Network construction type matching control strategy of integrated energy management in black start scene

Abstract

The invention discloses a network construction type matching control strategy for integrated energy management in a black-start scene, and relates to the field of energy storage system network construction control, and the strategy comprises the following steps: S1, an energy storage system supplies power through a transformer; s2, limiting the impact current generated by the transformer in the power supply process through an inverter; s3, energy storage system load power is provided through an energy storage battery and a direct current side capacitor; s4, the three-phase voltage amplitude, frequency and phase angle of the grid-connected point are obtained, difference calculation is carried out on the three-phase voltage amplitude, frequency and phase angle of the grid side, and the difference is limited within a threshold value through pre-synchronization; s5, closing and grid connection are carried out after pre-synchronization is completed, the power grid and the energy storage system supply power at the same time, the direct-current side capacitor is charged, and the rated voltage is recovered; a net-forming type energy storage system is adopted as a black-start power supply, a matching control strategy is adopted, an energy management function is integrated, inertia and damping are flexibly provided for the energy storage system, and the pressure of an energy storage battery serving as the black-start power supply under extreme conditions is relieved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage system networking control, and in particular to a networking matching control strategy integrating energy management in a black start scenario. Background Art

[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 the event of a large-scale power outage, the power system must restore power supply under the drive of generators with self-starting capabilities, that is, black start. At the same time, with the increase in the penetration rate of renewable energy RES, the black start power source has gradually shifted 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 system BESS is widely used in RES. Generally, the battery state of charge SOC must be strictly controlled within a certain range to prevent overcharging or over-discharging. Most energy management methods simply adjust the output power of the battery according to the SOC. However, simple adjustment methods usually use rough technical means, which makes it difficult to achieve precise control of the output power. Unstable output power will lead to unstable equipment performance or direct damage, and it is difficult to maintain stable operation in complex environments. In addition, simple adjustment methods cannot dynamically adjust the output power according to actual needs, which will lead to energy waste;

[0004] In the black start application scenario, the control strategy of the energy storage side inverter also directly affects the efficiency and reliability of the 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, but the above strategy control cannot avoid steady-state errors. Research in black start scenarios is relatively lacking. When facing rapidly changing loads or grid disturbances, the GFM system has a slow response speed and cannot adjust the output in time to maintain stability, which will cause oscillations and seriously affect the stability and reliability of the system.

[0005] Therefore, a grid-connected matching control strategy with integrated energy management in a black start scenario is provided to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a grid-type matching control strategy with integrated energy management in a black start scenario. The integrated energy management function can flexibly provide inertia and damping for the energy storage system, while helping to alleviate the pressure of the energy storage battery as a black start power supply under extreme conditions.

[0007] To achieve the above object, the present invention provides a network matching control strategy for integrated energy management in a black start scenario, comprising the following steps:

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

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

[0010] S3: Provide energy storage system load power through energy storage batteries and DC side capacitors;

[0011] S4: Obtain the three-phase voltage amplitude, frequency and phase angle of the grid-connected point, calculate the difference with the three-phase voltage amplitude, frequency and phase angle of the grid side, and limit the difference within the threshold through pre-synchronization;

[0012] S5: After pre-synchronization is completed, the switch is closed and the grid is connected. The grid and the energy storage system supply power at the same time and charge the DC side capacitors. The DC side capacitors restore the rated voltage and remain stable.

[0013] Preferably, in step S1, the power supply method adopts a zero-start voltage boost power supply method.

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

[0015] S21: Set the rated reference voltage of the inverter output to the ramp voltage v ref , ramp voltage v ref Set to:

[0016]

[0017] Among them, T ramp Represents the ramp voltage v ref Rise time;

[0018] S22: The rotor motion of the synchronous generator is simulated by the dynamic change of the DC link capacitor. The swing equation of the rotor motion is set as:

[0019]

[0020] Among them, ω n Indicates the rated angular frequency, ω g Indicates the grid angular frequency, C dc Indicates the DC side capacitance 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 Indicates the output power of the power supply, P e Indicates the output power of the inverter;

[0021] S23: Control the output power P of the inverter through matching control strategye , and add a cascaded voltage and current closed-loop control structure into the control structure.

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

[0023]

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

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

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

[0027] S32: The load power greater than the rated power is fully compensated by the DC side capacitor, and the compensation formula is set as:

[0028]

[0029] Among them, ΔP load Indicates load power fluctuation.

[0030] Preferably, in step S32, if the load power fluctuation ΔP load Keep constant, the DC side capacitor voltage v dc Track the reference value v of the DC side voltage dcref , the reference value of DC voltage v dcref Set to:

[0031]

[0032] Among them, v dcn Indicates the DC side capacitor voltage v dc Rated value, t f Indicates the moment when the load power begins to fluctuate.

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

[0034]

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

[0036] S41: Perform amplitude synchronization, modify the amplitude of the corresponding loop of the grid connection point, 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: Perform frequency synchronization, modify the frequency of the corresponding loop of the grid connection point, 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: Obtain the phase angle at the grid connection point through the phase-locked loop, input the difference between the phase angle at the grid connection point and the inverter phase angle into the PI controller and generate an additional angular frequency to obtain a new reference value ω′ ref , the new reference value ω′ ref Set to:

[0039] ω′ ref =ω ref +ω sync

[0040] in, ωref represents the original angular frequency reference value, ωsync Indicates the synchronous angular frequency.

[0041] Therefore, the present invention adopts a network-type matching control strategy for integrated energy management in a black start scenario using the above structure, which has the following beneficial effects:

[0042] (1) The present invention uses a grid-type energy storage system as a black start power source, which can be started without external power or fuel supply. It can still operate independently when the power is completely cut off, and can achieve a rapid response of milliseconds to quickly provide the required power to the power grid, effectively shortening the recovery time;

[0043] (2) The grid-connected inverter of the present invention adopts a matching control strategy, which can flexibly provide inertia and damping for the energy storage system, making the energy storage system more stable when facing different load conditions or grid disturbances. At the same time, by optimizing the impedance characteristics, the oscillation phenomenon in the energy storage system is effectively suppressed to avoid large fluctuations in voltage and frequency;

[0044] (3) The grid-connected inverter of the present invention integrates an energy management function, dynamically adjusts the output power according to actual needs, avoids waste of resources, and provides auxiliary supply through DC side capacitors, which helps to alleviate the pressure of the energy storage battery as a black start power supply in extreme cases.

[0045] The method scheme of the present invention is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a topological structure diagram of the energy storage system of the present invention;

[0047] Figure 2 is a control block diagram of a DC / DC converter of the present invention;

[0048] Figure 3 is a control block diagram of the inverter of the present invention;

[0049] Figure 4 A schematic diagram of power flow of the energy storage system of the present invention;

[0050] Figure 5 A diagram showing the change of the a-phase current output by the inverter of the present invention during the entire black start process;

[0051] Figure 6 It is a waveform simulation diagram of the output power of the energy storage battery and the DC side capacitor of the present invention;

[0052] Figure 7 This is a waveform simulation diagram when the matching control strategy of energy management is implemented in the present invention;

[0053] Figure 8 This is a waveform simulation diagram of the matching control strategy without energy management in the present invention. DETAILED DESCRIPTION

[0054] The method scheme of the present invention is further described below through drawings and embodiments.

[0055] Unless otherwise defined, method terms or scientific terms used in the present invention shall have the common meanings understood by one of ordinary skill in the art to which the present invention belongs.

[0056] The words "include" or "comprises" and the like used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms "inside", "outside", "upper", "lower", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly specified and limited, the terms "attachment" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] Example

[0058] like Figures 1 to 4As shown, the present invention provides a network matching control strategy for integrated energy management in a black start scenario, comprising the following steps:

[0059] S1: The energy storage system is powered by a transformer;

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

[0061] S2: Since a saturated transformer may generate an excitation inrush current as high as 6-8 times the rated value during the power-on process, a slow start measure is required to limit the impact current. The inverter is used to limit the impact current generated by the transformer during the power supply process. In this embodiment, the slow start time is set to 0.5s. Figure 5 As shown in the figure, the a-phase current output by the inverter rises linearly from 0 until it reaches the rated value. At the same time, there is no surge current in the transformer during the startup process, that is, the slow start measure is effective.

[0062] Step S2 specifically includes the following steps:

[0063] S21: Set the rated reference voltage of the inverter output to the ramp voltage v ref , ramp voltage v ref Set to:

[0064]

[0065] Among them, T ramp Represents the ramp voltage v ref Rise time;

[0066] S22: The rotor motion of the synchronous generator is simulated by the dynamic change of the DC link capacitor. The swing equation of the rotor motion is set as:

[0067]

[0068] Among them, ω n Indicates the rated angular frequency, ω g Indicates the grid angular frequency, C dc Indicates the DC side capacitance 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 Indicates the output power of the power supply, P e Indicates the output power of the inverter;

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

[0070]

[0071] Among them, ω ref Indicates the reference value of the inverter angular frequency, K T Indicates 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, s represents the complex frequency;

[0072] By converting the angular frequency ω and the DC side capacitor voltage v dc Coupling can achieve synchronization with the grid frequency without a phase-locked loop. In the inverter control with matching control, the active power P is controlled by the DC side capacitor voltage v dc Instead, there is no control over the active power P, but in the network system, the control of the active power P is actually necessary;

[0073] Therefore, it is necessary to give a power reference value P in the front-end DC / DC link. ref , power reference value P ref is a fixed value, but there is a power difference between the power on the power supply side and the power consumed by the load, so a voltage v dc Related feedback (v dcref ) 2 -(v dc ) 2 Offset the power imbalance between power source and load to achieve the function of active power control;

[0074] S23: Control the output power P of the inverter through matching control strategy e , and adding a cascaded voltage and current closed-loop control structure to the control structure not only makes the inverter output characteristics closer to the ideal voltage source, but also realizes the d and q axis decoupling of current and voltage.

[0075] S3: After the energy storage system reaches steady state for 1 second, switch S2 is closed to connect the 10kW load, and the energy storage system load power is provided by the energy storage battery and the DC side capacitor, such as Figure 7 As shown in the figure, when the load is connected, the total active power P output by the inverter is about 12kW, and the reactive power Q is about 2kW. At this time, the DC side capacitor voltage v dc A small decrease and a slight increase in the output frequency f;

[0076] Step S3 specifically includes the following steps:

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

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

[0079]

[0080] S32: During black start, the load power may fluctuate greatly. When the energy storage battery is low in energy, the fluctuating load may cause it to over-discharge, thereby damaging its life and reducing safety. When load power fluctuations are detected, in order to ensure that the output power of the energy storage battery is constant, the DC side capacitor is used to fully compensate for the load power greater than the rated power. The compensation formula is set as:

[0081]

[0082] Among them, ΔP load Indicates load power fluctuation;

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

[0084] In step S32, if the load power fluctuation ΔP load Keep constant, the DC side capacitor voltage v dc Track the reference value v of the DC side voltage dcref , the reference value of DC voltage v dcref Set to:

[0085]

[0086] Among them, v dcn Indicates the DC side capacitor voltage v dc Rated value, t f Indicates the moment when the load power begins to fluctuate. Since the calculation process includes time-varying quantities, which 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 in the figure, the total active power P increases by about 0.5kW, and the reactive power Q remains almost unchanged. dc Track the reference value v of the DC side voltage dcref , DC side capacitor voltage v dc It continues to decrease until the moment before grid connection.

[0088] S4: In order to meet the limitation of DC side capacitor storage energy and the requirement of pre-synchronization time, pre-synchronization is also set to start at 1.5s. The three-phase voltage amplitude, frequency and phase angle of the grid connection point are obtained, and the difference between them and the three-phase voltage amplitude, frequency and phase angle of the grid side is calculated. The difference is limited within the threshold through pre-synchronization.

[0089] Step S4 specifically includes the following steps:

[0090] S41: Perform amplitude synchronization, modify the amplitude of the corresponding loop of the grid connection point, so that the amplitude of the corresponding loop of the grid connection point is the same as the amplitude of the grid side;

[0091] S42: Perform frequency synchronization, modify the frequency of the corresponding loop of the grid connection point, so that the frequency of the corresponding loop of the grid connection point is the same as the frequency of the grid side;

[0092] S43: Obtain the phase angle at the grid connection point through the phase-locked loop, input the difference between the phase angle at the grid connection point and the inverter phase angle into the PI controller and generate an additional angular frequency to obtain a new reference value ω′ ref , the new reference value ω′ ref Set to:

[0093] ω r ' ef =ω ref +ω sync

[0094] in, ωref represents the original angular frequency reference value, ωsync Indicates the synchronous angular frequency.

[0095] like Figure 8 As shown, in order to eliminate the influence of pre-synchronization on the total active power P, reactive power Q, and DC side capacitor voltage v dc The influence of the output frequency f is analyzed. Graphical simulation is performed when there is no energy management. The reference value of the DC side capacitor voltage is always kept at 800V. The changes of each circuit parameter are analyzed.

[0096] like Figure 7 and Figure 8 As shown in Figure 2, regardless of whether there is energy management or not, when the energy storage system reaches steady state for 1.5s, the output frequency of the inverter suddenly increases to 50.7Hz, indicating that this drastic change comes from the pre-synchronization strategy. Figure 8 There is no energy management in the system, only the pre-synchronization curve. The DC side capacitor voltage v dc There is no obvious change, indicating that the pre-synchronization has an influence on the DC side capacitor voltage v dc There was no significant impact, proving that the energy management strategy was effective.

[0097] S5: When the energy storage system reaches steady state for 2s, the three-phase voltage amplitude, frequency and phase angle of the grid connection point meet the grid connection requirements. After pre-synchronization is completed, switch S3 is closed, and the grid and energy storage system supply power at the same time. The grid injects 5kW of active power at the grid connection point and charges the DC side capacitor. The DC side capacitor switches from discharge mode to charging mode. The DC side capacitor slowly charges back to the rated value and remains stable. The recovery time is about 0.25s. Figure 6 As shown, the energy storage battery output power P b After a small shock, it remains stable;

[0098] like Figure 7 As shown in the figure, the total active power P and reactive power Q remain stable after a small fluctuation. The total active power P finally stabilizes at about 7.5kW, which meets the condition of 5kW injection into the grid. After the energy storage system reaches steady state for 2s, the DC side capacitor voltage v dc It rises steadily and finally stabilizes at 800V after 0.25s. The output frequency f quickly stabilizes at 50Hz after a small jitter.

[0099] Therefore, the present invention adopts the above-mentioned grid-type matching control strategy with integrated energy management in the black start scenario, and adopts a grid-type energy storage system as the black start power supply. Its grid-connected inverter adopts a matching control strategy with integrated energy management function, which can not only flexibly provide inertia and damping for the energy storage system, but also help alleviate the pressure of the energy storage battery as a black start power supply under extreme conditions.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the method scheme of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary method personnel in the field should understand that they can still modify or replace the method scheme of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified method scheme to deviate from the spirit and scope of the method scheme of the present invention.

Claims

1. A network matching control strategy with integrated energy management in a black start scenario, characterized in that: The following steps are involved: S1: The energy storage system is powered by a transformer; S2: Limit the inrush current generated by the transformer during power supply through the inverter; S3: Provide energy storage system load power through energy storage batteries and DC side capacitors; S4: Obtain the three-phase voltage amplitude, frequency and phase angle of the grid-connected point, calculate the difference with the three-phase voltage amplitude, frequency and phase angle of the grid side, and limit the difference within the threshold through pre-synchronization; S5: After pre-synchronization is completed, the switch is closed and the grid is connected. The grid and the energy storage system supply power at the same time and charge the DC side capacitors. The DC side capacitors restore the rated voltage and remain stable.

2. According to claim 1, a meshing matching control strategy for integrated energy management in a black start scenario is characterized in that: In step S1, the power supply method adopts the zero-voltage boost power supply method.

3. According to claim 1, a meshing matching control strategy for integrated energy management in a black start scenario is characterized in that: Step S2 specifically includes the following steps: S21: Set the rated reference voltage of the inverter output to the ramp voltage vref , ramp voltage v ref Set to: Among them, T ramp Represents the ramp voltage v ref Rise time; S22: The rotor motion of the synchronous generator is simulated by the dynamic change of the DC link capacitor. The swing equation of the rotor motion is set as: Among them, ω n Indicates the rated angular frequency, ω g Indicates the grid angular frequency, C dc Indicates the DC side capacitance 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 Indicates the output power of the power supply, P e Indicates the output power of the inverter; S23: Control the output power P of the inverter through matching control strategy e , and add a cascaded voltage and current closed-loop control structure into the control structure.

4. According to claim 3, a meshing matching control strategy for integrated energy management in a black start scenario is characterized in that: In step S22, the angular frequency ω and the DC link capacitor voltage v dc The coupling relationship is set as: Among them, ω ref Indicates the reference value of the inverter angular frequency, K T Indicates the DC side voltage tracking coefficient, K J represents the inertia simulation coefficient, K D represents the damping coefficient, v dcref It represents the reference value of DC side voltage, and s represents the complex frequency.

5. According to claim 1, a grid-type matching control strategy for integrated energy management in a black start scenario is characterized in that: Step S3 specifically includes the following steps: S31: providing a load power not greater than the rated power through the energy storage battery, combining the swing equation of the rotor motion of the synchronous generator, and controlling the output power of the energy storage battery through a matching control strategy integrated with energy management; S32: The load power greater than the rated power is fully compensated by the DC side capacitor, and the compensation formula is set as: Among them, ΔP load Indicates load power fluctuation.

6. According to claim 5, a meshing matching control strategy for integrated energy management in a black start scenario is characterized in that: In step S32, if the load power fluctuation ΔP load Keep constant, the DC side capacitor voltage v dc Track the reference value v of the DC side voltage dcref , the reference value of DC voltage v dcref Set to: Among them, v dcn Indicates the DC side capacitor voltage v dc Rated value, t f Indicates the moment when the load power begins to fluctuate.

7. According to claim 5, a meshing matching control strategy for integrated energy management in a black start scenario is characterized in that: In step S31, the matching control strategy integrated with energy management is set as:

8. According to claim 1, a grid-type matching control strategy for integrated energy management in a black start scenario is characterized in that: Step S4 specifically includes the following steps: S41: Perform amplitude synchronization, modify the amplitude of the corresponding loop of the grid connection point, so that the amplitude of the corresponding loop of the grid connection point is the same as the amplitude of the grid side; S42: Perform frequency synchronization, modify the frequency of the corresponding loop of the grid connection point, so that the frequency of the corresponding loop of the grid connection point is the same as the frequency of the grid side; S43: Obtain the phase angle at the grid connection point through the phase-locked loop, input the difference between the phase angle at the grid connection point and the inverter phase angle into the PI controller and generate an additional angular frequency to obtain a new reference value ω′ ref , the new reference value ω′ ref Set to: oh r ′ ef =ω ref +oh sync in, ωref Represents the original angular frequency reference value, ωsync Indicates the synchronous angular frequency.

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