Double-side network construction control method and system for multi-port flexible power supply system of electrified railway

Abstract

The application discloses a kind of electrified railway multi-port flexible power supply system double-side network construction control method and system, when voltage drop, frequency deviation and other stability problems appear in power grid, system enters double-side network construction working mode: energy storage converter adopts V / f network construction control, establishes and maintains traction network voltage and frequency by voltage closed loop regulation, guarantees continuous stable power supply on traction side;Traction side converter adopts fixed DC bus voltage rectification control, closed loop regulation is carried out to ±12.5kV DC bus voltage, introduces adaptive feedforward compensation based on bus voltage error, weakens bus voltage drop and overshoot caused by power fluctuation on both sides, provides stable DC support for power grid side network construction inverter;Power grid side converter is adaptive VSG network construction control, adaptively adjusts virtual inertia and damping parameters, so that it can provide more matched inertia and damping under different power grid intensity and disturbance intensity conditions, realize the cooperation stability of power grid support and traction power supply.

Description

Technical Field

[0001] This invention relates to the field of traction power supply and power electronic conversion control technology for electrified railways, and in particular to a dual-side grid control method and system for a multi-port flexible power supply system for electrified railways. Background Technology

[0002] Electrified railways typically draw power from regional power grids, stepping down the three-phase 220 / 110kV voltage to construct a single-phase 25kV traction power supply system. With the expansion of railway networks and increased transport volume, traction loads exhibit single-phase, high-power, high-impact, and bidirectional power characteristics, easily leading to problems such as low voltage at the traction network endpoints, excessive harmonics / negative sequence, wide-frequency oscillations, and protection malfunctions. Simultaneously, some regional power grids have low short-circuit ratios and a high proportion of renewable energy, resulting in insufficient system equivalent inertia and damping. Under the impact of traction loads, the stability margin further decreases, potentially even causing renewable energy units to disconnect from the grid.

[0003] Existing solutions such as phase-in / through-phase mainly focus on railway-side management and generally use grid-based control, which makes it difficult to achieve unified coordination between grid-side support and reliable power supply to the traction side under weak grid conditions. Furthermore, the use of large capacitors / hardware filtering will significantly increase costs and reduce power density. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dual-side grid control method and system for a multi-port flexible power supply system for electrified railways, which can provide more matched inertia, damping, voltage and frequency support under different grid strength and disturbance levels, taking into account both grid support and traction power supply stability.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a dual-side grid-connected control method for a multi-port flexible power supply system for electrified railways. The multi-port flexible power supply system for electrified railways includes a grid-side converter connected to the power grid, a traction grid-side converter connected to the traction grid, and an energy storage converter connected to an energy storage module; the energy storage converter is connected to the traction grid; the grid-side converter control process includes the following steps:

[0006] Given active power P set With the measured active power P e The difference is calculated to obtain the active power deviation; within each sampling period, the angular frequency change rate dω / dt is calculated based on the angular frequencies of the previous and current periods, and the rotor angular velocity deviation Δω is obtained based on the difference between the angular frequency and the rated angular frequency; using dω / dt and Δω as adaptive inputs, the virtual inertia parameter J and damping coefficient D are adaptively adjusted, and the adjusted virtual inertia parameter and damping coefficient are substituted into the VSG active power control loop to obtain the angular frequency ω, and the electrical angle θ is obtained by integrating ω; the grid-connected voltage u of the grid-side converter is... a ub u c Perform effective value calculation to obtain U m U m With the given effective voltage value U m * Subtract the values ​​to obtain the first error; then, given the reactive power Q... set With the measured reactive power Q e The difference between the first and second errors is used to obtain the second error; the first and second errors are then processed by a voltage-reactive power regulation stage to generate an equivalent internal potential amplitude E. m Based on the electrical angle θ and the equivalent internal potential amplitude E m Command e to generate three-phase sinusoidal voltage a e b e c ; will e a e b e c With grid-side converter output voltage u oa u ob u oc By taking the difference, a virtual impedance R is introduced. f and filter inductor L f The dynamic process yields the three-phase current reference value I. aref I bref I cref , will I aref I bref I cref The inner current loop reference value I is obtained through abc / dq transformation. d_ref and I q_ref ; Set the current inner loop reference value I d_ref and I q_ref Respectively related to the d-axis component I of the grid connection point current d q-axis component I q The difference is calculated, and the error is controlled by a current PI controller and superimposed with ω. n L f The decoupling term and the grid connection point voltage feedforward term are used to obtain the modulation voltage command e. d e q ;

[0007] e d e q The modulation wave is generated by inverse abc / dq transformation. The number of conducting switches in each bridge arm is generated by combining circulating current suppression and the nearest level approximation modulation strategy. Finally, the modulation signal of the corresponding switch is generated by voltage equalization control to control the switching on and off of the switch.

[0008] Existing in-phase and through-type control schemes mostly employ grid-following control, which struggles to balance grid-side support and reliable traction power supply under weak grid conditions. This invention utilizes an adaptive VSG grid-connected inverter on the grid side. It generates voltage amplitude and phase commands based on active / reactive power deviations and adjusts inertia and damping online according to dω / dt and Δω. This achieves smooth regulation under small disturbances and suppresses over-regulation through bounded mapping under large disturbances. It provides more matched inertia, damping, voltage, and frequency support under different grid strengths and disturbance levels, balancing grid support and traction power supply stability.

[0009] The specific implementation process of adaptively adjusting the virtual inertia parameter J includes:

[0010] Normalize and limit dω / dt according to its preset upper bound, then linearly map the limited value to the interval [-π / 2, π / 2] and perform a sine mapping to obtain the virtual inertia adjustment factor sin(θ) located in [-1, 1]. J The virtual inertia adjustment factor sin(θ) J The allowable range of variation D of the virtual inertia parameter J Linear multiplication yields the adjustment amount of the virtual inertia parameter. This adjustment amount is then added to the rated value to obtain the adaptively updated virtual inertia parameter. Specifically, when Δω is less than 0 and dω / dt is greater than 0, the adjustment amount of the virtual inertia parameter is negatively calculated before being added to the rated value. Existing fixed J control is prone to slow response or excessive fluctuations. This scheme uses the frequency change rate dω / dt and the rotor angular velocity deviation Δω as inputs, and achieves adaptive adjustment of J through normalization, limiting, and sinusoidal mapping. This not only avoids over-adjustment and improves frequency dynamic stability, but also has a clear structure, simple algorithm, and higher safety and engineering feasibility.

[0011] The specific implementation process of adaptively adjusting the damping coefficient D includes: taking the absolute value of the rotor angular velocity deviation Δω and dividing it by its preset upper limit of variation range D. ω Normalize and limit the amplitude so that |Δω| / D ω Located between 0 and 1; the value after limiting is linearly mapped to the interval [0, π / 2] and sinusoidally mapped to obtain the damping adjustment factor sin(θ) located in [0, 1]. D The adjustment factor and the allowable variation range D of the damping coefficient are used. DLinear multiplication yields the adjustment amount of the damping coefficient. This adjustment amount is added to the rated value of the damping coefficient to obtain the adaptively updated damping coefficient. Existing fixed D control suffers from insufficient damping under large disturbances and slow response under small disturbances. This scheme uses the absolute value of the rotor angular velocity deviation Δω as input, and achieves adaptive adjustment of D through normalization, limiting, and sine mapping. It adapts to different disturbance levels, enhances the system stability margin, and has a clear structure, simple algorithm, and is safe and reliable, making it more suitable for practical engineering applications.

[0012] The present invention also includes a control method for an energy storage converter, the control method comprising: calculating the voltage u at the traction grid connection point. s effective value u s_rms The effective value u s_rms With a given value U rms * The difference is calculated, and the error is controlled by the PI controller on the energy storage side to obtain the output voltage amplitude V. s * Output voltage amplitude V s * The reference phase θ is then generated by integrating with the given frequency. s Multiplying them together yields the modulated wave v. s * The modulated wave v s * The duty cycle signal of the energy storage converter switching transistor is obtained through unipolar SPWM modulation, which controls the switching transistor to turn on and off.

[0013] The present invention also includes a traction grid-side converter control method, the traction grid-side converter control method comprising:

[0014] The sampled traction grid connection point voltage u s Current i at the traction network connection point s After generating orthogonal virtual quantities through a second-order generalized integrator, the orthogonal virtual quantities are transformed by αβ / dq to obtain the d-axis component u of the traction network connection point voltage. sd q-axis component u sq d-axis component of traction grid connection point inductor current i sd q-axis component i sq ;

[0015] The DC bus voltage of the traction-side converter u dc With a given value U dc * The difference is calculated, and the error is controlled by the traction-side voltage controller PI to obtain the d-axis reference value of the current inner loop, while the q-axis reference value of the current inner loop is 0. An adaptive feedforward compensation circuit is introduced, which divides the error Δu between the DC bus voltage and the set value by the preset upper limit of the variation range D. u The normalized result Δu / D is obtained.u and for Δu / D u The amplitude is limited within the interval [-1, 1]; then Δu / D u Take the absolute value; set |Δu / D u | Linearly map to the interval [0, π / 2] and perform a sine mapping to obtain the feedforward adjustment factor sin(θ) qk ); The normalized and limited value Δu / D u Multiply by the set maximum feedforward value I qk_max The feedforward component is obtained, and the feedforward component is compared with the feedforward adjustment factor sin(θ). qk Multiplying them together yields the feedforward value I. qk The feedforward value is then superimposed with the d-axis output current reference value of the outer voltage loop to generate the final d-axis current reference command i. sd_ref ; control the d-axis component i of the reference signal sd_ref q-axis component i sq_ref The d-axis components of the inductor current at the traction grid connection point are respectively... sd q-axis component i sq The difference is calculated, and the difference is controlled by a PI current controller, with decoupling and voltage feedforward terms (u) added respectively. sd u sq The d-axis component v of the modulated wave signal is obtained. qy_d q-axis component v qy_q ;

[0016] The d-axis component v of the modulated wave signal qy_d With the q-axis component v of the modulated wave signal qy_q After inverse αβ / dq transformation, circulating current suppression and nearest-level approximation modulation are applied to obtain the number of bridge arm switching transistors. Finally, through voltage equalization control, the modulation signal of the corresponding switching transistor is generated to control the switching transistors to turn on and off.

[0017] Feedforward value I qk The calculation formula is:

[0018] ,

[0019] Where Δu is the error between the DC bus voltage and the set value, D u It is the upper bound of the preset range of change of Δu, θ qk It is the intermediate angle quantity in the traction-side feedforward adaptive compensation stage, I qk_max It is the maximum feedforward value.

[0020] In this invention, the equivalent internal potential amplitude E m The calculation formula is: Where E0 is the rated equivalent internal potential amplitude, K s D is the voltage-reactive power loop integral coefficient. sD is the reactive power deviation adjustment coefficient. q This is the voltage amplitude deviation adjustment coefficient.

[0021] In this invention, the reference value I for phase a current is... aref The calculation formula is: .

[0022] In this invention, the formula for calculating the virtual inertia parameter J is:

[0023] ,

[0024] Where sat is the saturation limiting function, used to constrain the input signal within a specified interval, dω / dt is the rate of change of angular frequency, and D... dω / dt It is the upper bound of the preset range of dω / dt, θ J It is the intermediate angle value for adaptive adjustment of virtual inertia, J0 is the nominal value of virtual inertia, and D... J It is the allowable range of variation for the virtual inertia parameter;

[0025] The formula for calculating the damping coefficient D is: Where Δω is the angular velocity deviation, D ω It is the upper bound of the preset range of variation of Δω, θ D This is the intermediate angle value during the adaptive adjustment process of the damping coefficient. D0 is the rated value of the damping coefficient. D It is the allowable range of variation of the damping coefficient.

[0026] Existing feedforward control systems often use fixed coefficients, which can lead to insufficient compensation accuracy due to DC bus voltage fluctuations. This solution uses the DC bus voltage error Δu as input, and through normalization, limiting, and sine mapping, achieves adaptive adjustment of feedforward compensation. This not only improves the stability accuracy of the DC bus voltage, but also, due to its clear structure, simple algorithm, safety, and reliability, is more suitable for traction load fluctuation scenarios in actual engineering projects.

[0027] As an inventive concept, the present invention also provides a control system for a multi-port flexible power supply system for electrified railways, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0028] This invention constructs a coordinated control architecture for the traction grid by establishing an adaptive virtual synchronous generator (VSG) on the grid side, a constant DC bus voltage rectification control system with adaptive feedforward compensation on the traction side, and voltage / frequency control (V / f) on the energy storage side. This architecture supports the traction grid and achieves unified coordination between weak grid support and traction power supply. In normal mode, the system operates with conventional grid-connected power supply. The grid-side converter maintains a stable DC bus voltage, the traction grid-side converter maintains the rated voltage and frequency of the traction grid, and the energy storage side converter is in a floating charge state. When the power grid experiences stability issues such as voltage dips and frequency deviations, the system enters a dual-side grid-connection mode: First, the energy storage-side converter is connected to the 25kV AC bus of the traction network and uses V / f grid-connection control. Through closed-loop voltage regulation, it quickly establishes and maintains the traction network voltage and frequency, ensuring continuous and stable power supply to the traction side. Second, the traction-side converter uses constant DC bus voltage rectification control to perform closed-loop regulation of the ±12.5kV DC bus voltage and introduces adaptive feedforward compensation based on bus voltage error to reduce bus voltage dips and overshoots caused by power fluctuations on both sides, providing stable DC support for grid-connected inverters. Finally, the grid-side converter uses adaptive VSG grid-connection control. Based on the adjustment of active and reactive power output by grid voltage / frequency deviation, it introduces parameter adaptive control to adaptively adjust virtual inertia and damping parameters, enabling it to provide more matched inertia and damping under different grid strength and disturbance intensity conditions, thereby achieving coordinated stability of grid support and traction power supply. This method is applicable to power supply scenarios for railways with high proportions of new energy and weak grids. It has a clear control structure, is simple to implement, and can improve the adaptability of weak grids and the continuity of traction power supply.

[0029] Compared with existing technologies, the beneficial effects of this invention are as follows: In the multi-port flexible power supply system of electrified railways, this invention configures grid-building and voltage stabilization control for the grid-side, traction-side, and energy storage-side converters respectively, achieving coordinated stability of weak grid support and traction power supply. When traction load impacts or grid strength decreases, the traction grid connection point voltage and DC bus voltage are used as key feedback quantities: the energy storage-side converter implements V / f grid-building control on the 25kV bus of the traction grid to quickly establish and maintain the voltage stiffness of the traction grid; the traction-side converter implements constant voltage rectification control on the ±12.5kV DC bus to stabilize the DC side voltage and complete power balance, and introduces an adaptive feedforward compensation link based on the DC bus voltage error before the current inner loop, which can provide sufficient fast compensation when the error is large and automatically weaken the compensation to avoid over-adjustment when the error is small, thereby improving the stability of the DC bus. The invention improves voltage and shock resistance by employing an adaptive VSG grid-connected inverter on the grid side. It generates voltage amplitude and phase commands based on the active / reactive power deviation, and performs online adaptive tuning of the equivalent inertia and damping parameters of the VSG active power component based on the frequency change rate dω / dt and the rotor angular velocity deviation Δω. This allows for smooth and precise adjustment under small disturbances and suppresses over-adjustment through bounded mapping under large disturbances. Consequently, it provides more suitable inertia, damping, and voltage / frequency support to weak grids under different grid strengths and disturbance levels, further suppressing voltage and frequency fluctuations and improving power supply reliability. This invention does not alter the traction grid-side power supply architecture. Each port control achieves closed-loop regulation based on local measurements and can update voltage, frequency, and power reference values ​​according to upper-level operating commands, enabling stable operation and continuous power supply of the multi-port flexible power supply system with dual-side grid connection. Attached Figure Description

[0030] Figure 1 This is a block diagram of the dual-side grid control method for a multi-port flexible power supply system for electrified railways, according to an embodiment of the present invention.

[0031] Figure 2 This is a comparison of the active power simulation waveforms of the grid-side adaptive VSG under the dual-side grid control mode of the multi-port flexible power supply system for electrified railways in an embodiment of the present invention, under the conditions of power command step and grid frequency drop.

[0032] Figure 3 This is a comparison of simulated DC bus voltage waveforms when the grid-side converter outputs an active power command step in the dual-side grid control mode of the multi-port flexible power supply system for electrified railways according to an embodiment of the present invention.

[0033] Figure 4 This is a simulation waveform of the traction network side voltage under the dual-side grid control mode of the multi-port flexible power supply system for electrified railways according to an embodiment of the present invention, when the traction load suddenly increases.

[0034] Figure 5The above is a simulation waveform diagram of active and reactive power when the grid side frequency drops during the dual-side grid control mode of the multi-port flexible power supply system for electrified railways in an embodiment of the present invention.

[0035] Figure 6 The above is a simulation waveform diagram of active and reactive power when the grid-side voltage drops during the dual-side grid control mode of the multi-port flexible power supply system for electrified railways, according to an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown, this invention includes a grid-traction network dual-side control method and control system for a multi-port flexible power supply system for electrified railways. The control system includes signal acquisition and synchronization, a V / f grid-connection control unit on the energy storage side, a DC bus voltage control unit with adaptive feedforward compensation on the traction side, and an adaptive VSG grid-connection control unit on the grid side. By monitoring and processing key electrical quantities such as the traction network connection point voltage, the traction side DC bus voltage, the grid side connection point voltage, and the grid connection current, the energy storage side generates an output voltage amplitude based on the effective value deviation of the traction network voltage and synthesizes a modulation signal with a given phase to drive the switching transistors, supporting the traction network voltage. The traction side uses the DC bus voltage as the control target and introduces adaptive feedforward compensation control to achieve DC bus voltage stabilization and power balance. The grid-side converter generates an angular frequency based on the active power deviation through an adaptive VSG active power link and integrates it to obtain the phase. Simultaneously, it combines voltage / reactive power regulation to generate an equivalent internal potential amplitude and introduces virtual impedance control before the current inner loop to achieve inertia damping and voltage frequency support for a weak grid. Through the coordinated action of the aforementioned multiple control units, the voltage source characteristics are synchronously constructed on both the grid side and the traction network side, maintaining stable operation and achieving the grid-traction network dual-side network control objective. In Example 1, the grid voltage level is 25kV, the DC bus voltage is ±12.5kV, and the traction network side voltage level is 25kV. Here, R and L represent the line resistance and line inductance between the grid and the grid-side converter; R... f L f These are the bridge arm resistors and inductors of the grid-side converter; R s L s It refers to the resistance and inductance of the traction grid-side converter bridge arm, R. line Lline This refers to the line resistance and inductance of the DC bus; the grid converter uses an FBSM (full-bridge submodule), the traction grid side uses an HBSM (hybrid full-bridge submodule), and the energy storage side uses a series-connected switching transistor configuration. At the beginning of each sampling period, the voltage u at the connection point between the energy storage side and the traction grid is measured. s , Traction side and traction network connection point current i s traction side DC bus voltage u dc , grid connection point voltage u a u b u c Grid-connected current i a i b i c Output voltage u of grid-side converter oa u ob u oc Output current i of grid-side converter oa i ob i oc Sampling is performed separately; the energy storage side samples u s The effective value of u is calculated. s_rms ; will u s_rms With voltage given U rms * The difference is calculated, and the error is adjusted by a PI controller to obtain the output voltage amplitude command V of the energy storage side. s * The reference phase θ is generated by integrating from a given frequency. s V s * With θ s Synthesized single-phase voltage command v s * ; for v s * Unipolar SPWM modulation is used to generate the duty cycle signal of the switching transistors in the energy storage-side converter to support the traction grid voltage. The traction side supports the grid connection point voltage u of the traction grid. s With grid current i s Orthogonal virtual variables are generated separately, and u is obtained by αβ / dq transformation. sd u sq andi sd i sq ; The traction side DC bus voltage u dc With a given U dc * The difference is calculated, and the error is adjusted by the outer loop PI control of the DC voltage, and the feedforward quantity generated by the adaptive feedforward compensation control is superimposed to generate the d-axis reference current in the inner loop. sd_ref And let the q-axis reference i sq_ref =0; change i sd_ref i sq_ref with isd i sq After subtraction, the modulation voltage command is obtained through current PI regulation. This modulation voltage command, after inverse transformation, combines circulating current suppression and nearest-level approximation modulation to generate the number of bridge arm submodules to be engaged. Corresponding switching transistor drive signals are then generated through voltage equalization control to achieve constant-voltage rectification control of the DC bus voltage. The grid-side converter supplies the three-phase voltage u at the grid connection point to the grid side. a u b u c With grid current i a i b i c Sample and obtain u through abc / dq transformation d u q and I d I q And the voltage u is output from the grid-side converter. oa u ob u oc With output current i oa i ob i oc Calculate active power P e With reactive power Q e ; P set With P e The angular frequency ω is obtained from the input adaptive VSG active power control loop. Integrating ω yields the electrical angle θ, which serves as the grid reference phase. The effective value of the grid connection point voltage U... m With voltage given U m * The error between and Q set With Q e The error between them is simultaneously input to the voltage / reactive power regulation circuit to obtain the equivalent internal potential amplitude E. m Based on E m Combined with θ to form a three-phase voltage command e abc And introduce virtual impedance R f and filter inductor L f Dynamic link generated current inner loop reference value I d_ref and I q_ref ; will I d_ref and I q_ref Corresponding to I d and I q After difference, the current is adjusted by PI and the decoupling term ω is added. n L f The modulation voltage command is obtained from the voltage feedforward term, and after inverse transformation, it is combined with circulating current suppression, nearest level approximation modulation and voltage equalization control to generate the switching transistor drive signal, so as to realize the grid-side converter grid inverter support.

[0039] The control process in this embodiment is as follows:

[0040] At the beginning of each sampling period, the voltage u at the connection point between the energy storage-side converter and the traction grid is measured. s The current i at the connection point between the traction-side converter and the traction grid s traction side converter DC bus voltage u dc Grid-side converter grid connection point voltage u a u b u c Grid-side converter grid-connected current i a i b i c Output voltage u of grid-side converter oa u ob u oc Output current i of grid-side converter oa i ob i oc Samples were taken separately;

[0041] The energy storage-side converter adopts V / f grid control: the sampled traction grid connection point voltage u s The effective voltage value u is calculated using the effective value (RMS). s_rms and with the given value U rms * The difference is calculated, and the error is controlled by the PI controller on the energy storage side to obtain the output voltage amplitude V. s * The reference phase θ is then generated by integrating with the given frequency. s Combined to form a modulated wave v s * The duty cycle signal of the energy storage converter switching transistor is obtained through unipolar SPWM modulation, which controls the switching transistor to turn on and off.

[0042] The traction side first samples the traction network connection point voltage u. s Current i at the traction network connection point s After generating orthogonal virtual quantities using a second-order generalized integrator, and then undergoing αβ / dq transformation, the d-axis component u of the traction network connection point voltage is obtained. sd q-axis component u sq d-axis component of traction grid connection point inductor current i sd q-axis component i sq ;

[0043] The traction grid-side converter adopts adaptive feedforward compensation constant DC bus voltage rectification control: the DC bus voltage u of the traction grid-side converter is... dc With a given value U dc *The difference is calculated, and the error is controlled by the traction-side voltage controller PI to obtain the d-axis reference value of the current inner loop, while the q-axis reference value of the current inner loop is 0. An adaptive feedforward compensation circuit is introduced to divide the error Δu between the DC bus voltage and the set value by the preset upper limit of the variation range D. u The normalized result Δu / D is obtained. u and for Δu / D u The amplitude is limited within the interval [-1, 1]; then Δu / D u Take the absolute value; set |Δu / D u | Linearly map to the interval [0, π / 2] and perform a sine mapping to obtain the feedforward adjustment factor sin(θ) qk ); The normalized and limited value Δu / D u Multiply by the set maximum feedforward value I qk_max The feedforward component is obtained, and the feedforward component is compared with the feedforward adjustment factor sin(θ). qk Multiplying them together yields the feedforward value I. qk The feedforward value is then superimposed with the d-axis output current reference value of the outer voltage loop to generate the final d-axis current reference command i. sd_ref ; control the d-axis component i of the reference signal sd_ref q-axis component i sq_ref The d-axis components of the inductor current at the traction grid connection point are respectively... sd q-axis component i sq The difference is calculated, and the difference is controlled by a PI controller and then superimposed with a decoupling term and a voltage feedforward term u. sd u sq The d-axis component v of the modulated wave signal is obtained. qy_d q-axis component v qy_q ;

[0044] d-axis component v of the modulated wave signal of the traction-side converter qy_d With the q-axis component v of the modulated wave signal qy_q After inverse αβ / dq transformation, circulating current suppression and nearest-level approximation modulation are applied to obtain the number of bridge arm switching transistors. Finally, through voltage equalization control, modulation signals for the corresponding switching transistors are generated to control their on / off states.

[0045] The grid-side converter first samples the grid connection point voltage u a u b u c , grid connection point current i a i b i c The d-axis component u of the grid connection point voltage is obtained after abc / dq transformation. d q-axis component u q and the d-axis component of the grid connection point current I d q-axis component I qBy sampling the output voltage u of the grid-side converter oa u ob u oc and output current i oa i ob i oc Calculate the output active power P e With reactive power Q e ;

[0046] The grid-side converter adopts adaptive VSG network control: the given active power P set With the measured active power P e The active power deviation is obtained by subtraction; within each sampling period, the frequency change rate dω / dt is calculated based on the angular frequencies of the previous period and the current period, and the rotor angular velocity deviation Δω is obtained based on the difference between the angular frequency and the rated angular frequency; using dω / dt and Δω as adaptive inputs, the virtual inertia parameter J and damping coefficient D in the VSG active power control loop are adaptively adjusted. The online adjustment is implemented using a normalized bounded sine mapping adaptive method: based on dω / dt adjustment J, dω / dt is normalized and limited according to its preset upper bound, and the limited value is linearly mapped to the interval [-π / 2, π / 2] and sinusoidally mapped to obtain the virtual inertia adjustment factor sin(θ) located in [-1, 1]. J The virtual inertia adjustment factor sin(θ) J The allowable range of variation D of the virtual inertia parameter J Linear multiplication yields the adjustment amount of the virtual inertia parameter. This adjustment amount is then added to the rated value to obtain the adaptively updated virtual inertia parameter. Specifically, when Δω is less than 0 and dω / dt is greater than 0, the adjustment amount of the virtual inertia parameter is negatively calculated before being added to the rated value. Based on the Δω adjustment D, the absolute value of the rotor angular velocity deviation Δω is taken and divided by its preset upper limit of variation range D. ω Normalize and limit the amplitude so that |Δω| / D ω Located between 0 and 1; the value after limiting is linearly mapped to the interval [0, π / 2] and sinusoidally mapped to obtain the damping adjustment factor sin(θ) located in [0, 1]. D The adjustment factor and the allowable variation range D of the damping coefficient are used. D Linear multiplication yields the adjustment amount of the damping coefficient, which is added to the rated value of the damping coefficient to obtain the adaptively updated damping coefficient D. The updated J and D are substituted into the VSG active power control loop to obtain the angular frequency ω, and ω is integrated to obtain the electrical angle θ, which is used as the grid-side reference phase.

[0047] The grid-connected voltage u of the grid-side converter a u b u cThe effective value of U is calculated. m and with the given voltage U m * Difference; simultaneously assign reactive power to Q set With the measured reactive power Q e The voltage and reactive power errors mentioned above are processed by a voltage-reactive power regulation stage to generate an equivalent internal potential amplitude E. m Based on electrical angle θ and amplitude E m Command e to generate three-phase sinusoidal voltage abc ; will e abc With grid-side converter output voltage u oa u ob u oc Divide the input and introduce a virtual impedance R. f and filter inductor L f The dynamic element is obtained by integration and abc / dq transformation to obtain the reference value I of the inner current loop. d_ref and I q_ref The reference value I of the inner current loop. d_ref and I q_ref Respectively related to the d-axis component I of the grid connection point current d q-axis component I q The difference is calculated, and the error is controlled by a current PI controller and superimposed with ω. n L f The decoupling term and the grid connection point voltage feedforward term are used to obtain the modulation voltage command e. d e q ;

[0048] The grid-side converter will e d e q The modulation wave V is generated by inverse abc / dq transform. ABC The number of conducting switches in each bridge arm is generated by combining circulating current suppression and nearest-level approximation modulation strategies. Finally, the modulation signal of the corresponding switch is generated by voltage equalization control to control the switching on and off of the switch.

[0049] Figure 2 The simulation waveforms comparing the proposed adaptive strategy and the traditional VSG under the same disturbance are shown to verify the differences in dynamic response and disturbance rejection performance of the adaptive VSG under power command step and grid frequency disturbance conditions. Operating condition: At 1.5 s, the active power command steps from 10 MW to 15 MW, recovers to 10 MW at 2.5 s, and the grid frequency drops from 50 Hz to 49.5 Hz at 3.5 s and recovers to 50 Hz at 4.5 s. Figure 2It is evident that under the conditions of three-port coupling and dynamic DC-side conditions, the power response of traditional VSG is more prone to significant secondary fluctuations and a longer recovery process. In contrast, the proposed adaptive strategy can still maintain smaller power fluctuations and better damping characteristics. Furthermore, it outputs more active power during grid frequency drops, indicating that the proposed method not only possesses excellent dynamic performance under ideal constant DC voltage source conditions but also achieves stronger disturbance suppression and stability recovery capabilities in multi-port system power coupling scenarios. This verifies the effectiveness of the proposed adaptive strategy.

[0050] Figure 3 This simulation waveform comparison of key traction-side voltage quantities in a multi-port flexible power supply system for electrified railways under a step-increase active power command from the grid-side converter is used to demonstrate the dynamic voltage regulation difference before and after introducing adaptive feedforward compensation in the traction-side constant DC bus voltage rectification control. The simulation sets the grid-side converter's active power command to increase from 10MW to 15MW in 1.5 seconds and then return to 10MW in 3 seconds. At the moment of the 1.5-second power command increase, compared to the scheme without adaptive feedforward compensation, the scheme with adaptive feedforward compensation exhibits a smaller voltage sag amplitude and weaker fluctuations. Subsequently, at the moment of the 3.0-second power command pullback, the traction-side voltage shows a corresponding short-term overshoot and drop dynamic process: similarly, the scheme with adaptive feedforward compensation exhibits a smaller overshoot amplitude and weaker fluctuations. Simulation results show that adaptive feedforward compensation can provide rapid compensation when power command changes cause errors to increase, and automatically weaken its effect when the system approaches steady state. Thus, it can effectively suppress traction side voltage fluctuations in both the power command up-up and down-down phases, thereby improving power supply quality and system operation stability.

[0051] Figure 4 This simulation waveform of the traction grid voltage in a multi-port flexible power supply system for electrified railways during a sudden increase in traction load demonstrates the voltage support effect of the grid-traction grid dual-side network control method under such conditions. In the simulation, the traction grid load power suddenly increases from 5MW to 20MW at 2.0s to simulate the impact power demand caused by train traction / acceleration. Before 2.0s, the system is in a steady-state power supply state (Figure 1.8s–2.0s). After the 2.0s load surge, the traction grid voltage does not fluctuate significantly and stabilizes at the rated level, indicating continuous stable system operation. Simulation results show that under drastic load changes, the dual-side network control effectively maintains traction grid voltage stability through the V / f network control of the energy storage-side converter, ensuring traction power supply quality and system operational stability.

[0052] Figure 5 and Figure 6This is a simulation waveform diagram of active / reactive power on the grid side of a multi-port flexible power supply system for electrified railways, used to demonstrate the active support capability of the grid-side VSG under external disturbance conditions under the grid-traction grid dual-side network control method. Figure 5 At 2.0 s, a frequency drop disturbance is applied to the grid frequency, causing it to drop from 50 Hz to 49.9 Hz. After the disturbance occurs, the adaptive VSG actively increases the active power output based on the active power-frequency droop and virtual inertia and damping elements to provide frequency support. The active power stabilizes at a high level after a brief transition. After the frequency recovers to 50 Hz at 3.0 s, the active power smoothly declines and stabilizes again during the frequency recovery process, while the reactive power only experiences a short-term small disturbance and converges quickly. Figure 6 Simulation results show that a grid voltage dip is applied within 1.5 seconds, dropping from 25 kV to 23.75 kV. Following this dip, the VSG voltage / reactive power regulation system rapidly outputs reactive power support. After a brief period of dynamic fluctuation, the reactive power stabilizes at the support level, while the active power remains largely near its original level with only minor transient fluctuations. After the voltage recovers to 25 kV within 2.5 seconds, the reactive power decreases and stabilizes near its original setpoint. Simulation results demonstrate that the dual-side grid control can achieve rapid incremental support and stable recovery of both active and reactive power under frequency and voltage disturbances, respectively, reflecting the active support capability and system stability of the grid-side converter VSG.

[0053] Example 2

[0054] Embodiment 2 of the present invention provides a terminal device corresponding to Embodiment 1 above. The terminal device can be a processing device for a client, such as a mobile phone, a laptop, a tablet computer, a desktop computer, etc., to execute the method of the above embodiments.

[0055] The terminal device in this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in Embodiment 1 described above.

[0056] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0057] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0058] Example 3

[0059] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to Embodiment 1 above, on which a computer program / instructions are stored. When the computer program / instructions are executed by a processor, they implement the steps of the method of Embodiment 1 above.

[0060] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0061] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0062] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0063] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0064] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0065] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A dual-side grid control method for a multi-port flexible power supply system for electrified railways, wherein the multi-port flexible power supply system for electrified railways includes a grid-side converter connected to the power grid, a traction grid-side converter connected to the traction grid, and an energy storage converter connected to an energy storage module; the energy storage converter is connected to the traction grid; characterized in that, The grid-side converter control process includes the following steps: Given active power P set With the measured active power P e The difference is calculated to obtain the active power deviation; within each sampling period, the angular frequency change rate dω / dt is calculated based on the angular frequencies of the previous and current periods, and the rotor angular velocity deviation Δω is obtained based on the difference between the angular frequency and the rated angular frequency; using dω / dt and Δω as adaptive inputs, the virtual inertia parameter J and damping coefficient D are adaptively adjusted, and the adjusted virtual inertia parameter and damping coefficient are substituted into the VSG active power control loop to obtain the angular frequency ω, and the electrical angle θ is obtained by integrating ω; the grid-connected voltage u of the grid-side converter is... a u b u c Perform effective value calculation to obtain U m U m With the given effective voltage value U m * Subtract the values ​​to obtain the first error; then, given the reactive power Q... set With the measured reactive power Q e The difference between the first and second errors is used to obtain the second error; the first and second errors are then processed by a voltage-reactive power regulation stage to generate an equivalent internal potential amplitude E. m Based on the electrical angle θ and the equivalent internal potential amplitude E m Command e to generate three-phase sinusoidal voltage a e b e c ; will e a e b e c With grid-side converter output voltage u oa u ob u oc By taking the difference, a virtual impedance R is introduced. f and filter inductor L f The dynamic process yields the three-phase current reference value I. aref I bref I cref , will I aref I bref I cref The inner current loop reference value I is obtained through abc / dq transformation. d_ref and I q_ref ; Set the current inner loop reference value I d_ref and I q_ref Respectively related to the d-axis component I of the grid connection point current d q-axis component I q The difference is calculated, and the error is controlled by a current PI controller and superimposed with ω. n L f The decoupling term and the grid connection point voltage feedforward term are used to obtain the modulation voltage command e. d e q ;ω n This is the rated angular frequency; e d e q The modulation wave is generated by inverse abc / dq transformation. The number of conducting switches in each bridge arm is generated by combining circulating current suppression and the nearest level approximation modulation strategy. Finally, the modulation signal of the corresponding switch is generated by voltage equalization control to control the switching on and off of the switch. The control method for the traction network-side converter includes: The sampled traction grid connection point voltage u s Current i at the traction network connection point s After generating orthogonal virtual quantities through a second-order generalized integrator, the orthogonal virtual quantities are transformed by αβ / dq to obtain the d-axis component u of the traction network connection point voltage. sd q-axis component u sq d-axis component of traction grid connection point inductor current i sd q-axis component i sq ; The DC bus voltage of the traction-side converter u dc With a given value U dc * The difference is calculated, and the error is controlled by the traction-side voltage controller PI to obtain the d-axis reference value of the current inner loop, while the q-axis reference value of the current inner loop is 0. An adaptive feedforward compensation circuit is introduced to divide the error Δu between the DC bus voltage and the set value by the preset upper limit of the variation range D. u The normalized result Δu / D is obtained. u and for Δu / D u The amplitude is limited within the interval [-1, 1]; then Δu / D u Take the absolute value; set |Δu / D u | Linearly map to the interval [0, π / 2] and perform a sine mapping to obtain the feedforward adjustment factor sin(θ) qk ); The normalized and limited value Δu / D u Multiply by the set maximum feedforward value I qk_max The feedforward component is obtained, and the feedforward component is compared with the feedforward adjustment factor sin(θ). qk Multiplying them together yields the feedforward value I. qk The feedforward value is then superimposed on the aforementioned d-axis reference value of the inner current loop to generate the final d-axis current reference command i. sd_ref ; control the d-axis component i of the reference signal sd_ref q-axis component i sq_ref The d-axis components of the inductor current at the traction grid connection point are respectively... sd q-axis component i sq The difference is calculated, and the difference is controlled by a PI current controller, with decoupling and voltage feedforward terms (u) added respectively. sd u sq The d-axis component v of the modulated wave signal is obtained. qy_d q-axis component v qy_q ; The d-axis component v of the modulated wave signal qy_d With the q-axis component v of the modulated wave signal qy_q After inverse αβ / dq transformation, circulating current suppression and nearest-level approximation modulation are applied to obtain the number of bridge arm switching transistors. Finally, through voltage equalization control, the modulation signal of the corresponding switching transistor is generated to control the switching transistors to turn on and off. Among them, the feedforward value I qk The calculation formula is: ， Where Δu is the error between the DC bus voltage and the set value, D u It is the upper bound of the preset range of change of Δu, θ qk It is the intermediate angle quantity in the traction-side feedforward adaptive compensation stage, I qk_max It is the maximum feedforward value.

2. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, The specific implementation process of adaptively adjusting the virtual inertia parameter J includes: adjusting dω / dt according to its preset upper bound D. dω / dt Normalization and amplitude limiting are performed, and the amplitude-limited values ​​are linearly mapped to the interval [-π / 2, π / 2] and then sinusoidal mapping is performed to obtain the virtual inertia adjustment factor sin(θ) located in [-1, 1]. J The virtual inertia adjustment factor sin(θ) is used. J The allowable range of variation D of the virtual inertia parameter J Linear multiplication yields the adjustment amount of the virtual inertia parameter. This adjustment amount is then added to the nominal value J0 to obtain the adaptively updated virtual inertia parameter. Wherein, when Δω is less than 0 and dω / dt is greater than 0, the adjustment amount of the virtual inertia parameter is negatively taken before being added to the nominal value.

3. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, The specific implementation process of adaptively adjusting the damping coefficient D includes: taking the absolute value of the rotor angular velocity deviation Δω and dividing it by its preset upper limit of variation range D. ω Normalize and limit the amplitude so that |Δω| / D ω Located between 0 and 1; the value after limiting is linearly mapped to the interval [0, π / 2] and sinusoidally mapped to obtain the damping adjustment factor sin(θ) located in [0, 1]. D The adjustment factor and the allowable variation range D of the damping coefficient are used. D Linear multiplication yields the adjustment amount of the damping coefficient, which is then added to the nominal value D0 of the damping coefficient to obtain the adaptively updated damping coefficient.

4. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, It also includes an energy storage converter control method, which includes: calculating the traction grid connection point voltage u. s effective value u s_rms The effective value u s_rms With a given value U rms * The difference is calculated, and the error is controlled by the PI controller on the energy storage side to obtain the output voltage amplitude V. s * Output voltage amplitude V s * The reference phase θ is then generated by integrating with the given frequency. s Multiplying them together yields the modulated wave v. s * The modulated wave v s * The duty cycle signal of the energy storage converter switching transistor is obtained through unipolar SPWM modulation, which controls the switching transistor to turn on and off.

5. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, The formula for calculating angular frequency ω is: .

6. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, Equivalent internal potential amplitude E m The calculation formula is: Where E0 is the rated equivalent internal potential amplitude, K s D is the voltage-reactive power loop integral coefficient. s D is the reactive power deviation adjustment coefficient. q This is the voltage amplitude deviation adjustment coefficient.

7. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, Phase a current reference value I aref The calculation formula is: .

8. The dual-sided grid control method for a multi-port flexible power supply system for electrified railways according to claim 1, characterized in that, The formula for calculating the virtual inertia parameter J is: ， Where sat is the saturation limiting function, used to constrain the input signal within a specified interval, dω / dt is the rate of change of angular frequency, and D... dω / dt It is the upper bound of the preset range of dω / dt, θ J It is the intermediate angle value for adaptive adjustment of virtual inertia, J0 is the nominal value of virtual inertia, and D J It is the allowable range of variation for the virtual inertia parameter; The formula for calculating the damping coefficient D is: Where Δω is the angular velocity deviation, D ω It is the upper bound of the preset range of variation of Δω, θ D This is the intermediate angle value during the adaptive adjustment process of the damping coefficient. D0 is the rated value of the damping coefficient. D It is the allowable range of variation of the damping coefficient.

9. A dual-sided grid control system for a multi-port flexible power supply system for electrified railways, comprising a memory, a processor, and a computer program stored in the memory; characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 8.

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