Novel power system full-band instability factor detection method and stabilizing control device

Abstract

The application discloses a novel power system full-frequency band instability factor detection method and a stabilizing control device, determines the value range of the equivalent impedance of the grid-connected converter when the novel power system is unstable and the value range of the included angle between the equivalent impedance of the grid-connected converter and the equivalent impedance of the grid-connected bus, and serves as the first condition for instability factor detection; determines the value range of the system power angle and the system impedance angle when the novel power system is unstable, and serves as the second condition for instability factor detection; when the related parameters in the novel power system satisfy any one condition, it is determined that the novel power system is unstable in the full-frequency band, and the related parameters satisfying the condition are taken as the full-frequency band instability factor of the novel power system; the control signals output by the grid-connected converter control module and the grid-connected converter control module are input into the instability detection control switching module; the grid-connected converter and the grid-connected converter coexist in the novel power system, and the stability of power transmission is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power electronics and converter technology, and in particular relates to a new type of power system full-frequency band instability factor detection method and a stability control device for coexistence of grid-following converters and grid-forming converters. BACKGROUND

[0002] In recent years, the power system is rapidly developing towards high proportion of renewable energy and high proportion of power electronic equipment. Due to the coupling effect and other complex factors existing in the new power system, frequency oscillation of system instability will occur, which will have a very serious impact on the power quality of the power grid. The currently adopted control mode of a single converter is mostly divided into two types of grid-following converters and grid-forming converters. The use of the two types of converters alone will expose the problem that the grid-following converter will worsen the oscillation problem as the network strength weakens, and the grid-forming converter will worsen the oscillation problem as the grid strength increases.

[0003] When facing the large-scale use of new energy, due to the strong uncertainty of new energy, it will directly lead to the drastic change of the load of the power grid, which will weaken the strength of the power grid. In this case, the power grid will have problems such as frequency oscillation and voltage fluctuation, which will directly affect the stability of the power grid operation and the safety of power supply to a certain extent. At the same time, the short-circuit capacity of the traditional power grid is relatively large, and the change of voltage and frequency is relatively small, which can quickly recover to stability when disturbed by the outside world, but in the context of the new energy system, the operation mode of the traditional power grid cannot meet the needs of the new energy system. At this time, by replacing the traditional power grid with a weak power grid, although it can meet the large-scale access of new energy, it will increase the instability of voltage and frequency of the entire weak power grid system when disturbed by the outside world, and in serious cases, it will cause the entire power grid to fail.

[0004] In the prior art, the dynamic optimization method of the grid-forming converter can make the system safely and stably operate in the environment of a weak power grid. The stability test system of the grid-following converter realizes the stability test of the grid-following converter after being connected to the power grid by simulating the power grid characteristics of the output port. The control method for accelerating the dynamic response capability of the grid-forming converter, although the selection of the converter is changed from the traditional grid-following converter to the grid-forming converter which can better adapt to the weak power grid environment, the use of the controller only controls the stability of a single converter, and does not involve the stability of the interaction between multiple converters and the stability of the frequency between complex power grids. Therefore, in the environment of the continuously advancing power market of "double high", there is an urgent need for a new type of power system full-frequency band instability mechanism analysis method and a stability control device for coexistence of grid-following converters and grid-forming converters in the new type of power system, and a system that will not cause the oscillation problem to worsen due to the change of the strength of the power grid, so as to ensure the reliability and safety of power supply of the power grid. SUMMARY

[0005] To solve the problems in the prior art, the application provides a novel full-band instability factor detection method and stability control device for a power system with grid-following converters and grid-forming converters, which fully utilizes the advantages of both grid-following converters and grid-forming converters, and enables the power grid system to safely and stably transmit power under different operating conditions of the power grid system, thereby ensuring the stability of power transmission. Meanwhile, in view of the difference in stability between the new power system with a high proportion of new energy power generation equipment and the traditional power system, the impedance angle stability is used to detect the full-band instability factors of the system.

[0006] The application adopts the following technical solutions.

[0007] The application provides a novel full-band instability factor detection method for a new power system, in which the converter operates as a grid-following converter in a grid-following control mode and as a grid-forming converter in a grid-forming control mode, and the method comprises the following steps.

[0008] Obtain the operating parameters of the new power system, and establish an equivalent circuit when the grid-following converter and the grid-forming converter coexist.

[0009] Based on the equivalent circuit, determine the output complex power of the grid-following converter, extract the impedance amplitude from the output complex power of the grid-following converter, and determine the value range of the equivalent impedance of the grid-following converter and the value range of the included angle between the equivalent impedance of the grid-following converter and the equivalent impedance of the grid-connected bus when the new power system is unstable, as the first condition for instability factor detection, based on the fact that the impedance amplitude is proportional to the equivalent impedance of the grid-following converter when the new power system is unstable.

[0010] Based on the equivalent circuit, determine the output complex power of the grid-forming converter, and determine the active power output by the grid-forming converter according to the output complex power of the grid-forming converter, and determine the value range of the system power angle and the system impedance angle when the new power system is unstable, as the second condition for instability factor detection, based on the fact that the new power system is unstable when the active power output by the grid-forming converter is not greater than the load active power.

[0011] When the related parameters in the new power system satisfy any one of the conditions, it is determined that the new power system is unstable in the full band, and the related parameters that satisfy the condition are used as the full-band instability factors of the new power system.

[0012] Preferably, based on the equivalent circuit, the output complex power of the grid-following converter satisfies the following relationship:

[0013]

[0014] In the formula, P is the output active power of the grid-following converter, Q is the output reactive power of the grid-following converter, and S is the output complex power of the grid-following converter. the output complex power of the grid-following converter, the voltage phasor of the grid-connected bus, the output current phasor conjugate of the grid-following converter, Z g the equivalent impedance of the grid-connected bus, Z2 the equivalent impedance of the grid-following converter, I GFL the output current of the grid-following converter, δ g , δ2 the power angle of the grid-connected bus and the power angle of the grid-following converter, respectively, θ g , θ2 the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-following converter, respectively.

[0015] Preferably, the impedance amplitude defining the output complex power of the grid-following converter is proportional to the equivalent impedance of the grid-following converter, and satisfies the new power system is unstable;

[0016] the equivalent impedance of the grid-following converter when the new power system is unstable is Z2∈[0,Z g cosθ g2 ] and the included angle between the equivalent impedance Z2 of the grid-following converter and the equivalent impedance Z g of the grid-connected bus is θ g2 ∈(π2,3π2), as the first condition for detecting the full-band instability factor of the new power system.

[0017] Preferably, based on the equivalent circuit, the output complex power of the grid-forming converter is constructed, and the following relationship is satisfied:

[0018]

[0019] wherein, the output complex power of the grid-following converter, the output voltage phasor of the grid-forming converter, U1 the output voltage of the grid-forming converter, U g the voltage of the grid-connected bus, the output current phasor conjugate of the grid-forming converter, Z g the equivalent impedance of the grid-connected bus, Z1 the equivalent impedance of the grid-forming converter, δ1 the power angle of the grid-forming converter, θ g , θ1 the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-forming converter, respectively.

[0020] Preferably, when the active power output by the grid-forming converter is not greater than the active power of the load, the new power system is unstable, and the following relationship is satisfied:

[0021]

[0022] In the formula, δ0 is a system power angle when the power system is stably operated, and θ0 is a system impedance angle when the power system is stably operated.

[0023] The value range of the system power angle and the system impedance angle when the new-type power system is unstable is arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], which is taken as the second condition for the full-frequency-band instability factor detection of the new-type power system.

[0024] The application further provides a new-type power system full-frequency-band instability factor detection device to realize the full-frequency-band instability factor detection method, which comprises:

[0025] An equivalent circuit module is configured to acquire the operation parameters of the new-type power system, and establish an equivalent circuit when the grid-connected type converter and the grid-constructing type converter coexist.

[0026] A detection condition generation module is configured to determine the output complex power of the grid-connected type converter based on the equivalent circuit, extract the impedance amplitude from the output complex power of the grid-connected type converter, determine the value range of the equivalent impedance of the grid-connected type converter and the value range of the included angle between the equivalent impedance of the grid-connected type converter and the equivalent impedance of the grid-connected bus when the new-type power system is unstable based on the fact that the impedance amplitude is proportional to the equivalent impedance of the grid-connected type converter, and take the value range as the first condition for the instability factor detection, determine the output complex power of the grid-constructing type converter based on the equivalent circuit, determine the active power output by the grid-constructing type converter according to the output complex power of the grid-constructing type converter, and determine the value range of the system power angle and the system impedance angle when the new-type power system is unstable based on the fact that the new-type power system is unstable when the active power output by the grid-constructing type converter is not greater than the load active power, and take the value range as the second condition for the instability factor detection.

[0027] An instability judgment module is configured to determine that the new-type power system is full-frequency-band unstable when the related parameters in the new-type power system meet any one of the conditions.

[0028] Preferably, the detection condition generation module comprises an output complex power calculation unit of the grid-connected type converter.

[0029] The output complex power calculation unit of the grid-connected type converter is configured to calculate the output complex power of the grid-connected type converter based on the equivalent circuit and the following relationship:

[0030]

[0031] In the formula, is the output complex power of the grid-connected type converter, is a voltage phasor of the grid-connected bus, is a conjugate of an output current phasor of the grid-connected type converter, and Z gZ2 is the equivalent impedance of the grid-following converter, I GFL I2 is the output current of the grid-following converter, δ g , δ2 are the power angles of the grid-connected bus and the grid-following converter respectively, θ g , θ2 are the equivalent impedance angles of the grid-connected bus and the grid-following converter respectively.

[0032] Preferably, the detection condition generation module further comprises: a first condition generation unit;

[0033] The first condition generation unit is configured to define the impedance amplitude of the output complex power of the grid-following converter When the impedance amplitude is proportional to the equivalent impedance of the grid-following converter, the following condition is satisfied: New power system instability; when the new power system instability is determined, the value range of the equivalent impedance of the grid-following converter is Z2∈[0,Z g cosθ g2 ] and the included angle between the equivalent impedance Z2 of the grid-following converter and the equivalent impedance Z g of the grid-connected bus is θ g2 ∈(π2,3π2), which is the first condition for detecting new power system instability in all frequency bands.

[0034] Preferably, the detection condition generation module further comprises: a grid-constructing converter output complex power calculation unit;

[0035] The grid-constructing converter output complex power calculation unit is configured to calculate the output complex power of the grid-constructing converter based on the equivalent circuit according to the following relationship:

[0036]

[0037] In the formula, is the output complex power of the grid-following converter, is the output voltage phase of the grid-constructing converter, U1 is the output voltage of the grid-constructing converter, U g is the voltage of the grid-connected bus, is the output current phase conjugate of the grid-constructing converter, Z g is the equivalent impedance of the grid-connected bus, Z1 is the equivalent impedance of the grid-constructing converter, δ1 is the power angle of the grid-constructing converter, θ g , θ1 are the equivalent impedance angles of the grid-connected bus and the grid-constructing converter respectively.

[0038] Preferably, the detection condition generation module further comprises: a second condition generation unit;

[0039] A second condition generating unit is configured to generate a second condition that the new power system is unstable when the active power output by the grid-forming converter is not greater than the active power of the load, and the second condition satisfies the following relationship:

[0040]

[0041] In the formula, δ0 is a system power angle when the power system is stably operated, and θ0 is a system impedance angle when the power system is stably operated.

[0042] The value range of the system power angle and the system impedance angle when the new power system is unstable is arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], which is used as the second condition for detecting the instability factor of the new power system in the full frequency band.

[0043] The application further provides a stability control device for the new power system, which comprises:

[0044] The grid-forming converter control module, the grid-following converter control module, the instability factor detection device, and the control conversion module; the grid-forming converter control module is configured to implement droop control on the converter, the grid-following converter control module is configured to implement phase-locked loop control on the converter, and the control signals output by the grid-forming converter control module and the grid-following converter control module are both input into the control conversion module.

[0045] The instability factor detection device is configured to determine whether the new power system is unstable in the full frequency band, and start the control conversion module when the new power system is unstable in the full frequency band.

[0046] The control conversion module is configured to detect the output current of the converter and the voltage of the grid-connected bus; when no system fault is detected, the output current of the converter is not greater than a set current threshold, and the voltage of the grid-connected bus is not less than a set voltage threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter; when the output current is detected to be greater than the set current threshold, the control conversion module outputs the control signal output by the grid-following converter control module to the converter, until the output current is not greater than the set current threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter; when a system fault is detected and the voltage of the grid-connected bus is less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-following converter control module to the converter, until no system fault is detected and the voltage of the grid-connected bus is not less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter; when a system fault is detected, but the output current is not greater than the set current threshold and the voltage of the grid-connected bus is less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter.

[0047] Preferably, the control conversion module comprises an input signal processing unit, a set signal processing unit, an RS trigger and a switching switch; the input signal processing unit is used to acquire the effective value of the three-phase output current of the converter and compare it with a set current threshold value, when the effective value of the output current of any phase is greater than the set current threshold value, a signal "1" is sent to one synchronous input end S of the RS trigger, otherwise a signal "0" is sent to one synchronous input end S of the RS trigger; the set signal processing unit is used to acquire the effective value of the voltage of the grid-connected bus after coordinate transformation and compare it with a set voltage threshold value u, when the effective value of the grid-connected bus voltage is greater than the set voltage threshold value, a signal "1" is sent to the other synchronous input end R of the RS trigger, otherwise a signal "0" is sent to one synchronous input end R of the RS trigger; the RS trigger takes the three-phase output current of the converter as a priority signal and takes the voltage of the grid-connected bus as a set signal, and the RS trigger output signal F, when F is a signal "1", the switching switch makes the grid-forming type converter control module conductive, and outputs the control signal output by the grid-forming type converter control module to the converter, when F is a signal "0", the switching switch makes the grid-following type converter control module conductive, and outputs the control signal output by the grid-following type converter control module to the converter.

[0048] Preferably, the structure of the phase-locked loop control in the grid-following type converter control module is improved, and the improved phase-locked loop control comprises a shielding link connected in parallel with an integral link.

[0049] The improved phase-locked loop control model satisfies the following relationship:

[0050]

[0051] In the formula, θ pll is the reference phase output by the phase-locked loop, k p and k i are the proportional coefficient and the integral coefficient of the integral link PI respectively, V qpll is the q-axis component after dq transformation of the three-phase grid voltage, ω is the grid frequency, K pll is the shielding coefficient of the integral link, when the output voltage of the converter is less than the set voltage threshold value but the voltage of the grid-connected bus is not less than the set voltage threshold value, K pll takes the value of 0, when the output voltage of the converter and the voltage of the grid-connected bus are both less than the set voltage threshold value, K pll takes the value of 1.

[0052] Preferably, the structure of the voltage and current loop in the grid-forming type converter control module is improved, and the forward gain function of the improved voltage and current loop satisfies the following relationship:

[0053]

[0054] where G'(s) is the forward gain function of the improved voltage current loop, K p is the proportional coefficient of the PWM rectifier, K i is the proportional coefficient of the current loop, K u is the proportional coefficient of the voltage loop, J is the moment of inertia, C is the equivalent capacitance, L is the equivalent inductance, and s is the integral operator.

[0055] Preferably, the improvement of the power balance control structure of the grid-following converter includes: a power control loop, a current control loop, and a phase-locked loop;

[0056] The power control loop is configured to obtain active power outer loop control values and reactive power outer loop control values by integrating differences between active power reference values and reactive power reference values and active power feedback values and reactive power feedback values, respectively; the current control loop is configured to obtain active power inner loop control values and reactive power inner loop control values by using capacitor current dq-axis components and capacitor feedback current dq-axis components based on the active power outer loop control values and the reactive power outer loop control values; and the phase-locked loop is configured to optimize control signals according to the active power inner loop control values and the reactive power inner loop control values.

[0057] Preferably, the improvement of the power balance control structure of the grid-forming converter includes: an algorithm loop, a voltage loop, and a current loop;

[0058] The algorithm loop is configured to adjust the grid point voltage according to dq-axis components of an output voltage reference value of the converter and dq-axis components of a voltage of a grid bus; and the voltage loop and the current loop are configured to adjust to optimize control signals based on differences between the adjusted grid point voltage and the output voltage reference value of the converter.

[0059] Preferably, after the improvement of the power balance control structure, the phases of related signals on the grid-following converter side and the grid-forming converter side are corrected according to the following relationship:

[0060]

[0061] wherein is the dq-axis component of the synchronous phase value of the impedance current, the grid current, the grid bus voltage, and the converter output voltage on the grid-following converter side or the grid-forming converter side, and is the dq-axis component of the synchronous phase value of the impedance current, the grid current, the grid bus voltage, and the converter output voltage on the system side, and Δθ is the equivalent impedance angle difference value of the corresponding signals on the grid-following converter side or the grid-forming converter side and the system side.

[0062] Preferably, the current threshold value is set to 1.1 p.u., and the voltage threshold value is set to 0.9 p.u.

[0063] The application further provides a novel power system stabilizing control method, and a novel power system stabilizing control device,

[0064] When the novel power system is unstable in a full frequency band, the output current of the converter and the voltage of the grid-connected bus are detected;

[0065] When no system fault is detected, the output current of the converter is not greater than a set current threshold, and the voltage of the grid-connected bus is not less than a set voltage threshold, a control signal output by the grid-forming converter control module is output to the converter; when the output current is detected to be greater than the set current threshold, a control signal output by the grid-following converter control module is output to the converter, until the output current is not greater than the set current threshold, the control signal output by the grid-forming converter control module is output to the converter;

[0066] When a system fault is detected and the voltage of the grid-connected bus is less than the set voltage threshold, the control signal output by the grid-following converter control module is output to the converter, until no system fault is detected and the voltage of the grid-connected bus is not less than the set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter;

[0067] When a system fault is detected, but the output current is not greater than the set current threshold and the voltage of the grid-connected bus is less than the set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter.

[0068] Preferably, the structure of a phase-locked loop control in the grid-following converter control module is improved, and the improved phase-locked loop control comprises a shielding link connected in parallel with an integral link.

[0069] The improved phase-locked loop control model satisfies the following relationship:

[0070]

[0071] In the formula, θ pll is a reference phase output by the phase-locked loop, k p and k i are a proportional coefficient and an integral coefficient of the integral link PI respectively, V qpll is a q-axis component after dq transformation of a three-phase grid voltage, ω is a grid frequency, K pll is a shielding coefficient of the integral link, when the output voltage of the converter is less than the set voltage threshold but the voltage of the grid-connected bus is not less than the set voltage threshold, K pll is 0, and when the output voltage of the converter and the voltage of the grid-connected bus are both less than the set voltage threshold, K pll is 1.

[0072] Preferably, the structure of the voltage and current loop in the grid-forming converter control module is improved, and the forward gain function of the improved voltage and current loop satisfies the following relationship:

[0073]

[0074] In the formula, G'(s) is the forward gain function of the improved voltage and current loop, K p is the proportional coefficient of the PWM rectifier, K i is the proportional coefficient of the current loop, K u is the proportional coefficient of the voltage loop, J is the moment of inertia, C is the equivalent capacitance, L is the equivalent inductance, and s is the integral operator.

[0075] Preferably, the grid-following converter power balance control structure is improved, and the improved power balance control structure includes a power control loop, a current control loop, and a phase-locked loop.

[0076] The power control loop is configured to obtain active power outer loop control values and reactive power outer loop control values by integrating differences between active power reference values and reactive power reference values and active power feedback values and reactive power feedback values. The current control loop is configured to obtain active power inner loop control values and reactive power inner loop control values by using capacitor current dq-axis components and capacitor feedback current dq-axis components based on the active power outer loop control values and the reactive power outer loop control values. The phase-locked loop is configured to optimize control signals according to the active power inner loop control values and the reactive power inner loop control values.

[0077] Preferably, the grid-forming converter power balance control structure is improved, and the improved power balance control structure includes an algorithm loop, a voltage loop, and a current loop.

[0078] The algorithm loop is configured to adjust the grid point voltage according to output voltage reference value dq-axis components of the converter and voltage dq-axis components of the grid bus. The voltage loop and the current loop are configured to adjust to optimize control signals based on differences between the adjusted grid point voltage and the output voltage reference value of the converter.

[0079] Preferably, after the power balance control structure is improved, the phases of related signals on the grid-following converter side and the grid-forming converter side are corrected according to the following relationship:

[0080]

[0081] In the formula, is the dq-axis component of the synchronous phase value of the impedance current, the grid current, the grid bus voltage, and the converter output voltage on the grid-following converter side or the grid-forming converter side, The delta theta is the difference between the equivalent impedance angles of the grid-connected converter side or the grid-constructing converter side and the corresponding signals of the system side for the synchronous phase values of the impedance current, the grid current, the grid-connected bus voltage and the dq-axis components of the converter output voltage.

[0082] Preferably, the current threshold is set to 1.1 p.u., and the voltage threshold is set to 0.9 p.u.

[0083] A terminal comprising a processor and a storage medium;

[0084] The storage medium is used to store instructions;

[0085] The processor is used to operate according to the instructions to perform the steps of the new power system full-band instability factor detection method;

[0086] The processor is used to operate according to the instructions to perform the steps of the new power system stability control method.

[0087] A computer readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the steps of the new power system full-band instability factor detection method.

[0088] A computer readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the steps of the new power system stability control method.

[0089] The beneficial effects of the present application at least include: compared with the prior art, the present application considers that the impedance matching relationship between the inverter and the grid is closely related to the new power system, and proposes to reflect the full-band instability of the new power system through the system impedance and the impedance angle transformation. The instability detection criterion proposed by the present application is a supplement to the existing voltage, frequency and power angle stability criteria of the power system, and takes the value range of the equivalent impedance of the grid-connected converter and the value range of the included angle between the equivalent impedance of the grid-connected converter and the equivalent impedance of the grid-connected bus as the first condition for instability factor detection; the value range of the system power angle and the system impedance angle is taken as the second condition for instability factor detection; when the related parameters in the new power system satisfy any one condition, the new power system is determined to be full-band unstable, and the related parameters that satisfy the condition are taken as the full-band instability factors of the new power system.

[0090] The application also proposes a stabilizing control device, the control signals output by the grid-forming converter control module and the control signals output by the grid-following converter control module are both input into the instability detection control switching module, realizing the coexistence of the grid-following converter and the grid-forming converter, giving full play to the outstanding advantages of the grid-following converter in adapting to the grid voltage and frequency and in grid connection, but the use effect of the grid-following converter in a weak grid environment is not good, and since the grid-forming converter has inductive phase, it can better adapt to the weak grid environment, when the system is normally operated, only the grid-forming converter needs to work, and when the system has a circuit fault, the system can be switched to the working mode of the grid-following converter through the instability detection control switching module. The complementary relationship between the two can realize good grid connection effect of new energy in a weak grid environment. BRIEF DESCRIPTION OF DRAWINGS

[0091] Figure 1 It is the flow chart of the new power system full-band instability factor detection method proposed by the application;

[0092] Figure 2 It is the equivalent circuit diagram established in the embodiment of the application;

[0093] Figure 3 It is the structure schematic diagram of the stabilizing control device of the new power system proposed by the application;

[0094] Figure 4 It is the structure schematic diagram of the control conversion module in the embodiment of the application;

[0095] Figure 5 It is the structure improvement schematic diagram of the grid-following converter control module in the application;

[0096] Figure 6 It is the structure improvement schematic diagram of the grid-forming converter control module in the application;

[0097] Figure 7 It is the improvement schematic diagram of the power balance control structure of the grid-following converter in the application;

[0098] Figure 8 It is the improvement schematic diagram of the power balance control structure of the grid-forming converter in the application. DETAILED DESCRIPTION

[0099] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the application will be described clearly and completely below in combination with the drawings in the embodiment of the application. The embodiments described in the application are only a part of the embodiments of the application, not all the embodiments. Based on the spirit of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0100] This invention proposes a novel method for detecting instability factors across the entire frequency band of a power system. In this novel power system, the converter operates as a grid-following converter when in grid-based control mode and as a grid-connected converter when in grid-building control mode. Figure 1 As shown, it includes:

[0101] Step 1: Obtain the operating parameters of the new power system and establish the equivalent circuit when the grid-type converter and the network-type converter coexist.

[0102] Specifically, establish such as Figure 2 The equivalent circuits of the grid-type converter and the ground wire converter are shown. Since the ground wire converter directly controls the output voltage of the converter, and the ground wire converter directly controls the output current of the converter, the ground wire converter is equivalent to a voltage source U. s1 Furthermore, it is connected in series with the equivalent impedance Z1 of the grid-type converter, thus making the grid-type converter equivalent to a current source i. s2 And it is connected in parallel with the equivalent impedance Z2 of the grid converter, I GFM and I GFL These are the output currents of the grid-type converter and the ground-type converter, respectively. g I g Z g These represent the voltage, current, and equivalent impedance of the grid-connected bus, respectively, Z. g1 and Z g2 These are the equivalent impedances of the transmission lines on the grid-type converter side and the equivalent impedances of the transmission lines on the grid-type converter side, respectively.

[0103] Step 2: Based on the equivalent circuit, determine the output complex power of the grid-connected converter; extract the impedance amplitude from the output complex power of the grid-connected converter; based on the fact that the new power system is unstable when the impedance amplitude is proportional to the equivalent impedance of the grid-connected converter, determine the range of the equivalent impedance of the grid-connected converter and the range of the angle between the equivalent impedance of the grid-connected converter and the equivalent impedance of the grid bus when the new power system is unstable, as the first condition for detecting instability factors.

[0104] Specifically, based on the equivalent circuit, the output complex power of the grid converter satisfies the following relationship:

[0105]

[0106] In the formula, To match the complex output power of the grid converter, For the voltage phasor of the grid-connected bus, To be conjugate with the output current phasor of the grid converter, Z g Z1 is the equivalent impedance of the grid-connected bus, Z2 is the equivalent impedance of the grid-connected converter, and I is the equivalent impedance of the grid-connected bus.GFL To match the output current of the grid converter, δ g δ2 and θ are the power angles of the grid-connected bus and the grid-connected converter, respectively. g θ1 and θ2 are the equivalent impedance angles of the grid-connected bus and the grid-type converter, respectively.

[0107] Define the impedance magnitude of the output complex power of the grid converter. If power oscillations occur in the power grid at this time, it is related to the output current I of the grid converter. GFL The output current I of the grid converter will decrease, while the equivalent impedance Z2 of the grid converter will increase. This will cause the impedance amplitude to decrease, and thus the output complex power of the grid converter will also decrease. GFL Increasing the impedance amplitude, along with decreasing the equivalent impedance Z2 of the grid converter, will lead to an increase in the impedance magnitude and thus an increase in the complex output power of the grid converter, thereby suppressing power oscillations. Therefore, when the impedance magnitude is inversely proportional to the equivalent impedance of the grid converter, i.e. The system can recover to a stable state after oscillation.

[0108]

[0109] In the formula, θ g2 The equivalent impedance Z2 of the grid-connected converter and the equivalent impedance Z of the grid bus are compared. g The angle between them.

[0110] From the above formula, we can obtain:

[0111] When θ g2 When ∈(0,π2), New power systems can become unstable after oscillations occur;

[0112] When θ g2 ∈(π2,3π2) and Z2∈[0,Z g cosθ g2 ]hour, New power systems can become unstable after oscillations occur;

[0113] When θ g2 ∈(π2,3π2) and Z2∈[Z g cosθ g2 When ,∞], The new power system can maintain stability after oscillations occur;

[0114] Therefore, based on the fact that the impedance magnitude is proportional to the equivalent impedance of the grid converter, i.e. For the instability of a new type of power system, the range of the equivalent impedance of the grid-connected converter during instability is determined to be Z2∈[0,Z2]. g cosθg2 ] and the equivalent impedance Z2 of the grid-connected converter and the equivalent impedance Z of the grid-connected bus. g The range of the angle between the equivalent impedance Z2 of the grid-connected converter and the equivalent impedance Z of the grid-connected bus is θ g2 ∈(π2,3π2), as the first condition of the full-band instability factor detection of the new power system.

[0115] Step 3, based on the equivalent circuit, the output complex power of the grid-connected converter is determined; the active power output by the grid-connected converter is determined according to the output complex power of the grid-connected converter; when the active power output by the grid-connected converter is not greater than the load active power, the new power system is unstable, and the value range of the system power angle and the system impedance angle when the new power system is unstable is determined as the second condition of the instability factor detection.

[0116] Specifically, based on the equivalent circuit, the output complex power of the grid-connected converter satisfies the following relationship:

[0117]

[0118] In the formula, is the output complex power of the grid-connected converter, is the output voltage phase of the grid-connected converter, U1 is the output voltage of the grid-connected converter, U g is the voltage of the grid-connected bus, is the conjugate of the output current phase of the grid-connected converter, Z g is the equivalent impedance of the grid-connected bus, Z1 is the equivalent impedance of the grid-connected converter, δ1 is the power angle of the grid-connected converter, θ g , θ1 are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-connected converter, respectively.

[0119] The active power and the reactive power output by the grid-connected converter satisfy the following relationship:

[0120]

[0121] In the formula, P and Q are the active power and the reactive power output by the grid-connected converter, respectively.

[0122] The load active power satisfies the following relationship:

[0123]

[0124] In the formula, P0 is the load active power, δ0 is the system power angle when the power system is stably operated, and θ0 is the system impedance angle when the power system is stably operated.

[0125] When the active power output by the grid-connected converter is greater than the load active power, the new power system is stably operated, and the following relationship is satisfied:

[0126]

[0127] Because This, new type The system impedance angle when the power system is stably running satisfies the following relationship:

[0128] 0 < theta0 <= arccos [-cos (delta0 + theta0) -1] and 2pi-arccos [-cos (delta0 + theta0) -1] < theta0 < 2pi

[0129] Therefore, when the active power output by the grid-forming converter is not greater than the active power of the load, the following is satisfied:

[0130]

[0131] New Type power When the system is unstable, the value range of the system power angle and the system impedance angle when the new power system is unstable is arccos [-cos (delta0 + theta0) -1] < theta0 <= 2pi-arccos [-cos (delta0 + theta0) -1], which is the second condition for detecting the full-band instability factor of the new power system.

[0132] Step 4, when the related parameters in the new power system satisfy any one condition, it is determined that the new power system is full-band unstable, and the related parameters that satisfy the condition are used as the full-band instability factor of the new power system.

[0133] The traditional power system stability is divided into frequency stability, voltage stability and rotor angle stability. However, due to the fact that the new power system dominated by new energy is often located in remote areas, the power grid exhibits the characteristics of weak power grid and is prone to low-frequency oscillation and harmonic oscillation. The instability reason comes from the fact that the values of various impedance angles, power angles and other parameters of the system running in different situations of grid-following converters and grid-forming converters exceed the stable value range. Therefore, the present application analyzes whether the values of various impedance angles, power angles and other parameters of the system running in different situations of grid-following converters and grid-forming converters satisfy the value range when the system is stable, so as to determine whether the system is unstable, and can significantly distinguish the different instability factors of grid-following converters and grid-forming converters, which is conducive to proposing specific implementation direction for stability control when grid-following converters and grid-forming converters coexist, and is more in line with the operation mode of the new power system.

[0134] The present application also proposes a full-band instability factor detection device for a new power system, to realize the full-band instability factor detection method, comprising:

[0135] An equivalent circuit module is used to obtain the operating parameters of the new power system, and to establish an equivalent circuit when grid-following converters and grid-forming converters coexist.

[0136] The detection condition generation module is used to: determine the output complex power of the grid-connected converter based on the equivalent circuit; extract the impedance amplitude from the output complex power of the grid-connected converter; determine the range of the equivalent impedance of the grid-connected converter and the range of the angle between the equivalent impedance of the grid-connected converter and the equivalent impedance of the grid-connected bus when the new power system is unstable, based on the principle that the impedance amplitude is proportional to the equivalent impedance of the grid-connected converter, as the first condition for detecting instability factors; determine the output complex power of the grid-connected converter based on the equivalent circuit; determine the active power output of the grid-connected converter based on the output complex power of the grid-connected converter; and determine the range of the system power angle and system impedance angle when the new power system is unstable, based on the principle that the active power output of the grid-connected converter is not greater than the active power of the load, as the second condition for detecting instability factors.

[0137] The instability detection module is used to determine that the new power system is unstable across the entire frequency band when any of the relevant parameters in the new power system meet any one of the conditions.

[0138] Preferably, the detection condition generation module includes: an output complex power calculation unit for the grid converter;

[0139] The complex power calculation unit for the grid-type converter is used to calculate the complex power output of the grid-type converter based on the equivalent circuit, using the following relationship:

[0140]

[0141] In the formula, To match the complex output power of the grid converter, For the voltage phasor of the grid-connected bus, To be conjugate with the output current phasor of the grid converter, Z g Z1 is the equivalent impedance of the grid-connected bus, Z2 is the equivalent impedance of the grid-connected converter, and I is the equivalent impedance of the grid-connected bus. GFL To match the output current of the grid converter, δ g δ2 and θ are the power angles of the grid-connected bus and the grid-connected converter, respectively. g θ1 and θ2 are the equivalent impedance angles of the grid-connected bus and the grid-type converter, respectively.

[0142] Preferably, the detection condition generation module further includes: a first condition generation unit;

[0143] The first condition generation unit is used to define the impedance magnitude of the output complex power of the grid converter. When the impedance magnitude is proportional to the equivalent impedance of the grid converter, it satisfies... Instability of a novel power system; the range of the equivalent impedance of the grid-connected converter during instability is determined to be Z2∈[0,Z2].g cosθ g2 Furthermore, the equivalent impedance Z2 of the grid converter and the equivalent impedance Z of the grid bus are... g The range of the included angle between them is θ. g2 ∈(π2,3π2), serves as the first condition for detecting instability factors across the entire frequency band of the new power system.

[0144] Preferably, the detection condition generation module further includes: an output complex power calculation unit for the grid-type converter;

[0145] The output complex power calculation unit of the network converter is used to calculate the output complex power of the network converter based on the equivalent circuit, using the following relationship:

[0146]

[0147] In the formula, To match the complex output power of the grid converter, U1 is the output voltage phasor of the grid-connected converter, and U2 is the output voltage of the grid-connected converter. g The voltage of the grid-connected bus. For the output current phasor conjugate of the grid-type converter, Z g Z1 is the equivalent impedance of the grid-connected bus, Z1 is the equivalent impedance of the grid-type converter, δ1 is the power angle of the grid-type converter, and θ is the equivalent impedance of the grid-connected bus. g θ1 and θ2 are the equivalent impedance angles of the grid-connected bus and the grid-type converter, respectively.

[0148] Preferably, the detection condition generation module further includes: a second condition generation unit;

[0149] The second condition generation unit is used to address the instability of the new power system when the active power output of the grid-type converter is not greater than the active power of the load, satisfying the following relationship:

[0150]

[0151] In the formula, δ0 is the system power angle when the power system is operating stably, and θ0 is the system impedance angle when the power system is operating stably.

[0152] The range of system power angle and system impedance angle during instability of the new power system is determined to be arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], which serves as the second condition for detecting instability factors across the entire frequency band of the new power system.

[0153] Based on the detection results of instability factors across the entire frequency band of a new power system, this invention proposes a novel stability control device suitable for power systems, such as... Figure 3 As shown, it includes:

[0154] The grid-constructing converter control module 10, the grid-following converter control module 20, the instability factor detection device, and the control conversion module 30; the grid-constructing converter control module is used for implementing droop control on the converter, the grid-following converter control module is used for implementing phase-locked loop control on the converter, and the control signals output by the grid-constructing converter control module and the control signals output by the grid-following converter control module are both input into the control conversion module;

[0155] The instability factor detection device determines that the new power system is unstable in the full frequency band, and starts the control conversion module;

[0156] The control conversion module is used for detecting the output current of the converter and the voltage of the grid-connected bus; when no system fault is detected, the output current of the converter is not greater than a set current threshold, and the voltage of the grid-connected bus is not less than a set voltage threshold, the control conversion module outputs the control signal output by the grid-constructing converter control module to the converter; when the output current is detected to be greater than the set current threshold, the control conversion module outputs the control signal output by the grid-following converter control module to the converter, until the output current is not greater than the set current threshold, the control conversion module outputs the control signal output by the grid-constructing converter control module to the converter; when a system fault is detected and the voltage of the grid-connected bus is less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-following converter control module to the converter, until no system fault is detected and the voltage of the grid-connected bus is not less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-constructing converter control module to the converter; when a system fault is detected, but the output current is not greater than the set current threshold and the voltage of the grid-connected bus is less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-constructing converter control module to the converter.

[0157] The new power system full-frequency band instability factor detection method provided by the application obtains the detection result of whether the new power system is unstable, which is used as a flag for determining whether the control conversion module is started, and can effectively ensure that the switching of the control mode is based on the premise of system stability, thereby further improving the working reliability of the stability device.

[0158] Preferably, the set current threshold is 1.1 p.u., and the set voltage threshold is 0.9 p.u.

[0159] Specifically, the grid-constructing converter model satisfies the following relationship:

[0160]

[0161] In the formula, v pcc , i pcc are the grid-connected point voltage and current, respectively, vg , R g , L g are the equivalent voltage, resistance and inductance of the line respectively;

[0162] By dq coordinate transformation, the following relationship is obtained:

[0163]

[0164] In the formula, v pccdq , i pccdq are the dq coordinate components of grid-connected point voltage and current, X g is the reactance of the line, and i gdq is the dq coordinate component of the line current;

[0165] Based on the grid-forming converter model, the control model of the grid-forming converter satisfies the following relationship:

[0166] ω out = ω ref + D e (P eref -P e )

[0167] θ out = ∫ ω out dt

[0168] In the formula, ω out is the output angular velocity, ω ref is the angular velocity reference value, D e is the damping coefficient of the actual value of active power, P eref , P e are the active power reference value and output active power respectively, and θ out is the output phase.

[0169] The grid-following converter model satisfies the following relationship:

[0170]

[0171] In the formula, u c , u t , u g are the port voltage, node voltage and AC grid voltage respectively, i c is the current instantaneous value, R is the line resistance, L f is the filter inductance, and L is the line inductance.

[0172] Based on the grid-following converter model, the control model of the grid-following converter satisfies the following relationship:

[0173]

[0174] wherein θ pll is the reference phase outputted by the phase-locked loop, k p and k i are the proportional coefficient and the integral coefficient of the PI regulation respectively, V qpll is the q-axis component of the three-phase grid voltage after dq transformation, and ω is the grid frequency.

[0175] The grid-following converter has a wide application in the power market due to its ability to keep synchronization with the grid and strong response capability. Although the grid-forming converter has better robustness than the grid-following converter, the grid-forming converter will cause damage to system components if it is in the system failure period for a long time. Therefore, the grid-following converter and the grid-forming converter are combined in the present application, and the two are connected in parallel into the system through the addition of an instability detection conversion module, as shown in Figure 3 .

[0176] Specifically, as shown in Figure 4 , the control conversion module includes an input signal processing unit, a set signal processing unit, an RS flip-flop and a switching switch; the input signal processing unit is used to obtain the effective value of the three-phase output current i a , i b and i c of the converter, and compare it with the set current threshold i. When the effective value of any phase output current is greater than the set current threshold, a signal "1" is sent to one synchronous input end S of the RS flip-flop, otherwise a signal "0" is sent to one synchronous input end S of the RS flip-flop; the set signal processing unit is used to obtain the effective value of the voltage V pcc of the grid-connected bus after coordinate transformation, and compare it with the set voltage threshold u. When the effective value of the grid-connected bus voltage is greater than the set voltage threshold, a signal "1" is sent to the other synchronous input end R of the RS flip-flop, otherwise a signal "0" is sent to one synchronous input end R of the RS flip-flop; the RS flip-flop takes the three-phase output current of the converter as the priority signal and takes the grid-connected bus voltage as the set signal, and the RS flip-flop output signal F. When F is a signal "1", the switching switch makes the grid-forming converter control module conductive, and outputs the control signal outputted by the grid-forming converter control module to the converter. When F is a signal "0", the switching switch makes the grid-following converter control module conductive, and outputs the control signal outputted by the grid-following converter control module to the converter.

[0177] In the embodiment, the set current threshold is 1.1 p.u. and the set voltage threshold is 0.9 p.u., which is a non-limiting optimal choice. Both of the two thresholds can be adjusted according to the actual grid needs, while meeting the detection effect and avoiding the chattering between the modes.

[0178] The application sets an instability detection conversion module to construct a new stability control device, realizes full-band instability detection of a new power system, starts control conversion when instability is detected, fully utilizes the characteristics of the grid-forming converter to ensure normal output of voltage and frequency while suppressing the circulation of reactive power to a certain extent, and solves the deviation of the amplitude and phase of the output voltage of the grid-forming converter and the grid-following converter by means of the instability detection conversion module.

[0179] When the converter operates in the grid-following control mode, the grid-following converter adopts phase-locked loop control, the frequency and phase of the integral element control system are adopted in the phase-locked loop control; in order to follow the system signal, the integral element has overshoot, the signal following is too fast or too slow in a short time, thereby causing the system to appear transient synchronization instability, and the change of the output voltage and the output current of the converter caused by the transient synchronization instability has the possibility of causing unnecessary switching of the control mode, therefore, the application improves the structure of the phase-locked loop control in the control module of the grid-following converter, as shown in Figure 5 The improved phase-locked loop control includes a shielding element connected in parallel with the integral element; based on the model of the grid-following converter, the improved phase-locked loop control model of the grid-following converter is established, and the following relationship is met:

[0180]

[0181] In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i are the proportional coefficient and the integral coefficient of the integral element PI respectively, V qpll is the q-axis component of the three-phase power grid voltage after dq transformation, ω is the power grid frequency, K pll is the shielding coefficient of the integral element, when the output voltage of the converter is less than the set voltage threshold but the voltage of the grid-connected bus is not less than the set voltage threshold, K pll is 0, when the output voltage of the converter and the voltage of the grid-connected bus are both less than the set voltage threshold, K pll is 1.

[0182] Figure 5 In the formula, v a , v b , v cV is the three-phase output voltage of the converter. d v q dq-axis components of the three-phase output voltage of the converter, PI is the integrator, and mod is the modulo operator.

[0183] In this embodiment, based on the improved phase-locked loop control, when a transient synchronous instability occurs in the power grid, causing the converter's output voltage to be lower than the set voltage threshold but the voltage of the grid-connected bus not to be lower than the set voltage threshold, the shielding effect of the integral link's shielding coefficient allows only the first-level control link to be retained while the second-level integral link is shielded. The retained first-level control link has overdamping performance and does not have overshoot problems, essentially suppressing the overshoot of the integral link, thereby ensuring that the converter can still operate in the grid-connected control mode without switching to the grid-following control mode. When a fault such as a short circuit occurs in the power grid, causing both the converter's output voltage and the grid-connected bus voltage to be lower than the set voltage threshold, the integral link's shielding coefficient does not play a role, allowing the integral link to perform the performance of following the system signal. The converter, operating in the grid-following control mode, can quickly control the converter's output voltage to recover until the fault is cleared.

[0184] When the converter operates in grid-connected control mode, the large number of nonlinear loads connected in a weak grid environment will generate harmonic components, affecting the power quality of the system. This degraded power quality will have numerous impacts on the control and conversion modules, which are composed of power electronic components, leading to decreased performance and efficiency. Therefore, to suppress the impact of harmonic components, measures such as... Figure 6 The voltage and current loop structure within the control module of the grid-type converter shown is improved to ensure control of the fundamental voltage while suppressing harmonic components.

[0185] Figure 6 In the middle, e ref (s) is the reference voltage, Z b (s) is the feedback impedance, G i (s) is the forward gain function of the current loop, G u (s) is the forward gain function of the voltage loop, I L (s) is the equivalent inductance current, I C (s) represents the equivalent capacitance current.

[0186] Figure 6 The solid line in the diagram represents the control loop of the original voltage-current dual closed-loop structure. The forward gain function of the original voltage-current loop satisfies the following relationship:

[0187]

[0188] In the formula, G(s) is the forward gain function of the voltage-current loop before the improvement, and K... pK is the proportional coefficient of the PWM rectification. i K is the proportionality coefficient of the current loop. u is the proportionality coefficient of the voltage loop, J is the moment of inertia, C is the equivalent capacitance, and s is the integral operator.

[0189] In the embodiments, Figure 6 The dashed lines represent the newly added control loop within the improved voltage-current dual closed-loop structure. Based on the above improvements, the forward gain function of the improved voltage-current loop is realized, satisfying the following relationship:

[0190]

[0191] In the formula, G′(s) is the forward gain function of the improved voltage-current loop, L is the equivalent inductance, and s is the integral operator.

[0192] The improved voltage and current dual closed-loop structure can effectively solve the converter current harmonic problem caused by grid background harmonics, without adding any extra control links, and is simple to implement.

[0193] While improvements to the control structure meet the requirements for control switching, they cannot fully satisfy the requirements for system power equalization. Therefore, this invention proposes a stabilization control device that incorporates a power equalization module.

[0194] In actual operation, when grid-connected and grid-connected converters are directly connected to the power grid, neither type of converter has power regulation capability during parallel operation, resulting in poor power quality. Therefore, this invention proposes a power balancing control structure for grid-connected and grid-connected converters, including:

[0195] 1) Improvements to the power balance control structure of the grid converter;

[0196] For grid converters, such as Figure 7 As shown, the improved power equalization control structure includes: a power control loop, a current control loop, and a phase-locked loop.

[0197] Figure 7 In the middle, P ref and Q ref P and Q are the active power reference value and reactive power reference value of the converter, respectively, and P and Q are the actual active power value and actual reactive power value of the converter, respectively. e and Q e These are the active power feedback value and reactive power feedback value of the converter, respectively. and These are the dq-axis components of the capacitor current, respectively. and These are the dq-axis components of the capacitor voltage, L fFor filtering inductors, and These are the dq-axis components of the capacitor feedback current, K. c θ is the gain coefficient of the capacitor feedback current, and θ is the actual value of the system's equivalent impedance angle.

[0198] The power control loop is used to obtain the outer loop control values ​​for active power and reactive power by integrating the differences between the active power reference value and the reactive power feedback value, respectively, through a PI converter. The current control loop is used to obtain the inner loop control values ​​for active power and reactive power based on the outer loop control values ​​for active power and reactive power, using the dq-axis components of the capacitor current and the capacitor feedback current. The phase-locked loop is used to optimize the control signal based on the inner loop control values ​​for active power and reactive power.

[0199] 2) Improvement of the power equalization control structure of the grid-type converter;

[0200] For network converters, such as Figure 8 As shown, the improved power equalization control structure includes an algorithm loop, a voltage loop, and a current loop.

[0201] Figure 8 Middle,U dref U qref These represent the dq-axis components of the converter's output voltage reference value. These are the dq-axis components of the voltage of the grid-connected bus, C f This is a filter capacitor.

[0202] The algorithm loop is used to adjust the grid connection point voltage based on the dq-axis component of the converter's output voltage reference value and the dq-axis component of the grid bus voltage; the voltage loop and current loop are used to adjust the control signal based on the difference between the adjusted grid connection point voltage and the converter's output voltage reference value.

[0203] 3) Correct the phase of related signals on both the grid-type converter side and the network-type converter side.

[0204] Regardless of whether it's a grid-type converter or a network-based converter, after improving the power equalization control structure, the phase of the relevant signals on the control module side needs to be corrected using the following formula:

[0205]

[0206] In the formula, The dq-axis components of the impedance current, grid current, grid bus voltage, and converter output voltage on the grid-connected converter side or the network-connected converter side are used to synchronize the phase values. The delta theta is the equivalent impedance angle difference value of the corresponding signals of the grid-connected converter side or the grid-constructing converter side and the system side for the dq-axis components of the synchronous phase values of the impedance current, the grid current, the grid-connected bus voltage and the converter output voltage of the system side.

[0207] When only the grid-connected converter or only the grid-constructing converter exists in the system, the control structure does not need to be improved and the phase of the related signals does not need to be corrected for the power balance allocation problem, but when the grid-connected converter and the grid-constructing converter are combined and exist together, the power balance control structure of the grid-connected converter needs to be improved, the power balance control structure of the grid-constructing converter needs to be improved, and the phase of the related signals of the grid-connected converter side and the grid-constructing converter side needs to be corrected, so as to accurately control the output power of the converter, reduce the fluctuation of voltage and current, improve the power quality, reduce the complexity of the system to a certain extent, and reduce the maintenance and management cost.

[0208] For the design of the control structure, since the grid-connected converter presents the related characteristics of a current source, the same phase relationship as the alternating current source can be obtained through the PLL phase-locked loop, while the grid-constructing converter presents the related characteristics of a voltage source, and the phase synchronization is maintained by using the droop control and the current loop and other power synchronization links. By using the PLL phase-locked loop and the power synchronization link as the dominant role, the coupling influence of the dynamic loop and the impedance can be effectively inhibited during the operation of the system, and the risk of oscillation distortion during the operation of the system is reduced.

[0209] For the power control, considering that the voltage provided by the new energy is unstable in the new power system, accurate processing of the output power of the system can greatly apply the new energy and improve the energy efficiency of the system. Different control modes such as the phase-locked loop control and the algorithm loop control are adopted according to the different properties of the grid-connected converter and the grid-constructing converter, so as to ensure accurate control of the output power of the grid-connected converter and the grid-constructing converter in different modes.

[0210] The application further provides a stability control method of the new power system, and the stability control method is realized by using a stability control device of the new power system.

[0211] When the new power system is unstable in the full frequency band, the output current of the converter and the voltage of the grid-connected bus are detected.

[0212] When no system fault is detected and the output current of the converter is not greater than a set current threshold and the voltage of the grid-connected bus is not less than a set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter; when the output current is detected to be greater than the set current threshold, the control signal output by the grid-following converter control module is output to the converter until the output current is not greater than the set current threshold, the control signal output by the grid-forming converter control module is output to the converter;

[0213] When a system fault is detected and the voltage of the grid-connected bus is less than a set voltage threshold, the control signal output by the grid-following converter control module is output to the converter until no system fault is detected and the voltage of the grid-connected bus is not less than the set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter;

[0214] When a system fault is detected, but the output current is not greater than a set current threshold and the voltage of the grid-connected bus is less than a set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter.

[0215] Preferably, the structure of the phase-locked loop control in the grid-following converter control module is improved, and the improved phase-locked loop control includes a shielding link in parallel with an integral link;

[0216] The improved phase-locked loop control model satisfies the following relationship:

[0217]

[0218] In the formula, θ pll is a reference phase output by the phase-locked loop, k p and k i are a proportional coefficient and an integral coefficient of the integral link PI respectively, V qpll is a q-axis component after dq transformation of a three-phase grid voltage, ω is a grid frequency, K pll is a shielding coefficient of the integral link, when the output voltage of the converter is less than a set voltage threshold but the voltage of the grid-connected bus is not less than the set voltage threshold, K pll is 0, when the output voltage of the converter and the voltage of the grid-connected bus are both less than the set voltage threshold, K pll is 1.

[0219] Preferably, the structure of the voltage and current loop in the grid-forming converter control module is improved, and the forward gain function of the improved voltage and current loop satisfies the following relationship:

[0220]

[0221] In the formula, G'(s) is the forward gain function of the improved voltage and current loop, K pK is the proportional coefficient of the PWM rectifier i K is the proportional coefficient of the current loop u J is the proportional coefficient of the voltage loop, J is the moment of inertia, C is the equivalent capacitance, L is the equivalent inductance, and s is the integral operator.

[0222] Preferably, the improvement of the power balance control structure of the grid-following converter includes: a power control loop, a current control loop, and a phase-locked loop.

[0223] The power control loop is used to obtain active power outer loop control values and reactive power outer loop control values by integrating the differences between active power reference values and reactive power reference values and active power feedback values and reactive power feedback values, respectively. The current control loop is used to obtain active power inner loop control values and reactive power inner loop control values based on the active power outer loop control values and the reactive power outer loop control values, using the capacitor current dq-axis components and the capacitor feedback current dq-axis components. The phase-locked loop is used to optimize the control signal according to the active power inner loop control values and the reactive power inner loop control values.

[0224] Preferably, the improvement of the power balance control structure of the grid-forming converter includes: an algorithm loop, a voltage loop, and a current loop.

[0225] The algorithm loop is used to adjust the grid point voltage according to the dq-axis components of the output voltage reference values of the converter and the voltage dq-axis components of the grid bus. The voltage loop and the current loop are used to adjust the differences between the adjusted grid point voltage and the output voltage reference values of the converter to optimize the control signal.

[0226] Preferably, after the improvement of the power balance control structure, the phases of the related signals on the grid-following converter side and the grid-forming converter side are corrected according to the following relationship:

[0227]

[0228] In the formula, is the dq-axis component of the synchronous phase values of the impedance current, the grid current, the grid bus voltage, and the converter output voltage on the grid-following converter side or the grid-forming converter side, is the dq-axis component of the synchronous phase values of the impedance current, the grid current, the grid bus voltage, and the converter output voltage on the system side, and Δθ is the equivalent impedance angle difference value of the corresponding signals on the grid-following converter side or the grid-forming converter side and the system side.

[0229] Preferably, the current threshold is set to 1.1 p.u., and the voltage threshold is set to 0.9 p.u.

[0230] The present disclosure can be a system, a method, and / or a computer program product. The computer program product can include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

[0231] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or punched tape, a

[0232] The computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0233] Computer readable program instructions for carrying out operations of the present disclosure can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or any combination of source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present disclosure.

[0234] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced, and any modification or replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A novel power system full-band instability factor detection method, the converter in the novel power system operates as a grid-following converter when operating in a grid-following control mode, and operates as a grid-forming converter when operating in a grid-forming control mode, characterized in that, The method comprises the following steps: obtaining the operating parameters of the new power system, and establishing an equivalent circuit when the grid-following converter and the grid-forming converter coexist; based on the equivalent circuit, determining the output complex power of the grid-following converter; extracting the impedance amplitude from the output complex power of the grid-following converter; when the impedance amplitude is proportional to the equivalent impedance of the grid-following converter, determining the value range of the equivalent impedance of the grid-following converter and the value range of the included angle between the equivalent impedance of the grid-following converter and the equivalent impedance of the grid-connected bus when the new power system is unstable, as the first condition for instability factor detection; based on the equivalent circuit, determining the output complex power of the grid-forming converter; determining the active power output by the grid-forming converter according to the output complex power of the grid-forming converter; when the active power output by the grid-forming converter is not greater than the load active power, determining the value range of the system power angle and the system impedance angle when the new power system is unstable, as the second condition for instability factor detection; when the related parameters in the new power system meet any one of the conditions, it is determined that the new power system is unstable in the full frequency range, and the related parameters that meet the condition are taken as the instability factor of the new power system in the full frequency range.

2. The new power system full-frequency instability factor detection method according to claim 1, wherein, based on the equivalent circuit, the output complex power of the grid-following converter satisfies the following relationship:

3. The new power system full-frequency instability factor detection method according to claim 2, wherein, wherein is the output complex power of the grid-following converter, is the voltage phasor of the grid bus, is the output current phasor of the grid-following converter, Z g is the equivalent impedance of the grid bus, Z2is the equivalent impedance of the grid-following converter, I GFL is the output current of the grid-following converter, δ g , δ2are the power angles of the grid bus and the grid-following converter, respectively, θ g , θ2are the equivalent impedance angles of the grid bus and the grid-following converter, respectively.

4. The new power system full-frequency instability factor detection method according to claim 1, wherein, Impedance magnitude defining output complex power of grid-following converter Impedance magnitude is proportional to the equivalent impedance of the grid-following converter New power system instability The value range of the equivalent impedance of the grid-connected converter when the new power system is unstable is Z2∈[0,Z g cosθ g2 The value range of the included angle between the equivalent impedance Z2 of the grid-connected converter and the equivalent impedance Z g of the grid-connected bus is θ g2 ∈(π2,3π2), as the first condition for detecting the full-band instability factor of the new power system. based on the equivalent circuit, the output complex power of the grid-forming converter satisfies the following relationship:

5. The new power system full-frequency instability factor detection method according to claim 4, wherein, wherein is the output complex power of the grid-forming converter, is the output voltage phasor of the grid-forming converter, U1 is the output voltage of the grid-forming converter, U g is the voltage of the grid-connected bus, is the output current phasor of the grid-forming converter, Z g is the equivalent impedance of the grid-connected bus, Z1 is the equivalent impedance of the grid-forming converter, δ1 is the power angle of the grid-forming converter, θ g and θ1 are the equivalent impedance angles of the grid-connected bus and the grid-forming converter, respectively. when the active power output by the grid-forming converter is not greater than the load active power, the new power system is unstable, and the following relationship is satisfied: wherein, δ0 is the system power angle when the power system is stably operated, and θ0 is the system impedance angle when the power system is stably operated; determining the value range of the system power angle and the system impedance angle when the new power system is unstable is arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], as the second condition for instability factor detection of the new power system in the full frequency range. The method comprises the following steps:

6. A novel power system full-band instability factor detection device to implement the full-band instability factor detection method of any one of claims 1 to 5, characterized in that, an equivalent circuit module is configured to obtain the operating parameters of the new power system, and establish an equivalent circuit when the grid-following converter and the grid-forming converter coexist; ​ The detection condition generation module is configured to determine the output complex power of the grid-following converter based on the equivalent circuit; extract the impedance amplitude from the output complex power of the grid-following converter; determine the value range of the equivalent impedance of the grid-following converter and the value range of the included angle between the equivalent impedance of the grid-following converter and the equivalent impedance of the grid-connected bus when the new power system is unstable, as the first condition for instability factor detection, based on the fact that the impedance amplitude is proportional to the equivalent impedance of the grid-following converter when the new power system is unstable; determine the output complex power of the grid-forming converter based on the equivalent circuit; determine the active power output by the grid-forming converter according to the output complex power of the grid-forming converter; determine the value range of the system power angle and the system impedance angle when the new power system is unstable, as the second condition for instability factor detection, based on the fact that the new power system is unstable when the active power output by the grid-forming converter is not greater than the load active power. The instability judgment module is configured to determine that the new power system is unstable in the full frequency range when the related parameters in the new power system meet any one of the conditions.

7. The new power system full-frequency instability factor detection device according to claim 6, wherein The detection condition generation module comprises an output complex power calculation unit of the grid-following converter. The output complex power calculation unit of the grid-following converter is configured to calculate the output complex power of the grid-following converter based on the equivalent circuit according to the following relationship: wherein is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor of the grid-following converter, Z g is the equivalent impedance of the grid-connected bus, Z2is the equivalent impedance of the grid-following converter, I GFL is the output current of the grid-following converter, δ g , δ2are the power angles of the grid-connected bus and the grid-following converter, respectively, θ g , θ2are the equivalent impedance angles of the grid-connected bus and the grid-following converter, respectively.

8. The new power system full-frequency instability factor detection device according to claim 7, wherein The detection condition generation module further comprises a first condition generation unit. The first condition generating unit is configured to define an impedance amplitude of output complex power of the grid-following converter The impedance amplitude is proportional to the equivalent impedance of the grid-following converter, and the condition is met The new power system is unstable, and the value range of the equivalent impedance of the grid-following converter when the new power system is unstable is Z2∈[0,Z g cosθ g2 The value range of the included angle between the equivalent impedance Z2 of the grid-following converter and the equivalent impedance Z g of the grid-connected bus is θ g2 ∈(π2,3π2), as the first condition for detecting the full-frequency instability factor of the new power system.

9. The new power system full-frequency instability factor detection device according to claim 6, wherein The detection condition generation module further comprises an output complex power calculation unit of the grid-forming converter. The output complex power calculation unit of the grid-forming converter is configured to calculate the output complex power of the grid-forming converter based on the equivalent circuit according to the following relationship: wherein is the output complex power of the grid-forming converter, is the output voltage phasor of the grid-forming converter, Ui is the output voltage of the grid-forming converter, g is the voltage of the grid-connected bus, is the output current phasor conjugate of the grid-forming converter, Zi is the output current of the grid-forming converter, g is the equivalent impedance of the grid-connected bus, Zi is the equivalent impedance of the grid-forming converter, δi is the power angle of the grid-forming converter, θi is the power angle of the grid-connected bus, g θi are the equivalent impedance angles of the grid-connected bus and the grid-forming converter, respectively.

10. The new power system full-frequency instability factor detection device according to claim 9, wherein The detection condition generation module further comprises a second condition generation unit. The second condition generation unit is configured to determine that the new power system is unstable when the active power output by the grid-forming converter is not greater than the load active power, and satisfy the following relationship: wherein δ0 is the system power angle when the power system is stably operated, and θ0 is the system impedance angle when the power system is stably operated; The value range of the system power angle and the system impedance angle when the new power system is unstable is arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], as the second condition for new power system full-frequency instability factor detection.

11. A stabilizing control device for a novel power system, characterized by The detection condition generation module comprises an output complex power calculation unit of the grid-following converter. The grid-forming converter control module is used for implementing droop control on the converter, the grid-following converter control module is used for implementing phase-locked loop control on the converter, and the control signal output by the grid-forming converter control module and the control signal output by the grid-following converter control module are both input into the control conversion module; The instability factor detection device determines that the new power system is unstable in the full frequency band, and starts the control conversion module; The control conversion module is used for detecting the output current of the converter and the voltage of the grid-connected bus; when no system fault is detected, the output current of the converter is not greater than a set current threshold, and the voltage of the grid-connected bus is not less than a set voltage threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter; when the output current is detected to be greater than the set current threshold, the control conversion module outputs the control signal output by the grid-following converter control module to the converter, until the output current is not greater than the set current threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter; when a system fault is detected and the voltage of the grid-connected bus is less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-following converter control module to the converter, until no system fault is detected and the voltage of the grid-connected bus is not less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter; when a system fault is detected, but the output current is not greater than the set current threshold and the voltage of the grid-connected bus is less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-forming converter control module to the converter.

12. The stability control device of the new power system according to claim 11, characterized in that, The control conversion module comprises an input signal processing unit, a set signal processing unit, an RS flip-flop and a switching switch; the input signal processing unit is used for acquiring the effective value of the three-phase output current of the converter and comparing the effective value with a set current threshold value; when the effective value of the output current of any phase is greater than the set current threshold value, a signal "1" is sent to a synchronous input end S of the RS flip-flop, otherwise a signal "0" is sent to the synchronous input end S of the RS flip-flop; the set signal processing unit is used for acquiring the effective value of the voltage of the grid-connected bus after coordinate transformation and comparing the effective value with a set voltage threshold value u; when the effective value of the grid-connected bus voltage is greater than the set voltage threshold value, a signal "1" is sent to another synchronous input end R of the RS flip-flop, otherwise a signal "0" is sent to the synchronous input end R of the RS flip-flop; the RS flip-flop takes the three-phase output current of the converter as a priority signal and takes the voltage of the grid-connected bus as a set signal, and outputs a signal F; when the signal F is a signal "1", the switching switch makes the grid-connected type converter control module conductive and outputs the control signal of the grid-connected type converter control module to the converter; when the signal F is a signal "0", the switching switch makes the grid-following type converter control module conductive and outputs the control signal of the grid-following type converter control module to the converter.

13. The stabilizing control device of the novel power system according to claim 11, wherein The structure of the phase-locked loop control in the grid-following type converter control module is improved, and the improved phase-locked loop control comprises a shielding link connected in parallel with an integral link; The improved phase-locked loop control model satisfies the following relationship: In the formula, θ pll is the reference phase output by the phase-locked loop, k p and k i are the proportional coefficient and integral coefficient of the integral element PI respectively, V qpll is the q-axis component of the three-phase grid voltage after dq transformation, ω is the grid frequency, K pll is the shielding coefficient of the integral element, when the output voltage of the converter is less than the set voltage threshold but the voltage of the grid-connected bus is not less than the set voltage threshold, K pll is 0, when the output voltage of the converter and the voltage of the grid-connected bus are both less than the set voltage threshold, K pll is 1.

14. The stabilizing control device of the novel power system according to claim 11, wherein The structure of the voltage and current loop in the grid-connected type converter control module is improved, and the forward gain function of the improved voltage and current loop satisfies the following relationship: where G'(s) is the forward gain function of the improved voltage current loop, K p is the proportional coefficient of the PWM rectifier, K i is the proportional coefficient of the current loop, K u is the proportional coefficient of the voltage loop, J is the moment of inertia, C is the equivalent capacitance, L is the equivalent inductance, and s is the integral operator.

15. The stabilizing control device of the novel power system according to claim 11, wherein The structure of the power balance control of the grid-following type converter is improved, and the improved power balance control structure comprises a power control loop, a current control loop and a phase-locked loop; The power control loop is used for obtaining the difference between the active power reference value and the active power feedback value and the difference between the reactive power reference value and the reactive power feedback value through the integral link, to obtain the active power outer loop control value and the reactive power outer loop control value; the current control loop is used for obtaining the active power inner loop control value and the reactive power inner loop control value based on the active power outer loop control value and the reactive power outer loop control value, by using the capacitor current dq-axis component and the capacitor feedback current dq-axis component; and the phase-locked loop is used for optimizing the control signal according to the active power inner loop control value and the reactive power inner loop control value.

16. The stabilizing control device of the novel power system according to claim 15, wherein The structure of the power balance control of the grid-connected type converter is improved, and the improved power balance control structure comprises an algorithm loop, a voltage loop and a current loop; The algorithm ring is configured to adjust the grid point voltage according to the dq axis component of the output voltage reference value of the converter and the dq axis component of the voltage of the grid bus; the voltage loop and the current loop are configured to adjust based on the difference between the adjusted grid point voltage and the output voltage reference value of the converter to optimize the control signal.

17. The stabilizing control device of the novel power system according to claim 16, wherein After the improvement of the power balance control structure, the phases of the relevant signals on the grid-connected converter side and the grid-forming converter side are corrected according to the following relationship: In the formula, is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid bus voltage, and converter output voltage on the grid-connected converter side or grid-forming converter side, is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid bus voltage, and converter output voltage on the system side, and Δθ is the equivalent impedance angle difference value of the corresponding signals on the grid-connected converter side or grid-forming converter side and the system side.

18. The stabilizing control device of the novel power system according to claim 11, wherein The current threshold is set to 1.1 p.u., and the voltage threshold is set to 0.9 p.u.

19. A stabilizing control method of a new power system, implemented by the stabilizing control device of the new power system according to any one of claims 11 to 18, characterized by, Comprising: When the novel power system is unstable in the full frequency band, the output current of the converter and the voltage of the grid bus are detected; When no system fault is detected, and the output current of the converter is not greater than the set current threshold, and the voltage of the grid bus is not less than the set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter; when the output current is detected to be greater than the set current threshold, the control signal output by the grid-connected converter control module is output to the converter until the output current is not greater than the set current threshold, the control signal output by the grid-forming converter control module is output to the converter; When a system fault is detected and the voltage of the grid bus is less than the set voltage threshold, the control signal output by the grid-connected converter control module is output to the converter until no system fault is detected and the voltage of the grid bus is not less than the set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter; When a system fault is detected, but the output current is not greater than the set current threshold and the voltage of the grid bus is less than the set voltage threshold, the control signal output by the grid-forming converter control module is output to the converter.

20. The stabilizing control method of the novel power system according to claim 19, wherein The structure of the phase-locked loop control in the grid-connected converter control module is improved, and the improved phase-locked loop control includes a shielding link in parallel with an integral link; The improved phase-locked loop control model satisfies the following relationship: In the formula, θ pll is the reference phase output by the phase-locked loop, k p and k i are the proportional coefficient and integral coefficient of the integral element PI respectively, V qpll is the q-axis component of the three-phase grid voltage after dq transformation, ω is the grid frequency, K pll is the shielding coefficient of the integral element, when the output voltage of the converter is less than the set voltage threshold but the voltage of the grid-connected bus is not less than the set voltage threshold, K pll is 0, when the output voltage of the converter and the voltage of the grid-connected bus are both less than the set voltage threshold, K pll is 1.

21. The stabilizing control method of the novel power system according to claim 19, wherein The structure of the voltage and current loop in the grid-forming converter control module is improved, and the forward gain function of the improved voltage and current loop satisfies the following relationship: where G'(s) is the forward gain function of the improved voltage current loop, K p is the proportional coefficient of the PWM rectifier, K i is the proportional coefficient of the current loop, K u is the proportional coefficient of the voltage loop, J is the moment of inertia, C is the equivalent capacitance, L is the equivalent inductance, and s is the integral operator.

22. The stabilizing control method of the novel power system according to claim 19, wherein The improvement of the power balance control structure of the grid-connected converter includes a power control loop, a current control loop and a phase-locked loop. The power control loop is used to obtain active power outer loop control value and reactive power outer loop control value by integrating the difference between active power reference value, reactive power reference value and active power feedback value, reactive power feedback value; the current control loop is used to obtain active power inner loop control value and reactive power inner loop control value by using capacitor current dq axis component and capacitor feedback current dq axis component based on active power outer loop control value and reactive power outer loop control value; the phase-locked loop is used to obtain the optimization control signal according to active power inner loop control value and reactive power inner loop control value.

23. The method of claim 22, wherein, The improvement of the power balance control structure of the grid-forming converter includes an algorithm loop, a voltage loop and a current loop; The algorithm loop is used to adjust the grid-connected point voltage according to the output voltage reference value dq axis component of the converter and the voltage dq axis component of the grid-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid-connected point voltage and the output voltage reference value of the converter to optimize the control signal.

24. The method of claim 23, wherein, After the improvement of the power balance control structure, the phase of the related signals on the grid-following converter side and the grid-forming converter side is corrected according to the following relationship: In the formula, is the dq-axis component of the impedance current, grid current, grid bus voltage, and synchronous phase value of the converter output voltage on the grid-connected converter side or grid-forming converter side, is the dq-axis component of the impedance current, grid current, grid bus voltage, and synchronous phase value of the converter output voltage on the system side, and Δθ is the equivalent impedance angle difference value of the corresponding signals on the grid-connected converter side or grid-forming converter side and the system side.

25. The method of claim 19, wherein, The current threshold is set to 1.1 p.u. and the voltage threshold is set to 0.9 p.u.

26. A terminal comprising a processor and a storage medium, wherein: The storage medium is used to store instructions; The processor is used to operate according to the instructions to perform the steps of the full-band instability factor detection method of the novel power system according to any one of claims 1-5; The processor is used to operate according to the instructions to perform the steps of the stabilizing control method of the novel power system according to any one of claims 19-25.

27. A computer readable storage medium having stored thereon a computer program, characterized in that The program is executed by the processor to implement the steps of the full-band instability factor detection method of the novel power system according to any one of claims 1-5.

28. A computer readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the steps of the stabilizing control method of the novel power system according to any one of claims 19-25.

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