A method and system for improving transient stability of an SG-VSG parallel system considering coupling of governor delay and damping

Abstract

The application discloses a kind of considering governor delay and damping coupling action SG-VSG parallel system transient stability optimization method, system, method includes, obtains equivalent input torque compensation item ΔT and output voltage compensation item ΔE, adjusts the output power angle and output voltage of virtual synchronous generator;Hysteresis comparator is used to judge whether to start fault controller, and amplify input signal;Wherein, when power angle difference is greater than set threshold value, fault controller starts, and the power angle difference signal after amplification will be input into proportional controller, respectively for adjusting equivalent input torque and output voltage, to realize the optimization control of system transient stability.The application can simultaneously adjust equivalent input torque and output voltage to realize adaptive control under different damping and delay conditions, improve the transient performance of system under different impedance configurations, improve fault ride-through capability, reduce the risk of instability induced by fault.

Description

Technical Field

[0001] This invention belongs to the field of power system control, and specifically relates to a method for improving the transient stability of SG-VSG parallel systems that considers the coupling effect of governor delay and damping. Background Technology

[0002] With the increasing integration of power electronic sources, the power grid is evolving from a system dominated by synchronous machines to a hybrid form where synchronous machines and grid-connected converters (GFMs) coexist. GFMs, represented by virtual synchronous generators (VSGs), actively shape bus voltage and frequency, providing new technical pathways for weak grid / islanded operation, inertia and damping support, and multi-source parallel operation. Thanks to continuous advancements in current-resistant devices, VSGs can operate continuously for more than 10 seconds under overcurrent conditions of 3 pu, maintaining voltage source characteristics even during large disturbance transients without switching to traditional current source control modes. This technological breakthrough has led to widespread attention being paid to the transient stability of VSG parallel systems.

[0003] Compared to single-unit or homogeneous VSG systems, SG-VSG heterogeneous parallel systems face more complex dynamic differences in transient stability. The SG (synchronous generator) and VSG differ significantly in physical structure, with large differences in dynamic performance between the mechanical shaft system and the virtual rotor. This makes the system more susceptible to the dynamic lag effect of the governor during faults and recovery. More seriously, the non-uniform damping effect introduced by the VSG is coupled with the mechanical delay on the SG side, further exacerbating stability risks during transient processes. Therefore, the transient instability faced by the SG-VSG parallel system stems from both the response lag caused by the governor delay and is closely related to the damping inconsistency between units. Furthermore, there is a clear coupling relationship between the delay effect and non-uniform damping: the delay weakens the equivalent damping support of the synchronous machine, and non-uniform damping may amplify this weakening effect under certain conditions, thus jointly inducing system power angle divergence or even instability.

[0004] However, existing typical grid-based control fault ride-through methods mostly focus on the transient stability of individual units. These methods may not be suitable for the parallel operation of SG and VSG in isolated microgrids. Although some studies have explored methods to improve the transient stability of multi-unit parallel systems, they generally ignore the impact of damping uniformity on system stability and do not fully consider the coupling effect caused by the damping differences between different units, thus limiting the application effect of control methods in complex heterogeneous systems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the transient stability of an SG-VSG parallel system that takes into account the delay and damping coupling effect of the speed governor. Based on the dynamic correction of the equivalent input torque and output voltage by the transient power angle difference, the transient stability performance of the system is significantly improved under the influence of delay and non-uniform damping coupling.

[0006] To address the above-mentioned technical problems, the specific technical solution proposed by this invention is as follows:

[0007] First, this invention proposes a method for improving the transient stability of an SG-VSG parallel system considering the coupling effect of governor delay and damping, comprising:

[0008] Obtain the equivalent input torque compensation term ΔT, the output voltage compensation term ΔE, and the output power angle δ of the VSG. vsg and internal potential reference value E vsg The equivalent input torque compensation term ΔT and output voltage compensation term ΔE are obtained through the power angle difference controllers of SG and VSG, respectively; the output power angle reference value δ of VSG is... vsg Based on the equivalent input torque compensation term ΔT and the active power reference value P 0,vsg Active electromagnetic power P e,vsg The rated angular frequency ω0 is obtained using a Pf control loop; the internal potential reference value E vsg Based on the output voltage compensation term ΔE and the reactive power reference value Q 0,vsg Reactive electromagnetic power Q e,vsg Voltage rating E 0,vsg Obtained using the QU control loop;

[0009] The hysteresis comparator is used to determine whether to activate the fault controller and amplify the input signal. When the power angle difference is greater than the set threshold, the fault controller is activated, and the amplified power angle difference signal is input to the proportional controller to adjust the equivalent input torque and output voltage, thereby achieving optimized control of the system's transient stability.

[0010] The expression for the hysteresis comparator includes:

[0011] ,

[0012] In the formula, v in and v out These are the input and output signals, V. OH It outputs a high level, V OL It outputs a low level; V T+ and V T- These are the upper and lower thresholds, respectively.

[0013] The Pf control loop includes,

[0014] Obtain the active power reference value P 0,vsg Active electromagnetic power P e,vsg Input the positive and negative input terminals of the first adder, respectively.

[0015] The output of the first adder is divided by the rated angular frequency ω0, and the value is input to the positive input of the second adder.

[0016] The equivalent input torque compensation term ΔT is connected to the negative input terminal of the second adder, and the output terminal of the damping element is connected to the negative input terminal of the second adder;

[0017] The output of the second adder passes through a feedback loop with an inertial damping system to obtain the change in angular frequency, which is then fed into the input of the damping loop.

[0018] The change in angular frequency and the rated angular frequency ω0 are connected to a third adder for addition, and then passed through a first integrator to obtain the power angle reference value δ. vsg .

[0019] The expression for the Pf control loop is as follows:

[0020] .

[0021]

[0022] The QU control component includes,

[0023] Obtain the reactive power reference value Q 0,vsg Reactive electromagnetic power Q e,vsg Input the positive and negative input terminals of the fourth adder respectively;

[0024] The output of the fourth adder is controlled by a reactive power control coefficient k. q,vsg The output voltage compensation term ΔE is input to the positive input terminal of the fifth adder.

[0025] The output of the fifth adder is connected to the voltage rating E. 0,vsg Connect to the sixth adder to perform addition operations and obtain the internal potential reference value E. vsg .

[0026] The expression for the QU control loop is as follows:

[0027] .

[0028] The acquisition of the equivalent input torque compensation term ΔT includes:

[0029] Obtain the output power angle δ of SGsg VSG output power angle reference value δ vsg The rated capacity ratio of SG and VSG to N, δ vsg With δ sg / N are input to the positive and negative input terminals of the seventh adder, respectively.

[0030] The output of the seventh adder is connected to the first multiplier and the first absolute value function controller, respectively. The absolute change of the power angle difference can be obtained through the first absolute value function controller.

[0031] The output of the first absolute value function controller is input to the first hysteresis comparator, which determines whether the controller should be started and amplifies the input signal based on a preset threshold.

[0032] The output of the first hysteresis comparator and the output of the seventh adder are both connected to the first multiplier, which is then processed by the transient torque correction coefficient k. d The equivalent input torque compensation term ΔT is obtained.

[0033] The acquisition of the output voltage compensation term ΔE includes:

[0034] Obtain the output power angle δ of SG sg VSG output power angle reference value δ vsg The rated capacity ratio of SG and VSG to N, δ vsg With δ sg / N are input to the positive and negative input terminals of the seventh adder, respectively.

[0035] The output of the seventh adder is connected to the first multiplier and the first absolute value function controller, respectively. The absolute change of the power angle difference can be obtained through the first absolute value function controller.

[0036] The output of the first absolute value function controller is input to the first hysteresis comparator, which determines whether the controller should be started and amplifies the input signal based on a preset threshold.

[0037] The output of the first hysteresis comparator and the output of the seventh adder are both connected to the first multiplier, which is then processed by the transient voltage correction coefficient k. q The output voltage compensation term ΔE is obtained.

[0038] The power loop expression for the transient stability improvement method of the SG-VSG parallel system considering the governor delay and damping coupling effect is as follows:

[0039] ,

[0040] Among them, P m,vsg The mechanical power determined for the speed controller; P 0,vsgand P e,vsg These are the active power reference value and the active electromagnetic power, respectively; Q 0,vsg and Q e,vsg These are the reactive power reference value and the reactive electromagnetic power, respectively; k p,vsg and k q,vsg These are the active power droop and reactive power droop coefficients, respectively; ω vsg For the actual angular frequency, ω0 and E 0,vsg These are the rated angular frequency and rated voltage, respectively, E vsg H is the internal potential reference voltage; vsg and D vsg These are the inertia and damping coefficients, respectively; k d k is the transient torque correction coefficient. v is the transient voltage correction factor, and N is the ratio of the rated capacity of SG to VSG.

[0041] Furthermore, the present invention also proposes an SG-VSG parallel system employing the above-mentioned transient stability optimization method, comprising: a synchronous generator power generation and regulation module, a virtual synchronous generator power generation and regulation module, and a common coupling and load module;

[0042] The synchronous generator power generation and regulation module includes a prime mover, a synchronous generator SG, and a line impedance connected in sequence. The active power regulation terminal of the synchronous generator SG is connected to a first active power-frequency droop control unit. The synchronous generator SG is connected to the AC bus via the line impedance.

[0043] The virtual synchronous generator power generation and regulation module includes a DC power supply, a three-phase full-bridge inverter, an L-type filter, a PWM modulator, an active power-frequency control loop, a reactive power-voltage control loop, and a voltage synthesis module. The DC power supply is connected to the AC bus via the three-phase full-bridge inverter, the L-type filter, and the line impedance. The PWM modulator is connected to the three-phase full-bridge inverter and is used to output drive pulses to the three-phase full-bridge inverter. The output terminals of the active power-frequency control loop and the reactive power-voltage control loop are respectively connected to the voltage synthesis module, and the output terminal of the voltage synthesis module is connected to the PWM modulator.

[0044] The active power-frequency control loop includes an integral element, an inertia-damping element, an active power droop coefficient, and a damping coefficient; the output of the integral element is connected to the voltage synthesis module, the input of the integral element is connected to the output of the inertia-damping element, and the input of the inertia-damping element is connected to the active power droop coefficient and the damping coefficient, respectively.

[0045] The reactive power-voltage control loop includes a QV controller, and the output terminal of the QV controller is connected to the voltage synthesis module.

[0046] The voltage synthesis module is connected to the PWM modulator;

[0047] The common coupling and load module includes an AC bus and a local load. The synchronous generator power generation and regulation module and the virtual synchronous generator power generation and regulation module are connected in parallel to the AC bus, and the local load is connected to the AC bus.

[0048] Furthermore, the system also includes a transient stability optimization control module, which includes an SG power angle detection unit, a VSG phase angle detection unit, a phase angle difference calculation unit, a hysteresis comparator, a signal amplification unit, a first proportional controller, and a second proportional controller.

[0049] The SG power angle detection unit is used to collect the power angle signal of the synchronous generator SG, and the VSG phase angle detection unit is used to collect the VSG phase angle signal output by the integrator. The output terminals of the SG power angle detection unit and the VSG phase angle detection unit are respectively connected to the input terminal of the phase angle difference calculation unit. The phase angle difference calculation unit is used to calculate the absolute value of the difference between the power angle signal and the VSG phase angle signal.

[0050] The output of the phase difference calculation unit is connected to the input of the hysteresis comparator, and the output of the hysteresis comparator is connected to the input of the signal amplification unit. The hysteresis comparator is used to compare the absolute value with a preset threshold to determine whether to start transient stability control. The signal amplification unit is used to amplify the signal output by the hysteresis comparator.

[0051] The output terminal of the signal amplification unit is connected to the input terminals of the first proportional controller and the second proportional controller, respectively; the output terminal of the first proportional controller is connected to the active power-frequency control loop and is used to adjust the input torque of the virtual synchronous generator VSG; the output terminal of the second proportional controller is connected to the QV controller and is used to adjust the output voltage of the virtual synchronous generator VSG.

[0052] Furthermore, the present invention also proposes an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method described in the present invention.

[0053] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0054] First, this invention collects the power angle information of the SG and inputs it into the VSG control system. Next, it calculates the phase angle difference between the SG and VSG, and inputs the absolute value of this difference into a hysteresis comparator. The hysteresis comparator is used to determine whether to activate the controller and amplifies the input signal. The use of the hysteresis comparator effectively avoids unnecessary control operations caused by small disturbances, and amplifies the input signal to solve the problem of small phase angle differences in the early stages of a fault, avoiding situations where the control signal is too weak and the control effect is not obvious. Subsequently, the amplified signal is input into the proportional controller to adjust the input torque and output voltage, thereby achieving optimized control of the system's transient stability. Attached Figure Description

[0055] Figure 1 This is the circuit topology diagram of the present invention.

[0056] Figure 2 This is the P-δ curve of the SG-VSG parallel system; where, (a)τ sg =τ vsg (b)τ sg ≠τ vsg .

[0057] Figure 3 This is the strategy diagram proposed in this invention.

[0058] Figure 4 The P-δ curves of the proposed method in this invention are compared with those of other control methods; where (a) is the traditional VSG (Tra-VSG), (b) is the voltage compensation type VSG (VC-VSG), (c) is the power angle suppression type VSG (AS-VSG), and (d) is the control method of this invention (TAD-VSG).

[0059] Figure 5 The figure shows the experimental results of short-circuit faults under different control strategies for line with resistive and inductive characteristics; where (a) is the difference of the equivalent power angle relative to the COI coordinate system, (b) is the active power, (c) is the active and reactive power, and (d) is the bus voltage and current.

[0060] Figure 6 The figure shows the experimental results of short-circuit faults under different control strategies when the line is inductive; where (a) is the difference of the equivalent power angle relative to the COI coordinate system, (b) is the active power, (c) is the active and reactive power, and (d) is the bus voltage and current.

[0061] Figure 7 This is a diagram showing the experimental results of short-circuit faults under the control parameter changes of the method proposed in this invention; where, (a) k v Change, (b) kd change. Detailed Implementation

[0062] The technical solution and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0063] Firstly, as Figure 1 The diagram shown is the topology and control structure of the SG-VSG parallel system to which this invention applies. SG and VSG are connected to a common load ZL via a transmission line. Xd′ is the transient reactance of SG, and Xf is the filter reactance of VSG. lsg and Z lvsg These are the line impedances for SG and VSG, respectively.

[0064] The mathematical models for the Pf ring and the QV ring are as follows:

[0065] ,

[0066] in,

[0067] ,

[0068] To unify the modeling forms of SG and VSG, a unified subscript notation is introduced, where the subscript k∈{SG, VSG} is used to distinguish the power source type. Unless otherwise specified, the formula with subscript k applies to both types of power sources. In the above formula: P m,k The mechanical power determined for the speed controller; P 0,k and P e,k These are the reference active power and the output active power, respectively; Q 0,k and Q e,k These are the reference reactive power and the output reactive power, respectively; k p,k and k q,k These are the active power droop and reactive power droop coefficients, respectively; ω k The actual angular frequency; ω0 and E0 are the angular frequency and voltage command value, respectively, E ref,k H is the internal potential reference voltage. k and D k These are the inertia and damping coefficients, respectively; T d This is the delay time of the speed controller.

[0069] To simplify the analysis, assume the capacity ratio of SG to VSG is 2:1, k p,sg / H sg = k p,vsg / H vsg Define τ k =D k / H k Therefore, the influence of damping uniformity on the transient power angle stability of the SG-VSG system is considered.

[0070] 1) When τ sg =τ vsg At this time, the system is a uniformly damped system. The swing equation of the system is similar in form to that of a single-machine infinite bus (SMIB) system, and the transient power angle stability of the system is mainly affected by the delay of the SG governor.

[0071] In an SG-VSG parallel system, the speed regulation system of the SG and the damping effect of the active power control of the VSG jointly adjust the equivalent input torque of the system, causing it to vary with the system's angular frequency. For example... Figure 2 As shown in (a), when the fault occurs, the system operating point moves from point a on curve I to point b on curve II. At this time, due to P m >P e The system's power angle accelerates. Under the action of the SG speed controller, P m The descent is slow, therefore the acceleration area S1 of the SG-VSG parallel system is larger than that of the VSG-VSG system (the shaded area represents the additional area). After the fault is cleared, the system operating point shifts from curve II to curve III, at which point P... m <P e The system reduces power angle, while the SG speed controller reduces the input power P. m The smaller increase in speed leads to a decrease in the deceleration area S2. Therefore, the governor delay increases the acceleration area and decreases the deceleration area, resulting in a significant decrease in the system's transient power angle stability.

[0072] 2) When τ sg ≠τ vsg At this point, the system is a non-uniformly damped system, and its swing equations differ from the conventional swing equations in SMIB. The transient power angle stability of the system depends on the combined effects of the governor delay and non-uniform damping.

[0073] Based on the sign and magnitude of the non-uniform damping energy, its impact on the system can be divided into three cases: If the non-uniform transient damping energy is positive, its effect is positively superimposed with that of the uniform transient damping energy. This will partially offset the negative impact of the governor delay, reduce S1 and increase S2, which is beneficial to transient stability. Figure 2 As shown in Case 1 of (b) in the diagram. If the non-uniform transient damping energy is negative, it cancels out the uniform transient damping energy, further weakening the transient stability (Case 2). In more severe cases, such as Case 3, the absolute value of the non-uniform damping energy is larger, greatly increasing the acceleration area S1 while compressing the deceleration area S2, making the transient stability face a more severe challenge.

[0074] To address this, this invention proposes a stability enhancement strategy based on transient power angle difference. During a fault, the SG-VSG parallel system experiences input / output power imbalance due to additional delay links and non-uniform damping effects, leading to system torque imbalance, which is a key factor in the transient power angle instability of the parallel system. Therefore, by dynamically adjusting the input torque, the input / output torque is balanced during the transient process, thereby improving the transient power angle stability of the system. Simultaneously, the output voltage of the VSG is dynamically corrected, utilizing the synergistic effect of torque compensation and voltage compensation to further extend the system's transient regulation capability and significantly improve the system's transient stability.

[0075] Figure 3 A block diagram of stability enhancement control is shown, where k d k is the transient torque correction coefficient. v Here, N is the transient voltage correction coefficient, and N is the rated capacity ratio of SG to VSG. To achieve this goal, the specific steps are as follows: First, collect the power angle information of SG and input it into the VSG control system; then, calculate the phase angle difference between SG and VSG, and input the absolute value of this difference into the hysteresis comparator. The hysteresis comparator is used to determine whether to start the controller and amplify the input signal. The use of the hysteresis comparator can effectively avoid unnecessary control operations caused by small disturbances, and at the same time, amplifying the input signal solves the problem of small phase angle differences in the early stages of a fault, avoiding situations where the control signal is too weak and the control effect is not obvious. Subsequently, the amplified signal is input into the proportional controller, which is used to adjust the input torque and output voltage, respectively, thereby achieving optimized control of the system's transient stability. The mathematical models of the Pf loop and QV loop in the strategy proposed in this invention are as follows:

[0076] .

[0077] With common δ sg >2δ vsg Taking the example of transient stability analysis, in this case, δ vsg Accelerating the equivalent work angle δ in the COI coordinate system coi Increase, SG relative to δ coi The work angle δ csg Decrease, where δ csg =δ sg -δ coi This effectively achieves the deceleration effect of the advanced engine. Figure 4Comparison results between the proposed method and traditional control (Tra-VSG), voltage-compensated VSG (VC-VSG), and power angle suppression VSG (AS-VSG) are presented. The P-δ curves show that VC-VSG enhances the support for bus voltage, improves the P-δ curve, and effectively reduces the acceleration area S1. AS-VSG effectively reduces the input torque of the parallel system, decreasing S1 and thus expanding the stable range of the power angle. The proposed method (TAD-VSG) combines the advantages of the above two methods, reducing S1 and increasing S2, achieving a better balance between input / output torque, and possessing a larger power angle stability margin.

[0078] Since the effect of non-uniform damping on transient stability is significantly condition-dependent, its effect may enhance or weaken system stability under different line impedance configurations. To verify the adaptability of the proposed TAD-VSG method in such parameter-sensitive scenarios, this paper compares it with the three control schemes mentioned above. The experimental results are as follows: Figure 5 and Figure 6 As shown, δ is given respectively. ck P e,k Q e,k and bus voltage U m With current I m Dynamic response.

[0079] Under inductive circuit conditions (such as) Figure 5 As shown), δ under Tra-VSG and VC-VSG operating conditions after fault clearance ck and P e,k Eventual instability occurred, with the VC-VSG exhibiting a relatively slow divergence rate, indicating that it improved the transient power angle response to some extent. In contrast, both the AS-VSG and the proposed TAD-VSG could converge the power angle and active power, maintaining system transient stability. Regarding reactive power and voltage support, both VC-VSG and TAD-VSG significantly improved Q... e,k Bus voltage RMS value U m The effective value is significantly higher than that of Tra-VSG and AS-VSG operating conditions. It is worth noting that TAD-VSG does not simply "add reactive power," but rather achieves a redistribution of active and reactive currents through the coordination of the power loop: while increasing the reactive current to support the bus voltage, it appropriately reduces the active current, resulting in an effective current value I... m Not only did it not exceed VC-VSG, but it actually decreased, improving the stability of transient voltage and transient power angle without triggering current over-limit.

[0080] When the line is inductive (e.g.) Figure 6As shown in the figure, the superposition of non-uniform damping and line impedance characteristics has significantly different effects on different control strategies. In this case, VC-VSG and AS-VSG, compared to Tra-VSG, not only fail to improve transient stability but also exacerbate power angle divergence: under the action of NUD, they suppress the acceleration catch-up of lagging units, causing the phase angle difference between SG and VSG to continue to widen, ultimately leading to faster system instability. In contrast, the proposed TAD-VSG can still maintain good transient stability performance under inductive lines: by using power angle difference feedback to accelerate power angle convergence and actively reduce the phase angle difference with SG; simultaneously, it reduces the output voltage, making U... m with I m All strategies maintain the lowest level among the four strategies, reducing reactive current while releasing fault current margin for active current, thereby prioritizing power angle stability and avoiding overcurrent.

[0081] In summary, under both resistive-inductive and inductive line configurations, the TAD-VSG method proposed in this invention can achieve the redistribution of fault current through the coordinated adjustment of active and reactive power channels, thereby improving the transient power angle stability of the SG-VSG parallel system while satisfying current limiting constraints. Compared with Tra-VSG, VC-VSG, and AS-VSG, the proposed method exhibits stronger adaptability and superior stability enhancement under different damping and line parameter conditions.

[0082] To examine the parameter sensitivity and adjustability of the proposed TAD-VSG method, Figure 7 The transient torque correction coefficient k is given. d and transient voltage correction factor k v Experimental results under varying conditions. Figure 7 In (a), while keeping k v Changing k under the condition that it remains unchanged d When k d = 1 and k d When k = 2, the system power angle still diverges after the fault is cleared, only changing with k d The increase of k significantly slows down the divergence rate; d When the gain is increased to 3, the power angle gradually converges, and the system returns to stable operation. This result indicates that increasing the torque correction gain can significantly enhance the TAD-VSG's ability to suppress transient power angles. Figure 7 In (b), as k vWhile the increase in voltage remains, the system remains unstable after the fault is cleared. However, the bus voltage level gradually decreases, the power angle divergence rate slows down, and the active current regulation margin increases accordingly. This indicates that relying solely on voltage correction is insufficient to fundamentally guarantee transient power angle stability under this operating condition. However, by reducing the voltage and releasing the fault current margin, instability can be delayed and the power angle stability margin improved to some extent.

[0083] In summary, the experimental results show that the torque channel k d It is crucial to ensure the stability of the system's transient power angle, and the voltage channel k v It is mainly used for redistributing active / reactive current and improving voltage and current margins. When the two work together, TAD-VSG can ensure transient power angle stability while taking into account current limit constraints and voltage support, achieving better overall transient performance.

[0084] Example 2: This example proposes an SG-VSG parallel system using the above-mentioned transient stability optimization method, including: a synchronous generator power generation and regulation module, a virtual synchronous generator power generation and regulation module, and a common coupling and load module;

[0085] The synchronous generator power generation and regulation module includes a prime mover, a synchronous generator SG, and a line impedance connected in sequence. The active power regulation terminal of the synchronous generator SG is connected to a first active power-frequency droop control unit. The synchronous generator SG is connected to the AC bus via the line impedance.

[0086] The virtual synchronous generator power generation and regulation module includes a DC power supply, a three-phase full-bridge inverter, an L-type filter, a PWM modulator, an active power-frequency control loop, a reactive power-voltage control loop, and a voltage synthesis module. The DC power supply is connected to the AC bus via the three-phase full-bridge inverter, the L-type filter, and the line impedance. The PWM modulator is connected to the three-phase full-bridge inverter and is used to output drive pulses to the three-phase full-bridge inverter. The output terminals of the active power-frequency control loop and the reactive power-voltage control loop are respectively connected to the voltage synthesis module, and the output terminal of the voltage synthesis module is connected to the PWM modulator.

[0087] The active power-frequency control loop includes an integral element, an inertia-damping element, an active power droop coefficient, and a damping coefficient; the output of the integral element is connected to the voltage synthesis module, the input of the integral element is connected to the output of the inertia-damping element, and the input of the inertia-damping element is connected to the active power droop coefficient and the damping coefficient, respectively.

[0088] The reactive power-voltage control loop includes a QV controller, and the output terminal of the QV controller is connected to the voltage synthesis module.

[0089] The voltage synthesis module is connected to the PWM modulator;

[0090] The common coupling and load module includes an AC bus and a local load. The synchronous generator power generation and regulation module and the virtual synchronous generator power generation and regulation module are connected in parallel to the AC bus, and the local load is connected to the AC bus.

[0091] Furthermore, the system also includes a transient stability optimization control module, which includes an SG power angle detection unit, a VSG phase angle detection unit, a phase angle difference calculation unit, a hysteresis comparator, a signal amplification unit, a first proportional controller, and a second proportional controller.

[0092] The SG power angle detection unit is used to collect the power angle signal of the synchronous generator SG, and the VSG phase angle detection unit is used to collect the VSG phase angle signal output by the integrator. The output terminals of the SG power angle detection unit and the VSG phase angle detection unit are respectively connected to the input terminal of the phase angle difference calculation unit. The phase angle difference calculation unit is used to calculate the absolute value of the difference between the power angle signal and the VSG phase angle signal.

[0093] The output of the phase difference calculation unit is connected to the input of the hysteresis comparator, and the output of the hysteresis comparator is connected to the input of the signal amplification unit. The hysteresis comparator is used to compare the absolute value with a preset threshold to determine whether to start transient stability control. The signal amplification unit is used to amplify the signal output by the hysteresis comparator.

[0094] The output terminal of the signal amplification unit is connected to the input terminals of the first proportional controller and the second proportional controller, respectively; the output terminal of the first proportional controller is connected to the active power-frequency control loop and is used to adjust the input torque of the virtual synchronous generator VSG; the output terminal of the second proportional controller is connected to the QV controller and is used to adjust the output voltage of the virtual synchronous generator VSG.

[0095] Example 3: This example proposes an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method described in this invention.

[0096] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0097] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0098] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0099] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0100] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0101] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A transient stability optimization method for an SG-VSG parallel system considering the coupling effect of governor delay and damping, characterized in that, include: Collect the power angle information of the synchronous generator SG and input it into the VSG control system; this includes obtaining the equivalent input torque compensation term ΔT, the output voltage compensation term ΔE, and the VSG output power angle reference value δ. vsg and internal potential reference value E vsg ; The phase angle difference between the synchronous generator SG and the virtual synchronous generator VSG is calculated, and the absolute value of the difference is input into the hysteresis comparator. The hysteresis comparator is used to determine whether to start the fault controller and amplify the input signal. When the phase angle difference is greater than the set threshold, the fault controller is started, and the amplified phase angle difference signal is input into the proportional controller to adjust the equivalent input torque and output voltage, thereby achieving optimized control of the system's transient stability.

2. The method according to claim 1, characterized in that, The equivalent input torque compensation term ΔT and the output voltage compensation term ΔE are obtained respectively through the power angle difference controllers of SG and VSG; VSG output power angle reference value δ vsg Based on the equivalent input torque compensation term ΔT and the active power reference value P 0,vsg Active electromagnetic power P e,vsg The rated angular frequency ω0 is obtained using a Pf control loop; Internal potential reference value E vsg Based on the output voltage compensation term ΔE and the reactive power reference value Q 0,vsg Reactive electromagnetic power Q e,vsg Voltage rating E 0,vsg It is obtained by using the QU control loop.

3. The method as described in claim 2, characterized in that: The Pf control loop includes... Obtain the active power reference value P 0,vsg Active electromagnetic power P e,vsg Input the positive and negative input terminals of the first adder, respectively. The output of the first adder is divided by the rated angular frequency ω0, and the value is input to the positive input of the second adder. The equivalent input torque compensation term ΔT is connected to the negative input terminal of the second adder, and the output terminal of the damping element is connected to the negative input terminal of the second adder; The output of the second adder passes through a feedback loop with an inertial damping system to obtain the change in angular frequency, which is then fed into the input of the damping loop. The change in angular frequency and the rated angular frequency ω0 are connected to a third adder for addition, and then passed through a first integrator to obtain the power angle reference value δ. vsg .

4. The method as described in claim 3, characterized in that: The QU control mechanism includes: Obtain the reactive power reference value Q 0,vsg Reactive electromagnetic power Q e,vsg Input the positive and negative input terminals of the fourth adder respectively; The output of the fourth adder is controlled by a reactive power control coefficient k. q,vsg The output voltage compensation term ΔE is input to the positive input terminal of the fifth adder. The output of the fifth adder is connected to the voltage rating E. 0,vsg Connect to the sixth adder to perform addition operations and obtain the internal potential reference value E. vsg .

5. The method as described in claim 4, characterized in that, The process of obtaining the equivalent input torque compensation term ΔT includes: Obtain the output power angle δ of SG sg VSG output power angle reference value δ vsg The rated capacity ratio of SG and VSG to N will be δ vsg With δ sg / N are input to the positive and negative input terminals of the seventh adder, respectively. The output of the seventh adder is connected to the first multiplier and the first absolute value function controller, respectively. The absolute change of the power angle difference can be obtained through the first absolute value function controller. The output of the first absolute value function controller is input to the first hysteresis comparator, which determines whether the controller should be started and amplifies the input signal based on a preset threshold. The output of the first hysteresis comparator and the output of the seventh adder are both connected to the first multiplier, which is then processed by the transient torque correction coefficient k. d The equivalent input torque compensation term ΔT is obtained.

6. The method as described in claim 1, characterized in that, The acquisition of the output voltage compensation term ΔE includes: Obtain the output power angle δ of SG sg VSG output power angle reference value δ vsg The rated capacity ratio of SG and VSG to N will be δ vsg With δ sg / N are input to the positive and negative input terminals of the seventh adder, respectively. The output of the seventh adder is connected to the first multiplier and the first absolute value function controller, respectively. The absolute change of the power angle difference can be obtained through the first absolute value function controller. The output of the first absolute value function controller is input to the first hysteresis comparator, which determines whether the controller should be started and amplifies the input signal based on a preset threshold. The output of the first hysteresis comparator and the output of the seventh adder are both connected to the first multiplier, which is then processed by the transient voltage correction coefficient k. q The output voltage compensation term ΔE is obtained.

7. The method as described in claim 1, characterized in that, The power loop expression for the transient stability improvement method of the SG-VSG parallel system considering the coupling effect of governor delay and damping is as follows: ， Among them, P m,vsg The mechanical power determined for the speed controller; P 0,vsg and P e,vsg These are the active power reference value and the active electromagnetic power, respectively; Q 0,vsg and Q e,vsg These are the reactive power reference value and the reactive electromagnetic power, respectively; k p,vsg and k q,vsg These are the active power droop and reactive power droop coefficients, respectively; ω vsg For the actual angular frequency, ω0 and E 0,vsg These are the rated angular frequency and rated voltage, respectively, E vsg H is the internal potential reference voltage; vsg and D vsg These are the inertia and damping coefficients, respectively; k d k is the transient torque correction coefficient. v is the transient voltage correction factor, and N is the ratio of the rated capacity of SG to VSG.

8. An SG-VSG parallel system employing the transient stability optimization method according to any one of claims 1 to 7, characterized in that, include: Synchronous generator power generation and regulation module, virtual synchronous generator power generation and regulation module, and common coupling and load module; The synchronous generator power generation and regulation module includes a prime mover, a synchronous generator SG, and a line impedance connected in sequence. The active power regulation terminal of the synchronous generator SG is connected to a first active power-frequency droop control unit. The synchronous generator SG is connected to the AC bus via the line impedance. The virtual synchronous generator power generation and regulation module includes a DC power supply, a three-phase full-bridge inverter, an L-type filter, a PWM modulator, an active power-frequency control loop, a reactive power-voltage control loop, and a voltage synthesis module; the DC power supply is connected to the AC bus via the three-phase full-bridge inverter, the L-type filter, and the line impedance. The PWM modulator is connected to the three-phase full-bridge inverter and is used to output drive pulses to the three-phase full-bridge inverter. The output terminals of the active power-frequency control loop and the reactive power-voltage control loop are respectively connected to the voltage synthesis module, and the output terminal of the voltage synthesis module is connected to the PWM modulator. The active power-frequency control loop includes an integral element, an inertia-damping element, an active power droop coefficient, and a damping coefficient; the output of the integral element is connected to the voltage synthesis module, the input of the integral element is connected to the output of the inertia-damping element, and the input of the inertia-damping element is connected to the active power droop coefficient and the damping coefficient, respectively. The reactive power-voltage control loop includes a QV controller, and the output terminal of the QV controller is connected to the voltage synthesis module. The voltage synthesis module is connected to the PWM modulator; The common coupling and load module includes an AC bus and a local load. The synchronous generator power generation and regulation module and the virtual synchronous generator power generation and regulation module are connected in parallel to the AC bus, and the local load is connected to the AC bus.

9. The system according to claim 8, characterized in that: The system also includes a transient stability optimization control module, which includes an SG power angle detection unit, a VSG phase angle detection unit, a phase angle difference calculation unit, a hysteresis comparator, a signal amplification unit, a first proportional controller, and a second proportional controller. The SG power angle detection unit is used to collect the power angle signal of the synchronous generator SG, and the VSG phase angle detection unit is used to collect the VSG phase angle signal output by the integrator. The output terminals of the SG power angle detection unit and the VSG phase angle detection unit are respectively connected to the input terminal of the phase angle difference calculation unit. The phase angle difference calculation unit is used to calculate the absolute value of the difference between the power angle signal and the VSG phase angle signal. The output of the phase difference calculation unit is connected to the input of the hysteresis comparator, and the output of the hysteresis comparator is connected to the input of the signal amplification unit. The hysteresis comparator is used to compare the absolute value with a preset threshold to determine whether to start transient stability control. The signal amplification unit is used to amplify the signal output by the hysteresis comparator. The output terminal of the signal amplification unit is connected to the input terminals of the first proportional controller and the second proportional controller, respectively; the output terminal of the first proportional controller is connected to the active power-frequency control loop and is used to adjust the input torque of the virtual synchronous generator VSG; the output terminal of the second proportional controller is connected to the QV controller and is used to adjust the output voltage of the virtual synchronous generator VSG.

10. An electronic device, comprising: At least one processor; And a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, characterized in that the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1-7.

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