive direction as shown in the figure; I op0 This is the starting value. k This is the braking coefficient, and its actual value typically ranges from 0.5 to 0.8. The action criterion is the differential momentum. I d Greater than braking amount I r of k In traditional synchronous machine systems, when an external fault occurs, the currents of the faulty phase and non-faulty phases flow through the through current, i.e., I W =- I M At this time, the differential current I d If the value is 0, the protection is reliable and will not activate.

[0036] When a fault occurs within the protected line zone, the current phasors at both ends are equal, the braking current is zero, and the differential current is greater than the braking current, so the device trips correctly. When a short circuit occurs outside the zone, a through current flows through the transmission line, and the differential current is less than the braking current, so the device can reliably not trip.

[0037] When a fault occurs on the connecting line MN, the phase of each phase current flowing through the differential protection on the grid side can be determined by formula (4). However, the phase angle of the grid-side current and the phase angle difference of the current flowing through the two protections on the line need to be calculated based on the specific fault conditions. Taking the current changes when different faults occur on the sending line as the research object, the operation of the longitudinal current differential relay is analyzed. The fault locations are as follows: Figure 3 As shown.

[0038] Taking a two-phase short circuit as an example, when a two-phase short circuit occurs within the transmission line area, the study focuses on the BC short circuit. Since a low-voltage control strategy is adopted during faults in grid-connected renewable energy sources, according to formula (5), the initial phase angle of each phase current on the grid-connected renewable energy side at the initial moment of the fault is... (5) It can be concluded that the initial phase angle difference of the two-phase current under any fault on the grid-connected new energy side will remain unchanged at 120° during the fault period, and different fault types will not change the magnitude of the initial phase angle difference.

[0039] Based on the simulation results of a two-phase short-circuit fault occurring at the midpoint of the system's output line, it is assumed that the initial moment of the fault... and The included angle is 180°; As a reference phasor Figure 4 The changes in the angle between the fault phase currents at both ends of the line are given when the phasor of the B-phase current on the grid-connected new energy side changes.

[0040] Depend on Figure 5 It can be seen that at the start of the short circuit, combined with the differential protection operating characteristic equation, a schematic diagram of the relationship between the braking current and differential current of the line under this condition can be drawn using the parallelogram law. θ B When <30°, θ C For acute angles, such as Figure 5 As shown in (a) and (b), when θ B When >30° θ C It is an obtuse angle, at this time and The size relationship is as follows Figure 5 (c) (d).

[0041] when θ B When it is in the 30-90° range, such as Figure 5 As shown in (b), it can be deduced that θ C Located within the 90-150° range. According to Figure 5 As shown in the parallelogram law definition, the phase angle difference between phases B and C is obtuse. In this case, the differential current is less than the braking current, and the sensitivity of the differential protection decreases. Whether the B-phase protection can operate depends on the value of the braking coefficient k. If the value of k is large, the protection is likely to operate correctly; if the value of k is small, the protection is very likely to fail to operate.

[0042] when θ B When it is in the 90-180° range, such as Figure 5 As shown in (c), it can be deduced that θ C Located within the 120-180° range. According to Figure 5 As shown in the parallelogram law definition, the phase angle difference between phases B and C is a large obtuse angle. At this time, the differential current is significantly smaller than the braking current, and the sensitivity of the differential protection is severely reduced, or even there is a significant risk of protection failure.

[0043] Therefore, in order to ensure the reliability of the bus differential protection operation when a grid fault occurs during the operation of the energy storage system, an adaptive ratio braking adjustment scheme for bus protection based on energy storage operation mode identification is proposed. That is, the protection adaptively adjusts the ratio braking coefficient according to the operating status of the energy storage system.

[0044] During the construction phase, the grid capacity and the proportion of energy storage are known. As can be seen from the previous analysis, when the proportion of energy storage capacity is small, the fault current is mainly provided by the grid side, and the impact of grid-type energy storage on short-circuit current can be ignored. Therefore, the first step is to determine whether to start the optimization strategy by the proportion of energy storage in the grid. Only when the proportion of energy storage is large should the optimization strategy be considered.

[0045] Specifically, the energy storage PCS system can output its operating status via hard contacts or GOOSE digital signals. Therefore, the protection device can obtain the operating status from the PCS system in real time using a hard loop or through communication. Simultaneously, based on the bus voltage and CT current of the energy storage access interval it collects, the protection device calculates the magnitude and direction of active and reactive power in real time to determine the operating mode of the energy storage system, classifying it into charging and discharging states.

[0046] During charging, the angle θ between the bus voltage and the CT current is greater than 90°. At this time, the active power P = U·Icosθ < 0 (a negative value), indicating that the energy storage system absorbs active power from the grid and the electrical energy is stored in the energy storage device in the form of chemical energy or electromagnetic energy. The sign of the reactive power Q = U·Isinθ depends on whether the current leads or lags the voltage, reflecting the characteristics of the system absorbing or generating reactive power.

[0047] During discharge, the angle θ between the bus voltage and the CT current is less than 90°. At this time, the active power P=U·Icosθ>0 (is a positive value), indicating that the energy storage system releases active power to the grid or load, and electrical energy is output from the energy storage device. The reactive power Q=U·Isinθ is also determined by the relative phase of the current and voltage, which represents the direction of reactive power compensation.

[0048] Therefore, the protection device determines the second operating state of the energy storage based on the active power and reactive power, including: if the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state; if the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharging state.

[0049] Then, the protection device verifies the first operating state of the energy storage system obtained from the PCS system and the second operating state it calculates based on analog quantities, and determines whether the two results are consistent.

[0050] When the identification result shifts to 3 and the energy storage is in a charging state, the value of the ratio braking coefficient k is dynamically adjusted based on the short-circuit ratio (SCR). Specifically, if the short-circuit ratio (SCR) is below 5.0, the braking coefficient k is set to 0.3; otherwise, it is set to 0.4. The specific process is as follows: Figure 6 As shown in (a).

[0051] When the identification results are consistent and the energy storage system is determined to be in a discharging state, a discharge optimization strategy is executed. The value of the ratio braking coefficient k is dynamically adjusted based on the short-circuit ratio (SCR). Specifically, when the SCR is below 5.0, the fault type is identified based on the differential current. If differential current is detected in any two phases of the bus, the braking coefficient k automatically takes a low value of 0.3 to improve the sensitivity of the differential protection operation; otherwise, the braking coefficient remains at a high setpoint. The specific process is as follows: Figure 6 As shown in (b).

[0052] In this invention, reference is made to Figure 2 A typical grid-connected energy storage topology is used to construct a grid-connected new energy grid simulation model. Based on the system-side approach, the following three operating modes are considered: (1) Island mode - full power generation of 9MW from photovoltaic and energy storage - load matching; (2) Island mode - energy storage single-band power generation 4.5MW - load matching; (3) Non-island mode - photovoltaic power generation without energy storage 4.5MW; Three-phase short-circuit grounding, two-phase short-circuit grounding, two-phase short circuit, single-phase short circuit, and single-phase short circuit through a 100Ω transition resistor were respectively set up on the new energy transmission line to analyze the main protection operation characteristics of the protection device.

[0053] For the main protection, in islanded mode, the system transient characteristics are significantly affected by the grid-type energy storage control strategy. 100ms after a fault, the grid-type photovoltaic-energy storage system uses virtual resistors to suppress the increase in current or voltage. Within 30ms after the fault, the device operates correctly, but there are issues with reduced sensitivity failing to meet standard requirements and the differential protection against power frequency surges failing to operate. The power frequency surge protection fails to operate because non-power frequency quantities increase after the fault. Furthermore, due to insufficient output power response of the grid-type energy storage, the control strategy cannot stabilize the system voltage in a short time.

[0054] To verify the effectiveness of the bus differential adaptive proportional braking strategy based on the energy storage system operation mode mentioned in this invention, under the condition of a short-circuit ratio (SCR) of 2.0, the sensitivity of differential protection during a fault in the bus zone was verified for both the optimized and unoptimized strategies. Figure 7 It can be seen that the differential protection had frequent return phenomena before optimization, but can operate correctly after optimization.

[0055] Figure 8 This is a schematic diagram of the adaptive control system 800 for a grid-connected energy storage system according to an embodiment of the present invention. Figure 8As shown, the adaptive control system 800 for the protection device of the grid-connected energy storage system provided in the embodiment of the present invention includes: an optimized process start-up unit 801, a first operating state acquisition unit 802, a second operating state determination unit 803, a state determination unit 804, and a control unit 805.

[0056] Preferably, the optimization process initiation unit 801 is used to initiate the optimization process when the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than a first preset short-circuit ratio threshold.

[0057] Preferably, the first preset short-circuit ratio threshold is 10.

[0058] Preferably, the first operating status acquisition unit 802 is used to determine the first operating status of energy storage based on the PCS system of energy storage in the grid-connected energy storage system.

[0059] Preferably, the first operating state acquisition unit 802 determines the first operating state of the energy storage based on the PCS system of the grid-connected energy storage system, including: The energy storage PCS system outputs the first operating state through hard contact or GOOSE digital input, and the protection device determines the first operating state of the energy storage in real time from the PCS system using a hard circuit or through communication.

[0060] Preferably, the second operating state determination unit 803 is used to calculate the active power and reactive power in real time based on the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, and determine the second operating state of the energy storage based on the active power and reactive power.

[0061] Preferably, the second operating state determination unit 803 determines the second operating state of the energy storage based on active power and reactive power, including: If the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state. If the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharge state.

[0062] Preferably, the state determination unit 804 is used to determine the state of the energy storage when the first operating state and the second operating state are consistent.

[0063] Preferably, the control unit 805 acquires the current short-circuit ratio of the energy storage and adjusts the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device.

[0064] Preferably, the control unit 805 adjusts the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio, including: When the energy storage is in a charging state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.3; if the current short-circuit ratio is greater than or equal to the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.4. When the energy storage is in the discharge state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, it is determined whether there is a differential current between any two phases of the bus. If there is a differential current, the braking coefficient of the protection device is adjusted to 0.3.

[0065] The adaptive control system 800 for the protection device of the grid-connected energy storage system in an embodiment of the present invention corresponds to the adaptive control method 100 for the protection device of the grid-connected energy storage system in another embodiment of the present invention, and will not be described again here.

[0066] The present invention has been described with reference to a few embodiments. However, it will be apparent to those skilled in the art that other embodiments besides those disclosed above fall equivalently within the scope of the present invention.

[0067] Generally, all terms used in this invention are interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless explicitly stated otherwise.

[0068] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0069] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0070] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0071] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. An adaptive control method for protection devices in grid-connected energy storage systems, characterized in that, The method includes: When the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than the first preset short-circuit ratio threshold, the optimization process is initiated. Based on the PCS system for energy storage in a grid-connected energy storage system, determine the first operating state of energy storage; Based on the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, the active power and reactive power are calculated in real time, and the second operating state of the energy storage is determined based on the active power and reactive power. When the first operating state and the second operating state are consistent, the state of the energy storage is determined. The current short-circuit ratio of the energy storage is obtained, and the braking coefficient of the protection device is adjusted according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device.

2. The method according to claim 1, characterized in that, The first preset short-circuit ratio threshold is 10.

3. The method according to claim 1, characterized in that, Based on the PCS system for energy storage in a grid-connected energy storage system, the first operating state of energy storage is determined, including: The energy storage PCS system outputs the first operating state through hard contact or GOOSE digital input, and the protection device determines the first operating state of the energy storage in real time from the PCS system using a hard circuit or through communication.

4. The method according to claim 1, characterized in that, The second operating state of energy storage is determined based on active and reactive power, including: If the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state. If the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharge state.

5. The method according to claim 1, characterized in that, The braking coefficient of the protection device is adjusted according to the state of the energy storage and the current short-circuit ratio, including: When the energy storage is in a charging state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.3; if the current short-circuit ratio is greater than or equal to the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.

4. When the energy storage is in the discharge state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, it is determined whether there is a differential current between any two phases of the bus. If there is a differential current, the braking coefficient of the protection device is adjusted to 0.

3.

6. An adaptive control system for protection devices of grid-connected energy storage systems, characterized in that, The system includes: The optimization process initiation unit is used to initiate the optimization process when the grid-connected energy storage system is in a fault state and the short-circuit ratio of the energy storage is less than the first preset short-circuit ratio threshold. The first operating status acquisition unit is used to determine the first operating status of energy storage based on the PCS system of energy storage in the grid-connected energy storage system. The second operating state determination unit is used to calculate the active power and reactive power in real time based on the bus voltage collected by the protection device and the secondary sampling current of the energy storage access interval, and determine the second operating state of the energy storage based on the active power and reactive power. A state determination unit is used to determine the state of energy storage when the first operating state and the second operating state are consistent. The control unit obtains the current short-circuit ratio of the energy storage and adjusts the braking coefficient of the protection device according to the state of the energy storage and the current short-circuit ratio to perform adaptive control of the protection device.

7. The system according to claim 6, characterized in that, The first preset short-circuit ratio threshold is 10.

8. The system according to claim 6, characterized in that, The first operating status acquisition unit, based on the PCS system of the energy storage in the grid-connected energy storage system, determines the first operating status of the energy storage, including: The energy storage PCS system outputs the first operating state through hard contact or GOOSE digital input, and the protection device determines the first operating state of the energy storage in real time from the PCS system using a hard circuit or through communication.

9. The system according to claim 6, characterized in that, The second operating state determination unit determines the second operating state of the energy storage based on active power and reactive power, including: If the active power is less than 0 and the reactive power is less than 0, then the second operating state of the energy storage is determined to be the charging state. If the active power is greater than 0 and the reactive power is greater than 0, then the second operating state of the energy storage is determined to be the discharge state.

10. The system according to claim 6, characterized in that, The control unit adjusts the braking coefficient of the protection device based on the state of the energy storage and the current short-circuit ratio, including: When the energy storage is in a charging state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.3; if the current short-circuit ratio is greater than or equal to the second preset short-circuit ratio threshold, the braking coefficient of the protection device is adjusted to 0.

4. When the energy storage is in the discharge state, if the current short-circuit ratio is less than the second preset short-circuit ratio threshold, it is determined whether there is a differential current between any two phases of the bus. If there is a differential current, the braking coefficient of the protection device is adjusted to 0.3.

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