A method and system for phase angle compensation of post-transient period suppression of active oscillations and desaturation delay

Abstract

The application provides a grid-connected inverter compensation method and system for restraining active oscillation and desaturation delay during a transient recovery period, which determines the entry and exit of a transient state through a grid-connected point voltage change rate dU / dt, respectively locks a steady-state power angle delta ss and a transient power angle delta sr , calculates a difference between the two to generate a compensation amount delta delta, converts the compensation amount delta delta into a radian system, and compensates the compensation amount delta delta to a phase angle theta (t ‑ c ) in a phase angle integrator before an exit moment of the transient state, and synthesizes to generate an initial phase angle theta init inside the integrator; and inputs the theta init as an initial condition to the phase angle integrator at a fault removal moment. The application eliminates the electromechanical power imbalance at the fault removal moment, restrains the active power oscillation, and eliminates the single-voltage-loop internal potential desaturation delay by instantaneously compensating the power angle deviation accumulated during the transient period under the premise of retaining the dynamic virtual impedance current-limiting effect.

Description

Technical Field

[0001] This invention belongs to the field of new energy power systems, specifically relating to a phase angle compensation method and system for suppressing active power oscillation and desaturation delay during transient recovery. Background Technology

[0002] With the high proportion of new energy sources connected to the grid, traditional grid-connected inverters are prone to control loop instability under weak grid conditions. Grid-connected inverters with voltage source characteristics provide voltage and frequency support to the grid by simulating the physical characteristics of synchronous generators. In grid-connected control, the single-voltage loop amplitude control architecture eliminates the current inner loop and decoupling links, eliminating parameter coupling problems and improving voltage response speed and adaptability to weak grids. However, this architecture cannot directly limit the output current, and transient voltage drops will occur during grid voltage dips, leading to transient overcurrents. Existing technologies typically introduce dynamic virtual impedance based on current amplitude triggering, injecting impedance voltage drops during faults to limit the current. However, when the system maintains a constant active power command during voltage dips, electromechanical and electrical imbalances will occur in the control loop, causing transient oscillations at the moment of fault clearing, mainly manifested in the following two dimensions:

[0003] First, there is the risk of active power oscillation and loss of synchronization caused by electromechanical power imbalance. According to the active power transfer equation, during a voltage sag, to maintain a constant active power command, the power angle loop generates a positive power deviation, which is accumulated by the integrator, leading to an increase in the physical power angle. At the moment of fault clearing, because the phase angle state cannot change abruptly, the power angle remains at its maximum value at the end of the transient. The restored grid voltage and this power angle state work together to cause transient active power overload and negative electromagnetic braking torque, resulting in power deceleration oscillation. Under deep sag conditions, if the power angle crosses the transient stability limit, the system state will diverge and a phase reversal will occur, causing the inverter to disconnect from the grid.

[0004] Second, the continuous activation of the dynamic virtual impedance causes a delay in the desaturation of the internal potential. During a fault, the voltage drop across the virtual impedance causes the grid connection point voltage to fall below the rated command. Due to the continuous positive error accumulation in the outer voltage loop, the internal potential reaches its saturation limit. After the fault is cleared, the overcurrent caused by transient power keeps the virtual impedance active, and its voltage drop hinders the recovery of the grid connection point voltage. The lack of negative error feedback in the outer voltage loop causes the internal potential to remain saturated after the fault is cleared, reducing the system's dynamic response speed to recover to steady state.

[0005] In summary, existing single-voltage-loop amplitude-controlled grid inverters lack intervention mechanisms for core state variables during the transient-to-steady-state transition in constant-power low-voltage ride-through conditions. Damping optimization methods based on small-signal signals struggle to address large-signal power angle divergence and state variable saturation. Therefore, for single-voltage-loop control systems with dynamic virtual impedance, a transient recovery period phase angle compensation method needs to be investigated. This method compensates for accumulated power angle deviations during fault clearing, thereby relieving internal potential saturation and suppressing active power oscillations. Summary of the Invention

[0006] Based on this, this invention proposes a phase angle compensation method and system for suppressing active power oscillation and desaturation delay during transient recovery. This addresses the active power oscillation and internal potential desaturation delay issues that exist in single-voltage loop inverters with dynamic virtual impedance after the clearing of a constant power low-voltage ride-through fault. This invention determines the system's transition to or from transient states by real-time calculation of the grid connection point voltage change rate and locks the corresponding power angle. At the moment of fault clearing, the phase angle integrator is reset to its steady-state value before the transient. This operation compensates for the accumulated power angle deviation during the transient period, reducing the system's electromechanical power difference. Simultaneously, the current drop caused by the phase angle reset prompts the dynamic virtual impedance to exit, ultimately suppressing active power oscillation and eliminating the internal potential desaturation delay.

[0007] The technical solution adopted in this invention is as follows:

[0008] A phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery, applied to a single-voltage-loop amplitude-controlled grid inverter with dynamic virtual impedance, includes the following steps:

[0009] Step 1: Real-time acquisition of grid-connected inverter grid-connected point voltage and output current; generation of system angular frequency ω and grid-connected point voltage command U through power outer loop calculation. ref The system angular frequency ω is then integratored to generate an internal phase angle θ.

[0010] Step 2: Based on the grid connection point voltage command U ref The compensated voltage drop output by the dynamic virtual impedance module generates a d-axis modulated voltage U. d With q-axis modulation voltage U q This is used for subsequent PWM modulation to drive the inverter;

[0011] Step 3: Calculate the rate of change of the voltage amplitude at the grid connection point, dU / dt, as the criterion for the system entering and exiting the transient state; when the system enters the transient state, trigger the first sample-and-hold logic to lock the steady-state power angle δ before entering the transient state. ss When the system is detected to exit the transient state, the second sample-and-hold logic is triggered to lock the instantaneous power angle δ before exiting the transient state. sr ;

[0012] Step 4: Calculate the instantaneous work angle δ sr With the steady-state work angle δ ss The difference between them generates the transient power angle compensation amount Δδ;

[0013] Step 5: Obtain the phase angle θ(t) of the phase integrator at the transient exit time. - c The transient power angle compensation amount Δδ is converted to radians to obtain the phase angle compensation amount from the phase angle θ(t). - c Remove from the initial phase angle θ inside the synthesized phase integrator. init ;

[0014] Step 6: At the instant the fault clearing exits the transient state, set the initial phase angle θ... init As an initial condition, state compensation is performed in the phase integrator to update the internal phase angle θ.

[0015] Further, in step one, the actual active power P and the active power command P ref The deviation is controlled by a swing equation controller and superimposed with the rated angular frequency to generate the system angular frequency ω and the phase angle θ; the deviation between the actual reactive power and the reactive power command is controlled by droop control and superimposed with the rated voltage command to generate the grid connection point voltage command U. ref .

[0016] Furthermore, in step two, the voltage amplitude U at the grid connection point pccmag With the grid connection point voltage command U ref The deviation, after proportional-integral adjustment, is subtracted by the d-axis virtual impedance voltage drop U. zd Generate the d-axis modulation voltage U d The q-axis modulation voltage U q Subtract the q-axis virtual impedance voltage drop U from the constant 0 zq generate.

[0017] Furthermore, the d-axis virtual impedance voltage drop U zd With q-axis virtual impedance voltage drop U zq The generation logic is as follows:

[0018] During the voltage sag, when the current amplitude I mag Exceeding the safety threshold I th At that time, the dead-zone nonlinear element is activated, and multiplied by the gain K respectively. Rv With K Xv Generate virtual resistance R v With virtual reactance X v Combined with the d-axis and q-axis components of the output current I d I q The formula for calculating pressure drop is:

[0019] ;

[0020] ;

[0021] By the d-axis virtual impedance voltage drop U zd With q-axis virtual impedance voltage drop U zq Compensation is applied to the single voltage loop to limit the inverter transient current. After phase angle compensation is performed in step six, the system current drops instantaneously, allowing the dynamic virtual impedance to exit quickly and relieving the desaturation delay of the potential E in the outer voltage loop.

[0022] Furthermore, in step three, the steady-state work angle δ ss and the instantaneous work angle δ sr The calculation logic is as follows: Collect the three-phase voltage of the power grid, use the internal phase angle of the inverter as the orientation reference, and calculate the d-axis voltage component U through abc / dq0 coordinate transformation. gd With q-axis voltage component U gq Subsequently, the physical work angle of the angle system is calculated using the nonlinear arctangent function. The calculation formula is as follows:

[0023] ;

[0024] Furthermore, in step three, the triggering logic for entering and exiting the transient state specifically involves: setting a sag threshold and a recovery threshold; when the voltage change rate dU / dt is lower than the sag threshold, an edge detection mechanism combined with a monostable multivibrator outputs a fault drop pulse to activate the first sample-and-hold circuit and lock the steady-state power angle δ. ss When the voltage change rate dU / dt is higher than the recovery threshold, a fault clearing pulse is output through edge detection in conjunction with a monostable trigger, activating the second sample-and-hold circuit to lock the instantaneous power angle δ. sr .

[0025] Furthermore, in step five, the initial phase angle θ init The specific synthesis formula is as follows:

[0026] ;

[0027] In the formula, π / 180 is the conversion coefficient from angle to radian, used to unify the transient power angle compensation Δδ with the phase angle θ(t) of the phase angle integrator at the transient exit time. - c The dimensions between )

[0028] A phase angle compensation system for suppressing active power oscillation and desaturation delay during transient recovery, used to implement the method described above, the system comprising:

[0029] The electromagnetic state extraction module is used to calculate the real-time physical power angle and voltage change rate dU / dt of the grid connection point voltage.

[0030] The dual sample-and-hold module is used to latch the steady-state power angle δ before the fault based on the event pulses emitted by the voltage change rate dU / dt. ss Instantaneous power angle δ at the end of the fault sr ;

[0031] The deviation compensation calculation module is used to calculate the instantaneous power angle δ. sr With the steady-state work angle δ ss The difference between them generates the transient power angle compensation amount Δδ;

[0032] The state phase angle synthesis and reset module is used to read the phase angle θ(t) of the phase angle integrator at the transient exit time. - c The transient power angle compensation amount Δδ is converted to radians to obtain the phase angle compensation amount from the phase angle θ(t). - c Remove from the initial phase angle θ inside the synthesized phase integrator. init And at the moment of fault clearing, the initial phase angle θ init The phase angle is directly injected into the phase angle integrator as the initial phase angle during the transient recovery period.

[0033] Furthermore, the dual sample-and-hold module includes a first sample-and-hold circuit and a second sample-and-hold circuit; the first sample-and-hold circuit is activated by a fault drop pulse triggered when the voltage change rate dU / dt falls below a sag threshold, and is used to lock the steady-state power angle δ. ss The second sample-and-hold circuit is activated by a fault clearing pulse triggered when the voltage change rate dU / dt exceeds the recovery threshold, and is used to lock the instantaneous power angle δ. sr .

[0034] Furthermore, the state phase angle synthesis and reset module includes a subtraction operation unit and a register overwrite unit; the subtraction operation unit is used to perform initial phase angle calculation. Algebraic operations; the register overwrite unit suspends the conventional integration and accumulation logic at the moment of fault clearing, and sets the initial phase angle θ init It is directly overwritten into the accumulator of the phase angle integrator.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) This invention determines the system’s transition to or from transient state by calculating the voltage change rate at the grid connection point in real time and locking the corresponding power angle. At the moment the fault is cleared, the phase angle integrator is directly reset to the steady-state value before the transient state. This operation compensates for the power angle deviation accumulated during the transient period, reduces the electromechanical power difference of the system, suppresses active power oscillation from the physical source, and avoids the risk of loss of synchronism and divergence under deep sag conditions.

[0037] (2) The present invention enables the power angle to converge rapidly by instantaneously resetting the phase angle, which drives the transient current to fall rapidly, prompting the dynamic virtual impedance to exit immediately after the fault is cleared and the impedance voltage drop to zero, so that the voltage outer loop obtains the error feedback required for reverse regulation, eliminates the desaturation delay of the internal potential, and significantly improves the dynamic response speed of the network system to recover to steady state. Attached Figure Description

[0038] Figure 1 The overall logic block diagram of the main circuit and control system of the grid-type energy storage inverter;

[0039] Figure 2 Logic diagram for dynamic virtual impedance generation and single voltage amplitude closed-loop control;

[0040] Figure 3 The logic diagram for triggering and transient phase angle compensation based on the voltage change rate dU / dt is shown below.

[0041] Figure 4 Comparison waveforms of fault recovery under the condition of voltage drop to 0.7 pu;

[0042] Figure 5 The waveforms show the fault recovery process when the voltage drops to 0.2 pu.

[0043] Figure 6 This is a flowchart of a grid inverter compensation method for suppressing active power oscillation and desaturation delay during the transient recovery period, according to an embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] To achieve precise phase angle compensation during fault clearing under constant power low-voltage ride-through conditions, suppress active power oscillations, and eliminate internal potential desaturation delay, this invention proposes a phase angle compensation method for the transient recovery period of a grid-type energy storage inverter with single-voltage loop amplitude control. This invention primarily relies on the digital control system of the grid-type inverter. For example... Figure 1 and Figure 2 As shown, the system hardware topology includes a DC-side energy storage power supply, a three-phase inverter bridge, and an LC filter. Figure 6 As shown, the method includes the following steps:

[0046] S1. High-frequency sampling of electromagnetic state and synchronous control of power outer loop. The control system uses voltage and current sensors to sample the three-phase voltage U at the grid connection point of the grid-connected inverter in real time at a set switching frequency. g With the inverter output three-phase current I g Using the real-time phase angle θ output by the phase integrator as the orientation reference, the d-axis voltage component U is calculated through the abc / dq0 coordinate transformation. gd With q-axis voltage component U gq The instantaneous power calculation module obtains the actual output active power P and reactive power Q of the system. In the power outer loop, a swing equation controller simulating the characteristics of a synchronous generator is used to handle active power: the actual active power P and the active power command P. ref The deviation is combined with the virtual inertia J and the damping coefficient D to calculate the real-time angular frequency ω of the system, and then integrators to generate the internal phase angle θ; simultaneously, the reactive power deviation is processed by droop control and superimposed with the rated voltage command to generate the grid connection point voltage reference amplitude U. ref .

[0047] S2. Transient current limiting threshold determination and dynamic virtual impedance voltage drop generation. The system calculates the inverter output current amplitude in real time.

[0048] ;

[0049] During voltage dips and ride-through, a current safety threshold I is set to protect core power devices such as inverters from overcurrent surges caused by large signal voltage differences. th .

[0050] The system controller incorporates dead-zone nonlinear judgment logic: when When the virtual impedance is not applied, the output voltage drop is 0; when When the dynamic virtual impedance module is activated, the current difference exceeding the threshold is multiplied by the set proportional gain K. Rv With K Xv Generate a dynamic virtual resistance R. v With virtual reactance X v Combining the d-axis and q-axis components I of the output currentd I q The formula for calculating pressure drop is:

[0051] ;

[0052] ;

[0053] Subsequently, the voltage amplitude U at the grid connection point pccmag with U ref The deviation, after proportional-integral adjustment, is subtracted by the d-axis virtual impedance voltage drop U. zd Generate d-axis modulated voltage U d ; q-axis modulation voltage U q Subtract the q-axis virtual impedance voltage drop U from the constant 0 zq This mechanism effectively reduces the modulation voltage during the sag, achieving passive current limiting.

[0054] S3. Transient boundary condition feature extraction and power angle dual sampling and hold logic. Using the grid voltage components obtained from coordinate transformation, the physical power angle in angle form is calculated using a nonlinear arctangent function. The calculation formula is as follows:

[0055] ;

[0056] Calculate the rate of change of voltage amplitude at the grid connection point Set positive recovery thresholds and negative drop thresholds (e.g., ...). Figure 3 (as shown)

[0057] when When the system enters a low-voltage ride-through transient, an output pulse signal is activated to activate the first sample-and-hold circuit, recording the power angle constant δ when the system is at its steady-state operating point. ss ;

[0058] when When the power grid fault is cleared and the system exits the transient state, an output pulse signal is used to activate the second sample-and-hold circuit to record the maximum instantaneous power angle δ at the end of the system fault. sr .

[0059] S4. Precise calculation and compensation of transient power angle deviation. At the instant of triggering the recovery edge of S3 (let this moment be t). c The deviation compensation calculation module is activated synchronously. The microprocessor reads the value from the dual sample-and-hold register and calculates the instantaneous power angle δ. sr With steady-state work angle δ ss The algebraic difference between the two values ​​generates the transient power angle compensation Δδ. This compensation precisely characterizes, in a physical sense, the excess electromechanical offset angle generated by the positive accumulation of the active power swing equation during the entire low-voltage ride-through transient period.

[0060] S5. Phase integrator state reset and initial value synthesis. Obtain transient exit time (t). - c The continuous phase angle output value θ(t) at the state port of the phase angle integrator - c To ensure data dimension consistency, the system converts the angle-based compensation Δδ to radians by multiplying it by π / 180. Then, it performs algebraic subtraction at the control algorithm's underlying level to synthesize the reset initial phase angle θ within the phase integrator. init :

[0061] ;

[0062] S6: Transient phase angle compensation during fault clearing. At fault clearing t... + c Instantly, the underlying control code temporarily suspends the regular phase angle integrator accumulation logic and uses a system interrupt or direct register assignment to process the initial phase angle θ synthesized in step S5. init The data is directly overwritten to the accumulator of the phase angle integrator, thus forcibly resetting the state. This leapfrog low-level write operation breaks the integral inertia of the continuous-time system, causing the physical work angle to change at time t. + c Mutations occur constantly, satisfying This directly leads to two physical evolutionary results: First, due to the instantaneous convergence of the power angle, the instantaneous electromagnetic power drops to... First, it eliminates the huge power difference at its physical source, suppressing transient oscillations in active power; second, due to phase angle compensation, the transient overcurrent can drop to the threshold I relatively quickly. th The following allows the dynamic virtual impedance module in step S2 to exit more quickly, reducing the impedance voltage drop U. zd U zq When the voltage is returned to zero, the PI regulator in the outer voltage loop immediately receives effective negative error feedback, thereby releasing the integrator from deadlock and greatly alleviating the desaturation delay of the internal potential E.

[0063] This invention utilizes a grid-connected inverter system model with single-voltage loop amplitude control constructed in Simulink using MATLAB simulation software. Simulation verification is performed using a dynamic virtual impedance and a constant active power command scheme during low-voltage ride-through. Focusing on 2-second transient release, the effectiveness of the method is determined primarily by observing the oscillation of active power and the desaturation delay time of the internal potential during transient recovery.

[0064] In this invention, the relevant system simulation data are set as follows:

[0065] Table 1. Relevant parameters of the simulation system

[0066]

[0067] To verify the effectiveness of this invention, a control group was set up, consisting of a "traditional single-voltage loop combined with dynamic virtual impedance control" without transient phase angle compensation, and an experimental group was set up, incorporating the phase angle compensation strategy of this invention. This was done while maintaining the active power command. Under constant conditions, two operating conditions were set up for comparison and analysis, with the grid voltage temporarily dropping to 0.7 pu and 0.2 pu respectively.

[0068] Operating Condition 1: The mains voltage temporarily drops to 0.7 pu.

[0069] like Figure 4 During the temporary descent, in order to maintain the active power command P ref Both the control and experimental groups exhibited positive integrals in their active swing equations, with the work angle δ increasing to approximately 22.5°. Due to the small voltage drop and limited current increase, the virtual impedance was triggered, but the voltage drop was small, causing the internal potential E to rise to approximately 344V, without entering deep saturation deadlock.

[0070] After the fault is cleared ( ):

[0071] Control group: Because the power angle δ deviates from the steady-state value and cannot change abruptly, at the instant of voltage recovery, the power P experiences a significant positive overshoot, with the peak active power reaching approximately [value missing]. It oscillates for about 0.4 seconds before entering a steady state. At the same time, the decrease curve of the internal potential E shows a significant hysteresis.

[0072] Experimental group (this invention): Phase angle compensation action makes the work angle at... Instantaneously, it recovers directly from the transient value of 22.5° to the steady-state value δ. ss (Approximately 11°). Electromagnetic power satisfies... The active power oscillation amplitude is small, and it enters steady state earlier. At the same time, the trajectory of the decrease in internal potential E is smooth, without desaturation delay.

[0073] Operating Condition 2: The grid voltage temporarily drops to 0.2 pu.

[0074] like Figure 5 During the voltage dip, limited by physical constraints, the maximum theoretical power output of the inverter is:

[0075] ;

[0076] Strictly less than the active power instruction P ref According to the active swing equation:

[0077] ;

[0078] The right side of the equation is always positive. The system's work angle δ diverges monotonically. Before the fault was cleared, the temperature had reached approximately 120°, exceeding the stability limit. The internal potential E had reached deep saturation.

[0079] After the fault is cleared ( ):

[0080] Control group: Because the power angle δ has severely diverged and lost its synchronous stable equilibrium point, the system cannot recover based on its own mechanical damping after the fault is cleared. As shown by the black dashed line in the figure, the physical power angle δ continues to diverge and... A phase reversal occurs when the fault exceeds 180°. The active power drops to a negative value, and the inverter experiences complete loss of synchronization and grid disconnection. At the same time, the internal potential E remains in a saturated flat-top state for a long period after the fault is cleared (up to 2.9s), resulting in desaturation delay.

[0081] Experimental group (this invention): at the fault clearing voltage recovery t c Instantaneously, the strategy of this invention does not rely on the inherent damping of the system, and the steady-state point δ is obtained through algebraic operations. ss The integrator phase angle is directly reset. As shown by the solid red line in the figure, the system power angle δ is forcibly pulled back from approximately 120° and constrained to a stable equilibrium point of approximately 11°. The active power quickly stabilizes at the commanded value. Nearby, the internal potential E immediately responds and exhibits a smooth decreasing curve.

[0082] This invention also provides a phase angle compensation system for suppressing active power oscillations and desaturation delay during the transient recovery period, used to implement the method described above. The system includes:

[0083] The electromagnetic state extraction module is used to calculate the real-time physical power angle and voltage change rate dU / dt of the grid connection point voltage.

[0084] The dual sample-and-hold module is used to latch the steady-state power angle δ before the fault based on the event pulses emitted by the voltage change rate dU / dt. ss Instantaneous power angle δ at the end of the fault sr ;

[0085] The deviation compensation calculation module is used to calculate the instantaneous power angle δ. sr With the steady-state work angle δ ss The difference between them generates the transient power angle compensation amount Δδ;

[0086] The state phase angle synthesis and reset module is used to read the phase angle θ(t) of the phase angle integrator at the transient exit time. - c The transient power angle compensation amount Δδ is converted to radians to obtain the phase angle compensation amount from the phase angle θ(t). - c Remove from the initial phase angle θ inside the synthesized phase integrator.init And at the moment of fault clearing, the initial phase angle θ init The phase angle is directly injected into the phase angle integrator as the initial phase angle during the transient recovery period.

[0087] Compared with the prior art, the present invention has the following beneficial effects:

[0088] (1) This invention uses the voltage change rate dU / dt at the grid connection point as the criterion for entering and exiting transient states, and locks the steady-state power angle δ respectively. ss With instantaneous work angle δ sr This generates a transient power angle compensation amount Δδ. At the instant the fault is cleared, this compensation amount is transferred from the current phase angle θ(t) of the phase angle integrator. - c The integrator is injected after the power angle deviation is removed from the transient state, thus achieving instantaneous compensation for the cumulative power angle deviation during the transient period. This mechanism directly eliminates the electromechanical power imbalance from the physical source, effectively suppresses active power oscillation, and avoids the risk of loss of synchronization and grid disconnection under deep sag conditions.

[0089] (2) By instantaneously resetting the phase angle integrator, the present invention enables the system power angle to converge rapidly to the steady-state value, thereby causing the transient current to fall rapidly below the safety threshold, and thus prompting the dynamic virtual impedance to exit immediately after the fault is cleared. The voltage outer loop thus obtains the error feedback required for reverse regulation, eliminates the desaturation delay of the internal potential E, and significantly improves the dynamic response speed of the grid system to recover to steady state.

[0090] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery, characterized in that, For application in single-voltage-loop amplitude-controlled grid-type inverters containing dynamic virtual impedance, the following steps are included: Step 1: Real-time acquisition of grid-connected inverter grid-connected point voltage and output current; generation of system angular frequency ω and grid-connected point voltage command U through power outer loop calculation. ref The system angular frequency ω is then integratored to generate an internal phase angle θ. Step 2: Based on the grid connection point voltage command U ref The compensated voltage drop output by the dynamic virtual impedance module generates a d-axis modulated voltage U. d With q-axis modulation voltage U q This is used for subsequent PWM modulation to drive the inverter; Step 3: Calculate the rate of change of the voltage amplitude at the grid connection point, dU / dt, as the criterion for the system entering and exiting the transient state; when the system enters the transient state, trigger the first sample-and-hold logic to lock the steady-state power angle δ before entering the transient state. ss When the system is detected to exit the transient state, the second sample-and-hold logic is triggered to lock the instantaneous power angle δ before exiting the transient state. sr ; Step 4: Calculate the instantaneous work angle δ sr With the steady-state work angle δ ss The difference between them generates the transient power angle compensation amount Δδ; Step 5: Obtain the phase angle θ(t) of the phase integrator at the transient exit time. - c The transient power angle compensation amount Δδ is converted to radians to obtain the phase angle compensation amount from the phase angle θ(t). - c Remove from the initial phase angle θ inside the synthesized phase integrator. init ; Step 6: At the instant the fault clearing exits the transient state, set the initial phase angle θ... init As an initial condition, state compensation is performed in the phase integrator to update the internal phase angle θ.

2. The phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 1, characterized in that: Step 1: Actual active power P and active power command P ref The deviation is controlled by a swing equation controller and superimposed with the rated angular frequency to generate the system angular frequency ω and the phase angle θ; the deviation between the actual reactive power and the reactive power command is controlled by droop control and superimposed with the rated voltage command to generate the grid connection point voltage command U. ref .

3. The phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 1, characterized in that: In step two, the voltage amplitude U at the grid connection point pccmag With the grid connection point voltage command U ref The deviation, after proportional-integral adjustment, is subtracted by the d-axis virtual impedance voltage drop U. zd Generate the d-axis modulation voltage U d The q-axis modulation voltage U q Subtract the q-axis virtual impedance voltage drop U from the constant 0 zq generate.

4. The phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 3, characterized in that: The d-axis virtual impedance voltage drop U zd With q-axis virtual impedance voltage drop U zq The generation logic is as follows: During the voltage sag, when the current amplitude I mag Exceeding the safety threshold I th At that time, the dead-zone nonlinear element is activated, and multiplied by the gain K respectively. Rv With K Xv Generate virtual resistance R v With virtual reactance X v Combined with the d-axis and q-axis components of the output current I d I q The formula for calculating pressure drop is: ； ； By the d-axis virtual impedance voltage drop U zd With q-axis virtual impedance voltage drop U zq Compensation is applied to the single voltage loop to limit the inverter transient current. After phase angle compensation is performed in step six, the system current drops instantaneously, allowing the dynamic virtual impedance to exit quickly and relieving the desaturation delay of the potential E in the outer voltage loop.

5. The phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 1, characterized in that: In step three, the steady-state work angle δ ss and the instantaneous work angle δ sr The calculation logic is as follows: Collect the three-phase voltage of the power grid, use the internal phase angle of the inverter as the orientation reference, and calculate the d-axis voltage component U through abc / dq0 coordinate transformation. gd With q-axis voltage component U gq Subsequently, the physical work angle of the angle system is calculated using the nonlinear arctangent function. The calculation formula is as follows: 。 6. The phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 1, characterized in that: In step three, the triggering logic for entering and exiting the transient state specifically involves: setting a sag threshold and a recovery threshold; when the voltage change rate dU / dt is lower than the sag threshold, an edge detection mechanism combined with a monostable multivibrator outputs a fault drop pulse to activate the first sample-and-hold circuit and lock the steady-state power angle δ. ss When the voltage change rate dU / dt is higher than the recovery threshold, a fault clearing pulse is output through edge detection in conjunction with a monostable trigger, activating the second sample-and-hold circuit to lock the instantaneous power angle δ. sr .

7. The phase angle compensation method for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 1, characterized in that: In step five, the initial phase angle θ init The specific synthesis formula is as follows: ； In the formula, π / 180 is the conversion coefficient from angle to radian, used to unify the transient power angle compensation Δδ with the phase angle θ(t) of the phase angle integrator at the transient exit time. - c The dimensions between ) 8. A phase angle compensation system for suppressing active power oscillation and desaturation delay during transient recovery, characterized in that, The system for implementing the method according to any one of claims 1 to 7, the system comprising: The electromagnetic state extraction module is used to calculate the real-time physical power angle and voltage change rate dU / dt of the grid connection point voltage. The dual sample-and-hold module is used to latch the steady-state power angle δ before the fault based on the event pulses emitted by the voltage change rate dU / dt. ss Instantaneous power angle δ at the end of the fault sr ; The deviation compensation calculation module is used to calculate the instantaneous power angle δ. sr With the steady-state work angle δ ss The difference between them generates the transient power angle compensation amount Δδ; The state phase angle synthesis and reset module is used to read the phase angle θ(t) of the phase angle integrator at the transient exit time. - c The transient power angle compensation amount Δδ is converted to radians to obtain the phase angle compensation amount from the phase angle θ(t). - c Remove from the initial phase angle θ inside the synthesized phase integrator. init And at the moment of fault clearing, the initial phase angle θ init The phase angle is directly injected into the phase angle integrator as the initial phase angle during the transient recovery period.

9. A phase angle compensation system for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 8, characterized in that: The dual sample-and-hold module includes a first sample-and-hold circuit and a second sample-and-hold circuit; the first sample-and-hold circuit is activated by a fault drop pulse triggered when the voltage change rate dU / dt falls below a sag threshold, and is used to lock the steady-state power angle δ. ss The second sample-and-hold circuit is activated by a fault clearing pulse triggered when the voltage change rate dU / dt exceeds the recovery threshold, and is used to lock the instantaneous power angle δ. sr .

10. A phase angle compensation system for suppressing active power oscillation and desaturation delay during transient recovery period according to claim 8, characterized in that: The state phase angle synthesis and reset module includes a subtraction operation unit and a register overwrite unit; the subtraction operation unit is used to perform initial phase angle calculation. Algebraic operations; the register overwrite unit suspends the conventional integration and accumulation logic at the moment of fault clearing, and sets the initial phase angle θ init It is directly overwritten into the accumulator of the phase angle integrator.

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