Optimization control method for dynamic and static characteristics of network-forming converter based on inertia damping parameters

Abstract

An inertia damping parameter-based dynamic and static characteristic optimization control method for a network-constructed converter is used in a network-constructed control grid-connected system to optimize the system control performance and improve the system anti-disturbance capability, and adopts an inertia damping parameter-based dynamic and static characteristic collaborative optimization control strategy on the basis of network-constructed control so as to improve the system anti-disturbance capability. A differential link is added into a forward channel, and the speed of recovering stability is increased under the condition that system output is not affected; and an improved damping link is incorporated into the feedback channel to improve the damping capability and reduce the steady-state error, so that the dynamic and static characteristics of the output power and frequency of the system after the optimal control strategy is adopted are more stable.

Description

Technical Field

[0001] This invention relates to the technical field of grid-type converters, and more specifically to the technical field of optimized control methods for grid-type converters. Background Technology

[0002] Virtual synchronous generator (VSG) control can simulate the primary frequency regulation, damping, inertia support, and voltage regulation functions of a synchronous generator, and is a typical grid-type control strategy that can actively support power systems. The virtual inertia J and damping coefficient D are two control parameters that primarily affect the stability and response accuracy of the grid-type converter. However, unreasonable settings of virtual inertia J and damping coefficient D can lead to a decrease in control accuracy during the dynamic response of the VSG. Oscillation suppression can be achieved by adjusting virtual inertia J and damping coefficient D, but increasing D will lead to an increase in the steady-state deviation of primary frequency regulation, creating a contradiction between stability and steady-state accuracy, which is difficult to solve by directly designing control parameters. Using a variable virtual inertia J strategy in the VSG can effectively suppress frequency drop, but when the VSG uses an excessively large virtual inertia J strategy, it will lead to a large overshoot. Grid-type converters face the problem of balancing dynamic response capability and static control accuracy, making it impossible to simultaneously guarantee fast response and high-precision control. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned shortcomings by providing a method for optimizing the dynamic and static characteristics of a grid-type converter based on inertia and damping parameters. By analyzing the influence of inertia and damping parameters on the control of the grid-type converter, improved inertia and damping control is introduced. This involves increasing transient damping and improving the inertia channel to adjust dynamic and static characteristics. Simultaneously, the transfer function of the system after introduction is analyzed using the root locus method and Bode plot analysis to determine the range of values ​​for relevant control parameters. A differential element is added to the forward channel to accelerate the recovery to stability without affecting the system output; an improved damping element is incorporated into the feedback channel to enhance damping capability and reduce steady-state error.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] A method for optimizing the dynamic and static characteristics of a grid-type converter based on inertia damping parameters is proposed, and the steps are as follows:

[0006] 1) Basic principle analysis of grid-type converters

[0007] The grid-connected circuit of a grid-connected converter includes a main circuit and a control circuit. The control circuit contains sampling, power calculation, virtual synchronization control algorithm, and voltage-current loop modules, where U dcIndicates the DC bus voltage; ia, ib, and i c This refers to the output current of a grid-connected converter, i.e., the current output by the converter to the power grid; u a u b and u c L is the phase voltage at the output of the grid-connected converter. f C f and R f These are the filter inductor, filter capacitor, and damping resistor for the VSG; L g and R g These are the equivalent line inductance and resistance of the power grid, respectively.

[0008] The main circuit uses a DC voltage source U as input, which is filtered by an LC filter circuit to eliminate high-frequency harmonics, resulting in a smooth three-phase capacitor voltage e. cabc Then through the line impedance (L) g +R g The voltage u that can be connected to the AC power grid is obtained. abc To achieve grid connection, the control loop collects grid voltage, current, and capacitor voltage. After coordinate transformation, virtual synchronous control adjusts the frequency and phase through active power deviation and the amplitude through voltage deviation to generate a reference signal. This reference signal is then output as a modulated wave via a dual-loop PI tracking mechanism to drive the inverter for autonomous frequency and voltage regulation.

[0009] The main purpose of the active power loop control is to simulate the primary frequency regulation characteristics of a traditional synchronous generator, maintain grid frequency stability, and rationally allocate active power. Its input is the active power reference command P. ref The output power is the virtual mechanical power P. m Its control expression is:

[0010] P m =P ref -K f (ω-ω0) (1)

[0011] In the formula: K f ω is the active power droop factor; ω0 is the rated angular frequency; ω is the actual output angular frequency of the grid-type converter.

[0012] The inertia-damped control element is used to simulate the rotor motion equation of a synchronous generator and calculate the active power P. m The mechanical power used in the oscillation equation is shown in equation (2):

[0013]

[0014] In the formula: J is the virtual inertia, D is the damping coefficient, and P... m 、P e and P dThese represent the mechanical, electromagnetic, and damping power of the synchronous generator, respectively.

[0015] The virtual inertia J is directly related to the rate of frequency change and is set according to the rate of frequency change.

[0016] 2) Power Response Principle Analysis of Grid-Type Converters

[0017] 2.1) Static power characteristics of grid-type converters

[0018] The output power P of the grid-type converter can be derived from the active power loop control structure. e The calculation expression is:

[0019]

[0020] Where: G Pref Active power reference command P ref Output active power P e Transfer function between components; G Δω The rated angular frequency ω0 and the actual output angular frequency ω are related to the output active power P. e Transfer function between components; K P This is the proportional gain coefficient.

[0021] According to the final value theorem of the Laplace transform, since t is infinite in the time domain and s tends to 0 in the complex domain, the limit value in equation (3) can be calculated to obtain the steady-state response:

[0022]

[0023] Substituting the calculated steady-state response into equation (3), we obtain the steady-state output power P. e :

[0024]

[0025] From equation (5), we can see that the active power P e Subject to active power reference command P ref and power deviation (K) f Considering the influence of +D)(ω0-ω), and taking into account the power deviation, when the system frequency variation is within a certain range, the active power P can be considered as... e The error is mainly due to K f And D influences, therefore when K f When the value is constant, the damping coefficient D is the main factor causing the steady-state error of the system.

[0026] 2.2) Dynamic power characteristics of grid-type converters

[0027] The influence of inertia damping control on the dynamic characteristics of active power in a network-type control system can be analyzed through the closed-loop small-signal transfer function. From equation (3), the transfer function of the network-type control can be obtained as follows:

[0028]

[0029] As shown in equation (6), the active power closed-loop small-signal transfer function is a typical second-order system with two closed-loop poles. When designing the control parameters of a grid-type converter, the positions of the closed-loop poles can be adjusted by assigning different values ​​to J and D, thereby achieving adjustment of the dynamic characteristics of the output active power.

[0030] Based on the specific circumstances of the aforementioned influences, we set J = 0.2, 1, 2.5, and D = 0 to 2K. f The root locus distribution of the system is obtained.

[0031] Root locus distribution analysis shows that as D increases, the imaginary part of the complex poles gradually decreases while the absolute value of the real part increases. When J increases, the absolute value of the real part of the complex poles decreases, and the imaginary part decreases simultaneously. When J is large, the poles become less sensitive to changes in D, making the system more prone to instability. When D = K... f At this point, the pole loci merge and separate on the real axis, forming two real root branches. Choose J = 2.5 and D = K. f The system can achieve stable operation and achieve a critical damping response with no overshoot and relatively fast response. Compared with other parameter combinations, this parameter corresponds to the best overall performance in terms of response speed, stability and robustness.

[0032] 3) Control method based on dynamic and static coordination

[0033] 3.1) Control principle based on dynamic and static coordinated control method

[0034] The transfer functions of the inertia and damping channels of the network control system are shown in equation (7).

[0035]

[0036] Based on the dynamic-static coordinated control method, control strategies are applied to the forward and feedback channels of the control loop, resulting in the inertia and damping control equations as shown in equation (8).

[0037]

[0038] A differential element is added to the forward path to accelerate the recovery to stability without affecting the system output; an improved damping element is incorporated into the feedback path to enhance damping capability and reduce steady-state error.

[0039] 3.2) Control parameter design based on dynamic-static coordinated control method

[0040] Based on the above analysis and combined with formula (8), the following dynamic and static coordinated network control method is derived:

[0041] The active power deviation first passes through the forward channel, where the differential inertia stage instantaneously amplifies the high-frequency components, accelerating the initial angular frequency response. The integrator then generates the phase. Simultaneously, the angular frequency is fed into the feedback channel, where the damping stage after low-pass filtering generates additional torque, suppressing oscillations and reducing steady-state error. Finally, the angular frequency ω and phase angle δ are output.

[0042] The transfer function G(s) of the active power loop in the dynamic-static coordinated network control method is:

[0043]

[0044] In the formula,

[0045]

[0046] In the formula, T1 is the time constant of the improved inertia channel; T2 is the time constant of the improved damping channel.

[0047] Based on the improved system transfer function, equation (9) shows that T2 = 1 and K = 0.5 are selected as the main parameters of this control method. The dynamic and static coordinated control method can give full play to its advantages and make the system operation effect of the grid converter the best.

[0048] The beneficial effects that can be achieved by adopting the above-mentioned technical solution in this invention are:

[0049] This invention can be used in grid-connected control systems to optimize system control performance and improve system disturbance rejection capability. Based on grid-connected control, it employs a dynamic and static characteristic co-optimization control strategy based on inertia damping parameters. A differential element is added to the forward channel to accelerate the recovery to stability without affecting the system output; an improved damping element is incorporated into the feedback channel to enhance damping capability and reduce steady-state error, resulting in more stable dynamic and static characteristics of the system output power and frequency after adopting the optimized control strategy. Attached Figure Description

[0050] Figure 1 This is a circuit topology and control principle diagram of the grid converter in this invention;

[0051] Figure 2 This is a root locus distribution diagram of the active small signal in the network-type control of this invention;

[0052] Figure 3 This is a Bode plot comparing different control methods in this invention.

[0053] Figure 4 This is a block diagram of the dynamic and static coordinated network control method in this invention;

[0054] Figure 5 This is the system pole-zero plot for parameter variations in this invention;

[0055] Figure 6 This is the Bode plot of the system when the parameters change in this invention;

[0056] Figure 7 This is a diagram showing the output waveform of the system when T2 changes in this invention;

[0057] Figure 8 This is a diagram showing the output waveform of the system when D changes in this invention.

[0058] Figure 9 This is a diagram showing the output waveform of the system when K changes in this invention.

[0059] Figure 10 The output waveforms of the system before and after the introduction of the improved control strategy in this invention are shown. Detailed Implementation

[0060] A method for optimizing the dynamic and static characteristics of a grid-type converter based on inertia damping parameters is proposed, and the steps are as follows:

[0061] 1) Basic principle analysis of grid-type converters

[0062] Grid-connected converter circuit topology as follows Figure 1 As shown, the entire control loop includes a main circuit and a control circuit. The control circuit includes sampling, power calculation, a virtual synchronization control algorithm, and a voltage-current loop module, where U dc Indicates the DC bus voltage; ia, ib, and i c This refers to the output current of a grid-connected converter, i.e., the current output by the converter to the power grid; u a u b and u c L is the phase voltage at the output of the grid-connected converter. f C f and R f These are the filter inductor, filter capacitor, and damping resistor for the VSG; L g and R g These are the equivalent line inductance and resistance of the power grid, respectively.

[0063] The main circuit uses a DC voltage source U as input, which is filtered by an LC filter circuit to eliminate high-frequency harmonics, resulting in a smooth three-phase capacitor voltage e. cabc Then through the line impedance (L) g +R g The voltage u that can be connected to the AC power grid is obtained. abcTo achieve grid connection, the control loop collects grid voltage, current, and capacitor voltage. After coordinate transformation, virtual synchronous control adjusts the frequency and phase through active power deviation and the amplitude through voltage deviation to generate a reference signal. This reference signal is then output as a modulated wave via a dual-loop PI tracking mechanism to drive the inverter for autonomous frequency and voltage regulation.

[0064] Figure 1 The main purpose of the active power loop control is to simulate the primary frequency regulation characteristics of a traditional synchronous generator, maintain grid frequency stability, and rationally allocate active power. Its input is the active power reference command P. ref The output power is the virtual mechanical power P. m Its control expression is:

[0065] P m =P ref -K f (ω-ω0) (2)

[0066] In the formula: K f ω is the active power droop factor; ω0 is the rated angular frequency; ω is the actual output angular frequency of the grid-type converter.

[0067] The inertia-damped control element is used to simulate the rotor motion equation of a synchronous generator and calculate the active power P. m The mechanical power used in the oscillation equation is shown in equation (2):

[0068]

[0069] In the formula: J is the virtual inertia, D is the damping coefficient, and P... m 、P e and P d These represent the mechanical, electromagnetic, and damping power of the synchronous generator, respectively.

[0070] The virtual inertia J is directly related to the rate of frequency change and is set based on the rate of frequency change. Assuming this value is pre-set, it does not need to be changed. The system will then be analyzed directly under this pre-set environment to verify the system output before and after the introduction of the control method.

[0071] 2) Power Response Principle Analysis of Grid-Type Converters

[0072] 2.1) Static power characteristics of grid-type converters

[0073] The active power loop control block diagram of a grid converter is as follows: Figure 1 The active power loop section is shown in the diagram.

[0074] The output power P of the grid-type converter can be derived from the active power loop control structure. e The calculation expression is:

[0075]

[0076] Where: G Pref Active power reference command P ref Output active power P e Transfer function between components; G Δω The rated angular frequency ω0 and the actual output angular frequency ω are related to the output active power P. e Transfer function between components; K P This is the proportional gain coefficient.

[0077] According to the final value theorem of the Laplace transform, since t is infinite in the time domain and s tends to 0 in the complex domain, the limit value in equation (3) can be calculated to obtain the steady-state response:

[0078]

[0079] Substituting the calculated steady-state response into equation (3), we obtain the steady-state output power P. e :

[0080]

[0081] From equation (5), we can see that the active power P e Subject to active power reference command P ref and power deviation (K) f Considering the influence of +D)(ω0-ω), and taking into account the power deviation, when the system frequency variation is within a certain range, the active power P can be considered as... e The error is mainly due to K f And D influences, therefore when K f When the value is constant, the damping coefficient D is the main factor causing the steady-state error of the system.

[0082] 2.2) Dynamic power characteristics of grid-type converters

[0083] The influence of inertia damping control on the dynamic characteristics of active power in a network-type control system can be analyzed through the closed-loop small-signal transfer function. From equation (3), the transfer function of the network-type control can be obtained as follows:

[0084]

[0085] As shown in equation (6), the active power closed-loop small-signal transfer function is a typical second-order system with two closed-loop poles. When designing the control parameters of a grid-type converter, the positions of the closed-loop poles can be adjusted by assigning different values ​​to J and D, thereby achieving adjustment of the dynamic characteristics of the output active power.

[0086] Based on the specific circumstances of the aforementioned influences, we set J = 0.2, 1, 2.5, and D = 0 to 2K.f The root locus distribution diagram of the system is obtained as follows: Figure 2 As shown,

[0087] Analysis of the root locus distribution shows that as D increases, the imaginary part of the complex poles gradually decreases, while the absolute value of the real part increases. When J increases, the absolute value of the real part of the complex poles decreases, and the imaginary part decreases simultaneously. When J is large, the poles become less sensitive to changes in D, making the system more prone to instability. When D = K... f At this point, the pole loci merge and separate on the real axis, forming two real root branches. Choose J = 2.5 and D = K. f The system can achieve stable operation and achieve a critical damping response with no overshoot and relatively fast response. Compared with other parameter combinations, this parameter corresponds to the best overall performance in terms of response speed, stability and robustness.

[0088] 3) Control method based on dynamic and static coordination

[0089] 3.1) Control principle based on dynamic and static coordinated control method

[0090] The transfer functions of the inertia and damping channels in the network control are shown in Equation (7). Increasing J can suppress low-frequency disturbances and improve steady-state accuracy, but it will prolong the dynamic response time; while increasing D can accelerate transient recovery, it will worsen the phase margin in the high-frequency band and increase the steady-state error.

[0091]

[0092] Based on the dynamic-static coordinated control method, control strategies are applied to the forward and feedback channels of the control loop, resulting in the inertia and damping control equations as shown in equation (8).

[0093]

[0094] A differential element is added to the forward path to accelerate the recovery to stability without affecting the system output; an improved damping element is incorporated into the feedback path to enhance damping capability and reduce steady-state error.

[0095] Figure 3 The Bode plots of the system before and after the introduction of the control method are shown, with the dark area representing the key comparison region. The main focus is on observing the synergistic optimization effect of different control methods between low-frequency steady-state accuracy and high-frequency dynamic disturbance rejection. The unmodified network control exhibits a high-gain, low-phase-margin contradiction in the low-frequency range, and resonance peaks and phase dips in the mid-to-high-frequency range. When using the dynamic-static synergistic control method, the amplitude-frequency response tends to be flatter, and the phase-frequency curve transitions smoothly, indicating that the dynamic-static synergistic strategy achieves improved stability over a wide frequency band through adaptive parameter optimization. The improved dynamic-static synergistic control strategy, by introducing a transient damping adjustment mechanism and dynamic inertia compensation, can achieve adaptive parameter optimization.

[0096] 3.2) Control parameter design based on dynamic-static coordinated control method

[0097] Based on the above analysis and formula (8), the dynamic and static coordinated network control method is derived as follows, and the block diagram of the control method is shown below. Figure 4 As shown,

[0098] The active power deviation first passes through the forward channel, where the differential inertia stage instantaneously amplifies the high-frequency components, accelerating the initial angular frequency response. The integrator then generates the phase. Simultaneously, the angular frequency is fed into the feedback channel, where the damping stage after low-pass filtering generates additional torque, suppressing oscillations and reducing steady-state error. Finally, the angular frequency ω and phase angle δ are output.

[0099] Depend on Figure 4 From this, we can derive the transfer function G(s) of the active power loop in the dynamic-static coordinated network control method as follows:

[0100]

[0101] In the formula,

[0102]

[0103] In the formula, T1 is the time constant of the improved inertia channel; T2 is the time constant of the improved damping channel.

[0104] Based on the improved system transfer function, equation (9) yields the zero-pole distribution diagram and Bode plot when the key system parameters change.

[0105] Figure 5 (a) and Figure 5 (b) shows the zero-pole distribution of the system when T2 and K change. Figure 5 (a) It can be seen that as T2 increases, the poles move towards the origin, enhancing system stability, but potentially slowing down the dynamic response speed; conversely, as T2 decreases, the poles move away from the origin, which may lead to a faster system response speed, but potentially worse stability. Meanwhile, analysis... Figure 5 (b) It can be seen that when K changes, it affects the distribution of poles in the complex plane, thereby affecting the damping and oscillation characteristics of the system.

[0106] analyze Figure 6 (a) and Figure 6(b) When system parameters T2 = 1 and K = 0.5, the amplitude-frequency response is relatively flat, and the phase-frequency curve transitions smoothly, indicating that the system has good stability and anti-interference capability over a wide frequency band. When system parameters T2 = 1 and K = 0.5, it can effectively suppress disturbances and improve steady-state accuracy in the low-frequency band without prolonging the dynamic response time as increasing J. In the mid-to-high frequency band, it does not worsen the phase margin and increase the steady-state error as increasing D, thus achieving the overall optimal balance between steady-state accuracy, dynamic response speed, and anti-interference capability, resulting in the best system performance.

[0107] Analysis shows that selecting T2=1 and K=0.5 as the main parameters of this control method allows the dynamic and static coordinated control method to fully leverage its advantages and achieve the best system operation performance of the grid-type converter.

[0108] To verify the correctness and effectiveness of this control method, a simulation platform was built using Matlab / Simulink software. Figure 4 The grid-connected converter control simulation model shown is used to verify the effectiveness of the system operation. The system simulation parameters are shown in Table 1 below:

[0109] Table 1 System Simulation Parameters

[0110]

[0111]

[0112] The simulation verified that the system frequency dropped by 0.5Hz at 3.8s until the end of the simulation. The system output before and after the improved method was compared, and the feasibility of the parameters given above was verified.

[0113] Let K = 0, and take T2 = 0.2 to 1, D = 0.2K respectively. f ~K f The study investigated the impact of introducing only a damping channel on the system output. Figure 7 and Figure 8 The waveforms of the output active power and output frequency after the frequency drops are given for different T2 and D values ​​of the system.

[0114] like Figure 7 As shown in (a), when the frequency drops, the fluctuation of the output active power is more obvious and the time required to recover to stability is relatively long; when T2 gradually increases from 0.2 to 1, the fluctuation shows a smaller trend and the recovery to stability time is faster. Figure 7 As can be seen from (b), the system output frequency oscillates the fewest times when T2 = 1, and the time required to recover stability is also the shortest. The main effect of T2 is to change the process of the system reaching a steady state; a suitable T2 can make the system stabilize in a shorter time.

[0115] The effect of parameter D on the system output follows roughly the same trend as the effect of T2 on the system. D mainly affects system stability by providing damping; appropriately increasing D can enhance damping, but excessively large D may introduce new fluctuations. Analysis Figure 8 Therefore, D = K f At this time, the output active power and the number of frequency oscillations are effectively reduced, thus mitigating frequency overshoot.

[0116] With other parameters remaining unchanged, let T2 = 1 and D = K. f K = 0, 0.1, 0.3, 0.5, which are considered as introducing an improved inertia channel after introducing a stable improved damping channel. The system output waveform is as follows. Figure 9 As shown.

[0117] Depend on Figure 9 Analysis shows that the dynamic characteristics of the system are significantly improved after introducing the improved inertia channel. Compared to before the introduction, when K=0, as the value of K gradually increases from 0.1 to 0.5, the overshoot of both the output active power and the output frequency gradually decreases, with the output active power overshoot decreasing by nearly 70% and the output frequency overshoot decreasing by nearly 73%. Therefore, the simulation results verify the previous analysis: increasing the value of K can effectively reduce the overshoot of the system and improve its dynamic characteristics.

[0118] To more intuitively demonstrate the system output before and after the control method improvement, a comparative experiment was conducted. Three sets of simulation waveforms were analyzed: one without the control method, one with only improved inertia control, and one with improved inertia damping control. The specific simulation waveforms are shown below. Figure 10 As shown.

[0119] Depend on Figure 10 It can be seen that the three methods take almost the same amount of time to reach the steady point, but the dynamic and static response characteristics of the system output active power and frequency are significantly improved during the period.

[0120] The simulation experiments described above demonstrate that the control of a grid-type converter based on dynamic and static coordination can effectively improve dynamic characteristics and static errors by introducing improved inertia damping control.

Claims

1. A method for optimizing the dynamic and static characteristics of a grid-type converter based on inertia damping parameters, characterized in that, The steps are as follows: 1) Basic principle analysis of grid-type converters The grid-connected circuit of a grid-connected converter includes a main circuit and a control circuit. The control circuit contains sampling, power calculation, virtual synchronization control algorithm, and voltage-current loop modules, where U dc Indicates the DC bus voltage; ia, ib, and i c This refers to the output current of a grid-connected converter, i.e., the current output by the converter to the power grid; u a u b and u c L is the phase voltage at the output of the grid-connected converter. f C f and R f These are the filter inductor, filter capacitor, and damping resistor for the VSG; L g and R g These are the equivalent line inductance and resistance of the power grid, respectively. The main circuit uses a DC voltage source U as input, which is filtered by an LC filter circuit to eliminate high-frequency harmonics, resulting in a smooth three-phase capacitor voltage e. cabc Then through the line impedance (L) g +R g The voltage u that can be connected to the AC power grid is obtained. abc To achieve grid connection, the control loop collects grid voltage, current and capacitor voltage, and after coordinate transformation, the virtual synchronous control adjusts the frequency and phase through active power deviation and adjusts the amplitude through voltage deviation to generate a reference signal. The voltage and current dual-loop PI tracking output modulated wave drives the inverter to achieve autonomous frequency and voltage regulation. The main purpose of the active power loop control is to simulate the primary frequency regulation characteristics of a traditional synchronous generator, maintain grid frequency stability, and rationally allocate active power. Its input is the active power reference command P. ref The output power is the virtual mechanical power P. m Its control expression is: P m =P ref -K f (ω-ω0) (1) In the formula: K f ω is the active power droop factor; ω0 is the rated angular frequency; ω is the actual output angular frequency of the grid-type converter. The inertia-damped control element is used to simulate the rotor motion equation of a synchronous generator and calculate the active power P. m The mechanical power used in the oscillation equation is shown in equation (2): In the formula: J is the virtual inertia, D is the damping coefficient, and P... m 、P e and P d These represent the mechanical, electromagnetic, and damping power of the synchronous generator, respectively. The virtual inertia J is directly related to the rate of frequency change and is set according to the rate of frequency change. 2) Power Response Principle Analysis of Grid-Type Converters 2.1) Static power characteristics of grid-type converters The output power P of the grid-type converter can be derived from the active power loop control structure. e The calculation expression is: Where: G Pref Active power reference command P ref Output active power P e Transfer function between components; G Δω The rated angular frequency ω0 and the actual output angular frequency ω are related to the output active power P. e Transfer function between components; K P This is the proportional gain coefficient. According to the final value theorem of the Laplace transform, since t is infinite in the time domain and s tends to 0 in the complex domain, the limit value in equation (3) can be calculated to obtain the steady-state response: Substituting the calculated steady-state response into equation (3), we obtain the steady-state output power P. e : From equation (5), we can see that the active power P e Subject to active power reference command P ref and power deviation (K) f Considering the influence of +D)(ω0-ω), and taking into account the power deviation, when the system frequency variation is within a certain range, the active power P can be considered as... e The error is mainly due to K f And D influences, therefore when K f When the value is constant, the damping coefficient D is the main factor causing the steady-state error of the system. 2.2) Dynamic power characteristics of grid-type converters The influence of inertia damping control on the dynamic characteristics of active power in a network-type control system can be analyzed through the closed-loop small-signal transfer function. From equation (3), the transfer function of the network-type control can be obtained as follows: As shown in equation (6), the active power closed-loop small-signal transfer function is a typical second-order system with two closed-loop poles. When designing the control parameters of a grid-type converter, the positions of the closed-loop poles can be adjusted by assigning different values ​​to J and D, thereby achieving adjustment of the dynamic characteristics of the output active power. Based on the specific circumstances of the aforementioned influences, we set J = 0.2, 1, 2.5, and D = 0 to 2K. f The root locus distribution of the system is obtained. Root locus distribution analysis shows that as D increases, the imaginary part of the complex poles gradually decreases while the absolute value of the real part increases. When J increases, the absolute value of the real part of the complex poles decreases, and the imaginary part decreases simultaneously. When J is large, the poles become less sensitive to changes in D, making the system more prone to instability. When D = K... f At this point, the pole loci merge and separate on the real axis, forming two real root branches. Choose J = 2.5 and D = K. f The system can achieve stable operation and achieve a critical damping response with no overshoot and relatively fast response. Compared with other parameter combinations, this parameter corresponds to the best overall performance in terms of response speed, stability and robustness. 3) Control method based on dynamic and static coordination 3.1) Control principle based on dynamic and static coordinated control method The transfer functions of the inertia and damping channels of the network control system are shown in equation (7). Based on the dynamic-static coordinated control method, control strategies are applied to the forward and feedback channels of the control loop, resulting in the inertia and damping control equations as shown in equation (8). A differential element is added to the forward path to accelerate the recovery to stability without affecting the system output; an improved damping element is incorporated into the feedback path to enhance damping capability and reduce steady-state error. 3.2) Control parameter design based on dynamic-static coordinated control method Based on the above analysis and combined with formula (8), the following dynamic and static coordinated network control method is derived: The active power deviation first passes through the forward channel, where the differential inertia stage instantaneously amplifies the high-frequency components, accelerating the initial angular frequency response. The integrator then generates the phase. Simultaneously, the angular frequency is fed into the feedback channel, where the damping stage after low-pass filtering generates additional torque, suppressing oscillations and reducing steady-state error. Finally, the angular frequency ω and phase angle δ are output. The transfer function G(s) of the active power loop in the dynamic-static coordinated network control method is: In the formula, In the formula, T1 is the time constant of the improved inertia channel; T2 is the time constant of the improved damping channel. Based on the improved system transfer function, equation (9) shows that T2 = 1 and K = 0.5 are selected as the main parameters of this control method. The dynamic and static coordinated control method can give full play to its advantages and make the system operation effect of the grid converter the best.

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