A controllable commutation inverter reactive power optimization control method under non-crossing working conditions

Abstract

The present invention discloses a method for optimizing the reactive power control of a controllable phase-shifting converter under non-overlimit conditions. This method first collects the fixed parameters and real-time parameters of the CLCC and calculates the real-time voltage drop degree coefficient k. Then, the critical voltage drop degree coefficient k1 is determined by solving a quartic equation of one variable. Next, according to the comparison result of k and k1, the theoretical commutation angle μ that maximizes the fundamental reactive current is adaptively selected: when k≥k1, μ takes the extreme point μ0; when 0≤k<k1, μ takes the maximum value of 60°. Finally, with the constraint that the natural commutation angle takes the maximum value, the optimal trigger angle α is obtained by solving the DC current constraint equation of the CLCC backwards. The present invention can quickly and accurately calculate the trigger angle corresponding to the maximum reactive power while ensuring commutation reliability and device safety, significantly improving the emergency reactive power support ability of the CLCC during AC faults and enhancing the transient stability of the system.

Description

Technical Field

[0001] This invention belongs to the field of high voltage direct current transmission technology, specifically relating to a method for optimizing reactive power control of a controllable commutator converter under non-over-limit operating conditions. Background Technology

[0002] The rapid development of High Voltage Direct Current (HVDC) technology has placed higher demands on the stability and reactive power support capabilities of AC systems. When a fault occurs in the receiving-end AC system, traditional line commutated converters (LCCs) experience a surge in reactive power compensation demand, often leading to commutation failure due to insufficient commutation voltage. This induces severe fluctuations in system power flow, seriously threatening the safe and stable operation of the power grid.

[0003] Controllable Line Commutated Converter (CLCC), as an emerging power electronic converter, possesses excellent reactive power regulation capabilities and fault ride-through potential. Especially in AC system voltage dip scenarios, CLCC can provide emergency reactive power support through firing angle control, suppressing voltage collapse and improving grid stability.

[0004] Existing converter firing angle control strategies are mostly based on fixed limit designs, failing to fully consider the actual impact of different voltage dips on the commutation process and reactive power output capability. For example, Chinese patent CN114123302A discloses a firing angle control method for an LCC-HVDC system, whose control objective is to prevent commutation failure rather than maximizing reactive power output. Under severe fault conditions, traditional methods struggle to quickly and accurately calculate the firing angle corresponding to the maximum reactive power output, often relying on empirical settings or conservative control, thus limiting the full realization of the reactive power support potential of the CLCC. Therefore, there is an urgent need for an optimized firing angle control method for the CLCC that maximizes reactive power output while ensuring commutation reliability under non-over-limit operating conditions. Summary of the Invention

[0005] The present invention aims to provide a controllable commutated converter and its reactive power optimization control method and system to solve the technical problem in the prior art that it is impossible to maximize the utilization of the reactive power support capability of CLCC when AC voltage drops.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for optimizing reactive power control of a controllable commutated converter under non-limit-crossing operating conditions includes the following steps: S1: Obtain the fixed and real-time parameters of the controllable commutator, and calculate the real-time voltage drop coefficient of the receiving-end AC grid based on the real-time parameters. ; S2: Calculate the critical voltage drop coefficient based on the fixed parameters. ; S3: Based on the real-time voltage drop coefficient With the critical voltage drop coefficient The comparison results show that the theoretical commutation angle that adaptively selects maximizes the fundamental reactive current is... ; S4: Using natural phase angle commutation Taking the maximum value as a constraint, based on the DC current constraint equation of the controllable commutator, the target firing angle corresponding to maximizing reactive power is solved. .

[0007] Furthermore, the non-over-limit operating condition is defined as the firing angle of the controllable commutator. satisfy .

[0008] Furthermore, the fixed parameters mentioned in step S1 include: the converter transformer ratio, and the equivalent reactance between the inverter station converter and the receiving-end AC system. Rated DC current on the DC side of the inverter station converter Surge arrester operating voltage The real-time parameters include the effective value of the AC line voltage at the receiving end AC grid connection point (PCC). The real-time voltage drop coefficient Calculated using the following formula: , in, This is the rated voltage of the AC power grid at the receiving end.

[0009] Furthermore, the critical voltage drop coefficient mentioned in step S2 The following quartic equation is obtained by solving: , Among them, coefficient The definition is as follows: , Select the one that satisfies The solution is used as the critical voltage drop coefficient. .

[0010] Furthermore, the adaptive selection of the theoretical commutation angle described in step S3... The rules are: when At that time, the theoretical commutation angle Take the extreme point ,in ; when At that time, the theoretical commutation angle Take the maximum value Wherein, the extreme point Solve using the following approximate expression: , Among them, coefficient The definition is as follows: .

[0011] Furthermore, the constraint condition for the natural commutation angle to reach its maximum value in step S4 is: This constraint is based on the critical condition of avoiding the separation of natural commutation processes from forced commutation processes. It is derived that...

[0012] Furthermore, the DC current constraint equation in step S4 is: , The constraints and the theoretical commutation angle adaptively selected in step S3 Substituting into the DC current constraint equation and approximating it, the target firing angle is obtained. The analytical solution expression: , in, Represents the instantaneous value of DC current, which is related to They are equal under steady state.

[0013] The present invention also provides a reactive power optimization control system for a controllable commutator under non-over-limit operating conditions, used to implement the method described in any of the above-mentioned embodiments, comprising: The parameter acquisition module is configured to acquire the fixed parameters and real-time parameters of the controllable commutator. The coefficient calculation module is configured to calculate the real-time voltage drop coefficient based on the real-time parameters. And calculate the critical voltage drop coefficient based on the fixed parameters. ; The phase angle adaptive selection module is configured to, based on and The comparison results show that the theoretical commutation angle that adaptively selects maximizes the fundamental reactive current is... ; The firing angle calculation module is configured to solve for the target firing angle based on the DC current constraint equation, with the maximum value of the natural commutation angle as a constraint. , so as to output to the trigger unit of the controllable commutator.

[0014] Furthermore, the system is integrated into a digital signal processor (DSP) or a field-programmable gate array (FPGA), and the parameter acquisition module, coefficient calculation module, commutation angle adaptive selection module, and trigger angle solving module are implemented by the processor executing a computer program stored in the memory, and the computer program implements the method described in any of the above-mentioned methods.

[0015] The present invention also provides a controllable commutated converter, including any of the above-mentioned reactive power optimization control systems.

[0016] Beneficial effects: This invention proposes an adaptive firing angle optimization control method that can accurately match and calculate the optimal firing angle based on the different degrees of AC grid voltage drop, making the reactive power generated by the CLCC approach the theoretical maximum value, providing strong emergency reactive power support for the grid, and significantly improving the transient stability of the system under fault conditions. The method of this invention has high engineering feasibility, requiring no additional hardware circuitry. Its core algorithm is based on analytical expression derivation, with low computational load, and can be easily embedded into existing CLCC control systems, reducing control complexity and engineering costs. By introducing the constraint of the maximum value of the natural commutation angle, this invention strictly limits the operating range of the firing angle and commutation angle, effectively avoiding the separation between natural and forced commutation processes, thereby preventing serious faults such as commutation failure and valve group shoot-through, and ensuring the safe and reliable operation of power electronic devices and the system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the topology of the controllable commutated converter (CLCC) involved in this invention; Figure 2 This is a schematic diagram of the internal current waveform change of the CLCC bridge arm sub-valve under AC fault conditions in this invention; Figure 3 The voltage sag coefficient under non-over-limit operating conditions in this invention is a coefficient for different voltage drop degrees. The corresponding fundamental reactive current and commutation angle Relationship diagram; Figure 4 This is a flowchart of the maximum reactive power trigger angle control strategy under non-limit-over operating conditions in an embodiment of the present invention; Figure 5 This is a simulation curve showing the change of reactive power with the increase of the firing angle when the natural commutation angle is at its maximum value in an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0019] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] In one embodiment, a method for optimizing reactive power control of a controllable commutator under non-over-limit operating conditions is provided, including: S1: Obtain the fixed and real-time parameters of the controllable commutator, and calculate the real-time voltage drop coefficient of the receiving-end AC grid based on the real-time parameters. ; S2: Calculate the critical voltage drop coefficient based on the fixed parameters. ; S3: Based on the real-time voltage drop coefficient With the critical voltage drop coefficient The comparison results show that the theoretical commutation angle that adaptively selects maximizes the fundamental reactive current is... ; S4: Using natural phase angle commutation Taking the maximum value as a constraint, based on the DC current constraint equation of the controllable commutator, the target firing angle corresponding to maximizing reactive power is solved. .

[0022] The core of this invention lies in constructing a complete control chain, from "voltage drop sensing" to "critical coefficient judgment," then to "adaptive matching of optimal commutation angle," and finally to "analytical solution of trigger angle." This chain overcomes the limitations of traditional empirical table lookup or fixed threshold control.

[0023] In another embodiment, the non-limit-crossing condition is defined as .

[0024] Therefore, the scope of application of this invention is the high-efficiency operating range of the inverter in a specific reactive power support region.

[0025] In another embodiment, the fixed parameters in step S1 further include: the converter transformer turns ratio, and the equivalent reactance between the inverter station converter and the receiving-end AC system. Rated DC current on the DC side of the inverter station converter Surge arrester operating voltage The real-time parameters include the effective value of the AC line voltage at the receiving end AC grid connection point (PCC). The real-time voltage drop coefficient Calculated using the following formula: , in, This is the rated voltage of the AC power grid at the receiving end.

[0026] In another embodiment, the critical voltage drop coefficient mentioned in step S2 is further... The following quartic equation is obtained by solving: , Among them, coefficient The definition is as follows: , Select the one that satisfies The solution is used as the critical voltage drop coefficient. .

[0027] This is one of the most crucial inventive concepts of the present invention. It quantitatively correlates the inflection point of the optimal commutation angle with the degree of voltage drop, thereby achieving accurate adaptive judgment.

[0028] In another embodiment, further, the adaptive selection of the theoretical commutation angle in step S3... The rules are: when At that time, the theoretical commutation angle Take the extreme point ,in ; when At that time, the theoretical commutation angle Take the maximum value Wherein, the extreme point Solve using the following approximate expression: , Among them, coefficient The definition is as follows: .

[0029] This embodiment provides The specific calculation method makes adaptive selection feasible for engineering implementation.

[0030] In another embodiment, the natural commutation angle described in step S4 is further... The constraint condition for taking the maximum value is: This constraint is based on the critical condition of avoiding the separation of natural commutation processes from forced commutation processes. It is derived that...

[0031] In this embodiment, this constraint is a key safety boundary for ensuring the continuity of the CLCC commutation process and preventing commutation failure. Solving the reactive power maximization problem under this safety boundary is the core safety strategy of this invention.

[0032] In another embodiment, the DC current constraint equation in step S4 is further defined as follows: , The constraints and the theoretical commutation angle adaptively selected in step S3 Substituting into the DC current constraint equation and approximating it, the target firing angle is obtained. The analytical solution expression: , in, Represents the instantaneous value of DC current, which is related to They are equal under steady state.

[0033] This embodiment provides a concise and physically clear analytical solution for the trigger angle, which facilitates fast real-time calculation by DSP / FPGA.

[0034] In another embodiment, a reactive power optimization control system for a controllable commutator under non-over-limit operating conditions is provided, for implementing the method described in any of the above embodiments, comprising: The parameter acquisition module is configured to acquire the fixed parameters and real-time parameters of the controllable commutator. The coefficient calculation module is configured to calculate the real-time voltage drop coefficient based on the real-time parameters. And calculate the critical voltage drop coefficient based on the fixed parameters. ; The phase angle adaptive selection module is configured to, based on and The comparison results show that the theoretical commutation angle that adaptively selects maximizes the fundamental reactive current is... ; The firing angle calculation module is configured to solve for the target firing angle based on the DC current constraint equation, with the maximum value of the natural commutation angle as a constraint. , so as to output to the trigger unit of the controllable commutator.

[0035] In another embodiment, the system is further integrated into a digital signal processor (DSP) or a field-programmable gate array (FPGA), and the parameter acquisition module, coefficient calculation module, commutation angle adaptive selection module, and trigger angle solving module are implemented by the processor executing a computer program stored in memory, wherein the computer program implements the method described in any of the above embodiments.

[0036] In another embodiment, the present invention also provides a controllable commutated converter, including any of the above-described reactive power optimization control systems.

[0037] The following is a more detailed example: Example 1 The following is combined Figures 1 to 5 The present invention will be further described below.

[0038] Figure 1 This diagram illustrates the basic 6-pulse topology of a controllable commutated converter (CLCC). The AC commutation reactance and AC power supply are referred to the transformer valve side via the converter transformer, forming equivalent AC commutation reactance and equivalent AC power supply. Each valve in the converter bridge arm adopts a composite parallel structure combining main and auxiliary branches. The main branch consists of a series of thyristors with high voltage and high current tolerance connected in series with insulated-gate bipolar transistors (IGBTs) exhibiting low voltage and high current characteristics. The auxiliary branch consists of a series of thyristors with high voltage and low current tolerance connected in series with IGBTs exhibiting high voltage and low current characteristics. Finally, the main and auxiliary branches are connected in parallel to form the CLCC valve. The auxiliary branch IGBTs are connected in parallel with an arrester branch to generate arrester operating voltage during faults, facilitating the commutation process.

[0039] Figure 2This diagram illustrates the changes in the internal current waveform of the CLCC bridge arm sub-valve under AC system fault conditions. It reveals the commutation process of the main and auxiliary branch currents of the bridge arm under fault conditions and defines relevant variable parameters. Specifically, the commutation process from the start to the end of commutation is defined as a complete commutation process, and the corresponding electrical angle is defined as the commutation angle. The commutation process from the start of commutation to the turn-off time of sub-valve V13 is a natural commutation process, and the corresponding electrical angle is the natural commutation angle. In a natural commutation process, only the grid voltage participates in the commutation; the period from V13 being turned off to the completion of commutation is a forced commutation process, and the corresponding electrical angle is the forced commutation angle. The commutation is aided by the combined action of the grid voltage and the surge arrester's operating voltage. Therefore... .

[0040] The core implementation of the present invention is as follows: Figure 4 As shown, the specific steps are as follows: 1. Fixed and Real-time Parameter Acquisition. Acquire fixed parameters when the CLCC is used as the inverter converter: converter transformer ratio, and equivalent reactance between the inverter converter and the receiving-end AC system. Rated DC current on the DC side of the inverter station converter Surge arrester operating voltage (Using the AC line voltage amplitude on the converter transformer valve side). Real-time parameters collected when CLCC is used as the inverter converter: RMS value of AC line voltage at point PCC in the receiving-end AC grid. .

[0041] 2. Calculate the real-time voltage drop coefficient of the receiving-end AC power grid. Calculate the real-time voltage drop of the receiving-end AC power grid: in The rated voltage of the AC power grid at the receiving end. The voltage drop factor of the AC grid at the receiving end is a per-unit value. This indicates that the AC grid voltage at the receiving end has not dropped; when The time indicates that the AC grid voltage at the receiving end has dropped to pu.

[0042] 3. Calculate the critical voltage drop coefficient. . Depend on Figure 3 It can be seen that the voltage drop coefficient The value of this factor affects the commutation angle at which the fundamental reactive current reaches its maximum value; therefore, a critical voltage drop coefficient is defined. The commutation angle that corresponds to the fundamental reactive current reaching its maximum value is exactly the value of the maximum value. ,when At that time, the fundamental reactive current curve increases and has no extreme points, but due to the commutation angle Restricted to Therefore, the commutation angle corresponding to the maximum value is taken as ;when At this time, the fundamental reactive current curve first increases and then decreases, with an extreme point, which is the commutation angle corresponding to the point where the fundamental reactive current reaches its maximum value. Less than .

[0043] Therefore, the critical voltage drop coefficient It can be calculated using formula (2): Where the coefficient for: Since the equation in formula (2) is a quartic equation in one variable, the solution to this equation is... There are 4 solutions, but due to the voltage drop coefficient... The range is Therefore, by retaining only the solutions within the specified range and discarding the rest, the degree of critical voltage drop can be obtained. The value of .

[0044] 4. Determine the natural commutation angle Maximum value. Considering that when a controllable commutation converter is used as an inverter converter in a DC transmission project, its commutation process during natural commutation is only supplied with commutation voltage by the receiving-end AC grid, and the grid voltage is at... Providing a positive commutation voltage at the same time promotes bridge arm commutation; When the grid voltage provides the reverse commutation voltage, it is detrimental to bridge arm commutation. To avoid separating the natural commutation process from the forced commutation process in a controlled commutation converter, it is necessary to satisfy... The constraints and natural commutation angle The maximum value according to Considering this, at this time It is the critical point where the natural commutation process and the forced commutation process are continuous.

[0045] 5. Theoretical commutation angle Optimal value adaptive selection As can be seen from the analysis in step 3, when When the fundamental reactive current curve first increases and then decreases, there is an extreme point. The extreme point that causes the fundamental reactive current to reach its maximum value under this condition is defined as (the point where the fundamental reactive current reaches its maximum value is also the maximum value). .

[0046] Therefore, the fundamental reactive current extreme points The solution expression is as follows: Where the coefficient for: Therefore, based on the voltage drop coefficient of the AC power grid at the receiving end... Real-time acquired values ​​and critical voltage drop coefficient By comparing the calculated values, the theoretical commutation angle can be obtained. The optimal value, i.e., the theoretical commutation angle, is defined. The optimal value is the coefficient for different voltage drop levels. The commutation angle that causes the fundamental reactive current to reach its maximum value within the defined domain is determined by the following parameters.

[0047] when At that time, theoretical phase angle change Take the extreme point ; when To avoid the bridge arm going straight through due to excessive commutation angle, the theoretical maximum commutation angle is taken. As shown in formula (6).

[0048] In actual control, only the trigger angle can be controlled. Phase angle exchanged with nature However, the actual commutation angle cannot be directly controlled, but it can be adjusted from the theoretical commutation angle through control methods. To trigger angle The transition of control.

[0049] 6. Determine the firing angle when reactive power output is maximized. Solution method. Under non-over-limit operating conditions, since the reactive power output of the converter is positively correlated with the fundamental reactive current, in order for the reactive power output of the converter to reach its maximum value, the fundamental reactive current must also reach its maximum value. For example... Figure 3 As shown, the fundamental reactive current is positively correlated with the commutation angle, and the natural commutation angle is also positively correlated with the commutation angle. Therefore, the larger the natural commutation angle, the larger the commutation angle, and the larger the fundamental reactive current. When the fundamental reactive current reaches its maximum value, the reactive power output by the converter is at its maximum value. Therefore, the maximum value of the natural commutation angle is taken. Substitute DC current Constraint equations: Further simplification and equivalence processing are performed, taking into account... ,and The forced commutation process is much smaller than the natural commutation process, therefore the forced commutation angle is smaller. The value of is relatively small, and can be approximated as . , After approximation, substituting into formula (7) yields the following relationship between the firing angle and the commutation angle: like Figure 4 As shown, the implementation flow of the maximum reactive power firing angle control strategy under non-over-limit operating conditions of this invention clearly demonstrates the data flow and logical relationships between the modules. First, the parameter acquisition module obtains necessary data from the CLCC operating site and the receiving-end power grid. This data is then transmitted to the coefficient calculation module, which calculates the real-time voltage sag coefficient. and critical coefficient .then, and The signal is fed into the adaptive commutation angle selection module, which outputs an optimal theoretical target commutation angle value based on preset judgment rules. Finally, the trigger angle calculation module receives... And combined with data from the parameter acquisition module , , , Using these parameters, the final control command—the target firing angle—is determined. It is then sent to the CLCC trigger unit for execution. The entire control link is serial and unidirectional, ensuring clear logic and efficient computation.

[0050] 7. Simulation verification of reactive power optimization trigger angle control method under non-limit operating conditions.

[0051] like Figure 5 As shown, the implementation steps of the reactive power optimization firing angle control method based on non-limit-over-limit operating conditions are illustrated. Simulation verification experiment one is set up: the natural commutation angle is fixed as the maximum value that can be obtained, and the firing angle is set from 0.5s... Started to grow linearly to The changes in waveforms such as reactive power and commutation angle are simulated and verified to confirm the correctness of the control method.

[0052] Simulation Verification Experiment 2: To reflect the impact of the AC grid voltage sag coefficient at the receiving end on the firing angle control and reactive power, the AC voltage sag coefficient was fixed at 0.8, 0.6, 0.4, and 0.2 respectively. The firing angle calculated by the firing angle optimization control method was compared with the actual firing angle that maximizes reactive power. The relevant comparison data of natural commutation angle, commutation angle, and maximum reactive power are shown in Table 1.

[0053] Table 1 Simulation data of trigger angle optimization control under non-limit-crossing conditions In another embodiment, the trigger angle The solution is not limited to the approximate expression of formula (8). For control systems with strong computational capabilities, the nonlinear equation system consisting of equation (7) can be solved directly using numerical methods (such as the Newton-Raphson method) to obtain a more accurate firing angle. Value. Specifically, the value adaptively selected in step S3. and constraints Substituting into equation (7), we construct about residual function And solve iteratively This method can serve as an alternative for high-precision requirements.

[0054] To address the problem of easy commutation failure in LCC in the background art, the control strategy of this invention naturally avoids this risk under non-limit-crossing operating conditions through the above formulas, especially formulas (6) and (8). Specifically, when When the impact is small (due to a severe drop), change the phase angle. Controlled And calculate the appropriate value using formula (8). This ensured This is one of the safest boundaries to ensure commutation margin. Furthermore, by setting... The constraints ensure a perfect connection between the end of natural commutation and the start of forced commutation, avoiding commutation failure that may be caused by reversal of commutation voltage polarity.

[0055] In a specific hardware implementation, the reactive power optimization control system of the present invention can be integrated into a specially designed digital signal processor (DSP, such as TI's TMS320F28379D) or field-programmable gate array (FPGA, such as Xilinx's Zynq-7000 series), which includes: Parameter acquisition module: Acquires parameters in real time at a high sampling rate (e.g., 10kHz) using the built-in ADC (analog-to-digital converter) of the DSP / FPGA or an external high-precision ADC chip (such as AD7606). Analog signals. Fixed parameters. These are stored in the external EEPROM or internal Flash of the DSP / FPGA and are read upon power-on.

[0056] The coefficient calculation module, the commutation angle adaptive selection module, and the trigger angle solution module: the functions of these modules are implemented through software algorithms executed by the processor core inside the DSP / FPGA. For FPGA implementation, these algorithms can be written into dedicated parallel computing circuits using hardware description languages ​​(such as Verilog / VHDL) to achieve ultra-high-speed calculations at the microsecond level. Specifically, the DSP / FPGA reads parameters from memory, executes the calculations of formulas (1)-(8) sequentially, and finally obtains... .

[0057] Output: Calculated target trigger angle It is converted into a trigger pulse signal synchronized with the power grid, and output to the drive circuits of each thyristor and IGBT in CLCC through the general purpose input / output interface (GPIO) of DSP / FPGA or a dedicated PWM (pulse width modulation) module.

[0058] In summary, this invention constructs a complete reactive power optimization control scheme for CLCC under non-over-limit operating conditions by introducing a series of key technologies, including a critical voltage drop coefficient, adaptive commutation angle selection, and analytical solution of the firing angle based on the maximum constraint of the natural commutation angle. This breaks away from the conservative approach of traditional control that only focuses on preventing commutation failure, and actively explores and utilizes the transient reactive power support potential of CLCC. Compared with existing technologies, this invention has significant advantages in control accuracy, response speed, reactive power support effect, and system safety.

[0059] Although embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the specific embodiments described above. Any equivalent substitutions, improvements, and modifications within the principles and conceptual framework of the present invention, or direct applications of the disclosure of the present invention to other related technical fields, shall be considered to fall within the protection scope of the present invention.

Claims

1. A method for optimizing reactive power control of a controllable commutated converter under non-limit-crossing operating conditions, characterized in that, Includes the following steps: S1: Obtain the fixed and real-time parameters of the controllable commutator, and calculate the real-time voltage drop coefficient of the receiving-end AC grid based on the real-time parameters. ; S2: Calculate the critical voltage drop coefficient based on the fixed parameters. ; S3: Based on the real-time voltage drop coefficient With the critical voltage drop coefficient The comparison results show that the theoretical commutation angle that adaptively selects maximizes the fundamental reactive current is... ; S4: Using natural phase angle commutation Taking the maximum value as a constraint, based on the DC current constraint equation of the controllable commutator, the target firing angle corresponding to maximizing reactive power is solved. .

2. The method according to claim 1, characterized in that, The non-over-limit operating condition is defined as the firing angle of the controllable commutator. satisfy .

3. The method according to claim 1, characterized in that, The fixed parameters mentioned in step S1 include: converter transformer turns ratio, and equivalent reactance between the inverter station converter and the receiving-end AC system. Rated DC current on the DC side of the inverter station converter Surge arrester operating voltage The real-time parameters include the effective value of the AC line voltage at the receiving end AC grid connection point (PCC). The real-time voltage drop coefficient Calculated using the following formula: ， in, This is the rated voltage of the AC power grid at the receiving end.

4. The method according to claim 3, characterized in that, The critical voltage drop coefficient mentioned in step S2 The following quartic equation is obtained by solving: ， Among them, coefficient The definition is as follows: ， Select the one that satisfies The solution is used as the critical voltage drop coefficient. .

5. The method according to claim 4, characterized in that, The adaptive selection of theoretical commutation angle in step S3 The rules are: when At that time, the theoretical commutation angle Take the extreme point ,in ; when At that time, the theoretical commutation angle Take the maximum value Wherein, the extreme point Solve using the following approximate expression: ， Among them, coefficient The definition is as follows: 。 6. The method according to claim 1, characterized in that, The constraint condition for the natural commutation angle to reach its maximum value in step S4 is: This constraint is based on the critical condition of avoiding the separation of natural commutation processes from forced commutation processes. It is derived that...

7. The method according to claim 6, characterized in that, The DC current constraint equation mentioned in step S4 is: ， The constraints and the theoretical commutation angle adaptively selected in step S3 Substituting into the DC current constraint equation and approximating it, the target firing angle is obtained. The analytical solution expression: ， in, Represents the instantaneous value of DC current, which is related to They are equal under steady state.

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