A nonlinear extended state observer-based power control system and method for a multi-virtual synchronous generator interconnected system

Abstract

The application provides a multi-virtual synchronous generator parallel system power control system and method based on a nonlinear extended state observer, and the system comprises: a multi-VSG parallel main circuit, which comprises a DC side energy storage unit, a VSG unit, a signal acquisition module, a nonlinear ESO module, a dynamic virtual impedance compensation module, a power control module, an upper computer module, a common AC bus and a load unit; through system initialization, signal acquisition, power calculation, ESO disturbance observation, dynamic virtual impedance adjustment, power deviation adjustment, comprehensive compensation and double closed loop driving, high-precision power control of the non-communication parallel system between the multiple VSGs is realized. The application improves the anti-interference ability, circulating current suppression ability and power control precision of the system, guarantees the power distribution consistency and power supply quality of the multiple VSGs in parallel, and has good universality and expansibility.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter and microgrid control technology, and in particular to a power control system and method for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer. Background Technology

[0002] Virtual synchronous generator (VSG) technology, by simulating the rotor motion equations, excitation characteristics, and speed regulation characteristics of a synchronous generator, endows power electronic inverters with the inertia and damping characteristics of a synchronous generator. This effectively improves the transient stability and grid-connected adaptability of microgrids and has become one of the core technologies for distributed power interface control in microgrids. In practical microgrid applications, to meet the demand for high-capacity power supply, multiple VSGs are typically connected in parallel to achieve power expansion and redundancy backup. However, during the operation of multiple VSG parallel systems, factors such as line impedance mismatch, load disturbances, parameter perturbations, and grid voltage fluctuations can easily lead to uneven power distribution, increased circulating current, and decreased system stability. Traditional VSG control often uses fixed virtual impedance, PI regulators, and linear disturbance observation methods, which have weak suppression capabilities for nonlinear disturbances, low power averaging accuracy, and slow dynamic response, making it difficult to meet the high-performance control requirements of microgrids. Summary of the Invention

[0003] In view of this, the present invention provides a power control system and method for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer, so as to at least solve the above-mentioned problems.

[0004] This invention provides a power control system for a parallel system of multiple virtual synchronous generators (VSGs) based on a nonlinear extended state observer. The system includes: a main circuit for multiple VSGs in parallel, comprising a DC-side energy storage unit, VSG units, a signal acquisition module, a nonlinear ESO module, a dynamic virtual impedance compensation module, a power control module, a host computer module, a common AC bus, and a load unit. The DC-side energy storage unit provides DC power to the VSG units. The signal acquisition module acquires the voltage and current signals of the corresponding VSGs, converts them into digital signals, and synchronously transmits them to the nonlinear ESO module and the host computer module. The nonlinear ESO module observes unknown disturbances in the system in real time and outputs observed values. The dynamic virtual impedance compensation module adaptively adjusts virtual impedance parameters based on the observed values ​​and output current, generates a virtual impedance voltage drop compensation signal, and transmits it to the power control module. The power control module combines the power deviation and the virtual impedance voltage drop compensation signal to generate control signals for the VSGs, achieving high-precision power control of the parallel system without communication between multiple VSGs. The host computer module is used for parameter configuration and status monitoring. The common AC bus consists of multiple VSGs. Provide parallel access points and supply power to the load unit.

[0005] Optionally, the VSG unit includes an inverter, an LC filter circuit, a line impedance, a grid-connected switch, and a virtual synchronization control circuit; the input terminal of the inverter is connected to the DC-side energy storage unit, and the output terminal is connected in parallel to the common AC bus via the LC filter circuit, the line impedance, and the grid-connected switch in sequence, thereby realizing DC-AC power conversion and grid-connected operation.

[0006] Optionally, the VSG unit uses an inverter as the core power conversion device to convert the DC power output from the DC-side energy storage unit into AC power that conforms to the grid standard, realizing DC-AC power conversion; the LC filter circuit consists of a filter inductor and a filter capacitor, used to filter out high-frequency PWM harmonics output by the inverter; the grid-connected switch controls the connection and disconnection of the VSG unit with the common AC bus, realizing the switching between grid-connected and off-grid modes, and quickly disconnecting the circuit in case of a fault; the line impedance is used to equivalently simulate the line resistance and line inductance between the VSG unit and the common AC bus; the virtual synchronization control circuit provides virtual inertia and damping for the inverter by simulating the rotor motion equation, excitation regulation characteristics and droop control characteristics of a synchronous generator, realizing the synchronous generator external characteristics of the VSG unit.

[0007] Optionally, the nonlinear ESO module includes a third-order nonlinear ESO unit, with its input terminal connected to the output terminal of the signal acquisition module of the corresponding VSG; the nonlinear ESO module uses the fal function to construct a third-order extended state observer, receives the voltage and current sampling signals of the corresponding VSG, observes the generalized disturbance of the system in real time, and outputs high-precision disturbance observation values.

[0008] Another aspect of the present invention provides a power control method for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer, comprising: independently configuring operating parameters for each VSG, closing the grid connection switch, and putting the system into standby mode; acquiring the output voltage and current signals of each VSG and converting them into digital signals, and calculating the actual active and reactive power of each VSG; independently observing system disturbances through a nonlinear ESO module and outputting disturbance observation values; dynamically adjusting virtual impedance parameters based on the disturbance observation values ​​and outputting virtual impedance voltage drop compensation signals; generating VSG control commands by combining power deviations and the virtual impedance voltage drop compensation signals; driving the corresponding VSG to run through PWM modulation of the VSG control commands; and repeatedly executing the above steps to achieve stable operation of the parallel system with no communication between multiple VSGs.

[0009] Optionally, the active power P i With reactive power Q i The calculation formula is:

[0010] in, U i , U p The first i The voltage amplitude of the VSG output and the voltage amplitude of the PCC; δ i , δ p The first i The phase angle of the VSG output voltage and the phase angle of the PCC voltage; R i For the first i One VSG to PCC connection line. X i The resistance and reactance of each branch are given.

[0011] Optionally, the nonlinear ESO module uses a third-order nonlinear ESO to observe line impedance disturbances and load disturbances in real time, and outputs high-precision observed values ​​of line resistance and inductance; the state equation of the third-order nonlinear ESO is expressed as:

[0012] in, u i This refers to the output voltage of the VSG. i L,i This refers to the line inductance current. u C,i This is the voltage across the filter capacitor; C i For filtering capacitors; R i , L i These are the nominal resistance and inductance of the circuit, respectively. For the first i ESO estimated state of a VSG parallel subsystem.

[0013] Optionally, the virtual impedance voltage drop compensation signal is represented as:

[0014] in, U d0 , U q0 Output voltage before compensation dq Axis reference value; U d,ref , U q,ref For the output voltage of VSG dq Actual values ​​of axis components; id,i , i q,i These correspond to the d-axis and q-axis components of the VSG output current, respectively. R v,i and X v,i These are virtual resistors and inductors.

[0015] In another aspect, the present invention provides an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, performs the steps of the method as described in any of the preceding claims. In another aspect, the present invention provides a computer storage medium storing a computer program that, when executed by a processor, implements the steps of the method as described in any of the preceding claims.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) High-precision power distribution: By observing the line impedance disturbance in real time through nonlinear ESO and combining it with dynamic virtual impedance adaptive adjustment, the active / reactive power of the multi-VSG parallel system is accurately distributed equally, which solves the problem of uneven power distribution caused by line impedance mismatch in the traditional fixed virtual impedance scheme.

[0017] (2) Strong anti-disturbance capability: Nonlinear ESO does not rely on the precise mathematical model of the system. It can uniformly observe and feed forward compensate for generalized disturbances such as internal parameter perturbation and external load disturbance, significantly improving the system's ability to suppress unknown disturbances and enhancing operational stability.

[0018] (3) Autonomous operation without communication between multiple VSGs: Each VSG is independently configured with a nonlinear ESO and a dynamic virtual impedance module, which can achieve collaborative control without communication between multiple machines. It has good scalability and plug-and-play characteristics and is suitable for large-scale multi-VSG parallel systems.

[0019] (4) Universality and engineering practicality: The device has a modular structure and a robust control algorithm. It can be directly adapted to the existing VSG control architecture without additional hardware modification, and has good engineering application prospects and promotion value. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. By reading the detailed description of the embodiments below, the advantages and benefits of the solutions will become clear to those skilled in the art. The accompanying drawings are only for illustrating preferred embodiments and are not intended to limit the present invention. In the accompanying drawings: Figure 1This is a system block diagram of the present invention.

[0021] Figure 2 This is a schematic diagram of the method flow of the present invention.

[0022] Figure 3 This is a schematic diagram of the power distribution results of the multi-VSG parallel system of the nonlinear ESO proposed in Embodiment 1 of the present invention.

[0023] Figure 4 This is a schematic diagram of the power distribution results of the multi-VSG parallel system of the nonlinear ESO proposed in Embodiment 2 of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art should fall within the protection scope of the present invention.

[0025] See Figure 1 The present invention provides a power control method for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer, comprising: The main circuit consists of multiple VSGs in parallel, including a DC-side energy storage unit, a VSG unit, a signal acquisition module, a nonlinear ESO module, a dynamic virtual impedance compensation module, a power control module, a host computer module, a common AC bus, and a load unit.

[0026] The DC-side energy storage unit is used to provide DC power to the VSG unit.

[0027] The signal acquisition module is used to acquire the voltage and current signals of the corresponding VSG, convert them into digital signals, and then transmit them synchronously to the nonlinear ESO module and the host computer module.

[0028] The nonlinear ESO module is used to observe unknown disturbances in the system in real time and output the observed values.

[0029] The dynamic virtual impedance compensation module is used to adaptively adjust the virtual impedance parameters according to the observed values ​​and output current, generate a virtual impedance voltage drop compensation signal, and transmit it to the power control module.

[0030] The power control module is used to combine the power deviation and the virtual impedance voltage drop compensation signal to generate a control signal for the VSG, thereby achieving high-precision power control of a multi-VSG parallel system without communication.

[0031] The host computer module is used for parameter configuration and status monitoring.

[0032] The common AC bus provides parallel access points for multiple VSGs and supplies power to the load unit.

[0033] For example, the multi-VSG parallel main circuit includes multiple VSG parallel branches, each branch corresponding to an independent control unit. Specifically: the first VSG branch includes: a DC-side energy storage unit 11, a VSG unit 21, a signal acquisition module 31, a nonlinear ESO module 41, a dynamic virtual impedance compensation module 51, and a power control module 61; the second VSG branch includes: a DC-side energy storage unit 12, a VSG unit 22, a signal acquisition module 32, a nonlinear ESO module 42, a dynamic virtual impedance compensation module 52, and a power control module 62. Similarly, the nth VSG branch includes: a DC-side energy storage unit 1n, a VSG unit 2n, a signal acquisition module 3n, a nonlinear ESO module 4n, a dynamic virtual impedance compensation module 5n, and a power control module 6n; the output terminals of all VSG units in all VSG branches are connected to a common AC bus 8, which is connected to the load unit 9; the host computer module 7 communicates bidirectionally with the power control modules 61, 62, ..., 6n of each VSG branch.

[0034] DC-side energy storage unit: The DC-side energy storage unit is composed of energy storage batteries that store the generated electricity from the microgrid. It outputs current to the DC / AC inverter to provide a stable DC power supply for each VSG unit, supporting the power output and dynamic response of the VSG unit.

[0035] Optionally, the VSG is connected in parallel to the common AC bus (PCC) via an LC filter circuit, line impedance, and grid-connected switch. The DC-side energy storage unit provides a stable DC power supply to each VSG, supporting its power output and dynamic response. Specifically, the VSG unit includes a DC / AC inverter, an LC filter circuit, and a virtual synchronization control circuit. The DC / AC inverter input is connected to the DC-side energy storage unit, and its output is connected to the line impedance and grid-connected switch via an LC filter circuit, ultimately connected in parallel to the common AC bus.

[0036] Optionally, the DC / AC inverter, as the core power conversion device of the VSG unit, inverts the DC power output from the DC-side energy storage unit into AC power conforming to grid standards, realizing DC-AC power conversion; the LC filter circuit, composed of filter inductors and filter capacitors, is used to filter out high-frequency PWM harmonics from the inverter output, improve the waveform quality of the output voltage and current, and reduce electromagnetic interference; the grid-connected switch controls the connection and disconnection of the VSG unit with the common AC bus, realizing grid-connected / off-grid mode switching, and quickly disconnecting the circuit in case of a fault to ensure system safety; line impedance, etc. The line resistance and inductance between the VSG unit and the common AC bus are key factors affecting the power distribution of multiple VSGs in parallel. The virtual synchronous control circuit provides virtual inertia and damping for the inverter by simulating the rotor motion equation, excitation regulation characteristics and droop control characteristics of the synchronous generator, realizing the synchronous generator external characteristics of the VSG unit. The input of the DC / AC inverter is connected to the DC-side energy storage unit, and the output is connected to the common AC bus in parallel through the LC filter circuit, line impedance and grid connection switch to realize DC-AC power conversion and grid-connected operation.

[0037] Signal acquisition module: Each VSG is independently equipped with a voltage sensor, a current sensor, and a high-speed sampling unit. The module acquires the output voltage and output current signals of the corresponding VSG, converts them into digital signals, and then transmits them synchronously to the nonlinear ESO module and the host computer module.

[0038] For example, the voltage sensor uses LV25. P-type Hall voltage sensor, current sensor uses LA25 NP-type Hall current sensor; the high-speed sampling unit uses the ADS8364 analog-to-digital converter chip to realize real-time acquisition and digital conversion of the output voltage and current signals of the VSG unit.

[0039] Optionally, a nonlinear ESO module is configured: a third-order nonlinear ESO unit is independently configured for each VSG, and its input is connected to the output of the corresponding VSG's signal acquisition module. The module uses the fal function to construct a third-order extended state observer, receives the voltage and current sampling signals of the corresponding VSG, observes generalized disturbances such as internal system parameter perturbations and external load disturbances in real time, and outputs high-precision disturbance observation values.

[0040] Dynamic Virtual Impedance Compensation Module: Each VSG is independently configured with a virtual impedance adjustment unit, the input of which is connected to the output of the corresponding VSG's nonlinear ESO module. The module dynamically adjusts the virtual impedance parameters based on the disturbance observations from the nonlinear ESO output. R v,i and X v,iIt generates a virtual impedance voltage drop compensation signal and transmits it to the power control module to achieve power decoupling, circulating current suppression and voltage drop compensation.

[0041] Power control module: Each VSG is independently configured with a power calculation unit, a deviation adjustment unit, and a control signal generation unit. Its input terminals are connected to the output terminals of the corresponding VSG's signal acquisition module and dynamic virtual impedance compensation module, and its output terminals are connected to the corresponding VSG's control terminal. The module combines power deviation and virtual impedance compensation signals for comprehensive compensation, generating reference values ​​for the VSG's excitation voltage and angular velocity. Through voltage and current dual closed-loop control and PWM modulation, it drives the corresponding VSG to operate stably, realizing high-precision power closed-loop control of a multi-VSG parallel system without communication.

[0042] Host computer module: An industrial control computer is used to connect bidirectionally to the power control module of each VSG. It is used to independently configure the operating parameters of each VSG, monitor the system operating status in real time, diagnose faults and alarms, and realize centralized monitoring and operation and maintenance of the system.

[0043] Common AC bus: The parallel connection point of multiple VSG units, which collects the output power of each VSG unit and provides AC power to the load unit.

[0044] Load unit: The AC load of the microgrid, connected to the common AC bus, consumes the electrical energy output by the common AC bus.

[0045] Another aspect of the present invention, such as Figure 2 As shown, a power control method for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer is provided, including: Configure operating parameters independently for each VSG, close the grid connection switch, and the system enters standby mode.

[0046] The output voltage and current signals of each VSG are collected and converted into digital signals to calculate the actual active and reactive power of each VSG.

[0047] The system disturbance is independently observed through the nonlinear ESO module, and the disturbance observation value is output.

[0048] The virtual impedance parameters are dynamically adjusted based on the observed disturbance values, and a virtual impedance voltage drop compensation signal is output.

[0049] By combining the power deviation and the virtual impedance voltage drop compensation signal, VSG control commands are generated.

[0050] The VSG control command is driven by PWM modulation to run the corresponding VSG.

[0051] Repeat the above steps to achieve stable operation of a multi-VSG parallel system without communication.

[0052] For example, step 1: System initialization The host computer module independently configures the rated capacity, virtual inertia, damping coefficient, virtual impedance reference value, and other operating parameters for each VSG. After closing the grid connection switch, the system enters standby mode, completing the pre-start preparation for the multi-VSG parallel topology.

[0053] Step 2: Signal Acquisition and Digitization Each VSG has a corresponding signal acquisition module that independently acquires the analog signals of the output voltage and output current of the corresponding VSG. These signals are then converted into digital signals by a high-speed sampling unit, providing basic data for subsequent power calculations and disturbance observations.

[0054] Step 3: The power control module corresponding to each VSG calculates the actual output active power of the corresponding VSG based on the collected voltage and current signals. P i With reactive power Q i The active power P i With reactive power Q i The calculation formula is: (1) in, U i , U p The first i The voltage amplitude of the VSG output and the voltage amplitude of the PCC; δ i , δ p The first i The phase angle of the VSG output voltage and the phase angle of the PCC voltage; R i For the first i One VSG to PCC connection line. X i The resistance and reactance of each branch are given.

[0055] Step 4: The nonlinear ESO module corresponding to each VSG, based on the acquired voltage and current signals, outputs high-precision disturbance observation values ​​through the generalized disturbance observation system of the third-order nonlinear ESO. For the VSG parallel system, the third... iThe line model of the VSG connected to the PCC via line impedance is simplified to an LC filter. Introducing line impedance perturbation, the KVL equations for the VSG output line are obtained: (2) in, u i This refers to the output voltage of the VSG. i L,i This refers to the line inductance current. u C,i This is the voltage across the filter capacitor; R i , L i These are the nominal resistance and inductance of the circuit, respectively; Δ R i For resistance disturbance; Δ L i This is an inductive disturbance.

[0056] The dynamic KCL equation for the filter capacitor is: (3) In the formula, the filter capacitor is C i , i o,i This is the load current.

[0057] Optionally, the nonlinear ESO module uses a third-order nonlinear ESO to observe line impedance disturbances and load disturbances in real time, and outputs high-precision observed values ​​of line resistance and inductance; defining the expansion state. The state equation of the third-order nonlinear ESO is expressed as: (4) in, x 1,i For inductor current, x 2,i This is the capacitor voltage. x 3,i For total disturbance; u i This refers to the output voltage of the VSG. i L,i This refers to the line inductance current. u C,i This is the voltage across the filter capacitor; C i For filtering capacitors; R i , L i These are the nominal resistance and inductance of the circuit, respectively. For the first iESO estimated state of a VSG parallel subsystem.

[0058] Introducing the nonlinear function fal( e , α , δ To enhance robustness, its expression is: (5) In the formula, 0 < α <1 ensures fast convergence and controls the function curvature; δ >0 is the threshold for the linear interval, which determines the switching boundary between the nonlinear and linear regions.

[0059] From the state equation, the equivalent of the line impedance change is: (6) After the transient process ends, The rate of change of current is extremely small, therefore Combining the convergence of the observer, the formula for identifying the line resistance can be obtained: (7) Similarly, utilizing transient states Given the characteristic that ≈0, we obtain the formula for identifying inductance: (8) The corresponding reactance estimate is: (9) Step 5: Adaptive Adjustment of Dynamic Virtual Impedance The dynamic virtual impedance compensation module corresponding to each VSG dynamically adjusts the virtual impedance parameters based on the disturbance observation values ​​output by the nonlinear ESO. R v,i and X v,i The compensated VSG output voltage signal is output.

[0060] To achieve high-precision power sharing in a multi-VSG parallel system, based on the design principle that virtual impedance is inversely proportional to rated capacity, the first... i The target equivalent impedance of the VSG is: (10) in, S Ni For the first i The rated capacity of the VSG unit R ref0 , X ref0 The reference equivalent impedance.

[0061] The virtual impedance parameter is adaptively updated through integral adjustment: (11) In the formula, k R , k X This is the integral adjustment coefficient.

[0062] Optionally, the virtual impedance voltage drop compensation signal is represented as: (12) in, U d0 , U q0 Output voltage before compensation dq Axis reference value; U d,ref , U q,ref For the output voltage of VSG dq Actual values ​​of axis components; i d,i , i q,i These correspond to the d-axis and q-axis components of the VSG output current, respectively. R v,i and X v,i These are virtual resistors and inductors.

[0063] Step 6: Comprehensive adjustment of power deviation Each VSG's corresponding power control module, combining the VSG virtual synchronization control algorithm, power deviation signal, and dynamic virtual impedance compensation signal, generates the VSG's excitation voltage reference value and angular velocity reference value to achieve power closed-loop control.

[0064] Step 7: The voltage and current dual closed-loop control unit corresponding to each VSG receives the excitation voltage reference value and angular velocity reference value, and generates a PWM modulation signal through closed-loop regulation of the voltage outer loop and current inner loop to drive the DC / AC inverter of the corresponding VSG to operate stably.

[0065] Step 8: Iterate Determine whether to iterate in a loop. If yes, repeat steps 2-7 to achieve stable operation of the parallel system with no communication between multiple VSGs, ensure that each VSG accurately allocates active / reactive power according to its rated capacity, suppress circulating current, compensate for voltage drops, and improve the system's immunity to disturbances. If no, stop control.

[0066] This invention utilizes dynamic virtual impedance technology to actively adjust the equivalent output impedance, improving power coupling, suppressing circulating current, and enhancing power sharing. The nonlinear ESO (Equivalent Output Impedance) requires no precise mathematical model, enabling unified observation and compensation of system uncertainties and external disturbances, resulting in strong anti-disturbance capabilities. Integrating the nonlinear ESO with dynamic virtual impedance in the parallel control of multiple VSGs significantly improves power control accuracy, dynamic performance, and system stability, thus possessing significant engineering application value.

[0067] The power control method for a multi-VSG parallel system based on nonlinear ESO proposed in this invention will be described below with reference to the relevant accompanying drawings and specific examples.

[0068] The following examples all use the construction of a parallel system of 3 VSGs with the same rated capacity as an example.

[0069] In this embodiment, the selected devices are as follows: DC-side energy storage unit: Uses a lithium energy storage battery pack with a rated voltage of 1000V and a rated capacity of 200Ah.

[0070] VSG Unit: The DC / AC inverter uses a two-level IGBT inverter with a rated capacity of 50kW and a switching frequency of 10kHz; the LC filter circuit has a filter inductance L=2mH and a filter capacitor C=50μF; the grid-connected switch uses an AC contactor with a rated current of 200A; the line impedance is: simulated equivalent line resistance R=0.25~0.35Ω and line inductance L=0.48~0.95mH.

[0071] Signal acquisition module: The voltage sensor uses an LV25. P-type Hall voltage sensor, current sensor uses LA25 NP-type Hall current sensor; the high-speed sampling unit uses the ADS8364 16-bit high-speed analog-to-digital converter chip with a sampling frequency of 10kHz.

[0072] Nonlinear ESO module: Employs a TMS320F28379D DSP control chip with a computation cycle of 100μs; fal function parameters α =0.5, δ =0.01, observer bandwidth ω o =100 rad / s.

[0073] Dynamic Virtual Impedance Compensation Module: Based on a DSP control chip, this module achieves adaptive adjustment of virtual impedance and dynamically adjusts virtual impedance parameters. R v,i and X v,i .

[0074] Power control module: The voltage and current dual closed-loop control is based on the sampling results of the DSP's built-in ADC to realize the PI closed-loop regulation of the voltage outer loop and the current inner loop, with a control period of 10kHz; the PWM modulation adopts the DSP's ePWM module to generate a 10kHz symmetrical triangular wave PWM signal, which is output to drive the gate drive circuit of the IGBT inverter.

[0075] Host computer module: It adopts an industrial control computer, runs a Windows system, and communicates with the control boards of each VSG unit via Ethernet.

[0076] Public AC bus: Rated voltage 380V / 50Hz three-phase AC bus.

[0077] Load unit: Adopts adjustable resistive-inductive load with a rated capacity of 20kW, and can achieve 0~100% load switching.

[0078] Example 1: Implementation of a system with multiple VSGs of the same capacity in parallel under sudden load changes: To verify the power distribution performance of this invention under line impedance mismatch scenarios, three VSG units with a rated capacity ratio of 1:1:1 were set, and the load was switched on and off in three stages: 0~1s: Only load 1 (active power) is applied. P Load1 =9kW, reactive power Q Load1 =9kVar).

[0079] 1~2s: Load 1 + Load 2 are put into operation (total active power 18kW, total reactive power 18kVar).

[0080] 2~3s: Disconnect load 2 and resume operation with only load 1.

[0081] This embodiment strictly follows the control method of the present invention, and the steps are as follows: Step 1: System Initialization: Configure the rated capacity, virtual inertia, damping coefficient, and nonlinear ESO parameters for the three VSGs via the host computer. α =0.5, δ =0.01, observer bandwidth ω o =100rad / s), close the grid connection switch, and the system enters standby mode.

[0082] Step 2, Signal Acquisition: The signal acquisition module of each VSG acquires the output voltage and current signals in real time and converts them into digital signals.

[0083] Step 3: Power Calculation: Based on the collected voltage and current signals, the power control module calculates the actual active power of each VSG. P ireactive power Q i .

[0084] Step 4: Nonlinear ESO Disturbance Observation: The third-order nonlinear ESO observes line impedance disturbances and load disturbances in real time, outputting high-precision observation values ​​of line resistance and inductance, and treating internal system parameter perturbations and external load disturbances as generalized disturbances for compensation.

[0085] Step 5: Adaptive Adjustment of Dynamic Virtual Impedance: The dynamic virtual impedance compensation module adaptively adjusts the virtual impedance parameters based on the impedance observations output by the ESO, following the principle that the equivalent impedance is inversely proportional to the rated capacity. R v,i and X v,i This ensures that the equivalent output impedance of the three VSGs is consistent, compensating for power distribution deviations caused by line impedance mismatch.

[0086] Step 6: Comprehensive adjustment of power deviation: The power control module combines the VSG virtual synchronous control algorithm, power deviation signal and virtual impedance compensation signal to generate excitation voltage reference value and angular velocity reference value to realize power closed-loop control.

[0087] Step 7: Dual-loop control and PWM drive: The voltage and current dual-loop control unit receives the reference value, adjusts it through the voltage outer loop and the current inner loop, generates a PWM modulation signal, and drives the DC / AC inverter of each VSG to operate.

[0088] Step 8: Iterative operation: Repeatedly execute steps 2 to 7 to achieve stable operation of the parallel system with no communication between multiple VSGs.

[0089] When the control strategy of this invention is adopted, the system power waveform is as follows: Figure 3 As shown: Active power: The active power of the three VSGs is completely consistent under steady state at each stage, achieving high-precision active power distribution, with small overshoot and fast dynamic response when the load is switched on and off.

[0090] Reactive power: During the 0-1s time period, the output reactive power of all three converters was 2971var. During the 1-2s time period, the output reactive power of all three converters was 5962var. During the 2-3s time period, the output reactive power of the three converters was 2971var for VSG2. These results indicate that the control strategy presented in this paper eliminates the limitation of line impedance on the distribution of active and reactive power, achieving power equalization while significantly improving accuracy.

[0091] This invention can stably control the absolute value of reactive power distribution error in a multi-VSG parallel system to within 1%, while achieving decoupling control of active and reactive power, effectively suppressing circulating current, and verifying the effectiveness and superiority of this invention in a multi-VSG parallel system of the same capacity.

[0092] Example 2: Implementation of a heterogeneous capacity multi-VSG parallel system under load change conditions In this embodiment, the rated capacity ratio of the three VSGs is set to 3:2:1, and the remaining system parameters are the same as in Embodiment 1, verifying the universality of the present invention in heterogeneous capacity systems. The load switching strategy is exactly the same as in Embodiment 1, ensuring consistency of operating conditions.

[0093] The control flow in this embodiment is completely the same as in Embodiment 1. The only difference is that during the host computer configuration phase, the rated capacity ratio of the three VSGs needs to be set to 3:2:1. The dynamic virtual impedance compensation module will automatically and adaptively adjust according to the principle that virtual impedance is inversely proportional to rated capacity. R v,i and X v,i This ensures that the equivalent output impedance of each VSG is inversely proportional to its rated capacity, thereby achieving precise power allocation according to capacity ratio.

[0094] When the control strategy of this invention is adopted, the power waveform of the heterogeneous capacity system is as follows: Figure 4 As shown, during the 0-1s time period, the reactive power outputs of the three converters are 4483, 2989, and 1494 var, respectively. During the 1-2s time period, the reactive power outputs are 8958, 5972, and 2986 var, respectively. During the 2-3s time period, the reactive power outputs are 4483, 2989, and 1494 var, respectively. The distribution of active and reactive power in the system after adopting the control strategy proposed in this paper is not affected by the line impedance and can be accurately distributed according to the capacity ratio of 3:2:1.

[0095] From the transient waveform characteristics, the system power response is stable under variable capacity conditions without continuous oscillations, indicating that the proposed nonlinear ESO strategy can maintain good dynamic stability even in scenarios with large capacity differences, thus expanding the engineering application boundaries of the strategy. Meanwhile, the precise matching of power allocation and capacity ratio between each VSG verifies that the proposed strategy effectively compensates for line impedance disturbances while preserving the VSG droop characteristics, achieving high-precision power allocation in heterogeneous capacity systems.

[0096] This invention achieves high-precision power distribution, circulating current suppression, and voltage support in multi-VSG parallel systems without communication by observing and compensating for unknown disturbances in the nonlinear ESO real-time observation system and adaptively adjusting virtual impedance parameters using a dynamic virtual impedance compensation module. This comprehensively improves the power control accuracy, disturbance rejection capability, operational stability, and power supply quality of multi-VSG parallel systems.

[0097] It should be understood that the system of the present invention is used to implement any of the above method embodiments and has the effects of the corresponding method embodiments, which will not be repeated here.

[0098] Another aspect of the present invention provides an electronic device, which includes a processor, a memory, a communication bus, and a communication interface.

[0099] in: The processor, memory, and communication interface communicate with each other via a communication bus.

[0100] A communication interface is used to communicate with other electronic devices or servers.

[0101] The processor is used to execute programs, specifically the steps of any of the methods described in the above embodiments.

[0102] Specifically, the program may include program code, which includes computer operation instructions.

[0103] The processor may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application. The one or more processors included in the smart device may be processors of the same type, such as one or more CPUs; or they may be processors of different types, such as one or more CPUs and one or more ASICs.

[0104] Memory is used to store programs. Memory may include high-speed RAM, and may also include non-volatile memory, such as at least one disk drive.

[0105] Specifically, the program can be used to cause the processor to execute the steps of any of the methods described in the embodiments. The specific implementation of each step in the program can be found in the corresponding descriptions of the steps and units executed by any of the methods described above, and will not be repeated here. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the devices and modules described above can be referred to the corresponding process descriptions in the foregoing method embodiments.

[0106] An exemplary embodiment of this application also provides a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to cause a computer to perform the methods of various embodiments of this application.

[0107] The methods described above according to embodiments of the present invention can be implemented in hardware, firmware, or as software or computer code that can be stored in a recording medium (such as a CD-ROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code originally stored on a remote recording medium or a non-transitory machine-readable medium and subsequently stored on a local recording medium, downloaded via a network. Thus, the methods described herein can be processed by software stored on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that the computer, processor, microprocessor controller, or programmable hardware includes storage components (e.g., RAM, ROM, flash memory, etc.) capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods described herein. Furthermore, when a general-purpose computer accesses code used to implement the methods shown herein, the execution of the code transforms the general-purpose computer into a dedicated computer for executing the methods shown herein.

[0108] Specific embodiments of the present invention have now been described. Other embodiments are within the scope of the appended claims. In some cases, the actions described in the claims can be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result.

[0109] It should be noted that all directional indications (such as up, down, left, right, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship between the components in a certain order (as shown in the figure). If the specific order changes, the directional indication will also change accordingly.

[0110] In the description of this invention, the terms "first" and "second" are used only for convenience in describing different components or names, and should not be construed as indicating or implying a sequential relationship, relative importance, or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" and "second" may explicitly or implicitly include at least one of that feature.

[0111] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0112] It should be noted that although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of the present invention. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of the present invention.

[0113] The examples of the embodiments of the present invention are intended to concisely illustrate the technical features of the embodiments of the present invention, so that those skilled in the art can intuitively understand the technical features of the embodiments of the present invention, and are not intended to be an improper limitation of the embodiments of the present invention.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power control system for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer, characterized in that, include: The main circuit with multiple VSGs in parallel includes a DC-side energy storage unit, a VSG unit, a signal acquisition module, a nonlinear ESO module, a dynamic virtual impedance compensation module, a power control module, a host computer module, a common AC bus, and a load unit. The DC-side energy storage unit is used to provide DC power to the VSG unit; The signal acquisition module is used to acquire the voltage and current signals of the corresponding VSG, convert them into digital signals, and then transmit them synchronously to the nonlinear ESO module and the host computer module. The nonlinear ESO module is used to observe unknown disturbances in the system in real time and output the observed values. The dynamic virtual impedance compensation module is used to adaptively adjust the virtual impedance parameters according to the observed values, generate a virtual impedance voltage drop compensation signal, and transmit it to the power control module. The power control module is used to combine the power deviation and the virtual impedance voltage drop compensation signal to generate the control signal of the VSG, so as to realize high-precision power control of the parallel system without communication between multiple VSGs; The host computer module is used for parameter configuration and status monitoring; The common AC bus provides parallel access points for multiple VSGs and supplies power to the load unit.

2. The system according to claim 1, characterized in that, The VSG unit includes an inverter, an LC filter circuit, a line impedance, a grid-connected switch, and a virtual synchronization control circuit. The input terminal of the inverter is connected to the DC-side energy storage unit, and the output terminal is connected in parallel to the common AC bus via the LC filter circuit, the line impedance and the grid-connected switch, thereby realizing DC-AC power conversion and grid-connected operation.

3. The system according to claim 2, characterized in that, The VSG unit uses an inverter as the core power conversion device to convert the DC power output from the DC-side energy storage unit into AC power that conforms to the grid standard, thereby realizing DC-AC power conversion. The LC filter circuit consists of a filter inductor and a filter capacitor, and is used to filter out high-frequency PWM harmonics from the inverter output. The grid-connected switch controls the connection and disconnection of the VSG unit with the common AC bus, realizes the switching between grid-connected and off-grid modes, and quickly cuts off the circuit in case of a fault; The line impedance is used to equivalently simulate the line resistance and line inductance between the VSG unit and the common AC bus. The virtual synchronous control circuit simulates the rotor motion equation, excitation regulation characteristics, and droop control characteristics of a synchronous generator to provide virtual inertia and damping for the inverter, thereby realizing the synchronous generator external characteristics of the VSG unit.

4. The system according to claim 1, characterized in that, The nonlinear ESO module includes a third-order nonlinear ESO unit, the input of which is connected to the output of the corresponding VSG signal acquisition module; The nonlinear ESO module uses the fal function to construct a third-order extended state observer, receives the voltage and current sampling signals of the corresponding VSG, observes the generalized disturbance of the system in real time, and outputs high-precision disturbance observation values.

5. A power control method for a parallel system of multiple virtual synchronous generators based on a nonlinear extended state observer, characterized in that, include: Configure operating parameters independently for each VSG, close the grid connection switch, and the system enters standby mode; The output voltage and current signals of each VSG are collected and converted into digital signals to calculate the actual active and reactive power of each VSG. The system perturbation is independently observed through the nonlinear ESO module, and the perturbation observation value is output. The virtual impedance parameters are dynamically adjusted based on the disturbance observation values, and a virtual impedance voltage drop compensation signal is output. By combining the power deviation and the virtual impedance voltage drop compensation signal, a VSG control command is generated; The VSG control command is driven by PWM modulation to run the corresponding VSG; Repeat the above steps to achieve stable operation of a multi-VSG parallel system without communication.

6. The method according to claim 5, characterized in that, The active power P i With reactive power Q i The calculation formula is: in, U i , U p The first i The voltage amplitude of the VSG output and the voltage amplitude of the PCC; δ i , δ p The first i The phase angle of the VSG output voltage and the phase angle of the PCC voltage; R i For the first i One VSG to PCC connection line. X i The resistance and reactance of each branch are given.

7. The method according to claim 5, characterized in that, The nonlinear ESO module uses a third-order nonlinear ESO to observe line impedance disturbances and load disturbances in real time, and outputs high-precision observation values ​​of line resistance and inductance. The state equation of the third-order nonlinear ESO is expressed as: in, x 1,i It is the inductor current; u i This refers to the output voltage of the VSG. i L,i This refers to the line inductance current. u C,i This is the voltage across the filter capacitor; C i For filtering capacitors; R i , L i These are the nominal resistance and inductance of the circuit, respectively. For the first i ESO estimated state of a VSG parallel subsystem.

8. The method according to claim 5, characterized in that, The virtual impedance voltage drop compensation signal is represented as follows: in, U d0 , U q0 Output voltage before compensation dq Axis reference value; U d,ref , U q,ref For the output voltage of VSG dq Actual values ​​of axis components; i d,i , i q,i These correspond to the d-axis and q-axis components of the VSG output current, respectively. R v,i and X v,i These are virtual resistors and inductors.

9. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the method as described in any one of claims 5 to 8.

10. A computer storage medium, characterized in that, The computer storage medium stores a computer program, which, when executed by a processor, implements the steps of the method as described in any one of claims 5 to 8.

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