CN-122000955-A - Dual-mode control method and system suitable for grid-formed energy storage converter

Abstract

The application relates to a dual-mode control method and a system suitable for a grid-formed energy storage converter, wherein the method comprises the steps of constructing a dynamic mapping model of power and virtual impedance, and realizing dynamic mapping between the power and the virtual impedance by establishing a mathematical relation model between the power and the virtual impedance; and a state prediction and compensation mechanism is introduced, a feedforward compensation link based on a system state prediction algorithm is designed, transient behaviors possibly occurring in the switching process are prospectively restrained, and a self-adaptive virtual impedance adjustment strategy is designed, so that dual-mode seamless switching control is realized. The application ensures the high-efficiency stable switching of the energy storage converter in the island and grid-connected operation state. The intelligent power system and the intelligent power system provide key technical support for the intelligent power grid, and flexibility and reliability of the power system are remarkably improved.

Inventors

• LI HANG
• LUO CHUANHUI
• ZHANG TING
• WANG XI
• CHEN YANXIA
• WANG YUANHAO
• YU KAIAN
• Mei Kuang
• Yin Zhengsheng
• LIU JIN

Assignees

• 武汉市充换电技术有限公司

Dates

Publication Date

20260508

Application Date

20251231

Claims (6)

1. 1. The dual-mode control method suitable for the grid-formed energy storage converter comprises the following specific steps of: Step 1, constructing a dynamic mapping model of power and virtual impedance The dynamic mapping between the power and the virtual impedance is realized by establishing a mathematical relation model between the power and the virtual impedance; Step 2, introducing state prediction and compensation mechanism The feedforward compensation link based on the system state prediction algorithm is designed to carry out prospective suppression on transient behaviors possibly occurring in the switching process; Step 3, designing a self-adaptive virtual impedance adjustment strategy Dynamically adjusting virtual impedance parameters according to the equivalent impedance change and the power disturbance level of the system, optimizing the virtual impedance value in real time through an impedance regulator to adapt to different running conditions, and effectively inhibiting transient oscillation and power fluctuation caused by mode switching; step 4, realizing dual-mode seamless switching control The embedded control unit executes switching logic and adjusts control parameters in real time, thereby ensuring smooth and rapid transition between the voltage source mode and the current source mode and remarkably improving the dynamic stability of the energy storage converter in island and grid-connected operation states.
2. 2. The method for dual-mode control of a grid-connected energy storage converter of claim 1, wherein the power and virtual impedance dynamic mapping model is constructed in step 1 as follows: Step 1.1 determining model input and output variables Input variables: the system power parameters acquired in real time comprise active power P output by the energy storage converter, reactive power Q output by the energy storage converter and a mode switching instruction signal S; The energy storage converter outputs active power P, and three-phase current signals i a 、i b 、i c collected by the three-phase current sensor and three-phase voltage signals u a 、u b 、u c collected by the voltage sensor are calculated according to the following formula: , wherein, T is acquisition time, T is time variable, the energy storage converter outputs reactive power Q, calculate according to the following formula: , A mode switching instruction signal S; the output variables comprise a virtual resistor R v and a virtual inductor L v ; Step 1.2, establishing a power virtual impedance mathematical relation model The mathematical relationship is constructed by adopting a piecewise linear mapping function, and the specific formula is as follows: when the voltage source mode s=0, the formula is: , , Wherein k R1 is the proportionality coefficient of active power and virtual resistance, and is set according to the power grid resistance R g , P rated is the rated active power of the converter, R v0 is the reference value of the virtual resistor, 15% of the power grid resistor R g is taken, k L1 is the ratio coefficient of the reactive power and the virtual inductance, and the ratio is calculated according to Setting, wherein Q rated is the rated reactive power of the converter, L v0 is a virtual inductance reference value, and 15% of the power grid inductance L g is taken; when the current source mode s=1, the formula is: , , Wherein k R2 is 1.3 times of k R1 , R v1 is 10 times of a load resistor R l , k L2 is 1.5 times of k L1 , and L v1 is 10% of a load inductor L l ; By adopting linear interpolation to carry out smooth transition, when the switching time is T 0 and the transition time is T tran , the virtual impedance at any time T ∈ [t 0 ,t 0 +T tran is as follows: , , Wherein, the Represented as a virtual resistance in the voltage source mode, Represented as a virtual resistance in the current source mode, Represented as a virtual inductance in the voltage source mode, Expressed as virtual inductance in current source mode, this interpolation process ensures that R v (t)、L v (t) is continuously conductive in the transition section, avoiding abrupt reference signal changes.
3. 3. The method for dual-mode control of a grid-connected energy storage converter of claim 1, wherein the state prediction and compensation mechanism introduced in step 2 is specifically: step 2.1 determining the State prediction input variable and the prediction target The input variables include: R v (t)、L v (t) is the real-time virtual impedance output in the step 1; The converter outputs three-phase voltage instantaneous value u a (t)、u b (t)、u c (t), and the three-phase voltage converts u d (t)、u q (t) under the dq coordinate system; The converter outputs three-phase current instantaneous value i a (t)、i b (t)、i c (t), and the three-phase current converts i d (t)、i q (t) in the dq coordinate system; The mode switching command signal S comprises a 0=voltage source mode and a 1=current source mode, wherein the advance T pred triggers a prediction algorithm, and the T pred is a prediction time window; The output variables include: state variables at time T pred after switching, including: Predicted voltage value: 、 ; predicting a current value: 、 ; step 2.2. Design of recursive least squares based state prediction algorithm Short-term prediction is carried out on the state variable by adopting a recursive least square RLS algorithm, the dynamic trend is fitted by utilizing historical data, and the formula is deduced as follows: Step 2.2.1 constructing a State variable observation matrix Defining a state vector in the dq coordinate system According to the power and virtual impedance model of step 1, the state variables satisfy the linear time-varying equation: , Wherein, the ; Representation of The state vector of the moment of time, Representation of A duty cycle signal of the time converter; For observing noise vector, A (t) is 4×4 state transition matrix, which is determined by R v (t)、L v (t) and grid angular frequency w: , b (t) is a4 x 2 control input matrix, abbreviated as: , wherein U dc is the DC side voltage of the converter, and T s is the sampling period; step 2.2.2 RLS Algorithm recursive computation The goal is to minimize the prediction error by historical observations x (T), x (T-T s )、…、x(t-nT s ), n=50, update the state transition matrix a (T), and predict the state at time t+t pred by decomposition Predicted voltage at time 、 And predicting current 、 ; Step 2.3 generating a feedforward compensation signal and correcting the reference value Step 2.3.1 calculating the transient error amount Comparing the predicted state with the target steady state value 、 、 、 Obtaining the error to be compensated 、 、 、 : Voltage error: 、 ; Current error: 、 ; step 2.3.2 design of the Compensation Signal transfer function To avoid excessive compensation causing new fluctuations, the compensation signal is designed by adopting first-order low-pass filtering 、 : , , Wherein, the , , 、 、 、 Is that 、 、 、 The conversion result from the time domain to the frequency domain is that K u is a voltage compensation coefficient and K i is a current compensation coefficient; 、 is a filter time constant.
4. 4. The method for dual-mode control of a grid-tied energy storage converter of claim 1, wherein the design of the adaptive virtual impedance adjustment strategy in step 3 is as follows: Step 3.1 defining an impedance correction coefficient When grid impedance is suddenly changed during grid connection and load is switched during island, the tracking sensitivity of virtual impedance needs to be adjusted, and an impedance correction coefficient K Z (t) is defined: , wherein Z eq (t) is the real-time equivalent impedance of the system, For the system rated equivalent impedance, the rated power S rated and the rated voltage U rated of the converter are calculated: , Step 3.2 generating disturbance coefficients 、 Reflecting the power fluctuation intensity, the disturbance factor K dist (t) is defined accordingly: , Wherein, the In order to be the active power disturbance intensity, As a threshold value for the active power disturbance, In order to be the reactive power disturbance intensity, As a reactive power disturbance threshold value, 、 K dist (t) realizes the force classification of weak disturbance, conventional regulation and strong disturbance through a piecewise function, and avoids the phenomenon that new oscillation is caused by excessive regulation in disturbance hours; Step 3.3 mode differentiation adjustment law According to S mode (t), distinguishing VSG/CSG modes, and designing PI regulation laws of different regulation targets: step 3.3.1 Voltage Source mode S mode (t) =0 Dummy resistor R v (t) regulation law, introducing for voltage loss deviation caused by active power fluctuation PI correction of (c): , wherein, the The reference value of the virtual resistor is the output of the step 1, Is that As a result of the conversion from the frequency domain to the time domain, Is a voltage error proportional coefficient, As the integral coefficient of voltage error, eliminating voltage static difference by PI when When the voltage is greater than 0, increasing R v to compensate the voltage loss, otherwise, reducing R v ; The regulation law of the virtual inductance L v (t) is that aiming at the phase deviation caused by reactive power fluctuation, the method introduces PI correction of (c): , wherein, the The reference value of the virtual inductance is the output of the step 1, Is a current error proportional coefficient, Integrating the coefficient for the current error; Step 3.3.2 current source mode S mode (t) =1 Dummy resistor R v (t) regulation law, introducing to current tracking deviation caused by load impedance variation PI correction of (c): , Wherein, the Is a current error proportional coefficient, Integral coefficient of current error When the current is greater than 0, R v is reduced to reduce current obstruction, otherwise R v is increased; the regulation law of the virtual inductance L v (t) is fixed as 1.1 Times of the current filtering effect: 。
5. 5. The method for controlling the dual modes of the grid-connected energy storage converter according to claim 1, wherein the step 4 is characterized in that the dual mode seamless switching control is realized specifically as follows: When a mode switching instruction is received, a preset transition control flow is started, a basic reference signal is called as a reference frame in a window period from switching moment to transition end, and compensation signals are synchronously overlapped And Respectively are superimposed to And On the basis of the above, obtain 、 , And Meanwhile, if the impedance mutation and the power fluctuation super threshold are detected, immediately starting the self-adaptive adjustment parameters, optimizing the virtual impedance in real time, and correcting the R v 、L v output in the step 1; The voltage reference signal of the voltage source is calculated by virtual impedance and current feedback, namely: , The current reference signal of the current source is calculated by virtual impedance and voltage feedback, namely: , Wherein, the Is the rated voltage and I is the output current.
6. 6. The system for the dual-mode control method of the grid-connected energy storage converter according to any one of claims 1 to 5, comprising a sensing acquisition module, a control module, an execution driving module and a monitoring feedback module, wherein: The sensing acquisition module is responsible for acquiring the running physical quantity of the system in real time, acquiring a three-phase voltage signal and a three-phase current signal output by the energy storage converter, and calculating to obtain active power and reactive power through a preset formula; the core control module integrates three functional units: the dynamic mapping unit performs dynamic association calculation of power and virtual impedance, and outputs a basic virtual resistor and a virtual inductor through a piecewise linear mapping function and a linear interpolation algorithm; The prediction compensation list comprises a corresponding state prediction and compensation mechanism, and based on a recursive least square algorithm, the system state after switching is predicted by using historical voltage and current data, a feedforward compensation signal is generated, and voltage and current reference values are corrected; the self-adaptive adjusting unit comprises a self-adaptive virtual impedance adjusting strategy, calculates an impedance correction coefficient and a disturbance coefficient, dynamically corrects an R v 、L v parameter through mode differentiation PI adjusting law, and adapts to system impedance change and power disturbance; The execution driving module receives the instruction of the control module, receives the dual-mode seamless switching control logic, receives the corrected voltage reference value or the current reference value after the superposition compensation signal, and generates a corresponding PWM driving signal; The monitoring feedback module monitors the running state of the system in real time, builds a closed-loop regulation mechanism, monitors the object consistent with the input requirement, tracks the dynamic changes of the output voltage, current and power of the converter, compares the predicted value with the actual value, calculates the transient error, detects the equivalent impedance mutation and the load switching abnormal working condition of the system, triggers the core control module to execute the self-adaptive regulation logic, and ensures the dynamic stability of the system.

Description

Dual-mode control method and system suitable for grid-formed energy storage converter Technical Field The invention relates to the technical field of power electronics and automation control, in particular to a dual-mode control method and system suitable for a grid-built energy storage converter. Background With global emphasis on renewable energy utilization and the development of distributed energy systems, the importance of energy storage converters (PCS) as a key component connecting energy storage devices to the grid is growing. The energy storage converter not only needs to perform energy conversion efficiently under the conventional condition, but also needs to have the capability of flexibly switching between a voltage source mode (VSG) and a current source mode (CSG) so as to adapt to different application scenarios, such as a micro grid, a smart grid, an off-grid power system and the like. However, existing energy storage converter control methods have some limitations and challenges: The stability problem in the mode switching process is that transient instability phenomenon is easily caused due to the dynamic characteristics of the system and the change of load conditions in the VSG and CSG mode switching process, and the electric energy quality and the system stability are influenced. The virtual impedance design is inflexible, in the traditional method, the virtual impedance value is usually fixed or set based on experience, and is difficult to adapt to complex operation environment and changeable working conditions, so that the performance optimization space of the energy storage converter is limited. The power regulation efficiency is low, and the lack of an effective mechanism in the prior art for adjusting the power output in real time leads to low energy conversion efficiency of the energy storage converter in different working modes. The state prediction capability is insufficient, and for load changes or power grid condition changes which may occur in the future, the traditional control strategy lacks prospective response measures, so that the response speed and the adaptability of the system are reduced. Disclosure of Invention The embodiment of the application aims to provide a dual-mode control method and system for a grid-built energy storage converter, which provide key technical support for a smart grid and remarkably improve the flexibility and reliability of a power system. In order to achieve the above purpose, the present application provides the following technical solutions: In a first aspect, an embodiment of the present application provides a dual-mode control method suitable for a grid-formation energy storage converter, which specifically includes the following steps, and is characterized in that: Step 1, constructing a dynamic mapping model of power and virtual impedance The dynamic mapping between the power and the virtual impedance is realized by establishing a mathematical relation model between the power and the virtual impedance; Step 2, introducing state prediction and compensation mechanism The feedforward compensation link based on the system state prediction algorithm is designed to carry out prospective suppression on transient behaviors possibly occurring in the switching process; Step 3, designing a self-adaptive virtual impedance adjustment strategy Dynamically adjusting virtual impedance parameters according to the equivalent impedance change and the power disturbance level of the system, optimizing the virtual impedance value in real time through an impedance regulator to adapt to different running conditions, and effectively inhibiting transient oscillation and power fluctuation caused by mode switching; step 4, realizing dual-mode seamless switching control The embedded control unit executes switching logic and adjusts control parameters in real time, thereby ensuring smooth and rapid transition between the voltage source mode and the current source mode and remarkably improving the dynamic stability of the energy storage converter in island and grid-connected operation states. The power and virtual impedance dynamic mapping model construction in the step 1 specifically comprises the following steps: Step 1.1 determining model input and output variables Input variables: the system power parameters acquired in real time comprise active power P output by the energy storage converter, reactive power Q output by the energy storage converter and a mode switching instruction signal S; The energy storage converter outputs active power P, and three-phase current signals i a、ib、ic collected by the three-phase current sensor and three-phase voltage signals u a、ub、uc collected by the voltage sensor are calculated according to the following formula: , wherein, T is acquisition time, T is time variable, the energy storage converter outputs reactive power Q, calculate according to the following formula: , A mode switching instruction signal S; the output variables c