VSG-based energy storage coordinated controller end damping control method and device

Abstract

This invention relates to a damping control method and device for a VSG-based energy storage coordinated controller. In the energy storage coordinated controller, the phase relationship between the damping control quantity and the grid oscillation frequency is analyzed. A quantitative relationship model between the virtual moment of inertia and the damping coefficient is constructed by combining phase delay, so that the damping power has a reverse damping effect on the oscillation component of the oscillation frequency to be suppressed. The amplitude-frequency characteristics of the small-signal increment of the damping control quantity are analyzed. Combined with the target damping strength and the aforementioned quantitative relationship model, a calculation model for the virtual moment of inertia and the damping coefficient is obtained. The energy storage coordinated controller detects the damping oscillation frequency in real time and obtains the current damping control quantity as a damping power command based on the calculation model, which is then sent to the grid-connected energy storage converter. This invention achieves rapid and accurate damping suppression of grid frequency oscillations at the coordinated controller level, improving the transient stability of power systems with a high proportion of new energy sources.

Description

Technical Field

[0001] This invention relates to the field of power system stability control technology, specifically to a damping control method and device for suppressing grid frequency oscillations, and particularly to a damping control method and corresponding energy storage coordination controller based on the principle of a virtual synchronous motor in the secondary side coordination control equipment of an energy storage system. Background Technology

[0002] As the penetration rate of intermittent and fluctuating renewable energy sources such as wind and solar power in the power system continues to increase, the inertia and damping characteristics of the power grid are significantly weakened, making the system more susceptible to frequency fluctuations, especially low-frequency oscillations. Low-frequency oscillations threaten the safe and stable operation of the power grid, and in severe cases, may lead to frequency instability or even large-scale power outages. Therefore, providing effective frequency damping support has become an urgent requirement for modern power systems.

[0003] Energy storage systems, especially battery energy storage systems based on power electronic converters (PCS), are considered ideal for providing frequency support and enhancing system damping due to their fast power response and flexible control. Virtual Synchronous Generator (VSG) technology, by simulating the rotor motion equations and external characteristics of a synchronous motor, endows the converter with inertia and damping, making it a crucial control strategy for improving grid stability. Currently, research and practice on using VSG technology to dampen grid frequency oscillations mainly focus on the local control level of a single converter or inverter. That is, the VSG algorithm is introduced into the converter's own control loop, making it behave externally as a synchronous voltage source with inertia and damping, thereby naturally suppressing grid frequency disturbances.

[0004] However, in large-scale energy storage power plants or distributed energy storage aggregation applications, a two-tier architecture of "coordination controller + multiple grid-connected PCS" is typically adopted. The coordination controller, as the upper-level monitoring unit, is responsible for receiving dispatch commands, power allocation, and energy management; the lower-level multiple PCS execute specific charging and discharging operations. In this architecture, the existing coordination controller functions are mostly concentrated on steady-state power allocation, economic dispatch, status monitoring, and protection, with relatively long control cycles, belonging to the second-level or slower optimization layer. Damping control, which involves system dynamic stability, requires precise response speed and phase control, and is usually implemented by the local VSG control loop of the PCS. This results in damping control functions being distributed across each PCS, making it difficult for the coordination controller to perform unified and coordinated damping optimization at the system level. When precise damping is required for specific oscillation modes (such as low-frequency oscillations of 0.2~2.5Hz), fixed local VSG parameters (such as virtual moment of inertia J and damping coefficient D) may not be adaptable to different grid conditions and oscillation frequencies, and the communication and control delays generated from the coordination controller issuing commands to the PCS's final execution are not fully considered. This delay causes the damping power to lag in phase. In severe cases, it not only fails to suppress oscillations but may even exacerbate them, a phenomenon known as "negative damping."

[0005] In summary, existing technologies have the following shortcomings: 1) Damping control functions are concentrated in a single device, lacking centralized and optimized implementation at the system-level coordinated controller level; 2) Traditional VSG damping parameters are mostly fixed values, making it difficult to adapt to different oscillation frequencies and time delay conditions; 3) The inherent control loop delay in the coordinated control architecture has not been systematically analyzed and compensated for its critical impact on the damping control phase, potentially affecting the damping effect or even jeopardizing system stability. Therefore, there is an urgent need for an efficient damping control method that can be implemented at the energy storage coordinated controller level, overcomes the phase lag problem, and allows for adaptive parameter tuning. Summary of the Invention

[0006] The present invention aims to solve the technical problems in the prior art where the damping control function is distributed locally in the converter, making it difficult to coordinate and optimize at the system level, and the damping effect is poor or even negative damping may be caused due to insufficient consideration and compensation of the inherent control delay in the coordinated control architecture. The invention provides a damping control method and device for the energy storage coordinated controller based on VSG.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A VSG-based energy storage coordinated controller-side damping control method, the method comprising:

[0009] In the energy storage coordinating controller, the phase relationship between the damping control quantity and the grid oscillation frequency is analyzed. Combined with the total delay from the issuance of the command from the energy storage coordinating controller to the actual power output of the grid-connected energy storage converter, a quantitative relationship model is constructed to satisfy the virtual moment of inertia and the damping coefficient when the damping power produces a reverse damping effect on the oscillation component of the oscillation frequency to be suppressed.

[0010] Amplitude-frequency characteristic analysis was performed on the small-signal increment of the damping control quantity to construct a model relating the target damping strength to the amplitude-frequency characteristic.

[0011] By combining the target damping strength and the aforementioned quantitative relationship model, a calculation model for the virtual moment of inertia and damping coefficient is obtained.

[0012] The energy storage coordination controller detects the damping oscillation frequency in real time, and calculates the current damping control quantity as a damping power command based on the calculation model of the virtual moment of inertia and damping coefficient, and sends it to the grid-connected energy storage converter.

[0013] In some embodiments of the present invention, the oscillation frequency to be suppressed is obtained based on the following method:

[0014] Based on the collected power grid angular velocity or frequency, identify the currently dominant low-frequency oscillation frequency and calculate its corresponding angular frequency, which is the oscillation frequency that needs to be suppressed.

[0015] In some embodiments of the present invention, a model of the phase difference relationship between damping power and grid oscillation frequency is obtained by establishing a transfer function of the small-signal increment of the damping control quantity relative to the grid angular velocity disturbance.

[0016] Based on the total delay, a phase lag value is introduced to obtain the total phase delay;

[0017] A quantitative model of the relationship between virtual moment of inertia and damping coefficient is obtained when the phase control target that makes the total phase delay equal to the reverse damping is obtained.

[0018] In some embodiments of the present invention, the damping strength is characterized based on the damping output coefficient, which is defined as the damping power amplitude required per unit frequency offset;

[0019] Based on the current frequency oscillation amplitude, the damping oscillation power amplitude is obtained as the output target by combining the damping output coefficient. The relevant model of the damping output coefficient and the amplitude-frequency characteristic is obtained by combining the output target and the amplitude-frequency characteristic.

[0020] In some embodiments of the present invention, the virtual moment of inertia and the damping coefficient satisfy the following quantitative relationship model:

[0021]

[0022] in, This is a virtual moment of inertia; The damping coefficient; The oscillation frequency that needs to be suppressed; Total delay.

[0023] In some embodiments of the present invention, the amplitude-frequency characteristics of the small-signal increment are characterized based on the following formula:

[0024]

[0025] in, For the small signal increment of the damping control quantity; This is the steady-state angular velocity; The oscillation frequency that needs to be suppressed; This is a virtual moment of inertia; The damping coefficient; This represents the frequency amplitude.

[0026] In some embodiments of the present invention, the expressions for obtaining the virtual moment of inertia and damping coefficient by combining the target damping strength and the quantitative relationship model are as follows:

[0027]

[0028]

[0029] in, This is a virtual moment of inertia; The damping coefficient; The damping output coefficient is defined as the amplitude of the damping power required per unit frequency offset. This is the steady-state angular velocity; The oscillation frequency that needs to be suppressed; Total delay.

[0030] The present invention further provides an energy storage coordination controller device, which includes a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above method.

[0031] The present invention further provides a computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0032] The present invention further provides a computer program product, including a computer program / instruction that, when executed by a processor, implements the steps of the above-described method.

[0033] The present invention has the following beneficial effects:

[0034] 1. System-level centralized damping control was achieved: The VSG damping control algorithm was moved to the energy storage coordination controller level, breaking the limitation that this function only existed locally on a single PCS. This enables damping control to make unified decisions and allocate resources from the perspective of the entire energy storage power station or aggregation system, improving the coordination and global optimization capabilities of the control.

[0035] 2. Achieved delay compensation and precise phase control: By explicitly introducing and modeling the total delay of the control loop in the small-signal model. Based on this, the parameter tuning formula is derived, enabling the algorithm to inherently possess delay compensation capabilities. This ensures that the final output damping power maintains a precise anti-phase relationship with the target oscillation frequency component, fundamentally avoiding the risk of "negative damping" that may be caused by phase lag, and significantly improving the effectiveness and reliability of damping control.

[0036] 3. Provides analytical and adaptive parameter tuning methods: The provided formulas for calculating J and D are analytical and related to the oscillation frequency. and system latency Directly related. Operators or the system can quickly calculate the optimal control parameters based on the real-time identified oscillation frequency and known system delay characteristics, enabling damping control to adapt to different power grid operating conditions and oscillation modes, thus enhancing the applicability and flexibility of the method.

[0037] 4. Improved grid transient stability: By rapidly and accurately applying damping power through the energy storage coordinating controller, the low-frequency oscillations of the grid can be effectively quelled, enhancing the inertial response and dynamic stability support capabilities of the power system under a high proportion of new energy access, which is of great significance for ensuring the safe and stable operation of the grid. Attached Figure Description

[0038] Figure 1 This is a flowchart of the method of the present invention.

[0039] Figure 2 It represents the phase control effect and output damping power after introducing damping in the simulation environment.

[0040] Figure 3 It describes the changes in power grid oscillations after introducing damping in the simulation environment. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0042] Example 1

[0043] This embodiment provides a damping control method for an energy storage coordination controller based on the virtual synchronous motor (VSG) principle, applied in an energy storage power station. The energy storage power station includes an energy storage coordination controller and multiple grid-connected energy storage converters (PCSs) operating in parallel. The coordination controller, acting as an upper-level monitoring and scheduling unit, is connected to each PCS via a communication network. This method is implemented by the processor in the energy storage coordination controller executing a stored computational program, specifically including the following steps:

[0044] S101. Real-time monitoring and data acquisition.

[0045] The energy storage coordinating controller collects voltage and current signals at the grid's point of common coupling (PCC) in real time and calculates the current grid angular velocity through a phase-locked loop (PLL). Simultaneously, it receives the actual output active power reported from each PCS. The coordinating controller determines the current target value of total active power based on upper-level scheduling instructions or local algorithms (such as frequency regulation and voltage regulation instructions). .

[0046] S102, Calculate virtual angular velocity and generate damping power command.

[0047] Within the coordinating controller, the dynamic behavior of a virtual synchronous motor is simulated based on the rotor motion equations of the VSG. The rotation equations of the VSG are as follows:

[0048]

[0049] Where J is the virtual moment of inertia and D is the damping coefficient. The virtual angular velocity to be calculated.

[0050] The coordinated controller solves the above differential equations in real time using numerical integration methods (such as the Euler method and the Runge-Kutta method) to obtain the virtual angular velocity. .

[0051] Subsequently, the damping control quantity is calculated according to the following formula. That is, the damping power command to be issued:

[0052]

[0053] This damping power command reflects the instantaneous power required to suppress the current frequency (angular velocity) deviation.

[0054] S103, Adaptive tuning of control parameters J and D.

[0055] To make damping control targeted at a specific oscillation frequency To achieve optimal results and compensate for system control delay, parameters J and D need to be adaptively tuned. The specific process is as follows:

[0056] 1. Oscillation frequency identification: Identifying the collected power grid angular velocity. or frequency Perform real-time analysis (such as using Fourier Transform (FFT), Prony algorithm, or bandpass filtering combined with zero-crossing detection) to identify the currently dominant low-frequency oscillation frequency. (Unit: Hz), and calculate its corresponding angular frequency. .

[0057] 2. System delay determination: Total system delay This includes the internal calculation delay of the coordination controller, the transmission delay of the communication network, and the response delay of the control loop after the PCS receives the command. This delay can be measured experimentally or pre-calibrated to a fixed value based on equipment performance specifications, for example... =0.1s.

[0058] 3. Set damping strength: Set the damping output coefficient according to the damping requirements. (Unit: MW / Hz). Its physical meaning is the expected damping power amplitude output by the energy storage system when the grid frequency deviates by 1 Hz. For example, it can be set... =0.4MW / Hz.

[0059] 4. Calculation parameters: Based on the above settings, calculate the optimal virtual moment of inertia J and damping coefficient D under the current operating conditions. The overall derivation process is as follows:

[0060] Let the angular velocity of the power grid be... Virtual angular velocity ,in It is the steady-state angular velocity value. Since the virtual angular velocity always tracks the grid angular velocity, the steady-state angular velocity values ​​of the two are consistent. and For small perturbations, neglecting second-order minor quantities, the linearization process is as follows:

[0061]

[0062] After simplification, we get:

[0063] (1)

[0064] The aforementioned damping control quantity is Linearization yields:

[0065] (2)

[0066] This is the small signal increment of the damping control quantity.

[0067] Perform a Laplace transform on equation (1) with zero initial conditions:

[0068]

[0069] Summarized as follows:

[0070]

[0071] Substituting into equation (2), we get:

[0072]

[0073] Analyze the phase relationship between the damping control quantity and the power grid oscillation frequency, and calculate... and transfer function for:

[0074]

[0075] make ,have to:

[0076]

[0077] The phase is calculated as follows:

[0078]

[0079] Since it is desirable for the damping power to be completely opposite to the oscillation power during frequency oscillation, i.e., with a phase difference of 180°, the phase calculation formula above shows that... The larger, The closer to 90°, the closer the phase difference is to 180°. However, considering the communication delay of the coordinating controller and the output delay of the network-type PCS, a certain phase lead is required. This phase lead can be achieved by adjusting the virtual moment of inertia and virtual damping.

[0080] Based on the aforementioned total delay The introduced phase lag is:

[0081]

[0082] The total phase delay is obtained. for:

[0083]

[0084] Control objective =180°, therefore:

[0085]

[0086] Solving for:

[0087]

[0088] Taking the tangent, we get:

[0089]

[0090] The calculated relationship between J and D is as follows:

[0091]

[0092] Converting the angle within the tan² region to radians gives:

[0093] (3)

[0094] The damped oscillation power with a phase lag of 180° can be calculated using equations (3) and (4).

[0095] Frequency response analysis:

[0096] make , Let be the oscillation frequency. Then the amplitude-frequency characteristic is:

[0097] = (4)

[0098] This formula shows that the oscillation amplitude of the damping control quantity is determined by D, J, , The decision was made jointly with A.

[0099] The damping output coefficient is redefined as If the frequency oscillation amplitude is At that time, the required output damped oscillation power amplitude is [value missing]. ,because Substitution (4):

[0100]

[0101] Eliminating A from both sides yields equation (5):

[0102] (5)

[0103] Substituting equation (3) into equation (5), we obtain equation (6):

[0104] (6)

[0105] Typically, the latency is small, satisfying... ,therefore ,but:

[0106] (7)

[0107] Substituting equation (7) into equation (6), we get:

[0108]

[0109] Therefore, the damping D setting value is obtained as shown in equation (8):

[0110] (8)

[0111] Substituting equation (8) into equation (3), the setting value of the virtual moment of inertia J is shown in equation (9):

[0112] (9)

[0113] in This is the steady-state angular frequency of the power grid. (e.g.) =50Hz or 60Hz).

[0114] S104, Issuing instructions and suppressing oscillations.

[0115] The damping power command calculated in real time in step S102 is used. The active power command (such as the planning curve) from other strategy modules within the coordinating controller is superimposed and distributed to one or more energy storage PCSs in grid-connected mode via the communication network. The PCS uses this superimposed power command as its total active power reference value and quickly adjusts its output current through its internal current loop control, thereby injecting a damping power into the grid that is out of phase with the frequency oscillation component on the basis of the original active power, effectively suppressing the low-frequency oscillation of the grid.

[0116] S105, Dynamic Updates.

[0117] The above process continues in a loop. The coordinated controller can periodically repeat the frequency identification and parameter calculation in step S103 (e.g., once per second or when a significant change in oscillation characteristics is detected), thereby achieving dynamic tracking and adaptation of parameters J and D to the current oscillation mode of the power grid, ensuring that the damping control is always in the optimal state.

[0118] Example 2

[0119] In this embodiment, a model is built in Simulink with a synchronous generator as the main power source, a load of 1MW, and a grid-connected PCS output power of 1MW. When the load oscillates at a frequency of 0.25Hz with an active power of 0.5MW, the output frequency of the synchronous generator oscillates at 0.25Hz. The calculation yields... 1.57 ras / s, oscillation range of 50.946 Hz to 48.924 Hz. The range is 320.4~307.8 rad / s, calculated as follows: The output delay is 314.1 rad / s. =0.1 seconds, With a current of 0.4 MW / Hz, the damping coefficient D = 205.2 and the moment of inertia J = 825.2 are calculated according to the following formula.

[0120]

[0121]

[0122] The coordinating controller uses this set of parameters J=825.2 and D=205.2 to run the VSG algorithm and generate damping power commands. The results are as follows: Figure 2 As shown, after introducing damping control, the set D and J parameters ensure that the command is sent with a 0.1-second lead, and after a 0.1-second execution delay, it lags by exactly 180°, with a frequency oscillation amplitude of 1.011Hz. With a setting of 0.4 MW / Hz, the output is 0.4044 MW, and the actual measured value is 0.3977 MW, which are basically consistent; Figure 3 As shown, the power grid oscillation has been significantly reduced.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A VSG-based energy storage coordinated controller terminal damping control method, characterized in that, The method comprises: In the energy storage coordination controller, the phase relationship between the damping control amount and the power grid oscillation frequency is analyzed, and the total delay from the energy storage coordination controller instruction to the actual power output of the grid-following energy storage converter is combined to construct a quantitative relationship model that the virtual moment of inertia and the damping coefficient satisfy when the damping power produces a reverse damping effect on the oscillation component of the oscillation frequency to be suppressed; The amplitude-frequency characteristic of the small signal increment of the damping control amount is analyzed to construct a relationship model of the target damping strength and the amplitude-frequency characteristic; The calculation model of the virtual moment of inertia and the damping coefficient is obtained in combination with the target damping strength and the quantitative relationship model; The energy storage coordination controller detects the damping oscillation frequency in real time, and calculates the current damping control amount as a damping power instruction in combination with the calculation model of the virtual moment of inertia and the damping coefficient, and issues the damping power instruction to the grid-following energy storage converter.

2. The method of claim 1, wherein, The oscillation frequency to be suppressed is obtained based on the following manner: Based on the collected power grid angular velocity or frequency, the current dominant low-frequency oscillation frequency is identified, and the corresponding angular frequency, i.e. the oscillation frequency to be suppressed, is calculated.

3. The method of claim 1, wherein, By establishing the transfer function of the small signal increment of the damping control amount relative to the power grid angular velocity disturbance, the phase difference relationship model of the damping power and the power grid oscillation frequency is obtained; Based on the total delay, a phase lag value is introduced to obtain a total phase delay; The quantitative relationship model of the virtual moment of inertia and the damping coefficient when the total phase delay is equal to the phase control target of the reverse damping is obtained.

4. The method of claim 1, wherein, The damping strength is represented based on the damping output coefficient, and the damping output coefficient is defined as the amplitude of the damping power required to be output per unit frequency offset; Based on the current frequency oscillation amplitude, the damping oscillation power amplitude is obtained as the output target in combination with the damping output coefficient, and the related model of the damping output coefficient and the amplitude-frequency characteristic is obtained in combination with the output target and the amplitude-frequency characteristic.

5. The method of claim 1, wherein, The virtual moment of inertia and the damping coefficient satisfy the quantitative relationship model as shown below: ； wherein, is a virtual moment of inertia; is a damping coefficient; is an oscillation frequency to be suppressed; is a total delay.

6. The method of claim 1, wherein, The amplitude-frequency characteristic of the small signal increment is represented based on the following formula: ； wherein is a small signal increment of the damping control variable; is a steady state angular velocity; is an oscillation frequency to be suppressed; is a virtual moment of inertia; is a damping coefficient; is a frequency amplitude.

7. The method of claim 1, wherein, The expression of the virtual moment of inertia and the damping coefficient obtained in combination with the target damping strength and the quantitative relationship model is as follows: ； ； wherein, is the virtual moment of inertia; is the damping coefficient; is the damping output coefficient, defined as the amplitude of the damping power required for a unit frequency deviation; is the steady-state angular velocity; is the oscillation frequency to be suppressed; is the total delay.

8. An energy storage coordination controller device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method of any one of claims 1-7.

9. A computer readable storage medium having stored thereon computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to implement the steps of the method of any one of claims 1-7.

10. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to implement the steps of the method of any one of claims 1-7.

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