Networking new energy station cooperative control method based on station controller scheduling

Abstract

The invention discloses a network construction new energy station cooperative control method based on station controller scheduling, and belongs to the technical field of grid-connected conversion. The control method comprises the following steps: (1) a power calculation link; (2) active frequency loop control; and (3) reactive voltage loop control. Compared with the prior art, the weak grid stability is improved, the problem of coupling resonance caused by parallel connection of multiple grid construction converters is avoided, and the support of the new energy station cluster on the voltage and frequency of the power grid is realized.

Description

Technical Field

[0001] The present invention relates to a grid-connected power conversion technology in the field of electrical engineering, and specifically to a method for collaboratively controlling a networked new energy station based on station controller scheduling. Background Art

[0002] With the high proportion of new energy connected to the power grid, the power grid is gradually tending to have weak inertia and low strength characteristics. At present, the converters in the power grid mostly use grid-following control technology, which is mature in application. However, its operation stability is poor under weak grid conditions, and it is difficult to support the voltage and frequency of the grid. In response to this problem, the following literature proposes solutions.

[0003] The document "Midtsund T, Suul JA, Undeland T. Evaluation of current controller performance and stability for voltage source converters connected to a weak grid [C]. Power Electronics for Distributed Generation Systems (PEDG), 2010 2nd IEEE International Symposium on, 2010." proposes that reducing the phase-locked loop bandwidth can further improve the weak grid stability of the grid-following converter. However, modifying the phase-locked loop cannot improve the converter's support performance for the grid.

[0004] The paper “Wu W, Leming Z, Yandong C, et al. Sequence-impedance-based stability comparison between vsgs and traditional grid-connected inverters [J]. IEEE Transactions on Power Electronics, 2018, 34 (1): 46-52.” proposed a sequence impedance modeling method for grid-connected VSG control. The analysis shows that the grid-connected VSG control can significantly improve the stability margin of the converter under weak grid conditions, and can play a certain supporting role in the grid voltage and frequency. However, the paper “M. Li, X. Zhang, Y. Yang and P. Cao. The grid impedance adaptation dualmode control strategy in

[0005] weak grid[C].2018International Power Electronics Conference(IPEC-Niigata 2018-ECCE Asia),2015:2973-2979."(M.Li,X.Zhang,Y.Yang and P.Cao.Grid impedance adaptive dual-mode control strategy in weak grid[C].2018International Power Electronics Conference(IPEC Niigata 2018-ECCE Asia),2015:2973-2979) analyzed that when multiple converters in a new energy station cluster are connected in parallel using grid-type control, coupling resonance between converters will occur, introducing new stability problems.

[0006] In summary, the existing solutions still have the following disadvantages:

[0007] 1) Although the current converter and grid control are relatively mature, the weak grid stability and grid voltage and frequency support performance are insufficient;

[0008] 2) Although the current inverter grid control can support the grid voltage frequency and has good weak grid stability, the technology is not mature enough and resonance is prone to occur when connected in parallel, making it difficult to apply on a large scale; Summary of the invention

[0009] The problem to be solved by the present invention is to overcome the limitations of the above-mentioned scheme and propose a collaborative control method for networked new energy stations based on station controller scheduling. The control method sets up a station controller, performs network control in the station controller, and sends a power command signal to the station converter by issuing communication instructions. The station converter still works in the grid-following mode, which effectively improves the frequency and voltage support performance of the new energy station to the power grid, improves the stability of the weak network, and avoids the coupling resonance problem of multiple network converters in parallel.

[0010] To solve the technical problem of the present invention, the present invention provides a coordinated control method of a networked new energy station based on station controller scheduling. The new energy station applying the control method includes N three-phase converters, N three-phase filters, N three-phase grid-connected transformers, three-phase grid-connected points, three-phase grid impedance and three-phase grid. The N three-phase converters are respectively connected in series with N three-phase filters and N three-phase grid-connected transformers in sequence and then connected to the three-phase grid point, and then connected to the three-phase grid through the three-phase grid impedance; the station controller is a controller that sends command signals to the N three-phase converters at a certain frequency through a communication line;

[0011] The collaborative control method includes a power calculation link, an active frequency loop control and a reactive voltage loop control, and includes the following steps:

[0012] Step 1: Power calculation

[0013] Step 1.1, sample and obtain the actual value of the three-phase grid connection point voltage v pcc_A ,v pcc_B ,v pcc_C And the actual value of the three-phase grid-connected current i g_A ,i g_B ,i g_C By transforming the three-phase stationary coordinate system to the two-phase stationary coordinate system, the two-phase grid-connected current i in the two-phase stationary coordinate system is obtained. g_α ,i g_β and the two-phase grid voltage v pcc_α ,v pcc_β ;

[0014] The actual value of the three-phase grid voltage v pcc_A ,v pcc_B ,v pcc_C The amplitude is detected, and its average amplitude is recorded as the three-phase grid-connected point voltage amplitude V amp , and then the voltage amplitude V of the three-phase grid connection point amp Phase lock is performed to obtain the grid connection point voltage frequency ω g , and calculate the grid-connected point voltage frequency ω g The voltage frequency of the grid point in the previous beat ω g ′The difference Δω g ;

[0015] Step 1.2, calculate the instantaneous active power P and instantaneous reactive power Q of the new energy station, and then obtain the filtered active power and reactive power of the new energy station through low-pass filtering, and record it as the filtered active power P fil And the filtered reactive power Q fil ;

[0016] Step 2, Active Frequency Loop Control

[0017] Step 2.1, according to the filtered active power P obtained in step 1 fil , the active frequency loop output power instruction P of the new energy station is obtained through the active frequency loop calculation formula ref , the active frequency loop calculation formula is:

[0018]

[0019] Among them, P set is the active power reference value of the active frequency loop, ω0 is the rated angular frequency of the power grid, k x is the transmission impedance adjustment coefficient, H v is the inertia coefficient, D v is the damping coefficient, S is the Laplace operator;

[0020] Step 2.2, let the rated power of the kth three-phase converter be P Nk , k = 1, 2, ..., N, according to the active frequency loop output power instruction P of the new energy station ref The active power command value P sent to the kth converter is calculated refk , and its calculation formula is;

[0021]

[0022] Step 3, reactive voltage loop control

[0023] The filtered reactive power Q obtained in step 1 fil , the reactive voltage loop output power command Q of the new energy station is obtained through the reactive voltage loop calculation formula ref , the reactive voltage loop calculation formula is:

[0024]

[0025] Among them, Q set is the reactive power reference value of the reactive voltage loop, V nAmp is the rated voltage amplitude of the grid connection point, K q is the reactive inertia coefficient, D q is the reactive damping coefficient;

[0026] According to the reactive voltage loop output power instruction Q of the new energy station ref The reactive power command value Q sent to the kth converter is calculated refk , and its calculation formula is:

[0027]

[0028] Preferably, the calculation formula for the instantaneous active power P and instantaneous reactive power Q of the new energy station in step 1 is:

[0029] P=v pcc_α i g_α +v pcc_β i g_β

[0030] Q=v pcc_β i g_α -v pcc_α i g_β

[0031] The filtered active power P fil And the filtered reactive power Q fil The calculation formula is:

[0032]

[0033] Among them, ω c is the cutoff frequency of the low-pass filter.

[0034] Preferably, the grid connection point voltage frequency ω in step 1 g The voltage frequency of the grid point in the previous beat ω g ′The difference Δω g The values ​​of are as follows:

[0035] When there is no previous data, take Δω g =0;

[0036] When there is data from the previous shot, take Δω g =ω g -ω g ′.

[0037] The beneficial effects of the present invention relative to the prior art are:

[0038] 1. While improving the stability of weak grid, it avoids the coupling resonance problem of parallel connection of multi-grid converters;

[0039] 2. The new energy station cluster supports the grid voltage and frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the new energy station architecture in the embodiment of the present invention.

[0041] Figure 2 It is a schematic diagram of the collaborative control method of the present invention.

[0042] Figure 3 It is the simulated waveform of the grid connection point voltage under the grid voltage frequency fluctuation. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0044] Figure 1 It is the architecture of the new energy station in the embodiment of the present invention. As can be seen from the figure, the new energy station applying the control method includes N three-phase converters, N three-phase filters, N three-phase grid-connected transformers, three-phase grid-connected points, three-phase grid impedance and three-phase grid. The N three-phase converters are respectively connected in series with N three-phase filters and N three-phase grid-connected transformers and then connected to the three-phase grid point, and then connected to the three-phase grid through the three-phase grid impedance. The station controller is a controller that sends command signals to N three-phase converters at a certain frequency through a communication line.

[0045] Depend on Figure 1 It can be seen that the whole of the three-phase converter and the three-phase filter connected in series is recorded as a three-phase converter circuit.

[0046] Figure 2 It is a schematic diagram of the collaborative control method of the present invention. Figure 2 It can be seen that the collaborative control method of the present invention includes a power calculation link, an active frequency loop control and a reactive voltage loop control, and includes the following steps:

[0047] The collaborative control method includes a power calculation link, an active frequency loop control and a reactive voltage loop control, and includes the following steps:

[0048] Step 1: Power calculation

[0049] Step 1.1, sample and obtain the actual value of the three-phase grid connection point voltage v pcc_A ,v pcc_B ,v pcc_C And the actual value of the three-phase grid-connected current i g_A ,i g_B ,i g_C By transforming the three-phase stationary coordinate system to the two-phase stationary coordinate system, the two-phase grid-connected current i in the two-phase stationary coordinate system is obtained. g_α ,i g_β and the two-phase grid voltage v pcc_α ,v pcc_β ;

[0050] The actual value of the three-phase grid voltage v pcc_A ,v pcc_B ,vpcc_C The amplitude is detected, and its average amplitude is recorded as the three-phase grid-connected point voltage amplitude V amp , and then the voltage amplitude V of the three-phase grid connection point amp Phase lock is performed to obtain the grid connection point voltage frequency ω g , and calculate the grid-connected point voltage frequency ω g The voltage frequency of the grid point in the previous beat ω g ′The difference Δω g ;

[0051] Step 1.2, calculate the instantaneous active power P and instantaneous reactive power Q of the new energy station, and then obtain the filtered active power and reactive power of the new energy station through low-pass filtering, and record it as the filtered active power P fil And the filtered reactive power Q fil .

[0052] In this embodiment, the calculation formulas for the instantaneous active power P and instantaneous reactive power Q of the new energy station are:

[0053] P=v pcc_α i g_α +v pcc_β i g_β

[0054] Q=v pcc_β i g_α -v pcc_α i g_β

[0055] The filtered active power P fil And the filtered reactive power Q fil The calculation formula is:

[0056]

[0057] Among them, ω c is the cutoff frequency of the low-pass filter.

[0058] In this embodiment, the grid connection point voltage frequency ω in step 1 g The voltage frequency of the grid point in the previous beat ω g ′The difference Δω g The values ​​of are as follows:

[0059] When there is no previous data, take Δω g =0;

[0060] When there is data from the previous shot, take Δω g =ω g -ω g ′.

[0061] Step 2, Active Frequency Loop Control

[0062] Step 2.1, according to the filtered active power P obtained in step 1 fil , the active frequency loop output power instruction P of the new energy station is obtained through the active frequency loop calculation formula ref , the active frequency loop calculation formula is:

[0063]

[0064] Among them, P set is the active power reference value of the active frequency loop, ω0 is the rated angular frequency of the power grid, k x is the transmission impedance adjustment coefficient, H v is the inertia coefficient, D v is the damping coefficient, S is the Laplace operator;

[0065] Step 2.2, let the rated power of the kth three-phase converter be P Nk , k = 1, 2, ..., N, according to the active frequency loop output power instruction P of the new energy station ref The active power command value P sent to the kth converter is calculated refk , and its calculation formula is;

[0066]

[0067] Step 3, reactive voltage loop control

[0068] The filtered reactive power Q obtained in step 1 fil , the reactive voltage loop output power command Q of the new energy station is obtained through the reactive voltage loop calculation formula ref , the reactive voltage loop calculation formula is:

[0069]

[0070] Among them, Q set is the reactive power reference value of the reactive voltage loop, V nAmp is the rated voltage amplitude of the grid connection point, K q is the reactive inertia coefficient, D q is the reactive damping coefficient;

[0071] According to the reactive voltage loop output power instruction Q of the new energy station ref The reactive power command value Q sent to the kth converter is calculated refk , and its calculation formula is:

[0072]

[0073] In this embodiment, N=4, ω c =60π,P set =80000,ω0=100π,k x =1.67, H v =5,D v =250, P N1 =P N2 =P N3 =P N4 =20000,Q set =0, V nAmp =311, K q =56.8, D q =2568.

[0074] Figure 3 is the active frequency loop output power instruction P of the new energy station under the fluctuation of grid voltage and frequency in the embodiment of the present invention. ref and the reactive voltage loop output power command Q of the new energy station ref The left side shows the voltage amplitude V of the remote power grid. gAmp When the simulation runs for 0.2s, the voltage drops from 311V to 280V. ref Basically unchanged, Q ref The right side shows that the grid frequency starts from 314.16 rad / s at 0.2s of simulation operation and then drops to 312.90 rad / s after 0.2s of ramp to enter the steady state. During the simulation time of [0.2s, 0.4s] when the grid frequency changes, P ref Increase, simulation time 0.4s after P ref Restore, Q ref There is only a slight fluctuation during the change process. The simulation results verify the supporting performance of the coordinated control method of the embodiment of the present invention on the grid frequency and voltage.

Claims

1. A method for collaborative control of a networked new energy station based on station controller scheduling, wherein the new energy station to which the control method is applied comprises N three-phase converters, N three-phase filters, N three-phase grid-connected transformers, three-phase grid-connected points, three-phase grid impedances and three-phase grids, wherein the N three-phase converters are respectively connected in series with the N three-phase filters and the N three-phase grid-connected transformers in sequence and then connected to the three-phase grid-connected points, and then connected to the three-phase grid through the three-phase grid impedances; the station controller is a controller that sends command signals to the N three-phase converters at a certain frequency through a communication line; It is characterized in that The collaborative control method includes a power calculation link, an active frequency loop control and a reactive voltage loop control, and includes the following steps: Step 1: Power calculation Step 1.1, sample and obtain the actual value of the three-phase grid connection point voltage v pcc_A ,v pcc_B ,v pcc_C And the actual value of the three-phase grid-connected current i g_A ,i g_B ,i g_C By transforming the three-phase stationary coordinate system to the two-phase stationary coordinate system, the two-phase grid-connected current i in the two-phase stationary coordinate system is obtained. g_α ,i g_β and the two-phase grid voltage v pcc_α ,v pcc_β ; The actual value of the three-phase grid-connected point voltage v pcc_A ,v pcc_B ,v pcc_C The amplitude is detected, and its average amplitude is recorded as the three-phase grid-connected point voltage amplitude V amp , and then the voltage amplitude V of the three-phase grid connection point amp Phase lock is performed to obtain the grid connection point voltage frequency ω g , and calculate the grid-connected point voltage frequency ω g The voltage frequency of the grid point in the previous beat ω g ′The difference Δω g ; Step 1.2, calculate the instantaneous active power P and instantaneous reactive power Q of the new energy station, and then obtain the filtered active power and reactive power of the new energy station through low-pass filtering, and record it as the filtered active power P fil And the filtered reactive power Q fil ; Step 2: Active frequency loop control Step 2.1, according to the filtered active power P obtained in step 1 fil , the active frequency loop output power instruction P of the new energy station is obtained through the active frequency loop calculation formula ref , the active frequency loop calculation formula is: Among them, P set is the active power reference value of the active frequency loop, ω0 is the rated angular frequency of the power grid, k x is the transmission impedance adjustment coefficient, H v is the inertia coefficient, D v is the damping coefficient, S is the Laplace operator; Step 2.2, let the rated power of the kth three-phase converter be P Nk , k = 1, 2, ..., N, according to the active frequency loop output power instruction P of the new energy station ref The active power command value P sent to the kth converter is calculated refk , and its calculation formula is; Step 3, reactive voltage loop control The filtered reactive power Q obtained in step 1 fil , the reactive voltage loop output power command Q of the new energy station is obtained through the reactive voltage loop calculation formula ref , the reactive voltage loop calculation formula is: Among them, Q set is the reactive power reference value of the reactive voltage loop, V nAmp is the rated voltage amplitude of the grid connection point, K q is the reactive inertia coefficient, D q is the reactive damping coefficient; According to the reactive voltage loop output power instruction Q of the new energy station ref The reactive power command value Q sent to the kth converter is calculated refk , and its calculation formula is:

2. The method for collaborative control of networked new energy stations based on station controller scheduling according to claim 1 is characterized in that: The calculation formula for the instantaneous active power P and instantaneous reactive power Q of the new energy station in step 1 is: P=v pcc_α i g_α +v pcc_β i g_β Q=v pcc_β i g_α -v pcc_α i g_β The filtered active power P fil And the filtered reactive power Q fil The calculation formula is: Among them, ω c is the cutoff frequency of the low-pass filter.

3. The method for collaborative control of networked new energy stations based on station controller scheduling according to claim 1 is characterized in that: The grid connection point voltage frequency ω in step 1 g The voltage frequency of the grid-connected point in the previous beat ω′ g The difference Δω g The values ​​of are as follows: When there is no previous data, take Δω g =0; When there is data from the previous shot, take Δω g =ω g -ω′ g .

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