A network construction type matching control strategy integrated with energy management in a black start scenario

Abstract

The application discloses a network-constructing type matching control strategy integrated with energy management in a black start scene and relates to the field of energy storage system network-constructing control, and comprises the following steps: S1: the energy storage system is powered through a transformer; S2: the impact current generated by the transformer in the power supply process is limited through an inverter; S3: the load power of the energy storage system is provided through an energy storage battery and a DC side capacitor; S4: the three-phase voltage amplitude, frequency and phase angle of a grid-connected point are acquired, difference value calculation is respectively performed on the three-phase voltage amplitude, frequency and phase angle of the grid-connected point and the three-phase voltage amplitude, frequency and phase angle of the grid side, and the difference value is limited within a threshold value through pre-synchronization; S5: after the pre-synchronization is completed, the grid is closed and connected, the power grid and the energy storage system supply power simultaneously, the DC side capacitor is charged, and the rated voltage is restored; the network-constructing type energy storage system is adopted as a black start power supply, the matching control strategy is adopted, the energy management function is integrated, inertia and damping are flexibly provided for the energy storage system, and the pressure of the energy storage battery in an extreme case as the black start power supply is relieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy storage system network configuration control, in particular to a network configuration type matching control strategy integrated with energy management in a black start scenario. BACKGROUND

[0002] With the continuous expansion of the power system and the gradual penetration of renewable energy, its safety and stability have been greatly challenged. In a large-scale power outage accident, the power system must be restored under the drive of the self-starting generator, that is, black start, and with the increasing penetration rate of renewable energy RES, the black start power gradually shifts from traditional gas turbines to renewable energy. However, the inherent variability and unpredictability of RES also reduce the reliability and stability of the black start process.

[0003] Battery energy storage systems (BESS) are widely used in RES. Generally, the state of charge (SOC) of the battery must be strictly controlled within a certain range to prevent overcharging or overdischarging. Most energy management methods simply adjust the output power of the battery according to the SOC. However, simple adjustment methods often use rough technical means and are difficult to achieve precise control of output power. Unstable output power can lead to unstable device performance or direct damage. In complex environments, it is difficult to maintain stable operation. In addition, simple adjustment methods cannot dynamically adjust the output power according to actual needs, which can lead to energy waste.

[0004] In the application scenario of black start, the control strategy of the energy storage side inverter directly affects the efficiency and reliability of black start. Common GFM control strategies include droop control, virtual synchronous generator (VSG) control, and virtual oscillator (VOC) control. They can all provide stable voltage and frequency support. However, the above strategy control cannot avoid steady-state error. Research in the black start scenario is lacking. When faced with rapidly changing loads or grid disturbances, the response speed of the GFM system is slow, and it cannot adjust the output in time to maintain stability, which can cause oscillation phenomena, seriously affecting the stability and reliability of the system.

[0005] Therefore, a network configuration type matching control strategy integrated with energy management in a black start scenario is provided to solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a network configuration type matching control strategy integrated with energy management in a black start scenario. The integrated energy management function can provide inertia and damping for the energy storage system flexibly, and help to alleviate the pressure on the energy storage battery as a black start power source in extreme cases.

[0007] To achieve the above purpose, the present application provides a network configuration type matching control strategy integrated with energy management in a black start scenario, comprising the following steps:

[0008] S1: the energy storage system is powered by a transformer;

[0009] S2: limiting the inrush current generated by the transformer during power supply by an inverter;

[0010] S3: providing load power of the energy storage system by an energy storage battery and a DC side capacitor;

[0011] S4: obtaining three-phase voltage amplitude, frequency and phase angle of the grid-connected point, respectively, and calculating the difference value with three-phase voltage amplitude, frequency and phase angle of the grid side, limiting the difference value within a threshold value through pre-synchronization;

[0012] S5: closing the grid after pre-synchronization is completed, the grid and the energy storage system supply power at the same time, and charge the DC side capacitor, the DC side capacitor restores the rated voltage and keeps stable.

[0013] Preferably, in step S1, the power supply method adopts zero-rise voltage boosting power supply method.

[0014] Preferably, step S2 specifically includes the following steps:

[0015] S21: setting the rated reference voltage of the inverter output as a ramp voltage v ref , the ramp voltage v ref is set as:

[0016]

[0017] Wherein, T ramp represents the rising time of the ramp voltage v ref ;

[0018] S22: simulating the rotor motion of the synchronous generator through the dynamic change of the DC side capacitor, the swing equation of the rotor motion is set as:

[0019]

[0020] Wherein, ω n represents the rated angular frequency, ω g represents the grid angular frequency, C dc represents the DC side capacitor value, v dc represents the DC side capacitor voltage, J represents the grid inertia, D represents the damping coefficient, P m represents the output power of the synchronous generator, P E represents the electromagnetic power of the synchronous generator, P s represents the output power of the power supply, P e represents the output power of the inverter;

[0021] S23: controlling the output power Pe And a cascaded voltage-current closed-loop control structure is added in the control structure.

[0022] Preferably, in step S22, the coupling relationship of the angular frequency ω and the DC side capacitor voltage v dc is set as:

[0023]

[0024] wherein ω ref represents the reference value of the inverter angular frequency, K T represents the DC side voltage tracking coefficient, K J represents the inertia simulation coefficient, K D represents the damping coefficient, v dcref represents the reference value of the DC side voltage, and s represents the complex frequency.

[0025] Preferably, step S3 specifically comprises the following steps:

[0026] S31: providing the load power not greater than the rated power by the energy storage battery, matching the swing equation of the rotor motion of the synchronous generator, and controlling the output power of the energy storage battery by the matching control strategy integrated with energy management;

[0027] S32: fully compensating the load power greater than the rated power by the DC side capacitor, and setting the compensation formula as:

[0028]

[0029] wherein ΔP load represents the load power fluctuation.

[0030] Preferably, in step S32, if the load power fluctuation ΔP load remains constant, the DC side capacitor voltage v dc tracks the reference value v dcref of the DC side voltage, and the reference value v dcref of the DC side voltage is set as:

[0031]

[0032] wherein v dcn represents the rated value of the DC side capacitor voltage v dc , and t f represents the time when the load power starts to fluctuate.

[0033] Preferably, in step S31, the matching control strategy integrated with energy management is set as:

[0034]

[0035] Preferably, step S4 specifically comprises the following steps:

[0036] S41: amplitude synchronization is performed, the amplitude of the corresponding loop of the grid connection point is modified, so that the amplitude of the corresponding loop of the grid connection point is the same as the amplitude of the grid side;

[0037] S42: frequency synchronization is performed, the frequency of the corresponding loop of the grid connection point is modified, so that the frequency of the corresponding loop of the grid connection point is the same as the frequency of the grid side;

[0038] S43: the phase angle at the grid connection point is obtained through a phase-locked loop, the difference between the phase angle at the grid connection point and the phase angle of the inverter is input into a PI controller to generate an additional angular frequency, and a new reference value ω' is obtained ref , the new reference value ω' is set as: ref

[0039] ω' = ω + ω ref ref + ω sync

[0040] wherein, ω represents the original angular frequency reference value, and ω represents the synchronization angular frequency. ωref ωsync

[0041] Therefore, the grid-forming matching control strategy integrated with energy management in the black start scenario has the following beneficial effects:

[0042] (1) The grid-forming energy storage system is used as a black start power supply in the present application, which can be started without external power supply or fuel supply, can still operate independently in the case of complete power interruption, can achieve millisecond-level fast response, can quickly provide the required power for the power grid, and can effectively shorten the recovery time.

[0043] (2) The grid-connected inverter adopts a matching control strategy, which can flexibly provide inertia and damping for the energy storage system, so that the energy storage system is more stable when facing different load conditions or power grid disturbances, and the oscillation phenomenon in the energy storage system is effectively suppressed through optimization of the impedance characteristics, thereby avoiding large fluctuations in voltage and frequency.

[0044] (3) The grid-connected inverter integrates an energy management function, dynamically adjusts the output power according to actual needs, avoids resource waste, and assists the supply through the DC side capacitor, which helps to alleviate the pressure on the energy storage battery as a black start power supply in extreme conditions.

[0045] The method scheme of the present application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is the topological structure diagram of the energy storage system of the present application; ​​​​

[0047] Figure 2 Control block diagram of DC / DC converter of the present application;

[0048] Figure 3 Control block diagram of inverter of the present application;

[0049] Figure 4 Power flow schematic diagram of energy storage system of the present application;

[0050] Figure 5 a-phase current of inverter output of the present application in the whole black start process;

[0051] Figure 6 Waveform simulation diagram of energy storage battery and DC side capacitor output power of the present application;

[0052] Figure 7 Waveform simulation diagram of matching control strategy of the present application in energy management implementation;

[0053] Figure 8 Waveform simulation diagram of matching control strategy of the present application without energy management. DETAILED DESCRIPTION

[0054] The method scheme of the present application is further described below by means of the accompanying drawings and examples.

[0055] Unless otherwise defined, the method terms or scientific terms used in the present application shall have the usual meanings understood by those with ordinary skills in the art to which the present application belongs.

[0056] The similar words such as "comprise" or "include" and the like used in the present application mean that the elements before the words cover the elements listed after the words, and do not exclude the possibility of also covering other elements. The directions or position relationships indicated by the terms "in", "out", "up", "down" and the like are based on the directions or position relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present application, unless otherwise specified and limited, the term "attached" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0057] EMBODIMENT

[0058] As Figures 1 to 4As shown, the application provides a network configuration type matching control strategy integrated with energy management in a black start scenario, including the following steps:

[0059] S1: The energy storage system is powered through the transformer;

[0060] In step S1, the power supply method adopts the zero-rise voltage boosting power supply method.

[0061] S2: Since the saturated transformer may generate a magnetic surge current of up to 6-8 times the rated value during energization, a soft start measure is needed to limit the impact current. The impact current generated by the transformer during power supply is limited by the inverter. In this embodiment, the soft start time is set to 0.5s, as shown in Figure 5 The a-phase current output by the inverter starts linearly from 0 and reaches the rated value, and at the same time, the transformer does not have an impact current during startup, i.e., the soft start measure is effective.

[0062] Step S2 specifically includes the following steps:

[0063] S21: Set the rated reference voltage output by the inverter to a ramp voltage v ref , and the ramp voltage v ref is set as:

[0064]

[0065] Where T ramp represents the rise time of the ramp voltage v ref .

[0066] S22: Simulate the rotor motion of the synchronous generator by the dynamic change of the DC side capacitor, and set the swing equation of the rotor motion as:

[0067]

[0068] Where ω n represents the rated angular frequency, ω g represents the grid angular frequency, C dc represents the DC side capacitor value, v dc represents the DC side capacitor voltage, J represents the grid inertia, D represents the damping coefficient, P m represents the output power of the synchronous generator, P E represents the electromagnetic power of the synchronous generator, P s represents the output power of the power supply, and P e represents the output power of the inverter.

[0069] In step S22, the coupling relationship between the angular frequency ω and the DC side capacitor voltage v dc is set as:

[0070]

[0071] wherein ω ref represents a reference value of the inverter angular frequency, K T represents a DC side voltage tracking coefficient, K J represents an inertia simulation coefficient, K D represents a damping coefficient, v dcref represents a reference value of the DC side voltage, s represents a complex frequency;

[0072] By coupling the angular frequency ω and the DC side capacitor voltage v dc , the synchronization of the phase-locked loop with the grid frequency can be achieved, and in the inverter control applied with the matching control, the active power P is replaced by the DC side capacitor voltage v dc , and there is no control of the active power P, but in the grid-connected system, the control of the active power P is actually necessary;

[0073] Therefore, the power reference value P ref is given in the front DC / DC link, and the power reference value P ref is a fixed value, but there is a power difference between the power supply side power and the power consumed by the load, so a feedback (v dc ) dcref -(v dc ) 2 related to the DC side capacitor voltage v 2 is added to offset the power imbalance between the power supply and the load, so as to realize the function of active power control;

[0074] S23: control the output power P of the inverter through the matching control strategy e , and add a cascaded voltage and current closed-loop control structure in the control structure, so that the inverter output characteristic is closer to the ideal voltage source, and the d and q axis decoupling of the current and voltage can be realized.

[0075] S3: after the energy storage system reaches the steady state for 1s, the switch S2 is closed, a 10kW load is connected, and the load power of the energy storage system is provided by the energy storage battery and the DC side capacitor, as shown in Figure 7 , when the load is connected, the total active power P of the inverter output is about 12kW, and the reactive power Q is about 2kW, at this time, the DC side capacitor voltage v dc drops slightly, and the output frequency f rises slightly;

[0076] The step S3 specifically comprises the following steps:

[0077] S31: provide the load power not greater than the rated power by the energy storage battery, and combine the swing equation of the rotor motion of the synchronous generator, and control the output power of the energy storage battery through the matching control strategy integrated with energy management;

[0078] In step S31, the matching control strategy integrating energy management is set as follows:

[0079]

[0080] S32: During black start, the load power may fluctuate significantly. When the energy storage battery is low, the fluctuating load may cause it to over-discharge, thereby damaging its lifespan and reducing safety. When load power fluctuations are detected, in order to ensure that the output power of the energy storage battery remains constant, the load power exceeding the rated power is fully compensated through the DC-side capacitor. The compensation formula is set as follows:

[0081]

[0082] Where, ΔP load This indicates load power fluctuation;

[0083] like Figure 6 As shown, when the energy storage system reaches steady state in 1.5 seconds, the load fluctuates by 0.5 kW. When the load fluctuates by 0.5 kW, in order to prevent the energy storage battery from discharging excessively, the DC capacitor releases energy to compensate for the fluctuating power. The energy storage battery output power P b It remains approximately constant within 1.5-2.0s, while the output power of the DC capacitor changes significantly within this time range;

[0084] In step S32, if the load power fluctuation ΔP load The DC-side capacitor voltage v remains constant. dc Reference value v for tracking DC side voltage dcref The reference value of DC side voltage v dcref Set to:

[0085]

[0086] Among them, v dcn Indicates the DC-side capacitor voltage v dc The rated value, t f This indicates the moment when the load power begins to fluctuate. Since the calculation process includes time-varying quantities that affect the angular frequency ω in real time, the grid inertia J and damping coefficient D need to be carefully designed.

[0087] like Figure 7 As shown, the total active power P increases by approximately 0.5kW, while the reactive power Q remains almost unchanged, due to the DC-side capacitor voltage v. dc Reference value v for tracking DC side voltage dcref DC side capacitor voltage v dc It kept dropping until just before grid connection.

[0088] S4: In order to meet the limit of DC side capacitor stored energy and the requirement of pre-synchronization time, the pre-synchronization is also set to 1.5s start, and the three-phase voltage amplitude, frequency and phase angle of the grid-connected point are obtained, and the difference value is calculated with the three-phase voltage amplitude, frequency and phase angle of the grid side, and the difference value is limited within the threshold value through pre-synchronization;

[0089] Step S4 specifically includes the following steps:

[0090] S41: Amplitude synchronization is performed, and the amplitude of the corresponding loop of the grid-connected point is modified so that the amplitude of the corresponding loop of the grid-connected point is the same as that of the grid side;

[0091] S42: Frequency synchronization is performed, and the frequency of the corresponding loop of the grid-connected point is modified so that the frequency of the corresponding loop of the grid-connected point is the same as that of the grid side;

[0092] S43: The phase angle at the grid-connected point is obtained through the phase-locked loop, and the difference between the phase angle at the grid-connected point and the phase angle of the inverter is input into a PI controller to generate an additional angular frequency, and a new reference value ω′ ref is obtained. ref The new reference value ω′ r is set as:

[0093] ω ef ′ ref = ω sync

[0094] wherein, ωref ω represents the original angular frequency reference value, ωsync ω represents the synchronized angular frequency.

[0095] As shown in Figure 8 , in order to exclude the influence of pre-synchronization on the total active power P, the reactive power Q, the DC side capacitor voltage v dc and the output frequency f, the graphical simulation is performed without energy management, the DC side capacitor voltage reference value is always kept at 800V, and the change of each circuit parameter is analyzed;

[0096] As shown in Figure 7 and Figure 8 , whether there is energy management or not, the output frequency of the inverter suddenly increases to 50.7Hz when the energy storage system reaches the steady state 1.5s, which indicates that this dramatic change is caused by the pre-synchronization strategy, and in Figure 8 , there is no energy management, only the pre-synchronization curve, and the DC side capacitor voltage v dc has no obvious change within 1.5-2.0s when the energy storage system reaches the steady state, which indicates that the pre-synchronization has no obvious influence on the DC side capacitor voltage v dc , and it is proved that the energy management strategy is effective.

[0097] S5: When the energy storage system reaches steady state 2s, the three-phase voltage amplitude, frequency and phase angle of the grid-connected point meet the grid-connected requirements, the pre-synchronization is completed, the switch S3 is closed, the grid and the energy storage system supply power at the same time, the grid injects 5kW of active power at the grid-connected point, and charges the DC side capacitor, the DC side capacitor is converted from the discharge mode to the charging mode, the DC side capacitor is slowly charged to recover to the rated value and remains stable, and the recovery time is about 0.25s, as shown in Figure 6 b After small amplitude oscillation, it remains stable.

[0098] As shown in Figure 7 The total active power P and the reactive power Q both remain stable after small amplitude oscillation, wherein the total active power P finally stabilizes at about 7.5kW, which meets the condition of 5kW of grid injection, and the DC side capacitor voltage v dc Steadily rises and finally stabilizes at 800V after 0.25s, and the output frequency f rapidly stabilizes at 50Hz after small amplitude oscillation.

[0099] Therefore, the application adopts the above-mentioned network type matching control strategy integrated with energy management in the black start scenario, adopts the network type energy storage system as the black start power supply, and adopts the matching control strategy for the grid-connected inverter, which integrates the energy management function, can not only provide inertia and damping for the energy storage system flexibly, but also helps to relieve the pressure of the energy storage battery as the black start power supply in extreme conditions.

[0100] Finally, it should be noted that: the above examples are only used to illustrate the method scheme of the application and not to limit it, although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the method scheme of the application can still be modified or replaced by the equivalent, and these modifications or equivalent replacements cannot make the modified method scheme deviate from the spirit and scope of the method scheme of the application.​

Claims

1. A grid-based matching control strategy integrating energy management in a black-start scenario, characterized in that, Includes the following steps: S1: The energy storage system is powered by a transformer; S2: Limits the inrush current generated by the transformer during power supply by using an inverter; S3: Provides the load power of the energy storage system through energy storage batteries and DC-side capacitors; Step S3 specifically includes the following steps: S31: The load power provided by the energy storage battery is no more than the rated power. The output power of the energy storage battery is controlled by the matching control strategy that integrates energy management, based on the swing equation of the rotor motion of the synchronous generator. S32: Full compensation for load power exceeding the rated power is achieved through a DC-side capacitor. The compensation formula is set as follows: Where, ΔP load This indicates load power fluctuation; S4: Obtain the three-phase voltage amplitude, frequency, and phase angle at the grid connection point, calculate the difference with the three-phase voltage amplitude, frequency, and phase angle on the grid side, and limit the difference to within the threshold through pre-synchronization; S5: After pre-synchronization is completed, the circuit is closed and connected to the grid. The grid and energy storage system supply power simultaneously and charge the DC side capacitor. The DC side capacitor restores its rated voltage and remains stable.

2. The grid-based matching control strategy for integrated energy management in a black-start scenario according to claim 1, characterized in that, In step S1, the power supply method adopts the zero-start boost power supply method.

3. The grid-based matching control strategy for integrated energy management in a black-start scenario according to claim 1, characterized in that, Step S2 specifically includes the following steps: S21: Set the rated reference voltage of the inverter output to the ramp voltage v. ref ramp voltage v ref Set to: Among them, T ramp Represents the ramp voltage v ref The rise time; S22: The rotor motion of the synchronous generator is simulated by the dynamic change of the DC-side capacitor. The swing equation of the rotor motion is set as follows: Where, ω n Indicates the rated angular frequency, ω g C represents the angular frequency of the power grid. dc This indicates the DC-side capacitance value, V. dc J represents the DC-side capacitor voltage, D represents the grid inertia, and P represents the damping coefficient. m P represents the output power of the synchronous generator. E P represents the electromagnetic power of a synchronous generator. s P represents the output power of the power supply. e This indicates the output power of the inverter; S23: Control the inverter's output power P through a matching control strategy. e Furthermore, a cascaded voltage and current closed-loop control structure is added to the control structure.

4. The grid-based matching control strategy for integrated energy management in a black-start scenario according to claim 3, characterized in that, In step S22, the angular frequency ω and the DC-side capacitor voltage v dc The coupling relationship is set as follows: Where, ω ref K represents the reference value for the inverter's angular frequency. T K represents the DC-side voltage tracking coefficient. J K represents the inertial simulation coefficient. D V represents the damping coefficient. dcref The value represents the reference value of the DC side voltage, and s represents the complex frequency.

5. The grid-based matching control strategy for integrated energy management in a black-start scenario according to claim 1, characterized in that, In step S32, if the load power fluctuation ΔP load The DC-side capacitor voltage v remains constant. dc Reference value v for tracking DC side voltage dcref The reference value of DC side voltage v dcref Set to: Among them, v dcn Indicates the DC-side capacitor voltage v dc The rated value, t f This indicates the moment when the load power begins to fluctuate.

6. The grid-based matching control strategy for integrated energy management in a black-start scenario according to claim 1, characterized in that, In step S31, the matching control strategy integrating energy management is set as follows:

7. The grid-based matching control strategy for integrated energy management in a black-start scenario according to claim 1, characterized in that, Step S4 specifically includes the following steps: S41: Perform amplitude synchronization by modifying the amplitude of the corresponding loop at the grid connection point so that the amplitude of the corresponding loop at the grid connection point is the same as the amplitude on the grid side. S42: Perform frequency synchronization by modifying the frequency of the corresponding loop at the grid connection point to make the frequency of the corresponding loop at the grid connection point the same as the frequency on the grid side. S43: Obtain the phase angle at the grid connection point through a phase-locked loop, input the difference between the phase angle at the grid connection point and the inverter phase angle into the PI controller to generate an additional angular frequency, and obtain a new reference value ω′. ref The new reference value ω′ ref Set to: oh' ref =ω ref +oh sync Where, ω ref Represents the original angular frequency reference value, ω sync This indicates the synchronization angular frequency.

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