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

Abstract

According to the novel electric power system full-band instability factor detection method and the stability control device, the value range of the equivalent impedance of a grid-following type converter and the value range of the included angle between the equivalent impedance of the grid-following type converter and the equivalent impedance of a grid-connected bus when the novel electric power system is unstable are determined to serve as the first condition of instability factor detection; determining a value range of a system power angle and a system impedance angle when the novel power system is unstable, wherein the value range is a second condition for instability factor detection; when the relevant parameters in the novel power system meet any one condition, judging that the novel power system is in full-band instability, and taking the relevant parameters meeting the condition as full-band instability factors of the novel power system; a control signal output by the network construction type converter control module and a control signal output by the network following type converter control module are input into the instability detection control switching module; the coexistence of the following network type and the construction network type in the novel power system is realized, and the stability of power transmission is ensured.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics technology and current conversion technology, and specifically relates to a new full-band instability factor detection method and a stabilization control device for a new power system in which a grid-following converter and a grid-building converter coexist. Background Art

[0002] In recent years, the power system has developed rapidly towards a high proportion of renewable energy and power electronic equipment. Due to the coupling effect and other complex factors inside the new power system, the system will cause frequency oscillations that cause instability, which will have a very serious impact on the power quality of the power grid. The control methods of single converters currently used are mostly divided into two types: grid-following converters and grid-building converters. If the two converters are used alone, the oscillation problem of the grid-following converter will worsen as the network strength weakens, and the oscillation problem of the grid-building converter will worsen as the grid strength increases.

[0003] When facing the large-scale commissioning of new energy, due to the strong uncertainty of new energy, it will directly lead to drastic changes in 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 system is relatively large, and the changes in voltage and frequency are relatively small. When it is disturbed by the outside world, it can quickly restore stability. However, 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 when the entire weak power grid system is disturbed by the outside world. In severe 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 operate safely and stably in a weak power grid environment. The stability grid test system of the grid-forming converter realizes the stability test of the grid-forming converter after it is connected to the grid by simulating the 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-forming converter to the grid-forming converter that can better adapt to the weak power grid environment, only controls the stability of a single converter in the use of the controller, 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 power market environment where "double high" is constantly advancing, there is an urgent need for a new power system full-band instability mechanism analysis method and stabilization control device that can adapt to the coexistence of grid-forming and grid-forming converters in the new power system, and a system that does not cause the oscillation problem to worsen for the change of the power grid strength, so as to ensure the reliability and safety of the power supply of the power grid. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a new type of power system full-band instability factor detection method and stabilization control device in which grid-following and grid-building converters coexist, which fully utilizes the advantages of both grid-following and grid-building converters, and enables the power grid system to safely and stably transmit electric energy under different operating conditions of the power grid system, thereby ensuring the stability of power transmission. At the same time, in the face of the different stability problems between the new power system with a high proportion of new energy power generation equipment and the traditional power system, the full-band instability factors of the system are detected through impedance angle stability.

[0006] The present invention adopts the following technical solution.

[0007] The present invention proposes a novel method for detecting instability factors of a power system in full frequency band. The converter in the novel power system acts as a grid-following converter when operating in a grid-following control mode and acts as a grid-forming converter when operating in a grid-forming control mode, comprising:

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

[0009] Based on the equivalent circuit, the output complex power of the grid-type converter is determined; the impedance amplitude is extracted from the output complex power of the grid-type converter; based on the instability of the new power system when the impedance amplitude is proportional to the equivalent impedance of the grid-type converter, the value range of the equivalent impedance of the grid-type converter when the new power system is unstable and the value range of the angle between the equivalent impedance of the grid-type converter and the equivalent impedance of the grid-connected bus are determined as the first condition for detecting the instability factor;

[0010] Based on the equivalent circuit, the output complex power of the grid-type converter is determined; the active power output by the grid-type converter is determined according to the output complex power of the grid-type converter; based on the instability of the new power system when the active power output by the grid-type converter is not greater than the active power of the load, 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 for detecting the instability factor;

[0011] When relevant 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 band, and the relevant parameters that meet the conditions are used as the instability factors of the new power system in the full frequency band.

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

[0013]

[0014] In the formula, is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 2 is the equivalent impedance of the grid-type converter, I GFL is the output current of the grid-following converter, δ g , δ 2 are the power angle of the grid-connected busbar and the power angle of the grid-following converter, θ g ,θ 2 They are 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 of the output complex power of the grid-following converter is defined as When the impedance amplitude is proportional to the equivalent impedance of the grid-type converter, New power system instability;

[0016] Determine the value range of the equivalent impedance of the grid-following converter when the new power system is unstable as Z 2 ∈[0,Z g cosθ g2 ] and the equivalent impedance Z of the grid-type converter 2 The equivalent impedance Z of the grid-connected busbar g The range of the angle between g2 ∈(π2,3π2), as the first condition for detecting instability factors in the full-band of the new power system.

[0017] Preferably, based on the equivalent circuit, the output complex power of the grid-type converter satisfies the following relationship:

[0018]

[0019] In the formula, is the output complex power of the grid-following converter, is the output voltage phasor of the grid-type converter, U 1 is the output voltage of the grid-type converter, U g is the voltage of the grid-connected busbar, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 1 is the equivalent impedance of the grid-type converter, δ 1 is the power angle of the grid-type converter, θ g ,θ 1 They are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-connected converter respectively.

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

[0021]

[0022] In the formula, δ 0 is the system power angle when the power system is in stable operation, θ 0 It is the system impedance angle when the power system is in stable operation;

[0023] The range of the power angle and impedance angle of the new power system when it is unstable is determined to be arccos[-cos(δ 0 +θ 0 )-1]<θ 0 ≤2π-arccos[-cos(δ 0 +θ 0 )-1], as the second condition for detecting the full-band instability factors of the new power system.

[0024] The present invention also proposes a novel power system full-band instability factor detection device to implement a full-band instability factor detection method, including:

[0025] The equivalent circuit module is used to obtain the operating parameters of the new power system and establish the equivalent circuit when the grid-following converter and the grid-building converter coexist;

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

[0027] The instability judgment module is used to judge that the new power system is instability in the entire frequency band when the relevant parameters in the new 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-following converter;

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

[0030]

[0031] In the formula, is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 2 is the equivalent impedance of the grid-type converter, I GFL is the output current of the grid-following converter, δ g , δ 2 are the power angle of the grid-connected busbar and the power angle of the grid-following converter, θ g ,θ 2 They are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of 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 used 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-type converter, The new power system is unstable; the equivalent impedance range of the grid-following converter when the new power system is unstable is determined to be Z 2 ∈[0,Z g cosθ g2 ] and the equivalent impedance Z of the grid-type converter 2 The equivalent impedance Z of the grid-connected busbar g The range of the angle between g2 ∈(π2,3π2), as the first condition for detecting instability factors in the full-band of the new power system.

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

[0035] The output complex power calculation unit of the meshed converter is used to calculate the output complex power of the meshed 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 phasor of the grid-type converter, U1 is the output voltage of the grid-type converter, U g is the voltage of the grid-connected busbar, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 1 is the equivalent impedance of the grid-type converter, δ 1 is the power angle of the grid-type converter, θ g ,θ 1 They are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-connected converter respectively.

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

[0039] The second condition generation unit is used to generate the new power system instability when the active power output by the grid-type converter is not greater than the active power of the load, and satisfies the following relationship:

[0040]

[0041] In the formula, δ 0 is the system power angle when the power system is in stable operation, θ 0 It is the system impedance angle when the power system is in stable operation;

[0042] The range of the power angle and impedance angle of the new power system when it is unstable is determined to be arccos[-cos(δ 0 +θ 0 )-1]<θ 0 ≤2π-arccos[-cos(δ 0 +θ 0 )-1], as the second condition for detecting the full-band instability factors of the new power system.

[0043] The present invention also proposes a novel stabilization control device for an electric power system, comprising:

[0044] A grid-forming converter control module, a grid-following converter control module, an instability factor detection device and a control conversion module; the grid-forming converter control module is used to implement droop control on the converter, the grid-following converter control module is used to implement 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;

[0045] When the instability factor detection device determines that the new power system is instability in the entire frequency band, the control conversion module is started;

[0046] A control conversion module is used to detect the output current of the converter and the voltage of the grid-connected bus; 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-connected bus is not less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-connected converter control module to the converter; when it is detected that the output current is 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-connected 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-connected 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-connected converter control module to the converter.

[0047] Preferably, the control conversion module includes an input signal processing unit, a setting signal processing unit, an RS trigger and a switching switch; the input signal processing unit is used to obtain the effective value of the three-phase output current of the converter and compare it with the 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 synchronization input terminal S of the RS trigger, otherwise a signal "0" is sent to a synchronization input terminal S of the RS trigger; the setting signal processing unit is used to obtain the effective value of the voltage of the grid-connected bus after coordinate transformation, and compare it with the set voltage threshold value u. When the effective value of the grid-connected bus voltage is greater than the set current threshold value, a signal "1" is sent to a synchronization input terminal S of the RS trigger; otherwise, a signal "0" is sent to a synchronization input terminal S of the RS trigger; When the voltage threshold is set, a signal "1" is sent to another synchronization input terminal R of the RS trigger, otherwise a signal "0" is sent to one synchronization input terminal R of the RS trigger; the RS trigger takes the three-phase output current of the converter as the priority signal and the grid-connected bus electricity as the set signal, and the RS trigger outputs a signal F. When F is a signal "1", the switching switch turns on the grid-forming converter control module, and outputs the control signal output by the grid-forming converter control module to the converter. When F is a signal "0", the switching switch turns on the grid-following converter control module, and outputs the control signal output by the grid-following converter control module to the converter.

[0048] 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 connected in parallel with the 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 of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of the integral link PI, 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 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 The value 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 The value is 1.

[0052] Preferably, the structure of the voltage and current loop in the control module of the networked converter 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 PWM rectification, K i is the proportionality 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 power balancing control structure of the grid-following converter is improved, and the improved power balancing control structure includes: a power control loop, a current control loop and a phase-locked loop;

[0056] The power control loop is used to obtain the active power outer loop control value and the reactive power outer loop control value after the difference between the active power reference value and the reactive power reference value and the active power feedback value and the reactive power feedback value through an integration link; the current control loop is used to obtain 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, using the capacitor current dq axis component and the capacitor feedback current dq axis component; the phase-locked loop is used to optimize the control signal according to the active power inner loop control value and the reactive power inner loop control value.

[0057] Preferably, the power balancing control structure of the grid-type converter is improved, and the improved power balancing control structure includes: an algorithm loop, a voltage loop and a current loop;

[0058] The algorithm loop is used to adjust the grid connection 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-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid connection point voltage and the output voltage reference value of the converter to optimize the control signal.

[0059] Preferably, after the power balancing control structure is improved, 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:

[0060]

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

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

[0063] The present invention also proposes a novel power system stabilization control method, which is implemented by using a novel power system stabilization control device.

[0064] When determining that the new power system is instability in the 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 and the output current of the converter is not greater than the set current threshold and the voltage of the grid-connected bus is not less than the set voltage threshold, the control signal output by the grid-connected converter control module is output to the converter; when it is detected that the output current is 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 no greater than the set current threshold, the control signal output by the grid-connected 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, a control signal output by the grid-connected converter control module is output to the converter.

[0068] 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 connected in parallel with the integral link;

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

[0070]

[0071] In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of the integral link PI, 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 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 The value 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 The value is 1.

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

[0073]

[0074] Where G′(s) is the forward gain function of the improved voltage-current loop, K p is the proportional coefficient of PWM rectification, K i is the proportionality 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 power balancing control structure of the grid-following converter is improved, and the improved power balancing control structure includes: a power control loop, a current control loop and a phase-locked loop;

[0076] The power control loop is used to obtain the active power outer loop control value and the reactive power outer loop control value after the difference between the active power reference value and the reactive power reference value and the active power feedback value and the reactive power feedback value through an integration link; the current control loop is used to obtain 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, using the capacitor current dq axis component and the capacitor feedback current dq axis component; the phase-locked loop is used to optimize the control signal according to the active power inner loop control value and the reactive power inner loop control value.

[0077] Preferably, the power balancing control structure of the grid-type converter is improved, and the improved power balancing control structure includes: an algorithm loop, a voltage loop and a current loop;

[0078] The algorithm loop is used to adjust the grid connection 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-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid connection point voltage and the output voltage reference value of the converter to optimize the control signal.

[0079] Preferably, after the power balancing control structure is improved, 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:

[0080]

[0081] In the formula, is the dq axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the grid-following converter side or the grid-forming converter side, It is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the system side, and Δθ is the equivalent impedance angle difference between the corresponding signals on the grid-type converter side or the grid-connected converter side and the system side.

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

[0083] A terminal comprises 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 instruction to execute the steps of the novel power system full-band instability factor detection method;

[0086] The processor is used to operate according to the instructions to execute the steps of the novel power system stabilization control method.

[0087] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a new method for detecting instability factors of a full-frequency band of a power system.

[0088] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a novel power system stabilization control method.

[0089] The beneficial effects of the present invention are that, compared with the prior art, at least include: considering the close impedance matching relationship between the inverter and the power grid of the new power system, the present invention proposes to reflect the full-band instability of the new power system through the transformation of system impedance and impedance angle. The instability detection criterion proposed by the present invention is a supplement to the three stability criteria of voltage, frequency and power angle of the existing power system. The value range of the equivalent impedance of the grid-type converter and the value range of the angle between the equivalent impedance of the grid-type converter and the equivalent impedance of the grid-connected bus are used as the first condition for detecting instability factors; the value range of the system power angle and the system impedance angle are used as the second condition for detecting instability factors; when the relevant parameters in the new power system meet any one of the conditions, it is determined that the new power system is instability in the full frequency band, and the relevant parameters that meet the conditions are used as the instability factors of the new power system in the full frequency band.

[0090] The present invention also proposes a stabilizing control device, in which 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 instability detection control switching module, so as to realize the coexistence of the grid-following and grid-forming converters, and give full play to the excellent advantages of the grid-following converter in adapting to the grid voltage and frequency and in grid connection. However, the grid-following converter has poor performance in a weak grid environment, and because the grid-forming converter has a perceptual phase, it can better adapt to the weak grid environment. When the system is operating normally, only the grid-forming converter is required to work, and when a circuit fault occurs in the system. The system can switch to the working mode of the grid-following converter through the instability detection control switching module. The complementary relationship between the two can achieve a good grid connection effect for new energy in a weak grid environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Figure 1 It is a flow chart of a novel method for detecting instability factors of a power system in full frequency band proposed by the present invention;

[0092] Figure 2 is an equivalent circuit diagram established in an embodiment of the present invention;

[0093] Figure 3 It is a structural schematic diagram of a novel power system stabilization control device proposed by the present invention;

[0094] Figure 4is a schematic diagram of the structure of a control conversion module in an embodiment of the present invention;

[0095] Figure 5 It is a schematic diagram of the structural improvement of the grid-following converter control module in the present invention;

[0096] Figure 6 It is a schematic diagram of the structural improvement of the control module of the network-type converter in the present invention;

[0097] Figure 7 It is a schematic diagram of the improvement of the power balancing control structure of the grid-following converter in the present invention;

[0098] Figure 8 It is a schematic diagram of the improvement of the power balancing control structure of the grid-type converter in the present invention. DETAILED DESCRIPTION

[0099] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0100] The present invention proposes a novel method for detecting instability factors of a power system in full frequency band. The converter in the novel power system acts as a grid-following converter when operating in a grid-following control mode and acts as a grid-forming converter when operating in a grid-forming control mode. Figure 1 As shown, including:

[0101] Step 1: 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.

[0102] Specifically, establish Figure 2 The equivalent circuits of the grid-following converter and the grid-building converter are shown in FIG. Since the grid-building converter directly controls the output voltage of the converter, and the grid-following converter directly controls the output current of the converter, the grid-building converter is equivalent to a voltage source U s1 , and the equivalent impedance Z of the grid-type converter 1 Connect in series, and the grid-type converter is equivalent to a current source i s2 , and the equivalent impedance Z of the grid-following converter 2 Parallel connection, I GFM and I GFL are the output current of the grid-building converter and the output current of the grid-following converter, U g ,I g , Z gare the voltage, current and equivalent impedance of the grid-connected bus, Z g1 and Z g2 They are the equivalent impedance of the transmission line on the grid-forming converter side and the equivalent impedance of the transmission line on the grid-following converter side respectively.

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

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

[0105]

[0106] In the formula, is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 2 is the equivalent impedance of the grid-type converter, I GFL is the output current of the grid-following converter, δ g , δ 2 are the power angle of the grid-connected busbar and the power angle of the grid-following converter, θ g ,θ 2 They are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-following converter respectively.

[0107] Define the impedance magnitude of the output complex power of the grid-following converter If the power grid oscillates at this time, the output current I GFL Will decrease, the equivalent impedance Z of the grid-type converter 2 will increase, which will cause the impedance amplitude to decrease, and the output complex power of the grid-following converter will also decrease. The output current I of the grid-following converter GFL Increase, the equivalent impedance Z of the grid-type converter 2 When the impedance amplitude is reduced, the impedance amplitude will increase, and the output complex power of the grid-following converter will also increase, thereby suppressing power oscillation. Therefore, when the impedance amplitude is inversely proportional to the equivalent impedance of the grid-following converter, that is, The system can still return to a stable state after an oscillation occurs.

[0108]

[0109] In the formula, θ g2 is the equivalent impedance Z of the grid-following converter 2 The equivalent impedance Z of the grid-connected busbar g The angle between.

[0110] From the above formula we can get:

[0111] When θ g2 ∈(0,π2), The new power system will become unstable after oscillation;

[0112] When θ g2 ∈(π2,3π2) and Z 2 ∈[0,Z g cosθ g2 ]hour, The new power system will become unstable after oscillation;

[0113] When θ g2 ∈(π2,3π2) and Z 2 ∈[Z g cosθ g2 ,∞], The new power system can maintain stability after oscillation;

[0114] Therefore, based on the impedance amplitude being proportional to the equivalent impedance of the grid-type converter, that is, The new power system is unstable. The equivalent impedance range of the grid-following converter when the new power system is unstable is determined as Z 2 ∈[0,Z g cosθ g2 ] and the equivalent impedance Z of the grid-type converter 2 The equivalent impedance Z of the grid-connected busbar g The range of the angle between g2 ∈(π2,3π2), as the first condition for detecting instability factors in the full-band of the new power system.

[0115] Step 3, based on the equivalent circuit, determine the output complex power of the grid-type converter; determine the active power output of the grid-type converter according to the output complex power of the grid-type converter; based on the fact that the new power system is unstable when the active power output of the grid-type converter is not greater than the active power of the load, 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 detecting the instability factor.

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

[0117]

[0118] In the formula, is the output complex power of the grid-following converter, is the output voltage phasor of the grid-type converter, U 1 is the output voltage of the grid-type converter, U g is the voltage of the grid-connected busbar, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 1 is the equivalent impedance of the grid-type converter, δ 1 is the power angle of the grid-type converter, θ g ,θ 1 They 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 reactive power output by the grid-type converter satisfy the following relationship:

[0120]

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

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

[0123]

[0124] Where P 0 is the load active power, δ 0 is the system power angle when the power system is in stable operation, θ 0 It is the system impedance angle when the power system is operating stably.

[0125] When the active power output by the grid-forming converter is greater than the active power of the load, the new power system operates stably and satisfies the following relationship:

[0126]

[0127] because This new When the power system is running stably, the system impedance angle satisfies the following relationship:

[0128] 0<θ 0 ≤arccos[-cos(δ 0 +θ 0 )-1] and 2π-arccos[-cos(δ 0 +θ 0 )-1]<θ 0 <2π

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

[0130]

[0131] new Type Power When the system is unstable, the range of the system power angle and system impedance angle when the new power system is unstable is determined to be arccos[-cos(δ 0 +θ 0 )-1]<θ 0 ≤2π-arccos[-cos(δ 0 +θ 0 )-1], as the second condition for detecting the full-band instability factors of the new power system.

[0132] Step 4: When the relevant parameters in the new power system meet any one of the conditions, it is determined that the new power system is unstable in the entire frequency band, and the relevant parameters that meet the conditions are used as the instability factors of the new power system in the entire frequency band.

[0133] The stability of traditional power systems is divided into frequency stability, voltage stability and rotor angle stability. However, since the new power systems based on new energy sources are often located in remote areas, the power grid shows the characteristics of a weak power grid and is prone to low-frequency oscillation and harmonic oscillation. The instability is caused by the values ​​of various impedance angles, power angles and other parameters exceeding the stable value range when the system is running in different situations of grid-following converters and grid-forming converters. Therefore, the present invention determines whether the system is unstable by analyzing whether the various impedance angles, power angles and other parameters meet the value range when the system is stable when the system is running in different situations of grid-following converters and grid-forming converters, and can significantly distinguish the different instability factors of the grid-following converter and the grid-forming converter in the system, which is conducive to proposing specific implementation directions for stabilization control when the grid-following converter and the grid-forming converter coexist, and is more in line with the operation mode of the new power system.

[0134] The present invention also proposes a novel power system full-band instability factor detection device to implement a full-band instability factor detection method, including:

[0135] The equivalent circuit module is used to obtain the operating parameters of the new power system and establish the equivalent circuit when the grid-following converter and the grid-building converter coexist;

[0136] A detection condition generation module is used to determine the output complex power of the grid-type converter based on an equivalent circuit; extract the impedance amplitude from the output complex power of the grid-type converter; based on the instability of the new power system when the impedance amplitude is proportional to the equivalent impedance of the grid-type converter, determine the value range of the equivalent impedance of the grid-type converter when the new power system is instability and the value range of the angle between the equivalent impedance of the grid-type converter and the equivalent impedance of the grid-connected bus as the first condition for instability factor detection; based on the equivalent circuit, determine the output complex power of the grid-forming converter; determine the active power output by the grid-forming converter according to the output complex power of the grid-forming converter; based on the instability of the new power system when the active power output of the grid-forming converter is not greater than the active power of the load, determine the value range of the system power angle and the system impedance angle when the new power system is instability as the second condition for instability factor detection;

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

[0138] Preferably, the detection condition generation module comprises: an output complex power calculation unit of the grid-following converter;

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

[0140]

[0141] In the formula, is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 2 is the equivalent impedance of the grid-type converter, I GFL is the output current of the grid-following converter, δ g , δ 2 are the power angle of the grid-connected busbar and the power angle of the grid-following converter, θ g ,θ 2 They are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-following converter respectively.

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

[0143] The first condition generation unit is used 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-type converter, The new power system is unstable; the equivalent impedance range of the grid-following converter when the new power system is unstable is determined to be Z 2 ∈[0,Z g cosθ g2 ] and the equivalent impedance Z of the grid-type converter 2 The equivalent impedance Z of the grid-connected busbar g The range of the angle between g2 ∈(π2,3π2), as the first condition for detecting instability factors in the full-band of the new power system.

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

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

[0146]

[0147] In the formula, is the output complex power of the grid-following converter, is the output voltage phasor of the grid-type converter, U 1 is the output voltage of the grid-type converter, U g is the voltage of the grid-connected busbar, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z 1 is the equivalent impedance of the grid-type converter, δ 1 is the power angle of the grid-type converter, θ g ,θ 1 They are the equivalent impedance angle of the grid-connected bus and the equivalent impedance angle of the grid-connected converter respectively.

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

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

[0150]

[0151] In the formula, δ 0 is the system power angle when the power system is in stable operation, θ 0 It is the system impedance angle when the power system is in stable operation;

[0152] The range of the power angle and impedance angle of the new power system when it is unstable is determined to be arccos[-cos(δ 0+θ 0 )-1]<θ 0 ≤2π-arccos[-cos(δ 0 +θ 0 )-1], as the second condition for detecting the full-band instability factors of the new power system.

[0153] Based on the detection results of the instability factors of the new power system in the full frequency band, the present invention proposes a stabilization control device suitable for the new power system, such as Figure 3 As shown, including:

[0154] A network-building converter control module 10, a network-following converter control module 20, an instability factor detection device and a control conversion module 30; the network-building converter control module is used to implement droop control on the converter, and the network-following converter control module is used to implement phase-locked loop control PLL on the converter. The control signal output by the network-building converter control module and the control signal output by the network-following converter control module are both input into the control conversion module;

[0155] When the instability factor detection device determines that the new power system is instability in the entire frequency band, the control conversion module is started;

[0156] A control conversion module is used to detect the output current of the converter and the voltage of the grid-connected bus; 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-connected bus is not less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-connected converter control module to the converter; when it is detected that the output current is 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-connected 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-connected 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-connected converter control module to the converter.

[0157] Based on the new power system full-band instability factor detection method proposed in the present invention, a detection result of whether the new power system is unstable is obtained. As a sign of whether the control conversion module is started, it can effectively ensure that the switching of the control mode is based on the premise of system stability, thereby further realizing the working reliability of the stabilizing device.

[0158] Preferably, the current threshold is set to 1.1 pu, and the voltage threshold is set to 0.9 pu.

[0159] Specifically, the meshed converter model satisfies the following relationship:

[0160]

[0161] In the formula, v pcc 、i pcc are the grid connection point voltage and current, v g , R g , L g are the equivalent voltage, resistance and inductance of the circuit respectively;

[0162] Through the dq coordinate transformation to the synchronous coordinate system, the following relationship is obtained:

[0163]

[0164] In the formula, v pccdq 、i pccdq are the dq coordinate components of the voltage and current at the grid connection point, respectively, g is the line reactance, i gdq is the dq coordinate component of the line current;

[0165] Based on the meshed converter model, the control model of the meshed converter is established to satisfy 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 active power reference value and output active power respectively, 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 、ug are the port voltage, node voltage and AC grid voltage respectively, i c is the instantaneous value of current, R is the line resistance, L f is the filter inductor, and L is the line inductor.

[0172] Based on the grid-following converter model, the control model of the grid-following converter is established to satisfy the following relationship:

[0173]

[0174] In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of PI regulation, 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 strong response capability because it can keep pace with the power grid, making it widely used in the power market. Although the robustness of the grid-building converter is better than that of the grid-following converter, if the grid-building converter is in a system failure period for a long time, it will cause damage to the system components. Therefore, the present invention combines the grid-following converter and the grid-building converter, and connects the two in parallel to the system by adding an instability detection conversion module, so as to obtain the following Figure 3 shown.

[0176] Specifically, Figure 4 As shown, the control conversion module includes an input signal processing unit, a set signal processing unit, an RS trigger and a switch; the input signal processing unit is used to obtain the three-phase output current i of the converter. a 、i b 、i c The effective value of the output current of any phase is compared with the set current threshold i. When the effective value of the output current of any phase is greater than the set current threshold, a signal "1" is sent to a synchronization input terminal S of the RS trigger, otherwise a signal "0" is sent to a synchronization input terminal S of the RS trigger; the signal processing unit is set to obtain the voltage V of the grid-connected bus pccThe effective value after coordinate transformation is compared 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 another synchronization input terminal R of the RS trigger, otherwise a signal "0" is sent to a synchronization input terminal R of the RS trigger; the RS trigger takes the three-phase output current of the converter as the priority signal and the grid-connected bus electricity as the set signal. The RS trigger outputs a signal F. When F is a signal "1", the switching switch turns on the grid-forming converter control module and outputs the control signal output by the grid-forming converter control module to the converter. When F is a signal "0", the switching switch turns on the grid-following converter control module and outputs the control signal output by the grid-following converter control module to the converter.

[0177] In the embodiment, setting the current threshold to 1.1 pu and setting the voltage threshold to 0.9 pu is a non-restrictive and preferred choice. Both thresholds can be adjusted according to actual grid needs to avoid chattering between modes while satisfying the detection effect.

[0178] The present invention constructs a new stabilizing control device by setting an instability detection conversion module, realizes the full-band instability detection of the new power system, starts the control conversion when instability is detected, and makes full use of the characteristics of the grid-building type converter to ensure the normal output of voltage and frequency in a droop control manner, while suppressing the circulation of reactive power to a certain extent. However, due to the large proportional difference between the grid-building type converter and the grid-following type converter, there will be a slight deviation in the voltage amplitude and phase output by the two. Therefore, when using the instability detection conversion module to solve the situation where the amplitude and phase of the output voltage of the two are biased, the grid-building type converter needs to be able to actively set the frequency and voltage amplitude, while the grid-following type converter can well adjust the output voltage. The two can well cope with different conditions of the system. Therefore, based on the working requirements of the control conversion module, the control structure of the grid-following type converter and the control structure of the grid-building type converter are improved.

[0179] When the converter operates in the grid-following control mode, the grid-following converter adopts phase-locked loop control, and the frequency and phase of the system are controlled by an integral link in the phase-locked loop control; in order to follow the system signal, the integral link has overshoot, and the signal follows too fast or too slow in a short time, which causes transient synchronization instability in the system, and the changes in the output voltage and output current of the converter caused by the transient synchronization instability may cause unnecessary switching of the control mode. Therefore, the present invention proposes to improve the structure of the phase-locked loop control in the control module of the grid-following converter, such as Figure 5 As shown, the improved phase-locked loop control includes a shielding link connected in parallel with the integral link; based on the grid-following converter model, an improved phase-locked loop control model of the grid-following converter is established, which satisfies the following relationship:

[0180]

[0181] In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of the integral link PI, 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 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 The value 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 The value is 1.

[0182] Figure 5 In, v a 、v b 、v c is the three-phase output voltage of the converter, v d 、v q is the dq axis component of the three-phase output voltage of the converter, PI is the integral link, and mod is the modulo operator.

[0183] In the embodiment, based on the improved phase-locked loop control, when the power grid suffers from transient synchronization instability, causing the output voltage of the converter to be less than the set voltage threshold but the voltage of the grid-connected bus is not less than the set voltage threshold, through the shielding effect of the integral link shielding coefficient, only the primary control link is retained and the secondary integral link is shielded, and the retained primary control link has over-damping performance without overshoot problem, which essentially suppresses the overshoot of the integral link, thereby ensuring that the converter can still operate in the grid-forming control mode and will not switch to the grid-following control mode; and when the power grid suffers from a short circuit or other fault, causing the output voltage of the converter and the voltage of the grid-connected bus to be less than the set voltage threshold, the integral link shielding coefficient does not play a role, so that the integral link plays the performance of following the system signal, and the converter operating in the grid-following control mode can quickly control the output voltage of the converter to be restored until the fault is cleared.

[0184] When the converter operates in the grid-forming control mode, due to the access to a large number of nonlinear loads in a weak grid environment, harmonic components will be generated, affecting the power quality of the system. The degradation of power quality will have many effects on the control conversion module composed of power electronic components, resulting in a decrease in working effect and performance. Therefore, in order to suppress the impact of harmonic components, the following are Figure 6 The structure of the voltage and current loop in the control module of the grid-type converter shown is improved and designed, and the harmonic components are suppressed while ensuring the control of the fundamental voltage.

[0185] Figure 6 In, 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 inductor current, I C (s) is the equivalent capacitor current.

[0186] Figure 6 The solid line in is the control loop of the voltage and current double closed-loop structure before improvement. The forward gain function of the voltage and current loop before improvement satisfies the following relationship:

[0187]

[0188] Where G(s) is the forward gain function of the voltage and current loop before improvement, K p is the proportional coefficient of PWM rectification, K i is the proportionality 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, and s is the integral operator.

[0189] In the embodiment, Figure 6 The dotted line in is the newly added control loop in the improved voltage and current double closed-loop structure. Based on the above improvements, the forward gain function of the improved voltage and current loop is realized, which satisfies the following relationship:

[0190]

[0191] Where 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-current dual closed-loop structure can effectively solve the converter current harmonic problem caused by the background harmonic of the power grid without adding additional control links, and is simple to implement.

[0193] The improvement of the control structure meets the demand for control conversion, but cannot fully meet the demand for balanced power distribution of the system. Therefore, the present invention proposes to introduce a power balanced distribution module into the stabilization control device.

[0194] In actual operation, when the grid-following converter and the grid-building converter are simply connected directly to the power grid, the two converters do not have the ability to adjust power during parallel operation, which will result in poor output power quality. Therefore, the present invention proposes a power balancing control structure for the grid-following converter and the grid-building converter, including:

[0195] 1) Improvement of the power balancing control structure of the grid-following converter;

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

[0197] Figure 7 In, P ref and Q ref are the active power reference value and reactive power reference value of the converter, P and Q are the actual active power value and reactive power actual value of the converter, P e and Q e are the active power feedback value and reactive power feedback value of the converter respectively, and are the dq axis components of the capacitor current, and are the dq axis components of the capacitor voltage, L f is the filter inductor, and are the dq axis components of the capacitor feedback current, K c is the gain coefficient of the capacitor feedback current, and θ is the actual value of the equivalent impedance angle of the system.

[0198] The power control loop is used to obtain the active power outer loop control value and the reactive power outer loop control value after the difference between the active power reference value and the reactive power reference value and the active power feedback value and the reactive power feedback value respectively through the integration link PI; the current control loop is used to obtain 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, using the capacitor current dq axis component and the capacitor feedback current dq axis component; the phase-locked loop is used to optimize the control signal according to the active power inner loop control value and the reactive power inner loop control value.

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

[0200] For a meshed converter, such as Figure 8 As shown, the improved power balancing control structure includes: an algorithm loop, a voltage loop and a current loop.

[0201] Figure 8 Middle,U dref , U qref are the dq axis components of the converter’s output voltage reference value, are the voltage dq axis components of the grid-connected bus, C f For the filter capacitor.

[0202] The algorithm loop is used to adjust the grid connection 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-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid connection point voltage and the output voltage reference value of the converter to optimize the control signal.

[0203] 3) Correct the phase of the relevant signals on the grid-following converter side and the grid-building converter side

[0204] Regardless of whether it is a grid-following converter or a grid-building converter, after the power balancing control structure is improved, the phase of the relevant signal on the control module side needs to be corrected according to the following relationship:

[0205]

[0206] In the formula, is the dq axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the grid-following converter side or the grid-forming converter side, It is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the system side, and Δθ is the equivalent impedance angle difference between the corresponding signals on the grid-type converter side or the grid-connected converter side and the system side.

[0207] When there are only grid-following converters or only grid-forming converters in the system, there is no need to improve the control structure and correct the phase of related signals for the problem of power balance distribution. However, when the grid-following converter and the grid-forming converter coexist, it is necessary to improve the power balance control structure of the grid-following converter, improve the power balance control structure of the grid-forming converter, and correct the phase of related signals on the grid-following converter side and the grid-forming converter side, so as to accurately control the output power of the converter, reduce voltage and current fluctuations, improve power quality, reduce system complexity to a certain extent, and reduce maintenance and management costs.

[0208] For the design of the control structure, since the grid-type converter presents the characteristics of the current source, the same phase relationship as the AC power supply can be obtained through the PLL phase-locked loop, while the grid-type converter presents the characteristics of the voltage source, and the phase synchronization is maintained by using the droop control and power synchronization links such as the current loop. By using the PLL phase-locked loop and power synchronization link as the leading role, the coupling effect of the dynamic loop and impedance can be effectively suppressed during the operation of the system, reducing the risk of oscillation distortion during system operation.

[0209] In terms of power control, considering the unstable voltage provided by new energy sources in new power systems, accurate processing of system output power can greatly apply new energy sources and improve system energy efficiency. In view of the different properties of grid-following converters and grid-building converters, different control methods such as phase-locked loop control and algorithm loop control are used to ensure that the output power of grid-following converters and grid-building converters can be accurately controlled in different modes.

[0210] The present invention also proposes a novel power system stabilization control method, which is implemented by using a novel power system stabilization control device.

[0211] When determining that the new power system is instability 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 the set current threshold and the voltage of the grid-connected bus is not less than the set voltage threshold, the control signal output by the grid-connected converter control module is output to the converter; when it is detected that the output current is 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 no greater than the set current threshold, the control signal output by the grid-connected 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 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;

[0214] 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, a control signal output by the grid-connected 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 connected in parallel with the integral link;

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

[0217]

[0218] In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of the integral link PI, V qpll is the q-axis component of the three-phase grid voltage after dq transformation, ω is the grid frequency, Kpll is the 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 The value 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 The value is 1.

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

[0220]

[0221] Where G′(s) is the forward gain function of the improved voltage-current loop, K p is the proportional coefficient of PWM rectification, K i is the proportionality 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.

[0222] Preferably, the power balancing control structure of the grid-following converter is improved, and the improved power balancing control structure includes: a power control loop, a current control loop and a phase-locked loop;

[0223] The power control loop is used to obtain the active power outer loop control value and the reactive power outer loop control value after the difference between the active power reference value and the reactive power reference value and the active power feedback value and the reactive power feedback value through an integration link; the current control loop is used to obtain 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, using the capacitor current dq axis component and the capacitor feedback current dq axis component; the phase-locked loop is used to optimize the control signal according to the active power inner loop control value and the reactive power inner loop control value.

[0224] Preferably, the power balancing control structure of the grid-type converter is improved, and the improved power balancing control structure includes: an algorithm loop, a voltage loop and a current loop;

[0225] The algorithm loop is used to adjust the grid connection 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-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid connection point voltage and the output voltage reference value of the converter to optimize the control signal.

[0226] Preferably, after the power balancing control structure is improved, 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 value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the grid-following converter side or the grid-forming converter side, It is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the system side, and Δθ is the equivalent impedance angle difference between the corresponding signals on the grid-type converter side or the grid-connected converter side and the system side.

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

[0230] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0231] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical 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 of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, 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 disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

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

[0233] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0234] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A new method for detecting instability factors of a full-band power system, wherein the converter in the new power system operates as a grid-following converter when in a grid-following control mode and as a grid-forming converter when in a grid-forming control mode, characterized in that: include: Obtain the operating parameters of the new power system and establish an equivalent circuit when the grid-following converter and the grid-building converter coexist; Based on the equivalent circuit, the output complex power of the grid-type converter is determined; the impedance amplitude is extracted from the output complex power of the grid-type converter; based on the instability of the new power system when the impedance amplitude is proportional to the equivalent impedance of the grid-type converter, the value range of the equivalent impedance of the grid-type converter when the new power system is unstable and the value range of the angle between the equivalent impedance of the grid-type converter and the equivalent impedance of the grid-connected bus are determined as the first condition for detecting the instability factor; Based on the equivalent circuit, the output complex power of the grid-type converter is determined; the active power output by the grid-type converter is determined according to the output complex power of the grid-type converter; based on the instability of the new power system when the active power output by the grid-type converter is not greater than the active power of the load, 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 for detecting the instability factor; When relevant 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 band, and the relevant parameters that meet the conditions are used as the instability factors of the new power system in the full frequency band.

2. The new method for detecting instability factors of a power system in full frequency band according to claim 1 is characterized in that: Based on the equivalent circuit, the output complex power of the grid-type converter satisfies the following relationship: In the formula, is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z2 is the equivalent impedance of the grid-connected converter, I GFL is the output current of the grid-following converter, δ g , δ2 are the power angles of the grid-connected busbar and the grid-following converter, θ g , θ2 are the equivalent impedance angles of the grid-connected bus and the equivalent impedance angle of the grid-following converter respectively.

3. The new method for detecting instability factors of a power system in full frequency band according to claim 2 is characterized in that: Define the impedance magnitude of the output complex power of the grid-following converter When the impedance amplitude is proportional to the equivalent impedance of the grid-type converter, New power system instability; The range of the equivalent impedance of the grid-following converter when the new power system is unstable is determined as Z2∈[0,Z g cosθ g2 ] 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 g2 ∈(π2,3π2), as the first condition for detecting instability factors in the full-band of the new power system.

4. The new method for detecting instability factors of a power system in full frequency band according to claim 1 is characterized in that: Based on the equivalent circuit, the output complex power of the grid-type converter satisfies the following relationship: In the formula, is the output complex power of the grid-following converter, is the output voltage phasor of the grid-type converter, U1 is the output voltage of the grid-type converter, and U g is the voltage of the grid-connected busbar, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, 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 angles of the grid-connected bus and the equivalent impedance angle of the grid-connected converter respectively.

5. The novel method for detecting instability factors of a power system in full frequency band according to claim 4 is characterized in that: When the active power output by the grid-forming converter is not greater than the active power of the load, the new power system becomes unstable and satisfies the following relationship: Where, δ0 is the system power angle when the power system is in stable operation, and θ0 is the system impedance angle when the power system is in stable operation; The range of system power angle and system impedance angle when the new power system is unstable is determined to be arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], which is used as the second condition for detecting full-band instability factors of the new power system.

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

7. The new type of power system full-band instability factor detection device according to claim 6 is characterized in that: The detection condition generation module includes: an output complex power calculation unit of the grid-following converter; The output complex power calculation unit of the grid-following converter is used to calculate the output complex power of the grid-following converter based on the equivalent circuit according to the following relationship: In the formula, is the output complex power of the grid-following converter, is the voltage phasor of the grid-connected bus, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, Z2 is the equivalent impedance of the grid-connected converter, I GFL is the output current of the grid-following converter, δ g , δ2 are the power angles of the grid-connected busbar and the grid-following converter, θ g , θ2 are the equivalent impedance angles of the grid-connected bus and the equivalent impedance angle of the grid-following converter respectively.

8. The new type of power system full-band instability factor detection device according to claim 7 is characterized in that: The detection condition generation module also includes: a first condition generation unit; The first condition generation unit is used 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-type converter, The new power system is unstable; the range of the equivalent impedance of the grid-following converter when the new power system is unstable is determined to be Z2∈[0,Z g cosθ g2 ] 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 g2 ∈(π2,3π2), as the first condition for detecting instability factors in the full-band of the new power system.

9. The new type of power system full-band instability factor detection device according to claim 6 is characterized in that: The detection condition generation module also includes: an output complex power calculation unit of the grid-forming converter; The output complex power calculation unit of the meshed converter is used to calculate the output complex power of the meshed converter based on the equivalent circuit according to the following relationship: In the formula, is the output complex power of the grid-following converter, is the output voltage phasor of the grid-type converter, U1 is the output voltage of the grid-type converter, and U g is the voltage of the grid-connected busbar, is the output current phasor conjugate of the grid-type converter, Z g is the equivalent impedance of the grid-connected busbar, 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 angles of the grid-connected bus and the equivalent impedance angle of the grid-connected converter respectively.

10. The novel power system full-band instability factor detection device according to claim 9 is characterized in that: The detection condition generation module further includes: a second condition generation unit; The second condition generation unit is used to generate the new power system instability when the active power output by the grid-type converter is not greater than the active power of the load, and satisfies the following relationship: Where, δ0 is the system power angle when the power system is in stable operation, and θ0 is the system impedance angle when the power system is in stable operation; The range of system power angle and system impedance angle when the new power system is unstable is determined to be arccos[-cos(δ0+θ0)-1]<θ0≤2π-arccos[-cos(δ0+θ0)-1], which is used as the second condition for detecting full-band instability factors of the new power system.

11. A new type of power system stabilization control device, characterized in that: include: A grid-forming converter control module, a grid-following converter control module, an instability factor detection device as claimed in any one of claims 6 to 10, and a control conversion module; the grid-forming converter control module is used to implement droop control on the converter, the grid-following converter control module is used to implement 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; When the instability factor detection device determines that the new power system is instability in the entire frequency band, the control conversion module is started; A control conversion module is used to detect the output current of the converter and the voltage of the grid-connected bus; 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-connected bus is not less than the set voltage threshold, the control conversion module outputs the control signal output by the grid-connected converter control module to the converter; when it is detected that the output current is 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-connected 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-connected 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-connected converter control module to the converter.

12. The novel power system stabilization control device according to claim 11 is characterized in that: The control conversion module includes an input signal processing unit, a setting signal processing unit, an RS trigger and a switching switch; the input signal processing unit is used to obtain the effective value of the three-phase output current of the converter and compare it with the set current threshold. When the effective value of the output current of any phase is greater than the set current threshold, a signal "1" is sent to a synchronization input terminal S of the RS trigger, otherwise a signal "0" is sent to a synchronization input terminal S of the RS trigger; the setting signal processing unit is used to obtain the effective value of the voltage 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 current threshold, a signal "1" is sent to a synchronization input terminal S of the RS trigger. When the voltage threshold is set, a signal "1" is sent to the other synchronization input terminal R of the RS trigger, otherwise a signal "0" is sent to one synchronization input terminal R of the RS trigger; the RS trigger takes the three-phase output current of the converter as the priority signal and the grid-connected bus voltage as the set signal, and the RS trigger outputs a signal F. When F is a signal "1", the switching switch turns on the grid-forming converter control module, and outputs the control signal output by the grid-forming converter control module to the converter. When F is a signal "0", the switching switch turns on the grid-following converter control module, and outputs the control signal output by the grid-following converter control module to the converter.

13. The novel power system stabilization control device according to claim 11, characterized in that: The structure of the phase-locked loop control in the control module of the grid-following converter is improved, and the improved phase-locked loop control includes a shielding link connected in parallel with the integral link; The improved phase-locked loop control model satisfies the following relationship: In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of the integral link PI, 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 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 The value 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 The value is 1.

14. The novel power system stabilization control device according to claim 11, characterized in that: The structure of the voltage and current loop in the control module of the networked converter 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 PWM rectification, K i is the proportionality 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 novel power system stabilization control device according to claim 11, characterized in that: Improvement of the power balance control structure of the grid-following converter, the improved power balance control structure includes: a power control loop, a current control loop and a phase-locked loop; The power control loop is used to obtain the active power outer loop control value and the reactive power outer loop control value after the difference between the active power reference value and the reactive power reference value and the active power feedback value and the reactive power feedback value through an integration link; the current control loop is used to obtain 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, using the capacitor current dq axis component and the capacitor feedback current dq axis component; the phase-locked loop is used to optimize the control signal according to the active power inner loop control value and the reactive power inner loop control value.

16. The novel power system stabilization control device according to claim 15 is characterized in that: Improvement of the power balance control structure of the grid-type converter, the improved power balance control structure includes: an algorithm loop, a voltage loop and a current loop; The algorithm loop is used to adjust the grid connection 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-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid connection point voltage and the output voltage reference value of the converter to optimize the control signal.

17. The novel power system stabilization control device according to claim 16 is characterized in that: After the power balancing control structure is improved, 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: In the formula, is the dq axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the grid-following converter side or the grid-forming converter side, It is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the system side, and Δθ is the equivalent impedance angle difference between the corresponding signals on the grid-type converter side or the grid-connected converter side and the system side.

18. The novel power system stabilization control device according to claim 11, characterized in that: The current threshold is set to 1.1 pu and the voltage threshold is set to 0.9 pu.

19. A novel power system stabilization control method, implemented by using the novel power system stabilization control device according to any one of claims 11 to 18, characterized in that: include: When determining that the new power system is instability in the full frequency band, the output current of the converter and the voltage of the grid-connected 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-connected bus is not less than the set voltage threshold, the control signal output by the grid-connected converter control module is output to the converter; when it is detected that the output current is 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 no greater than the set current threshold, the control signal output by the grid-connected converter control module is output 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 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; 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, a control signal output by the grid-connected converter control module is output to the converter.

20. The novel power system stabilization control method according to claim 19, characterized in that: The structure of the phase-locked loop control in the control module of the grid-following converter is improved, and the improved phase-locked loop control includes a shielding link connected in parallel with the integral link; The improved phase-locked loop control model satisfies the following relationship: In the formula, θ pll is the reference phase of the phase-locked loop output, k p , k i They are the proportional coefficient and integral coefficient of the integral link PI, 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 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 The value 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 The value is 1.

21. The novel power system stabilization control method according to claim 19, characterized in that: The structure of the voltage and current loop in the control module of the networked converter 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 PWM rectification, K i is the proportionality 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 novel power system stabilization control method according to claim 19, characterized in that: Improvement of the power balance control structure of the grid-following converter, the improved power balance control structure includes: a power control loop, a current control loop and a phase-locked loop; The power control loop is used to obtain the active power outer loop control value and the reactive power outer loop control value after the difference between the active power reference value and the reactive power reference value and the active power feedback value and the reactive power feedback value through an integration link; the current control loop is used to obtain 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, using the capacitor current dq axis component and the capacitor feedback current dq axis component; the phase-locked loop is used to optimize the control signal according to the active power inner loop control value and the reactive power inner loop control value.

23. The novel power system stabilization control method according to claim 22, characterized in that: Improvement of the power balance control structure of the grid-type converter, the improved power balance control structure includes: an algorithm loop, a voltage loop and a current loop; The algorithm loop is used to adjust the grid connection 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-connected bus; the voltage loop and the current loop are used to adjust the difference between the adjusted grid connection point voltage and the output voltage reference value of the converter to optimize the control signal.

24. The novel power system stabilization control method according to claim 23, characterized in that: After the power balancing control structure is improved, 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: In the formula, is the dq axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the grid-following converter side or the grid-forming converter side, It is the dq-axis component of the synchronous phase value of the impedance current, grid current, grid-connected bus voltage and converter output voltage on the system side, and Δθ is the equivalent impedance angle difference between the corresponding signals on the grid-type converter side or the grid-connected converter side and the system side.

25. The novel power system stabilization control method according to claim 19, characterized in that: The current threshold is set to 1.1 pu and the voltage threshold is set to 0.9 pu.

26. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is used to operate according to the instruction to execute the steps of the new method for detecting instability factors of a full-band power system according to any one of claims 1 to 5; The processor is used to operate according to the instructions to execute the steps of the stabilization control method of the new power system described in any one of claims 19-25.

27. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the new method for detecting full-band instability factors of a power system as described in any one of claims 1 to 5 are implemented.

28. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the novel power system stabilization control method described in any one of claims 19-25 are implemented.

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