Grid impedance simulation control method based on new energy grid-connected detection platform

Abstract

The present application relates to the technical field of power grid impedance simulation control, and discloses a power grid impedance simulation control method based on a new energy grid-connected detection platform, which comprises the steps of sampling data, calculating phase voltage, coordinate transformation, voltage regulation, calculating modulation wave, power calculation, output current reference value calculation, simulating power grid impedance, conversion into a stationary coordinate system, SVPWM modulation and the like. The power grid impedance simulation control method can effectively adjust the grid-connected equipment through dynamic simulation of the power grid impedance, so that the grid-connected equipment remains stable under various loads and disturbance conditions; accurate power and current control is achieved, which helps to maximize the utilization rate of new energy, improve the energy efficiency and economy of the system; the output can be adjusted according to the real-time power grid state, thereby improving the response capability of the system to different load conditions; through real-time monitoring and dynamic control, faults can be found and handled in time, and the potential impact on the system and the probability of fault occurrence are reduced; and the power grid impedance is simulated in a wide frequency domain, and the engineering implementation is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of grid impedance simulation control, in particular to a grid impedance simulation control method based on a new energy grid-connected detection platform. BACKGROUND

[0002] At present, new energy is the main body of new power system, and the continuous influx of high proportion of new energy power and the large number of access of power electronic equipment will bring great challenges to the safe and stable operation of the system. The power system puts forward increasingly strict requirements on the operation ability of new energy and power electronic equipment connected to the external grid under fault. In order to study and test the operation ability of new energy and power electronic equipment under various grid faults, special equipment is needed to accurately reproduce various states and fault conditions of the grid, i.e. new energy grid-connected detection platform.

[0003] Due to the fact that new energy power generation systems mainly composed of photovoltaic and wind power are mostly distributed in remote places such as deserts and islands, they need to be connected to the grid through long-distance transmission and distribution lines. At this time, the system line impedance not only changes the impedance characteristics of the grid, making the grid exhibit weak grid characteristics, but also affects the working performance of power electronic grid-connected devices, causing system stability problems. Therefore, in order to more realistically simulate the working conditions of the actual grid and detect the weak grid adaptability of power electronic grid-connected devices, the new energy grid-connected detection platform should have the function of grid impedance simulation. Considering that the grid contains high-frequency harmonics, simulating the grid impedance characteristics at the fundamental frequency alone cannot reflect the actual grid situation. Therefore, scholars have made some research on the grid impedance simulation control of the new energy grid-connected detection platform. For example, the control method, control device and grid simulator of the grid simulator disclosed in the Chinese patent application publication (CN116819210A) on September 29, 2023, discloses a grid impedance simulation control method. The method uses an improved voltage and current double closed-loop control strategy to control the grid simulator. It obtains the direct-axis optimized voltage command by superimposing the direct-axis virtual impedance voltage on the direct-axis set voltage command, and obtains the quadrature-axis optimized voltage command by superimposing the quadrature-axis virtual impedance voltage on the quadrature-axis set voltage command, thereby realizing the simulation of grid impedance. The control method of the grid simulator with transmission line impedance wide frequency domain simulation function disclosed in the Chinese patent application publication (CN118068125A) on May 24, 2024, discloses a wide frequency domain grid impedance simulation control method. The method uses a distributed parameter circuit model to process the transmission line, and realizes the wide frequency domain, high precision, dynamic and real-time simulation of grid impedance by combining the voltage and current closed-loop feedback control loop through the multi-order linearization approximation method.

[0004] However, the Chinese invention patent application publication (CN116819210A) published on September 29, 2023, entitled "A Control Method, Control Device, and Power Grid Simulator for a Power Grid Simulator," only simulates the power grid impedance characteristics at the fundamental frequency. However, real power grids contain high-frequency harmonics, and the simulation of the power grid impedance at the fundamental frequency cannot reflect the actual power grid characteristics. The Chinese invention patent application publication (CN118068125A) published on May 24, 2024, entitled "A Control Method for a Power Grid Simulator with Wide-Frequency Domain Simulation Function for Transmission Line Impedance," while simulating the power grid impedance in a wide frequency domain, is overly complex and difficult to implement in engineering.

[0005] In summary, there is an urgent need for a grid impedance simulation and control method for a new energy grid connection detection platform that can simulate grid impedance in a wide frequency domain. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a grid impedance simulation control method based on a new energy grid connection detection platform.

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

[0008] A grid impedance simulation and control method based on a new energy grid connection testing platform is proposed. This method utilizes the new energy grid connection testing platform, which includes a DC / AC inverter unit, a DC power supply connected to the DC side of the DC / AC inverter unit, a filter circuit connected to the AC side of the DC / AC inverter unit, a transformer connected to the filter circuit, and the device under test connected to the transformer. This grid impedance simulation and control method, based on the new energy grid connection testing platform, studies and tests the grid connection performance of various new energy power electronic devices by simulating and controlling the grid impedance.

[0009] The power grid impedance simulation control method includes the following steps:

[0010] Step 1, sampling the output voltage and current:

[0011] The actual value of the three-phase output line voltage of the new energy grid-connected testing platform is sampled and recorded as U. ab U bc U ca Sample the actual value of the three-phase output line current of the new energy grid-connected testing platform and record it as I. a I b I c ;

[0012] Step 2, calculate the phase voltage:

[0013] Based on the actual value U of the three-phase output line voltage sampled in step 1 ab U bc Uca The three-phase output phase voltage U is calculated. a U b U c ;

[0014] Step 3, coordinate transformation:

[0015] By synchronously rotating the coordinates, the three-phase output phase voltage U obtained in step 2 is transformed. a U b U c Converting the three-phase output voltage d-axis component U in a rotating coordinate system d and the q-axis component of the three-phase power grid voltage U q ;

[0016] Step 4, Voltage Adjustment:

[0017] Based on the reference value U of the d-axis component of the system's three-phase output voltage. dref Reference value U of the q-axis component of the system's three-phase output voltage qref And the d-axis component U of the three-phase output voltage obtained in step 3 d and the q-axis component of the three-phase power grid voltage U q The output U of the d-axis voltage regulator is calculated using both the d-axis and q-axis voltage regulators. cnt_d and q-axis voltage regulator output U cnt_q ;

[0018] Step 5, Calculate the modulated wave:

[0019] Based on the reference value U of the d-axis component of the system's three-phase output voltage. dref Reference value U of the q-axis component of the system's three-phase output voltage qref And the d-axis voltage regulator output U obtained in step 4 cnt_d and q-axis voltage regulator output U cnt_q The d-axis component U of the three-phase output voltage modulation wave of the system was calculated. od and the q-axis component U of the system's three-phase output voltage modulation wave oq ;

[0020] Step 6, Power Calculation:

[0021] Based on the actual value U of the three-phase output line voltage sampled in step 1 ab U bc U ca Actual value of three-phase output line current I a I b I c And the three-phase output phase voltage U obtained in step 2 a U b U cThe instantaneous active power P and instantaneous reactive power Q of the system output are calculated.

[0022] Step 7, Calculate the output current reference value:

[0023] Based on the instantaneous active power P and instantaneous reactive power Q of the system output obtained in step 6, and the d-axis component U of the three-phase output voltage obtained in step 3... d and the q-axis component of the three-phase power grid voltage U q Calculate the reference value I of the d-axis component of the three-phase output current of the system. d Reference value I of the q-axis component of the three-phase output current of the system q ;

[0024] Step 8, Simulate grid impedance:

[0025] Based on the d-axis component U of the system's three-phase output voltage modulation wave obtained in step 5 od and the q-axis component U of the system's three-phase output voltage modulation wave oq And the reference value I of the d-axis component of the system three-phase output current obtained in step 7. d Reference value I of the q-axis component of the three-phase output current of the system q The d-axis component E of the three-phase output voltage modulation wave of the simulated grid impedance was calculated. d And the q-axis component E of the system's three-phase output voltage modulation wave q ;

[0026] Step 9, convert to a stationary coordinate system:

[0027] Based on the simulated grid impedance obtained in step 8, the d-axis component E of the three-phase output voltage modulation wave of the system d After simulating the grid impedance, the q-axis component E of the three-phase output voltage modulation wave of the system q After synchronously rotating the coordinates to simulate the grid impedance in the stationary coordinate system, the three-phase output voltage modulation wave e of the system is obtained. a e b e c ;

[0028] Step 10, SVPWM modulation:

[0029] The three-phase output voltage modulation wave e of the system after simulating the grid impedance in the stationary coordinate system obtained in step 9. a e b e c The signal is fed into the SVPWM modulation module for modulation and waveform generation.

[0030] Furthermore, in step 2, the three-phase output phase voltage U a U b U c The formula for calculation is:

[0031]

[0032] In the formula, U a U b U c This refers to the three-phase output phase voltage; U ab U bc U ca The actual value of the three-phase output line voltage of the new energy grid-connected testing platform was sampled.

[0033] Furthermore, in step 3, the formula for calculating the coordinate transformation is:

[0034]

[0035] In the formula, U d U represents the d-axis component of the three-phase output voltage in a rotating coordinate system. q U represents the q-axis component of the three-phase grid voltage in a rotating coordinate system. a U b U c θ represents the three-phase output phase voltage; θ is the initial impedance angle of the system.

[0036] Furthermore, in step 4, the d-axis voltage regulator outputs U cnt_d and q-axis voltage regulator output U cnt_q The formula for calculation is:

[0037]

[0038] In the formula, U cnt_d For the d-axis voltage regulator output; U cnt_q For q-axis voltage regulator output; K up K is the proportional coefficient of the voltage regulator. ui The integral coefficient of the voltage regulator; z represents the variable in the discrete-time domain, used to describe the dynamic behavior of the system; T s For control cycle; U dref U is the reference value for the d-axis component of the system's three-phase output voltage; d U represents the d-axis component of the three-phase output voltage in a rotating coordinate system. qref U is the reference value for the q-axis component of the system's three-phase output voltage; q Let q be the q-axis component of the three-phase grid voltage in a rotating coordinate system.

[0039] Furthermore, in step 5, the d-axis component U of the system's three-phase output voltage modulation wave... od and the q-axis component U of the system's three-phase output voltage modulation wave oq The formula for calculation is:

[0040]

[0041] In the formula, U od U represents the d-axis component of the system's three-phase output voltage modulation wave. oq For the q-axis component of the system's three-phase output voltage modulation wave; U dref U is the reference value for the d-axis component of the system's three-phase output voltage; qref U is the reference value for the q-axis component of the system's three-phase output voltage; cnt_d For the d-axis voltage regulator output; U cnt_q This is the output of the q-axis voltage regulator.

[0042] Furthermore, in step 6, the formulas for calculating the instantaneous active power P and instantaneous reactive power Q output by the system are as follows:

[0043]

[0044] In the formula, P is the instantaneous active power output of the system; Q is the instantaneous reactive power output of the system; U a U b U c For three-phase output phase voltage; I a I b I c To sample the actual value of the three-phase output line current of the new energy grid-connected testing platform; U ab U bc U ca The actual value of the three-phase output line voltage of the new energy grid-connected testing platform was sampled.

[0045] Furthermore, in step 7, the reference value I of the d-axis component of the system's three-phase output current. d Reference value I of the q-axis component of the three-phase output current of the system q The formula for calculation is:

[0046]

[0047] In the formula, I d U is the reference value for the d-axis component of the system's three-phase output current; P is the instantaneous active power output by the system; U d U represents the d-axis component of the three-phase output voltage; Q represents the instantaneous reactive power output of the system; U q For the q-axis component of the three-phase power grid voltage; I q This is the reference value for the q-axis component of the system's three-phase output current.

[0048] Furthermore, in step 8, the d-axis component E of the three-phase output voltage modulation wave of the simulated grid impedance is... d And the q-axis component E of the system's three-phase output voltage modulation wave q The formula for calculation is:

[0049]

[0050] In the formula, E d The system's three-phase output voltage modulation wave; U od R represents the d-axis component of the system's three-phase output voltage modulation wave. g I is the equivalent resistance of the power grid impedance; d This is the reference value for the d-axis component of the system's three-phase output current; L g Let be the equivalent inductance of the power grid impedance; z is a variable representing the discrete-time domain, used to describe the dynamic behavior of the system; T s The control period is ω0, which is the fundamental angular frequency; I is the control period. q E is the reference value for the q-axis component of the system's three-phase output current. q This refers to the q-axis component of the system's three-phase output voltage modulation wave.

[0051] Furthermore, in step 9, the three-phase output voltage modulation wave e of the system after simulating the grid impedance in the stationary coordinate system... a e b e c The formula for calculation is:

[0052]

[0053] In the formula, e a e b e c E represents the modulated three-phase output voltage waveform of the system after simulating the grid impedance in a stationary coordinate system. d The d-axis component of the three-phase output voltage modulation wave of the system after simulating the grid impedance; E q The q-axis component of the three-phase output voltage modulation wave of the system after simulating the grid impedance is θ; θ is the initial impedance angle of the system.

[0054] Compared with existing technologies, this grid impedance simulation control method based on a new energy grid connection detection platform has the following advantages:

[0055] Improve system stability: This grid impedance simulation control method based on the new energy grid connection detection platform can effectively adjust grid-connected equipment through dynamic simulation of grid impedance, so that it can remain stable under various load and disturbance conditions.

[0056] Optimized energy management: This grid impedance simulation control method based on the new energy grid connection detection platform achieves accurate power and current control, which helps to maximize the utilization rate of new energy and improve the energy efficiency and economy of the system.

[0057] Enhanced load adaptability: The grid impedance simulation control method based on the new energy grid connection detection platform has strong adaptability and can adjust the output according to the real-time grid status, thereby improving the system's response capability to different load conditions.

[0058] Reduce fault risk: This grid impedance simulation control method based on the new energy grid connection detection platform can detect and handle faults in a timely manner through real-time monitoring and dynamic control, thereby reducing the potential impact on the system and the probability of fault occurrence.

[0059] Enhancing environmental benefits: This grid impedance simulation control method based on a new energy grid connection detection platform reduces dependence on traditional energy sources and lowers carbon emissions through efficient utilization of new energy sources, thus contributing to the achievement of sustainable development goals.

[0060] Facilitating the construction of smart grids: This grid impedance simulation control method based on a new energy grid connection detection platform helps to achieve intelligent management, improve the access capability of new energy sources, and promote the development of the power grid towards intelligence and digitalization.

[0061] In summary, the grid impedance simulation and control method based on the new energy grid connection detection platform can simulate grid impedance in a wide frequency domain and is simple to implement in engineering. Attached Figure Description

[0062] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] in:

[0064] Figure 1 This is a schematic diagram of the structure of the new energy grid connection detection platform of the present invention;

[0065] Figure 2 This is a control block diagram of the new energy grid connection detection platform of the present invention;

[0066] Figure 3 This is a flowchart of the power grid impedance simulation control method of the present invention. Detailed Implementation

[0067] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0068] To address the issues that existing technologies only simulate the grid impedance characteristics at the fundamental frequency, but the actual grid contains high-frequency harmonics, and the grid impedance simulation at the fundamental frequency cannot reflect the actual grid characteristics; at the same time, although the grid impedance is simulated in a wide frequency domain, it is too complex and difficult to implement in engineering; therefore, this embodiment provides a grid impedance simulation and control method based on a new energy grid connection detection platform.

[0069] This grid impedance simulation and control method is based on a new energy grid connection detection platform; such as... Figure 1 As shown, the new energy grid-connected testing platform includes a DC / AC inverter unit, a DC power supply connected to the DC side of the DC / AC inverter unit, a filter circuit connected to the AC side of the DC / AC inverter unit, a transformer connected to the filter circuit, and a device under test connected to the transformer. The device under test is a new energy and power electronic device whose grid-connected performance needs to be studied and tested. This grid impedance simulation and control method is based on the new energy grid-connected testing platform. By simulating and controlling the grid impedance, it studies and tests the grid-connected performance of various new energy power electronic devices.

[0070] This power grid impedance simulation control method, such as Figure 2 and Figure 3 As shown, it includes the following steps:

[0071] Step 1, sampling the output voltage and current:

[0072] The actual value of the three-phase output line voltage of the new energy grid-connected testing platform is sampled and recorded as U. ab U bc U ca Sample the actual value of the three-phase output line current of the new energy grid-connected testing platform and record it as I. a I b I c By accurately sampling the three-phase output line voltage and current, an accurate data foundation can be provided for subsequent analysis, ensuring the reliability of the overall system performance.

[0073] Step 2, calculate the phase voltage:

[0074] Based on the actual value U of the three-phase output line voltage sampled in step 1 ab U bc U ca The three-phase output phase voltage U is calculated. a U b U c .

[0075] Three-phase output phase voltage U a U b U c The formula for calculation is:

[0076]

[0077] In the formula, U a U b U c This refers to the three-phase output phase voltage; U ab U bc U ca The actual value of the three-phase output line voltage of the new energy grid-connected testing platform was sampled.

[0078] Although the calculation of phase voltage is limited by line voltage, it can make the analysis and subsequent control of the system simpler and more intuitive, and enhance the controllability of the system.

[0079] Step 3, coordinate transformation:

[0080] By synchronously rotating the coordinates, the three-phase output phase voltage U obtained in step 2 is transformed. a U b U c Converting the three-phase output voltage d-axis component U in a rotating coordinate system d and the q-axis component of the three-phase power grid voltage U q .

[0081] The formula for calculating coordinate transformation is:

[0082]

[0083] In the formula, U d U represents the d-axis component of the three-phase output voltage in a rotating coordinate system. q U represents the q-axis component of the three-phase grid voltage in a rotating coordinate system. a U b U c θ represents the three-phase output phase voltage; θ is the initial impedance angle of the system.

[0084] Synchronous rotating coordinate transformation can effectively simplify the processing of voltage parameters, converting complex three-phase AC quantities into easily operable DC quantities, which facilitates the implementation of subsequent control strategies.

[0085] Step 4, Voltage Adjustment:

[0086] Based on the reference value U of the d-axis component of the system's three-phase output voltage. dref Reference value U of the q-axis component of the system's three-phase output voltage qref And the d-axis component U of the three-phase output voltage obtained in step 3 d and the q-axis component of the three-phase power grid voltage U q The output U of the d-axis voltage regulator is calculated using both the d-axis and q-axis voltage regulators. cnt_d and q-axis voltage regulator output U cnt_q .

[0087] d-axis voltage regulator output U cnt_d and q-axis voltage regulator output U cnt_q The formula for calculation is:

[0088]

[0089] In the formula, U cnt_d For the d-axis voltage regulator output; U cnt_q For q-axis voltage regulator output; K up K is the proportional coefficient of the voltage regulator. ui The integral coefficient of the voltage regulator; z represents the variable in the discrete-time domain, used to describe the dynamic behavior of the system; T s For control cycle; U dref U is the reference value for the d-axis component of the system's three-phase output voltage; d U represents the d-axis component of the three-phase output voltage in a rotating coordinate system. qref U is the reference value for the q-axis component of the system's three-phase output voltage; q Let q be the q-axis component of the three-phase grid voltage in a rotating coordinate system.

[0090] By calculating the output of the voltage regulator, precise voltage regulation can be achieved, improving the stability and reliability of the system during grid-connected operation.

[0091] Step 5, Calculate the modulated wave:

[0092] Based on the reference value U of the d-axis component of the system's three-phase output voltage. dref Reference value U of the q-axis component of the system's three-phase output voltage qref And the d-axis voltage regulator output U obtained in step 4 cnt_d and q-axis voltage regulator output U cnt_q The d-axis component U of the three-phase output voltage modulation wave of the system was calculated. od and the q-axis component U of the system's three-phase output voltage modulation wave oq .

[0093] The d-axis component U of the system's three-phase output voltage modulation wave od and the q-axis component U of the system's three-phase output voltage modulation wave oq The formula for calculation is:

[0094]

[0095] In the formula, U od U represents the d-axis component of the system's three-phase output voltage modulation wave. oq For the q-axis component of the system's three-phase output voltage modulation wave; U dref U is the reference value for the d-axis component of the system's three-phase output voltage; qref U is the reference value for the q-axis component of the system's three-phase output voltage;cnt_d For the d-axis voltage regulator output; U cnt_q This is the output of the q-axis voltage regulator.

[0096] The calculated voltage modulation waveform provides a reference for subsequent current control, thereby enhancing the system's response capability and dynamic performance, and better adapting to changes in the power grid.

[0097] Step 6, Power Calculation:

[0098] Based on the actual value U of the three-phase output line voltage sampled in step 1 ab U bc U ca Actual value of three-phase output line current I a I b I c And the three-phase output phase voltage U obtained in step 2 a U b U c The instantaneous active power P and instantaneous reactive power Q of the system output are calculated.

[0099] The formulas for calculating the instantaneous active power P and instantaneous reactive power Q output by the system are as follows:

[0100]

[0101] In the formula, P is the instantaneous active power output of the system; Q is the instantaneous reactive power output of the system; U a U b U c For three-phase output phase voltage; I a I b I c To sample the actual value of the three-phase output line current of the new energy grid-connected testing platform; U ab U bc U ca The actual value of the three-phase output line voltage of the new energy grid-connected testing platform was sampled.

[0102] Real-time calculation of instantaneous power helps to assess the energy transmission efficiency of a system, better identify and resolve potential technical problems, and ensure the effective utilization of new energy sources.

[0103] Step 7, Calculate the output current reference value:

[0104] Based on the instantaneous active power P and instantaneous reactive power Q of the system output obtained in step 6, and the d-axis component U of the three-phase output voltage obtained in step 3... d and the q-axis component of the three-phase power grid voltage U q Calculate the reference value I of the d-axis component of the three-phase output current of the system. dReference value I of the q-axis component of the three-phase output current of the system q .

[0105] Reference value I of the d-axis component of the three-phase output current of the system d Reference value I of the q-axis component of the three-phase output current of the system q The formula for calculation is:

[0106]

[0107] In the formula, I d U is the reference value for the d-axis component of the system's three-phase output current; P is the instantaneous active power output by the system; U d U represents the d-axis component of the three-phase output voltage; Q represents the instantaneous reactive power output of the system; U q For the q-axis component of the three-phase power grid voltage; I q This is the reference value for the q-axis component of the system's three-phase output current.

[0108] By calculating the reference value of current through the relationship between power and voltage, effective current control can be achieved, thereby improving the power factor and overall efficiency of the generator.

[0109] Step 8, Simulate grid impedance:

[0110] Based on the d-axis component U of the system's three-phase output voltage modulation wave obtained in step 5 od and the q-axis component U of the system's three-phase output voltage modulation wave oq And the reference value I of the d-axis component of the system three-phase output current obtained in step 7. d Reference value I of the q-axis component of the three-phase output current of the system q The d-axis component E of the three-phase output voltage modulation wave of the simulated grid impedance was calculated. d And the q-axis component E of the system's three-phase output voltage modulation wave q .

[0111] After simulating the grid impedance, the d-axis component E of the three-phase output voltage modulation wave of the system d And the q-axis component E of the system's three-phase output voltage modulation wave q The formula for calculation is:

[0112]

[0113] In the formula, E d The system's three-phase output voltage modulation wave; U od R represents the d-axis component of the system's three-phase output voltage modulation wave. g I is the equivalent resistance of the power grid impedance; d This is the reference value for the d-axis component of the system's three-phase output current; L gLet be the equivalent inductance of the power grid impedance; z is a variable representing the discrete-time domain, used to describe the dynamic behavior of the system; T s The control period is ω0, which is the fundamental angular frequency; I is the control period. q E is the reference value for the q-axis component of the system's three-phase output current. q This refers to the q-axis component of the system's three-phase output voltage modulation wave.

[0114] Calculating the voltage waveform after simulating the grid impedance can effectively simulate the impedance characteristics of the real grid and improve the similarity between the system model and the real grid.

[0115] Step 9, convert to a stationary coordinate system:

[0116] Based on the simulated grid impedance obtained in step 8, the d-axis component E of the three-phase output voltage modulation wave of the system d After simulating the grid impedance, the q-axis component E of the three-phase output voltage modulation wave of the system q After synchronously rotating the coordinates to simulate the grid impedance in the stationary coordinate system, the three-phase output voltage modulation wave e of the system is obtained. a e b e c

[0117] The three-phase output voltage modulation wave e of the system after simulating the grid impedance in the stationary coordinate system a e b e c The formula for calculation is:

[0118]

[0119] In the formula, e a e b e c E represents the modulated three-phase output voltage waveform of the system after simulating the grid impedance in a stationary coordinate system. d The d-axis component of the three-phase output voltage modulation wave of the system after simulating the grid impedance; E q The q-axis component of the three-phase output voltage modulation wave of the system after simulating the grid impedance is θ; θ is the initial impedance angle of the system.

[0120] By rotating the coordinates, the voltage waveform in the stationary coordinate system can be obtained, making the subsequent modulation process simpler and more effective.

[0121] Step 10, SVPWM modulation:

[0122] The three-phase output voltage modulation wave e of the system after simulating the grid impedance in the stationary coordinate system obtained in step 9. a e b e cThe signal is fed into the SVPWM modulation module for modulation and waveform generation. Modulation via the SVPWM module ensures high-quality output waveform, reduces harmonic interference, and improves the overall performance of the new energy grid-connected system.

[0123] In summary, this grid impedance simulation and control method based on a new energy grid-connected detection platform can simulate grid impedance over a wide frequency domain and is simple to implement in engineering. Through dynamic simulation of grid impedance, grid-connected equipment can be effectively adjusted to maintain stability under various load and disturbance conditions. Accurate power and current control helps maximize the utilization rate of new energy sources, improving the system's energy efficiency and economy. It possesses strong adaptability, adjusting output according to real-time grid conditions, thereby improving the system's responsiveness to different load conditions. Real-time monitoring and dynamic control enable timely detection and handling of faults, reducing potential impacts on the system and the probability of fault occurrence.

[0124] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the same elements of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A grid impedance simulation and control method based on a new energy grid-connected testing platform. This method is based on the new energy grid-connected testing platform, which includes a DC / AC inverter unit, a DC power supply connected to the DC side of the DC / AC inverter unit, a filter circuit connected to the AC side of the DC / AC inverter unit, a transformer connected to the filter circuit, and the device under test connected to the transformer. This grid impedance simulation and control method, based on the new energy grid-connected testing platform, studies and tests the grid-connected performance of various new energy power electronic devices by simulating and controlling the grid impedance. The power grid impedance simulation control method includes the following steps: Step 1, Data sampling: The actual value of the three-phase output line voltage of the new energy grid-connected testing platform is sampled and recorded as U. ab U bc U ca Sample the actual value of the three-phase output line current of the new energy grid-connected testing platform and record it as I. a I b I c ; Step 2, calculate the phase voltage: Based on the actual value U of the three-phase output line voltage sampled in step 1 ab U bc U ca The three-phase output phase voltage U is calculated. a U b U c ; Step 3, coordinate transformation: By synchronously rotating the coordinates, the three-phase output phase voltage U obtained in step 2 is transformed. a U b U c Converting the three-phase output voltage d-axis component U in a rotating coordinate system d and the q-axis component of the three-phase power grid voltage U q ; Step 4, Voltage Adjustment: Based on the reference value U of the d-axis component of the system's three-phase output voltage. dref Reference value U of the q-axis component of the system's three-phase output voltage qref And the d-axis component U of the three-phase output voltage obtained in step 3 d and the q-axis component of the three-phase power grid voltage U q The output U of the d-axis voltage regulator is calculated using both the d-axis and q-axis voltage regulators. cnt_d and q-axis voltage regulator output U cnt_q ; Step 5, Calculate the modulated wave: Based on the reference value U of the d-axis component of the system's three-phase output voltage. dref Reference value U of the q-axis component of the system's three-phase output voltage qref And the d-axis voltage regulator output U obtained in step 4 cnt_d and q-axis voltage regulator output U cnt_q The d-axis component U of the three-phase output voltage modulation wave of the system was calculated. od and the q-axis component U of the system's three-phase output voltage modulation wave oq ; Step 6, Power Calculation: Based on the actual value U of the three-phase output line voltage sampled in step 1 ab U bc U ca Actual value of three-phase output line current I a I b I c And the three-phase output phase voltage U obtained in step 2 a U b U c The instantaneous active power P and instantaneous reactive power Q of the system output are calculated. Step 7, Calculate the output current reference value: Based on the instantaneous active power P and instantaneous reactive power Q of the system output obtained in step 6, and the d-axis component U of the three-phase output voltage obtained in step 3... d and the q-axis component of the three-phase power grid voltage U q Calculate the reference value I of the d-axis component of the three-phase output current of the system. d Reference value I of the q-axis component of the three-phase output current of the system q ; Step 8, Simulate grid impedance: Based on the d-axis component U of the system's three-phase output voltage modulation wave obtained in step 5 od and the q-axis component U of the system's three-phase output voltage modulation wave oq And the reference value I of the d-axis component of the system three-phase output current obtained in step 7. d Reference value I of the q-axis component of the three-phase output current of the system q The d-axis component E of the three-phase output voltage modulation wave of the simulated grid impedance was calculated. d And the q-axis component E of the system's three-phase output voltage modulation wave q ; In step 8, the d-axis component E of the three-phase output voltage modulation wave of the simulated grid impedance is calculated. d And the q-axis component E of the system's three-phase output voltage modulation wave q The formula for calculation is: In the formula, E d The system's three-phase output voltage modulation wave; U od R represents the d-axis component of the system's three-phase output voltage modulation wave. g I is the equivalent resistance of the power grid impedance; d This is the reference value for the d-axis component of the system's three-phase output current; L g Let be the equivalent inductance of the power grid impedance; z is a variable representing the discrete-time domain, used to describe the dynamic behavior of the system; T s The control period is ω0, which is the fundamental angular frequency; I is the control period. q E is the reference value for the q-axis component of the system's three-phase output current. q This refers to the q-axis component of the system's three-phase output voltage modulation wave. Step 9, convert to a stationary coordinate system: Based on the simulated grid impedance obtained in step 8, the d-axis component E of the three-phase output voltage modulation wave of the system d After simulating the grid impedance, the q-axis component E of the three-phase output voltage modulation wave of the system q After synchronously rotating the coordinates to simulate the grid impedance in the stationary coordinate system, the three-phase output voltage modulation wave e of the system is obtained. a e b e c ; Step 9, SVPWM modulation: The three-phase output voltage modulation wave e of the system after simulating the grid impedance in the stationary coordinate system obtained in step 9. a e b e c The signal is fed into the SVPWM modulation module for modulation and waveform generation.

2. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 2, the three-phase output phase voltage U a U b U c The formula for calculation is: In the formula, U a U b U c This refers to the three-phase output phase voltage; U ab U bc U ca The actual value of the three-phase output line voltage of the new energy grid-connected testing platform was sampled.

3. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 3, the formula for calculating the coordinate transformation is: In the formula, U d U represents the d-axis component of the three-phase output voltage in a rotating coordinate system. q U represents the q-axis component of the three-phase grid voltage in a rotating coordinate system. a U b U c θ represents the three-phase output phase voltage; θ is the initial impedance angle of the system.

4. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 4, the d-axis voltage regulator outputs U cnt_d and q-axis voltage regulator output U cnt_q The formula for calculation is: In the formula, U cnt_d For the d-axis voltage regulator output; U cnt_q For q-axis voltage regulator output; K up K is the proportional coefficient of the voltage regulator. ui is the integral coefficient of the voltage regulator; z represents the variable in the discrete-time domain, used to describe the dynamic behavior of the system; T s For control cycle; U dref U is the reference value for the d-axis component of the system's three-phase output voltage; d U represents the d-axis component of the three-phase output voltage in a rotating coordinate system. qref U is the reference value for the q-axis component of the system's three-phase output voltage; q Let q be the q-axis component of the three-phase grid voltage in a rotating coordinate system.

5. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 5, the d-axis component U of the system's three-phase output voltage modulation wave od and the q-axis component U of the system's three-phase output voltage modulation wave oq The formula for calculation is: In the formula, U od U represents the d-axis component of the system's three-phase output voltage modulation wave. oq For the q-axis component of the system's three-phase output voltage modulation wave; U dref U is the reference value for the d-axis component of the system's three-phase output voltage; qref U is the reference value for the q-axis component of the system's three-phase output voltage; cnt_d For the d-axis voltage regulator output; U cnt_q This is the output of the q-axis voltage regulator.

6. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 6, the formulas for calculating the instantaneous active power P and instantaneous reactive power Q output by the system are as follows: In the formula, P is the instantaneous active power output of the system; Q is the instantaneous reactive power output of the system; U a U b U c For three-phase output phase voltage; I a I b I c To sample the actual value of the three-phase output line current of the new energy grid-connected testing platform; U ab U bc U ca The actual value of the three-phase output line voltage of the new energy grid-connected testing platform was sampled.

7. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 7, the reference value I of the d-axis component of the system's three-phase output current. d Reference value I of the q-axis component of the three-phase output current of the system q The formula for calculation is: In the formula, I d U is the reference value for the d-axis component of the system's three-phase output current; P is the instantaneous active power output by the system; U d U represents the d-axis component of the three-phase output voltage; Q represents the instantaneous reactive power output of the system; U q For the q-axis component of the three-phase power grid voltage; I q This is the reference value for the q-axis component of the system's three-phase output current.

8. The grid impedance simulation control method based on a new energy grid connection detection platform according to claim 1, characterized in that: In step 9, the three-phase output voltage modulation wave e of the system after simulating the grid impedance in the stationary coordinate system a e b e c The formula for calculation is: In the formula, e a e b e c E represents the modulated three-phase output voltage waveform of the system after simulating the grid impedance in a stationary coordinate system. d The d-axis component of the three-phase output voltage modulation wave of the system after simulating the grid impedance; E q The q-axis component of the three-phase output voltage modulation wave of the system after simulating the grid impedance is θ; θ is the initial impedance angle of the system.

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