Power grid impedance analog control method based on new energy grid-connected detection platform

Abstract

The invention 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 data sampling, phase voltage calculation, coordinate transformation, voltage regulation, modulation wave calculation, power calculation, output current reference value calculation, power grid impedance simulation, conversion into a static coordinate system, SVPWM modulation and the like. According to the power grid impedance simulation control method, the grid-connected equipment can be effectively adjusted through dynamic simulation of the power grid impedance, so that the grid-connected equipment is kept stable under various load and disturbance conditions; through accurate power and current control, the utilization rate of new energy is maximized, and the energy efficiency and economical efficiency of the system are improved; the output can be adjusted according to the real-time power grid state, so that the response capability of the system to different load conditions is improved; through real-time monitoring and dynamic control, faults can be found and processed in time, and the potential influence on the system and the probability of fault occurrence are reduced; moreover, the impedance of the power grid is simulated in a wide frequency domain, and the engineering implementation is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid impedance simulation control, and in particular to a power grid impedance simulation control method based on a new energy grid connection detection platform. Background Art

[0002] At present, the new power system with new energy as the main body is gradually approaching. The continuous influx of high-proportion new energy power and the large-scale access of power electronic equipment will bring huge challenges to the safe and stable operation of the system. The power system has put forward increasingly stringent requirements on the operation ability of grid-connected new energy and power electronic equipment under external power grid faults. In order to study and test the operation ability of new energy and power electronic equipment under various power grid faults, special equipment is needed to accurately reproduce various states and fault conditions of the power grid, that is, the new energy grid-connected detection platform.

[0003] Since new energy power generation systems, mainly 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 will not only change the impedance characteristics of the power grid, making the power grid present weak grid characteristics, but also affect the working performance of the power electronic grid-connected device, causing system stability problems. Therefore, in order to more realistically simulate the working conditions of the actual power grid and detect the weak grid adaptability of the power electronic grid-connected device, the new energy grid-connected detection platform should have the function of grid impedance simulation. Considering that the power grid contains high-frequency harmonics, only simulating the grid impedance characteristics at the fundamental frequency can no longer reflect the actual power grid situation. To this end, scholars have done some research on the grid impedance simulation control of the new energy grid-connected detection platform. For example, the Chinese invention patent application disclosure specification (CN116819210A) published on September 29, 2023, entitled "A control method, control device and power grid simulator for a power grid simulator", discloses a power grid impedance simulation control method, which uses an improved voltage and current dual closed-loop control strategy to control the power grid simulator, and obtains a direct-axis optimized voltage instruction by superimposing a direct-axis virtual impedance voltage divider on the direct-axis setting voltage instruction, and obtains a quadrature-axis optimized voltage instruction by superimposing a quadrature-axis virtual impedance voltage divider on the quadrature-axis setting voltage instruction, thereby simulating the power grid impedance. For example, the Chinese invention patent application disclosure specification (CN118068125A) published on May 24, 2024, entitled "Power grid simulator control method with transmission line impedance wide-frequency domain simulation function", discloses a wide-frequency domain power grid impedance simulation control method, which uses a distributed parameter circuit model to process the transmission line, and realizes a wide-frequency domain, high-precision, dynamic and real-time simulation of the power grid impedance through a multi-order linearization approximation method combined with a voltage and current closed-loop feedback control loop.

[0004] However, the "Control method, control device and power grid simulator of a power grid simulator" published in the Publication Specification of the Chinese Invention Patent Application (CN116819210A) on September 29, 2023, only simulates the power grid impedance characteristics at the fundamental frequency, but the actual power grid contains high-frequency harmonics, and the power grid impedance simulation at the fundamental frequency cannot reflect the actual power grid characteristics. The "Power grid simulator control method with wide-frequency domain simulation function of transmission line impedance" published in the Publication Specification of the Chinese Invention Patent Application (CN118068125A) on May 24, 2024, although this method simulates the power grid impedance in the wide frequency domain, is too complex and difficult to implement in engineering.

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

[0006] In order to solve the above problems, the present invention proposes a grid impedance simulation control method based on a new energy grid connection detection platform.

[0007] The technical solution adopted by the present invention is:

[0008] A grid impedance simulation control method based on a new energy grid-connected detection platform, the grid impedance simulation control method is based on a new energy grid-connected detection platform; the new energy grid-connected detection 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 grid impedance simulation control method is based on the new energy grid-connected detection platform, and through simulation and control of grid impedance, the grid-connected performance of various new energy power electronic equipment is studied and tested;

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

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

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

[0012] Step 2, calculate the phase voltage:

[0013] According to 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] Through synchronous rotating coordinate transformation, the three-phase output phase voltage U obtained in step 2 is a , U b , U c Converted into the d-axis component U of the three-phase output voltage in the rotating coordinate system d And the q-axis component U of the three-phase grid voltage q ;

[0016] Step 4, voltage regulation:

[0017] According to the system three-phase output voltage d-axis component reference value U dref , System three-phase output voltage q-axis component reference value U qref , and the three-phase output voltage d-axis component U obtained in step 3 d And the q-axis component U of the three-phase grid voltage q , respectively through the d-axis voltage regulator and the q-axis voltage regulator, the d-axis voltage regulator output U is calculated cnt_d and the q-axis voltage regulator output U cnt_q ;

[0018] Step 5, calculate the modulation wave:

[0019] According to the system three-phase output voltage d-axis component reference value U dref , System three-phase output voltage q-axis component reference value U qref , and the d-axis voltage regulator output U obtained in step 4 cnt_d and the q-axis voltage regulator output U cnt_q , the d-axis component U of the system three-phase output voltage modulation wave is calculated od The q-axis component U of the system three-phase output voltage modulation wave oq ;

[0020] Step 6, power calculation:

[0021] According to 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, calculate the instantaneous active power P and instantaneous reactive power Q output by the system;

[0022] Step 7, output current reference value calculation:

[0023] According to the instantaneous active power P and instantaneous reactive power Q of the system output obtained in step 6, and the three-phase output voltage d-axis component U obtained in step 3 d And the q-axis component U of the three-phase grid voltage q , calculate the system three-phase output current d-axis component reference value I d , System three-phase output current q-axis component reference value I q ;

[0024] Step 8, simulate grid impedance:

[0025] According to the system three-phase output voltage modulation wave d-axis component U obtained in step 5 od The q-axis component U of the system three-phase output voltage modulation wave oq , and the system three-phase output current d-axis component reference value I obtained in step 7 d , System three-phase output current q-axis component reference value I q , the d-axis component E of the system three-phase output voltage modulation wave after simulating the grid impedance is calculated d The q-axis component E of the system three-phase output voltage modulation wave q ;

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

[0027] According to the simulated grid impedance obtained in step 8, the system three-phase output voltage modulation wave d-axis component E d After simulating the grid impedance, the q-axis component E of the system three-phase output voltage modulation wave q After the synchronous rotating coordinate system is transformed into the simulated grid impedance in the stationary coordinate system, the system three-phase output voltage modulation wave e a 、e b 、e c ;

[0028] Step 10, SVPWM modulation:

[0029] After simulating the grid impedance in the stationary coordinate system obtained in step 9, the three-phase output voltage modulation wave e a 、e b 、e c Send it to the SVPWM modulation module for modulation and wave generation.

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

[0031]

[0032] Where U a , U b , U c is the three-phase output phase voltage; U ab , U bc , U ca To sample the actual value of the three-phase output line voltage of the new energy grid-connected detection platform.

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

[0034]

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

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

[0037]

[0038] Where U cnt_d is the output of the d-axis voltage regulator; U cnt_q is the output of the q-axis voltage regulator; K up is the voltage regulator proportional coefficient; K ui is the voltage regulator integral coefficient; z represents the variable in the discrete time domain, which is used to describe the dynamic behavior of the system; T s is the control period; U dref is the reference value of the d-axis component of the system three-phase output voltage; U d is the d-axis component of the three-phase output voltage in the rotating coordinate system; U qref is the reference value of the q-axis component of the system three-phase output voltage; U q is the q-axis component of the three-phase grid voltage in the rotating coordinate system.

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

[0040]

[0041] Where U od is the d-axis component of the system three-phase output voltage modulation wave; U oq is the q-axis component of the system three-phase output voltage modulation wave; U dref is the reference value of the d-axis component of the system three-phase output voltage; U qref is the reference value of the q-axis component of the system three-phase output voltage; U cnt_d is the output of the d-axis voltage regulator; U cnt_q is the q-axis voltage regulator output.

[0042] Further, in step 6, the calculation formula of the instantaneous active power P and instantaneous reactive power Q output by the system is:

[0043]

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

[0045] Further, in step 7, the system three-phase output current d-axis component reference value I d , System three-phase output current q-axis component reference value I q The calculation formula is:

[0046]

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

[0048] Further, in step 8, after simulating the grid impedance, the system three-phase output voltage modulation wave d-axis component E d The q-axis component E of the system three-phase output voltage modulation wave q The calculation formula is:

[0049]

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

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

[0052]

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

[0054] Compared with the existing technology, the grid impedance simulation control method based on the new energy grid connection detection platform has the following beneficial effects:

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

[0056] Optimize energy management: This grid impedance simulation control method based on the new energy grid-connected detection platform is achieved through accurate power and current control, which helps to maximize the utilization 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-connected detection platform has strong adaptability and can adjust the output according to the real-time grid status, thereby improving the system's responsiveness to different load conditions.

[0058] Reduce the risk of failure: The grid impedance simulation control method based on the new energy grid-connected 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 failure.

[0059] Improve environmental benefits: This grid impedance simulation control method based on the new energy grid-connected detection platform reduces dependence on traditional energy and reduces carbon emissions through efficient use of new energy, thus helping to achieve sustainable development goals.

[0060] Assisting in the construction of smart grids: This grid impedance simulation control method based on the new energy grid-connected detection platform helps to realize intelligent management, improve the access capacity of new energy, and promote the development of the grid towards intelligence and digitalization.

[0061] In summary, the grid impedance simulation control method based on the new energy grid-connected detection platform can simulate the grid impedance in a wide frequency domain, and the engineering implementation is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0063] in:

[0064] Figure 1 It is a schematic diagram of the composition of the new energy grid-connected detection platform of the present invention;

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

[0066] Figure 3 The figure is a flow chart of the grid impedance simulation control method of the present invention. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] The prior art only simulates 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 complicated and difficult to implement in engineering. Therefore, this embodiment provides a grid impedance simulation control method based on a new energy grid connection detection platform.

[0069] The grid impedance simulation control method is based on the new energy grid connection detection platform; Figure 1 As shown, the new energy grid-connected detection 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, wherein the device under test is a new energy and power electronic device whose grid-connected performance needs to be studied and tested; the grid impedance simulation control method is based on the new energy grid-connected detection platform, and the grid-connected performance of various new energy power electronic devices is studied and tested by simulating and controlling the grid impedance;

[0070] The grid impedance simulation control method, such as Figure 2 and Figure 3 As shown, the following steps are included:

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

[0072] Sample the actual value of the three-phase output line voltage of the new energy grid-connected detection platform and record it as U ab , U bc , U ca ; Sample the actual value of the three-phase output line current of the new energy grid-connected detection 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 basis can be provided for subsequent analysis, ensuring the reliability of the overall system performance.

[0073] Step 2, calculate the phase voltage:

[0074] According to 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 calculation formula is:

[0076]

[0077] Where U a , U b , U c is the three-phase output phase voltage; U ab , U bc , U ca To sample the actual value of the three-phase output line voltage of the new energy grid-connected detection platform.

[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] Through synchronous rotating coordinate transformation, the three-phase output phase voltage U obtained in step 2 is a , U b , U c Converted into the d-axis component U of the three-phase output voltage in the rotating coordinate system d And the q-axis component U of the three-phase grid voltage q .

[0081] The calculation formula for coordinate transformation is:

[0082]

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

[0084] Synchronous rotating coordinate transformation can effectively simplify the processing of voltage parameters, convert complex three-phase AC quantities into easy-to-operate DC quantities, and facilitate the implementation of subsequent control strategies.

[0085] Step 4, voltage regulation:

[0086] According to the system three-phase output voltage d-axis component reference value U dref , System three-phase output voltage q-axis component reference value U qref , and the three-phase output voltage d-axis component U obtained in step 3 d And the q-axis component U of the three-phase grid voltage q , respectively through the d-axis voltage regulator and the q-axis voltage regulator, the d-axis voltage regulator output U is calculated cnt_d and the q-axis voltage regulator output U cnt_q .

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

[0088]

[0089] Where U cnt_d is the output of the d-axis voltage regulator; U cnt_q is the output of the q-axis voltage regulator; K up is the voltage regulator proportional coefficient; K ui is the voltage regulator integral coefficient; z represents the variable in the discrete time domain, which is used to describe the dynamic behavior of the system; T s is the control period; U dref is the reference value of the d-axis component of the system three-phase output voltage; U d is the d-axis component of the three-phase output voltage in the rotating coordinate system; U qref is the reference value of the q-axis component of the system three-phase output voltage; U q is the q-axis component of the three-phase grid voltage in the rotating coordinate system.

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

[0091] Step 5, calculate the modulation wave:

[0092] According to the system three-phase output voltage d-axis component reference value U dref , System three-phase output voltage q-axis component reference value U qref , and the d-axis voltage regulator output U obtained in step 4 cnt_d and the q-axis voltage regulator output U cnt_q , the d-axis component U of the system three-phase output voltage modulation wave is calculated od The q-axis component U of the system three-phase output voltage modulation wave oq .

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

[0094]

[0095] Where U od is the d-axis component of the system three-phase output voltage modulation wave; U oq is the q-axis component of the system three-phase output voltage modulation wave; U dref is the reference value of the d-axis component of the system three-phase output voltage; U qref is the reference value of the q-axis component of the system three-phase output voltage; Ucnt_d is the output of the d-axis voltage regulator; U cnt_q is the q-axis voltage regulator output.

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

[0097] Step 6, power calculation:

[0098] According to 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 output by the system are calculated.

[0099] The calculation formula for the instantaneous active power P and instantaneous reactive power Q output by the system is:

[0100]

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

[0102] Real-time calculation of instantaneous power helps to evaluate the energy transfer efficiency of the system, better identify and solve potential technical problems, and ensure the effective use of new energy.

[0103] Step 7, output current reference value calculation:

[0104] According to the instantaneous active power P and instantaneous reactive power Q of the system output obtained in step 6, and the three-phase output voltage d-axis component U obtained in step 3 d And the q-axis component U of the three-phase grid voltage q , calculate the system three-phase output current d-axis component reference value I d, System three-phase output current q-axis component reference value I q .

[0105] System three-phase output current d-axis component reference value I d , System three-phase output current q-axis component reference value I q The calculation formula is:

[0106]

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

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

[0109] Step 8, simulate grid impedance:

[0110] According to the system three-phase output voltage modulation wave d-axis component U obtained in step 5 od The q-axis component U of the system three-phase output voltage modulation wave oq , and the system three-phase output current d-axis component reference value I obtained in step 7 d , System three-phase output current q-axis component reference value I q , the d-axis component E of the system three-phase output voltage modulation wave after simulating the grid impedance is calculated d The q-axis component E of the system three-phase output voltage modulation wave q .

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

[0112]

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

[0114] The voltage waveform after calculating the simulated 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 stationary coordinate system:

[0116] According to the simulated grid impedance obtained in step 8, the system three-phase output voltage modulation wave d-axis component E d After simulating the grid impedance, the q-axis component E of the system three-phase output voltage modulation wave q After the synchronous rotating coordinate system is transformed into the simulated grid impedance in the stationary coordinate system, the system three-phase output voltage modulation wave e a 、e b 、e c

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

[0118]

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

[0120] By rotating the coordinate transformation, 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] After simulating the grid impedance in the stationary coordinate system obtained in step 9, the three-phase output voltage modulation wave e a 、e b 、e cThe SVPWM modulation module is sent to the modulation and wave generation. Modulation through the SVPWM modulation module can ensure the high quality of the output waveform, reduce harmonic interference, and improve the overall performance of the new energy grid-connected system.

[0123] In summary, the grid impedance simulation control method based on the new energy grid-connected detection platform simulates the grid impedance in a wide frequency domain, and the engineering implementation is simple. Through the dynamic simulation of the grid impedance, the grid-connected equipment can be effectively adjusted to keep it stable under various load and disturbance conditions; through accurate power and current control, it helps to maximize the utilization of new energy and improve the energy efficiency and economy of the system; it has strong adaptability and can adjust the output according to the real-time grid status, thereby improving the system's responsiveness to different load conditions; through real-time monitoring and dynamic control, faults can be discovered and handled in a timely manner, reducing the potential impact on the system and the probability of faults.

[0124] It will be apparent to those skilled in the art that the 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 the spirit or essential features of the invention. 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, and it is intended that all variations falling within the meaning and scope of the same elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A grid impedance simulation control method based on a new energy grid-connected detection platform, the grid impedance simulation control method is based on a new energy grid-connected detection platform; the new energy grid-connected detection 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 grid impedance simulation control method is based on the new energy grid-connected detection platform, and through simulation and control of grid impedance, the grid-connected performance of various new energy power electronic equipment is studied and tested; The grid impedance simulation control method comprises the following steps: Step 1, sampling data: Sample the actual value of the three-phase output line voltage of the new energy grid-connected detection platform and record it as U ab , U bc , U ca ; Sample the actual value of the three-phase output line current of the new energy grid-connected detection platform and record it as I a ,I b ,I c ; Step 2, calculate the phase voltage: According to 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: Through synchronous rotating coordinate transformation, the three-phase output phase voltage U obtained in step 2 is a , U b , U c Converted into the d-axis component U of the three-phase output voltage in the rotating coordinate system d And the q-axis component U of the three-phase grid voltage q ; Step 4, voltage regulation: According to the system three-phase output voltage d-axis component reference value U dref , System three-phase output voltage q-axis component reference value U qref , and the three-phase output voltage d-axis component U obtained in step 3 d And the q-axis component U of the three-phase grid voltage q , respectively through the d-axis voltage regulator and the q-axis voltage regulator, the d-axis voltage regulator output U is calculated cnt_d and the q-axis voltage regulator output U cnt_q ; Step 5, calculate the modulation wave: According to the system three-phase output voltage d-axis component reference value U dref , System three-phase output voltage q-axis component reference value U qref , and the d-axis voltage regulator output U obtained in step 4 cnt_d and the q-axis voltage regulator output U cnt_q , the d-axis component U of the system three-phase output voltage modulation wave is calculated od The q-axis component U of the system three-phase output voltage modulation wave oq ; Step 6, power calculation: According to 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 , calculate the instantaneous active power P and instantaneous reactive power Q output by the system; Step 7, output current reference value calculation: According to the instantaneous active power P and instantaneous reactive power Q of the system output obtained in step 6, and the three-phase output voltage d-axis component U obtained in step 3 d And the q-axis component U of the three-phase grid voltage q , calculate the system three-phase output current d-axis component reference value I d , System three-phase output current q-axis component reference value I q ; Step 8, simulate grid impedance: According to the system three-phase output voltage modulation wave d-axis component U obtained in step 5 od The q-axis component U of the system three-phase output voltage modulation wave oq , and the system three-phase output current d-axis component reference value I obtained in step 7 d , System three-phase output current q-axis component reference value I q , the d-axis component E of the system three-phase output voltage modulation wave after simulating the grid impedance is calculated d The q-axis component E of the system three-phase output voltage modulation wave q ; Step 9, convert to stationary coordinate system: According to the simulated grid impedance obtained in step 8, the system three-phase output voltage modulation wave d-axis component E d After simulating the grid impedance, the q-axis component E of the system three-phase output voltage modulation wave q After the synchronous rotating coordinate system is transformed into the simulated grid impedance in the stationary coordinate system, the system three-phase output voltage modulation wave e a 、e b 、e c ; Step 9, SVPWM modulation: After simulating the grid impedance in the stationary coordinate system obtained in step 9, the three-phase output voltage modulation wave e a 、e b 、e c Send it to the SVPWM modulation module for modulation and wave generation.

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

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

4. The grid impedance simulation control method based on the new energy grid connection detection platform according to claim 1 is characterized in that: In step 4, the d-axis voltage regulator outputs U cnt_d and the q-axis voltage regulator output U cnt_q The calculation formula is: Where U cnt_d is the output of the d-axis voltage regulator; U cnt_q is the output of the q-axis voltage regulator; K up is the voltage regulator proportional coefficient; K ui is the voltage regulator integral coefficient; z represents a variable in the discrete time domain, which is used to describe the dynamic behavior of the system; T s is the control period; U dref is the reference value of the d-axis component of the system three-phase output voltage; U d is the d-axis component of the three-phase output voltage in the rotating coordinate system; U qref is the reference value of the q-axis component of the system three-phase output voltage; U q is the q-axis component of the three-phase grid voltage in the rotating coordinate system.

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

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

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

8. The grid impedance simulation control method based on the new energy grid connection detection platform according to claim 1 is characterized in that: In step 8, after simulating the grid impedance, the system three-phase output voltage modulation wave d-axis component E d The q-axis component E of the system three-phase output voltage modulation wave q The calculation formula is: In the formula, E d is the system three-phase output voltage modulation wave; U od is the d-axis component of the system three-phase output voltage modulation wave; R g is the equivalent resistance of the grid impedance; I d is the reference value of the d-axis component of the system three-phase output current; L g is the equivalent inductance of the grid impedance; z is a variable in the discrete time domain, which is used to describe the dynamic behavior of the system; T s is the control period; ω0 is the fundamental angular frequency; I q is the reference value of the q-axis component of the system three-phase output current; E q It is the q-axis component of the system's three-phase output voltage modulation wave.

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

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