Hybrid Synchronous Control Method and System for Grid-Based Energy Storage Converters Considering Active Power Tracking

Abstract

This invention discloses a hybrid synchronization control method and system for a grid-connected energy storage converter that considers active power point tracking, belonging to the field of power electronic converter control technology. The method includes: determining a grid fault when the grid positive-sequence voltage exceeds the start-up threshold range; implementing voltage droop control for reactive power and calculating reactive power in real time; calculating a target reference value for active power based on voltage droop depth and reactive power priority support constraints; calculating a target value for AC q-axis capacitor voltage based on the target reference value for active power to adjust the output power; when the grid positive-sequence voltage recovers to the start-up threshold range, restoring the target reference value for active power to the pre-fault active power target value, and synchronously restoring the target value for AC q-axis capacitor voltage; during the recovery process, real-time tracking of the grid phase is achieved through output power until the grid stabilizes and hybrid synchronization control is completed. This invention accelerates phase angle tracking speed after voltage surges and improves transient stability.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter control technology, and in particular to a hybrid synchronous control method and system for grid-type energy storage converters that takes into account active power tracking. Background Technology

[0002] With the large-scale integration of wind power, photovoltaic, and energy storage converters into the power system, and the increasing proportion of renewable energy sources, traditional current-source inverters lack the ability to construct voltage and frequency, posing a severe challenge to system stability. Grid-connected converters, possessing the external characteristics of an ideal synchronous voltage source, can autonomously sense changes in power source amplitude and frequency to support the grid and improve grid stability. Their control strategies have become a research hotspot in recent years, especially in achieving stable operation under large disturbances such as grid faults, and maintaining voltage source characteristics in the "active power-frequency" loop when the converter is current-limited. This is a key focus of research for the widespread application of grid-connected converters.

[0003] To improve the transient stability of grid-connected converters, hybrid synchronous control has been proposed. Under grid fault conditions, a phase-locked loop (PLL) is used to track the reference phase generated by the active power control loop, avoiding the converter output voltage phase from failing to quickly track the reference phase under large disturbances, thus preventing loss of synchronization with the grid. Its function is similar to the damping winding of a synchronous generator. Meanwhile, in addition to ensuring fault ride-through stability, relevant national standards stipulate that active power should remain constant during faults. This means that active power output still needs to be considered during grid faults, and active power demand and power angle balance issues must be comprehensively considered. Grid-type energy storage converters often need to consider multiple units in parallel to increase capacity. However, the parallel connection of multiple voltage sources requires the addition of virtual impedance control to ensure that the line is inductive in order to achieve current sharing. Due to the existence of virtual impedance, there will always be an angle difference between the phase-locked loop angle and the actual internal potential angle. The magnitude of this difference is related to the power transmission magnitude and the line. If this difference is not considered, even if hybrid synchronization only uses proportional control, oscillations or overcurrent phenomena often occur at the moment of grid fault due to different target values. Therefore, it is urgent to solve the problem of achieving rapid response of active power transmission under the constraint of maximum active power transmission capacity and reducing the risk of grid-type converters losing synchronization with the grid. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hybrid synchronous control method and system for grid-type energy storage converters that takes into account active power tracking. This method can ensure that the power angle and power curve have a balanced intersection point, and can quickly respond to changes in grid phase angle, thereby accelerating power response speed and improving stability. It does not require an additional backup PLL circuit and reduces the amount of code.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] This invention provides a hybrid synchronous control method for grid-type energy storage converters that takes active power tracking into account, comprising:

[0007] Obtain the positive sequence voltage value of the grid-connected energy storage converter;

[0008] When the positive sequence voltage value of the power grid exceeds the start-up threshold range, a power grid fault is determined, voltage droop control is implemented for reactive power, and reactive power is calculated in real time; and, based on the voltage droop depth and reactive power priority support constraints, the active power target reference value is calculated.

[0009] The target value of AC q-axis capacitor voltage is calculated based on the active power target reference value. The output power is adjusted using a proportional controller based on the difference between the target value of AC q-axis capacitor voltage and the actual capacitor voltage feedback value.

[0010] When the positive sequence voltage value of the power grid recovers to the starting threshold range, the active power target reference value is restored to the active power target value before the fault, and the AC q-axis capacitor voltage target value is restored synchronously. During the recovery process, the output power tracks the power grid phase in real time until the power grid stabilizes and completes the hybrid synchronous control.

[0011] Optionally, the formula for calculating the reactive power is:

[0012] ;

[0013] ;

[0014] in, Indicates reactive power; This represents the voltage reactive power droop coefficient; Indicates the rated voltage; Indicates the positive sequence voltage value of the power grid; Indicates the rated capacity of the converter; This indicates the reactive power after limiting. Indicates the maximum apparent power; This indicates taking the minimum value.

[0015] Optionally, the calculation of the active power target reference value based on voltage sag depth and reactive power priority support constraints includes:

[0016] The first active power setpoint is calculated based on voltage dip depth feedback;

[0017] Under the constraint of prioritizing reactive power support, the remaining support capacity is used as the second active power given value;

[0018] The minimum value between the first active power setpoint and the second active power setpoint is used as the active power target reference value.

[0019] Optionally, the formula for calculating the active power target reference value is:

[0020] ;

[0021] ;

[0022] in, This represents the first active power setpoint; This indicates the setpoint of active power before the fault; Indicates the positive sequence voltage value of the power grid; , These represent the low penetration threshold and the high penetration threshold, respectively. This represents the target reference value for active power. This indicates the reactive power after limiting. Indicates the maximum apparent power; This indicates taking the minimum value.

[0023] Optionally, the formula for calculating the target value of the AC q-axis capacitor voltage is as follows:

[0024] ;

[0025] ;

[0026] in, Represents the internal electric potential Using the capacitor voltage as a reference point Steady-state power at the location; Indicates reference point To capacitor voltage Total line impedance at the location; Indicates capacitor voltage The angle of attack at the location; This represents the target value of the AC q-axis capacitor voltage; This refers to the AC filter of a grid-type energy storage converter; This represents virtual impedance.

[0027] Optionally, the actual capacitor voltage feedback value is calculated by removing the negative sequence voltage component based on a positive-negative sequence separation method, as shown in the formula:

[0028] ;

[0029] ;

[0030] ;

[0031] in, This indicates that the transformation matrix is ​​calculated for the orthogonal components. Indicates the calculation of the transformation matrix for negative-order components; superscript Indicates matrix transpose; Indicates the output angle of the Pf ring; This represents the AC d-axis value of the positive sequence voltage component after filtering and extraction. This represents the AC q-axis value of the positive sequence voltage component after filtering and extraction. This represents the actual capacitor voltage feedback value; This represents the AC dq axis value of the positive sequence voltage component after filtering and extraction. This represents the instantaneous value of the positive sequence voltage along the dq axis. This represents the negative-order component after being filtered by a low-pass filter.

[0032] Optional, also includes:

[0033] The output power and mechanical power are superimposed and then the output frequency is adjusted by a virtual synchronizer.

[0034] After converting the output frequency to angular velocity, the phase angle is obtained through an integration stage. The phase angle is then superimposed with the internal potential and passed through a virtual impedance stage to obtain the inner current loop command.

[0035] The current inner loop command is current-limited by a ring limiter and then modulated by the current inner loop. The modulated signal is then input into the PWM module to achieve current closed-loop control.

[0036] Optionally, the annular limiter is represented as:

[0037] ;

[0038] in, This indicates the current inner loop command after limiting; Indicates the inner loop current command; Indicates the effective value of the maximum allowable output current; This indicates the current d-axis command after limiting. This indicates the current q-axis command after limiting.

[0039] Optional, also includes:

[0040] When the positive sequence voltage value of the power grid exceeds the start-up threshold range, the power grid fault flag bit... Set to 1;

[0041] When the positive sequence voltage value of the power grid recovers to the start-up threshold range and the power grid stably completes hybrid synchronization control, the power grid fault flag bit... Clear 0.

[0042] On the other hand, the present invention provides a hybrid synchronous control system for a grid-type energy storage converter that takes into account active power tracking, comprising:

[0043] The voltage acquisition module is used to: acquire the positive sequence voltage value of the grid for the grid-connected energy storage converter;

[0044] The active power calculation module is used to: determine that a grid fault has occurred when the positive sequence voltage value of the grid exceeds the start-up threshold range, implement voltage droop control on reactive power, and calculate reactive power in real time; and calculate the target reference value of active power based on the voltage droop depth and reactive power priority support constraints.

[0045] The frequency adjustment module is used to: calculate the target value of AC q-axis capacitor voltage based on the active power target reference value, and adjust the output power using a proportional controller based on the difference between the target value of AC q-axis capacitor voltage and the actual capacitor voltage feedback value.

[0046] Stability control is used to: restore the active power target reference value to the active power target value before the fault when the positive sequence voltage value of the power grid recovers to the range of the start-up threshold, and synchronously restore the AC q-axis capacitor voltage target value. During the recovery process, the output power tracks the power grid phase in real time until the power grid stabilizes and completes the hybrid synchronous control.

[0047] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0048] This invention enhances the weighting effect of phase-locked loop (PLL) synchronization without requiring additional PLL for real-time phase locking, thus reducing valuable code resources for engineering implementation. It considers the need to add virtual inductive reactance in parallel multi-machine configurations in practical engineering, and the difference in weighted control target input caused by the inconsistency between the PLL and phase angle when active power demand is non-zero. By adjusting the AC q-axis capacitor voltage target value of the hybrid synchronization control input in consideration of the active power target value, it reduces the output instability caused by the inconsistency in the weighted control targets, thereby improving the stability of the grid-connected inverter during fault ride-through transients. Attached Figure Description

[0049] Figure 1 A flowchart illustrating the hybrid synchronous control method for a grid-type energy storage converter that takes active power tracking into account, provided in an embodiment of the present invention.

[0050] Figure 2 A flowchart illustrating the hybrid synchronous control method for a grid-type energy storage converter that takes active power tracking into account, provided in an embodiment of the present invention.

[0051] Figure 3 The equivalent circuit diagram of the grid-type energy storage converter provided in the embodiments of the present invention;

[0052] Figure 4This is a control block diagram of a grid-type energy storage converter provided in an embodiment of the present invention;

[0053] Figure 5 This is a block diagram of voltage positive and negative sequence separation control for a grid-type energy storage converter provided in an embodiment of the present invention;

[0054] Figure 6 A schematic diagram comparing the positive sequence voltage simulation of the power grid using the method of the present invention and methods other than those of the present invention, provided for embodiments of the present invention;

[0055] Figure 7 A schematic diagram comparing the active power simulation of the power grid using the method of the present invention and methods other than those of the present invention, provided for embodiments of the present invention;

[0056] Figure 8 A schematic diagram showing a comparison of reactive power simulation of the power grid using the method of the present invention and methods other than those of the present invention, provided for embodiments of the present invention. Detailed Implementation

[0057] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0058] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0059] Example 1

[0060] like Figure 1 As shown, this embodiment introduces a hybrid synchronous control method for grid-type energy storage converters that takes active power tracking into account. Figure 3 The diagram shown is the equivalent circuit diagram of a grid-connected energy storage converter. It exhibits voltage source characteristics externally. In a single-input system, the voltage is supplied by the power grid. The phase angle of the power grid is Grid impedance Voltage amplitude at grid connection point The voltage phase angle at the grid connection point is Transformer equivalent impedance capacitor voltage The phase angle at the capacitor voltage is Energy storage converter AC filter Virtual impedance Internal potential The phase angle of the internal potential is Composition, including the power grid One end is grounded, and the other end is connected in sequence to the power grid impedance. Voltage amplitude at grid connection point Transformer equivalent impedance Virtual impedance Internal potential Internal potential Grounding.

[0061] Converters typically use the voltage direct (d) axis as the reference direction, i.e., assuming zero power point tracking is completed, the capacitor voltage... The angle of attack Approaching 0, i.e., voltage loop command , .

[0062] The method includes the following steps:

[0063] Step 1: Obtain the positive sequence voltage value of the grid-connected energy storage converter, specifically:

[0064] The controller acquires the AC filter capacitor voltage of the grid-type energy storage converter. The input positive and negative sequence separation module directly outputs the angle as the active power (Pf) loop. The calculated feedback voltage value after positive-sequence decoupling in the Cartesian coordinate system is the actual capacitor voltage q-axis feedback value, which is also the actual capacitor voltage q-axis feedback value in this embodiment. d-axis feedback voltage value And based on this, the per-unit amplitude of the positive sequence voltage is calculated. The per-unit amplitude of the negative-sequence voltage can be calculated from the feedback voltage value after negative-sequence decoupling. The per-unit amplitude of the positive sequence voltage This refers to the positive sequence voltage value of the grid for a grid-type energy storage converter.

[0065] Step 2: Calculate the target reference value of active power when a power grid fault occurs, specifically:

[0066] like Figure 4 The diagram shows the control block diagram of a grid-type energy storage converter. The frequency and voltage are mainly composed of an active power (Pf) loop and a reactive power (QV) loop. In the Pf loop, the output frequency... With the rated frequency of the power grid After subtraction and one frequency adjustment, the target reference value of active power is given. The output mechanical power is obtained by subtracting the output of the primary frequency modulation. In the QV loop, the voltage rating is... Actual feedback quantity of voltage amplitude After subtraction, the voltage reactive power droop factor is applied. The control output, which is related to the limited reactive power. Summing and then adding to the reactive power feedback quantity The difference between the output and the voltage rating after proportional-integral (PI) control is calculated. Summing them up yields the internal potential. .

[0067] When a power grid fault occurs, the target reference value of active power needs to be reduced to avoid power angle instability. This ensures a new equilibrium point, while the QV ring guarantees amplitude building capability before current limiting, but will lock the reactive power ring and lose amplitude building capability after current limiting.

[0068] like Figure 2 As shown, in order to initiate adaptive switching of the active power reference value after a change in grid connection point voltage to ensure a stable operating point for the power angle curve, the Pf loop runs continuously without saturation throughout the entire process. Meanwhile, the QV loop, due to current limiting, restricts the output of its internal potential. This means that even after a grid fault, at least the frequency conversion capability is guaranteed. When the controller detects the positive sequence voltage value of the grid... A power grid fault is determined when the fault exceeds the initiation threshold range, where the initiation threshold range is: There is a hybrid synchronous control for both high-pass and low-pass processes. The only difference between the two is the triggering condition; all other control processes are the same. or The power grid fault flag is used to determine when a power grid fault has occurred. Set to 1 to initiate hybrid synchronous control of the grid-type energy storage converter, which includes active power tracking; among which, , These represent the low penetration threshold and the high penetration threshold, respectively.

[0069] Voltage droop control is implemented for reactive power, and reactive power is calculated in real time, ensuring that the maximum reactive power does not exceed the maximum apparent power allowed by the equipment. The calculation formula is:

[0070] ;

[0071] ;

[0072] in, Indicates reactive power; This represents the voltage reactive power droop coefficient; Indicates the rated voltage; Indicates the positive sequence voltage value of the power grid; Indicates the rated capacity of the converter; This indicates the reactive power after limiting. Indicates the maximum apparent power; This indicates taking the minimum value.

[0073] Based on voltage sag depth and reactive power priority support constraints, the active power target reference value is calculated. Active power tracking is considered, meaning the active power target reference value must satisfy two constraints: first, to ensure a stable operating point, the maximum active power limit must be considered; here, a first active power setpoint is calculated based on voltage sag depth feedback. Second, under the reactive power priority support constraint, the remaining support capacity is calculated and used as the second active power setpoint. The minimum of the two first active power setpoints is selected as the final active power tracking target reference value, calculated using the following formula:

[0074] ;

[0075] ;

[0076] in, This represents the first active power setpoint; This indicates the setpoint of active power before the fault; Indicates the positive sequence voltage value of the power grid; A low penetration threshold of 0.85 is generally recommended. A high penetration threshold of 1.2 is generally recommended. Therefore, the voltage rises to maintain the active power reference value before the fault unchanged; This indicates the target reference value for active power.

[0077] Step 3: Calculate the target value of the AC q-axis capacitor voltage, specifically:

[0078] After the system reaches a metastable state, according to the phase angle transformation of the internal potential, and based on the active power target reference value... Calculate the target value of the AC quadrature (q) axis capacitor voltage. The calculation formula is:

[0079] ;

[0080] ;

[0081] in, Represents the internal electric potential Using the capacitor voltage as a reference point The steady-state power at that point, i.e., the active power target reference value calculated above. You can directly substitute the corresponding values ​​here. It is only used to derive the target value of AC q-axis capacitor voltage. The calculation formula; Indicates reference point To capacitor voltage Total line impedance at the location; Indicates capacitor voltage The angle of attack at the location; This represents the target value of the AC q-axis capacitor voltage; This refers to the AC filter of a grid-type energy storage converter; Represents virtual impedance; where, It is the total impedance between the internal potential and the voltage of the AC filter capacitor (grid side), which is related to the virtual impedance value and the actual filter circuit. Therefore, when the active power is known, it can be derived relatively accurately. Steady-state value when outputting target power.

[0082] Step 4: Hybrid synchronization control of the output frequency, specifically:

[0083] Calculating the actual capacitor voltage feedback value, considering the negative sequence effect during unbalanced faults, requires removing the influence of the negative sequence voltage component using a positive-negative sequence separation method. Hybrid synchronous control is also based on the positive sequence voltage component. Figure 5 The diagram shows the voltage positive and negative sequence separation control block diagram of a grid-type converter, based on decoupling decomposition using a dual-synchronous reference frame (DDSRF). The grid-side voltage... Based on the output angle of the Pf ring Calculate the transformation matrix based on the orthogonal components. Obtain the instantaneous value of the positive sequence voltage dq axis Calculate the transformation matrix according to the negative order components. Obtain the instantaneous value of the negative sequence voltage along the dq axis. Actual capacitor voltage feedback value That is, the positive sequence voltage component AC dq axis value after filtering and extraction. The filtered positive sequence voltage component AC q-axis value The positive sequence voltage component AC dq axis value after filtering and extraction It uses the positive-sequence decoupling formula to change the instantaneous value of the positive-sequence voltage dq axis. Subtract the negative-order component after filtering by the low-pass filter (LPF). The result of the second harmonic interference is:

[0084] ;

[0085] ;

[0086] .

[0087] Similarly, the AC dq axis value of the negative sequence voltage component after filtering is obtained. It uses the negative-sequence decoupling formula to change the instantaneous value of the negative-sequence voltage dq axis. Subtract the positive-sequence component after LPF filtering The result of the second harmonic interference is:

[0088] .

[0089] in, This indicates that the transformation matrix is ​​calculated for the orthogonal components. This indicates that the transformation matrix is ​​calculated for the negative-order components; Indicates matrix transpose; Indicates the output angle of the Pf ring; This represents the AC d-axis value of the positive sequence voltage component after filtering and extraction. This represents the AC q-axis value of the positive sequence voltage component after filtering and extraction. This represents the actual capacitor voltage feedback value; This represents the AC dq axis value of the positive sequence voltage component after filtering and extraction. This represents the AC dq axis value of the negative sequence voltage component after filtering and extraction. This represents the instantaneous value of the positive sequence voltage along the dq axis. This represents the instantaneous value of the negative sequence voltage along the dq axis. This represents the positive-sequence component after filtering by a low-pass filter. This represents the negative-order component after being filtered by a low-pass filter.

[0090] Based on the target value of AC q-axis capacitor voltage Feedback value of actual capacitor voltage The difference is used to adjust the output power using a proportional controller. The proportional control coefficient is proportional control coefficient To comprehensively consider response speed and stability, the bandwidth can be set to 2-3 times that of a normal phase-locked loop design to accelerate phase tracking speed, allowing the phase to converge quickly to the grid voltage phase angle, and thus increasing the output power. With mechanical power After superposition, the output frequency is adjusted by a virtual synchronizer. mechanical power With active power feedback quantity After taking the difference, multiply by the rated capacity of the converter. The reciprocal output, which is related to the output power. Summing and then adding the damping power The power obtained by subtraction is multiplied by The output frequency can be adjusted. ;in, , Indicates the damping coefficient; Indicates the moment of inertia; This represents a complex frequency variable.

[0091] When the positive sequence voltage value of the power grid Return to the starting threshold range, so that the active power target reference value is... Restore active power to the pre-fault target value, AC q-axis capacitor voltage target value. Based on the active power target reference value Synchronous recovery continues during the recovery process, with hybrid synchronous control maintained through output power. Real-time acceleration of grid phase tracking allows the phase to quickly converge to the grid voltage phase angle until the grid stabilizes and hybrid synchronization control is completed. As the grid stabilizes, active power recovers to pre-fault levels, the input to hybrid synchronization control approaches zero, and the output power... It is also close to 0, exiting hybrid synchronous control, fault flag bit. Clear 0.

[0092] At this time, the output frequency will be Multiply Convert to angular velocity After the points-based system The phase angle is obtained, which is the output angle of the Pf loop. Combining the internal electromotive force command obtained from reactive power control, the phase angle is... With internal potential The superposition is followed by a virtual impedance stage to obtain the inner current loop command. ;

[0093] To suppress transient overcurrent, the inner current loop command is... The current inner loop command is obtained by current limiting through a ring limiter. The modulation signal is then generated through the inner current loop. To avoid overcurrent problems caused by faults, the modulation signal is input into the Pulse Width Modulation (PWM) module to drive the Insulated Gate Bipolar Transistor (IGBT) to switch, thereby achieving closed-loop current control. The ring limiter is represented as follows:

[0094] ;

[0095] in, This indicates the current inner loop command after limiting; Indicates the inner loop current command; Indicates the effective value of the maximum allowable output current; This indicates the current d-axis command after limiting. This indicates the current q-axis command after limiting.

[0096] In this embodiment, the entire hybrid synchronous control process is smoothly switched. The active power loop always runs without saturation, while the reactive power loop automatically runs or latches depending on whether the inverter is current-limited. Through hybrid synchronous control, the phase angle tracking speed after voltage surges is accelerated, and the transient stability of the grid-type energy storage converter is improved.

[0097] Example 2

[0098] Based on Example 1, this example introduces an experimental example of a hybrid synchronous control method for grid-connected energy storage converters that takes active power tracking into account:

[0099] like Figures 6 to 8 The figure shown is a simulation comparison between the method of this embodiment and the method without using the method of this embodiment. Figure 6 A graph showing the change of positive sequence voltage of the power grid over time. Figure 7 A graph showing the change of active power in the power grid over time. Figure 8 This embodiment shows the change of reactive power in the power grid over time, considering only... Figure 7 The active power of the power grid is shown. After a grid fault, current limiting was not triggered. The reactive power during the fault period was 1.43 pu, which is within the maximum allowable apparent power range. Therefore, the active power is calculated based on a voltage drop depth of 0.54 pu, and the active power reference value is reduced to 0.43 pu. The red curve in the figure represents the active power fast tracking response time of about 5 ms and the adjustment time of about 50 ms after a grid fault using the method described in this invention. The blue curve does not use the method described in this invention. The response time is similar, but the adjustment time is about 400 ms, indicating that the phase angle tracking is very slow.

[0100] Right now, Figure 7 In the method of this invention, the time of grid fault is time t0, the end time of active power fast tracking response is time t1, and the end time of regulation is time t2, while the end time of regulation in the method of this invention is time t3.

[0101] Example 3

[0102] This embodiment introduces a hybrid synchronous control system for a grid-type energy storage converter that considers active power tracking, including:

[0103] The voltage acquisition module is used to: acquire the positive sequence voltage value of the grid for the grid-connected energy storage converter;

[0104] The active power calculation module is used to: determine that a grid fault has occurred when the positive sequence voltage value of the grid exceeds the start-up threshold range, implement voltage droop control on reactive power, and calculate reactive power in real time; and calculate the target reference value of active power based on the voltage droop depth and reactive power priority support constraints.

[0105] The frequency adjustment module is used to: calculate the target value of AC q-axis capacitor voltage based on the active power target reference value, and adjust the output power using a proportional controller based on the difference between the target value of AC q-axis capacitor voltage and the actual capacitor voltage feedback value.

[0106] Stability control is used to: restore the active power target reference value to the active power target value before the fault when the positive sequence voltage value of the power grid recovers to the range of the start-up threshold, and synchronously restore the AC q-axis capacitor voltage target value. During the recovery process, the output power tracks the power grid phase in real time until the power grid stabilizes and completes the hybrid synchronous control.

[0107] The specific functions of each module described above are explained in the relevant content of the method in Embodiment 1, and will not be repeated here.

[0108] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application 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.

[0109] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. 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... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0110] 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.

[0111] 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.

[0112] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A hybrid synchronous control method for a grid-type energy storage converter considering active power tracking, characterized in that, include: Obtain the positive sequence voltage value of the grid-connected energy storage converter; When the positive sequence voltage value of the power grid exceeds the starting threshold range, it is determined that a power grid fault has occurred. Voltage droop control is implemented on reactive power, and reactive power is calculated in real time. In addition, based on the voltage drop depth and reactive power priority support constraints, the target reference value of active power is calculated; The target value of AC q-axis capacitor voltage is calculated based on the active power target reference value. The output power is adjusted using a proportional controller based on the difference between the target value of AC q-axis capacitor voltage and the actual capacitor voltage feedback value. When the positive sequence voltage value of the power grid recovers to the range of the start-up threshold, the active power target reference value is restored to the active power target value before the fault, and the AC q-axis capacitor voltage target value is restored synchronously. During the recovery process, the output power tracks the phase of the power grid in real time until the power grid stabilizes and completes the hybrid synchronous control. The calculation of the active power target reference value based on voltage sag depth and reactive power priority support constraints includes: The first active power setpoint is calculated based on voltage dip depth feedback; Under the constraint of prioritizing reactive power support, the remaining support capacity is used as the second active power given value; The minimum value between the first active power setpoint and the second active power setpoint is used as the active power target reference value. The formula for calculating the target value of the AC q-axis capacitor voltage is as follows: ； ； in, Represents the internal electric potential Using the capacitor voltage as a reference point Steady-state power at the location; Indicates reference point To capacitor voltage Total line impedance at the location; Indicates capacitor voltage The angle of attack at the location; This represents the target value of the AC q-axis capacitor voltage; This refers to the AC filter of a grid-type energy storage converter; This represents virtual impedance.

2. The hybrid synchronous control method for grid-type energy storage converters considering active power tracking according to claim 1, characterized in that, The formula for calculating the reactive power is: ； ； in, Indicates reactive power; Indicates the voltage reactive power droop coefficient; Indicates the rated voltage; Indicates the positive sequence voltage value of the power grid; Indicates the rated capacity of the converter; This indicates the reactive power after limiting; Indicates the maximum apparent power; This indicates taking the minimum value.

3. The hybrid synchronous control method for grid-type energy storage converters considering active power tracking according to claim 1, characterized in that, The formula for calculating the active power target reference value is as follows: ； ； in, This represents the first active power setpoint; This indicates the active power setpoint before the fault; Indicates the positive sequence voltage value of the power grid; , These represent the low penetration threshold and the high penetration threshold, respectively. This represents the target reference value for active power. This indicates the reactive power after limiting; Indicates the maximum apparent power; This indicates taking the minimum value.

4. The hybrid synchronous control method for grid-type energy storage converters considering active power tracking according to claim 1, characterized in that, The actual capacitor voltage feedback value is calculated by removing the negative sequence voltage component based on a positive-negative sequence separation method, using the following formula: ； ； ； in, This indicates that the transformation matrix is ​​calculated for the orthogonal components. Indicates the calculation of the transformation matrix for negative-order components; superscript Indicates matrix transpose; Indicates the output angle of the Pf ring; This represents the AC d-axis value of the positive sequence voltage component after filtering and extraction. This represents the AC q-axis value of the positive sequence voltage component after filtering and extraction. This represents the actual capacitor voltage feedback value; This represents the AC dq axis value of the positive sequence voltage component after filtering and extraction. This represents the instantaneous value of the positive sequence voltage along the dq axis; This represents the negative-order component after being filtered by a low-pass filter.

5. The hybrid synchronous control method for grid-type energy storage converters considering active power tracking according to claim 1, characterized in that, Also includes: The output power and mechanical power are superimposed and then the output frequency is adjusted by a virtual synchronizer. After converting the output frequency to angular velocity, the phase angle is obtained through an integration stage. The phase angle is then superimposed with the internal potential and passed through a virtual impedance stage to obtain the inner current loop command. The current inner loop command is current-limited by a ring limiter and then modulated by the current inner loop. The modulated signal is then input into the PWM module to achieve current closed-loop control.

6. The hybrid synchronous control method for grid-type energy storage converters considering active power tracking according to claim 5, characterized in that, The annular limiter is represented as follows: ； in, This indicates the current inner loop command after limiting; Indicates the inner loop current command; Indicates the effective value of the maximum permissible output current; This indicates the current d-axis command after limiting. This indicates the current q-axis command after limiting.

7. The hybrid synchronous control method for grid-type energy storage converters considering active power tracking according to claim 1, characterized in that, Also includes: When the positive sequence voltage value of the power grid exceeds the start-up threshold range, the power grid fault flag bit... Set to 1; When the positive sequence voltage value of the power grid recovers to the start-up threshold range and the power grid stably completes hybrid synchronization control, the power grid fault flag bit... Clear 0.

8. A hybrid synchronous control system for a grid-type energy storage converter that considers active power tracking, characterized in that, include: The voltage acquisition module is used to: acquire the positive sequence voltage value of the grid for the grid-connected energy storage converter; The active power calculation module is used to: determine that a grid fault has occurred when the positive sequence voltage value of the grid exceeds the start-up threshold range, implement voltage droop control on reactive power, and calculate reactive power in real time; In addition, based on the voltage drop depth and reactive power priority support constraints, the target reference value of active power is calculated; The frequency adjustment module is used to: calculate the target value of AC q-axis capacitor voltage based on the active power target reference value, and adjust the output power using a proportional controller based on the difference between the target value of AC q-axis capacitor voltage and the actual capacitor voltage feedback value. Stability control is used to: restore the active power target reference value to the active power target value before the fault when the positive sequence voltage value of the power grid recovers to the range of the start-up threshold, and synchronously restore the AC q-axis capacitor voltage target value. During the recovery process, the output power is used to track the power grid phase in real time until the power grid stabilizes and completes the hybrid synchronous control. The calculation of the active power target reference value based on voltage sag depth and reactive power priority support constraints includes: The first active power setpoint is calculated based on voltage dip depth feedback; Under the constraint of prioritizing reactive power support, the remaining support capacity is used as the second active power given value; The minimum value between the first active power setpoint and the second active power setpoint is used as the active power target reference value. The formula for calculating the target value of the AC q-axis capacitor voltage is as follows: ； ； in, Represents the internal electric potential Using the capacitor voltage as a reference point Steady-state power at the location; Indicates reference point To capacitor voltage Total line impedance at the location; Indicates capacitor voltage The angle of attack at the location; This represents the target value of the AC q-axis capacitor voltage; This refers to the AC filter of a grid-type energy storage converter; This represents virtual impedance.

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