SLCC control method and system based on similar network type SVF assistance

Abstract

The invention discloses an SLCC control method and system based on similar network type SVF assistance, and the method comprises the steps: generating a first SVF voltage instruction value through an active outer ring and a reactive outer ring, processing the first SVF voltage instruction value through a voltage ring, and obtaining a fundamental frequency reactive compensation current instruction value; processing the LCC output current by using a multi-synchronous rotation coordinate method to obtain a harmonic compensation current reference value; and superposing the fundamental frequency reactive compensation current instruction value and the harmonic compensation current reference value, obtaining a second SVF voltage instruction value in combination with a current inner loop controller, and processing the second SVF voltage instruction value by using a voltage-sharing control strategy and a carrier phase-shifting modulation strategy to obtain a switching signal for controlling the SVF. According to the method, the dependence of the SVF on an alternating current system is reduced, stable and independent operation of the SVF in the SLCC by virtue of the self regulation capability is favorably realized, and the operation reliability and stability of the SLCC are improved.

Description

Technical Field

[0001] The present invention relates to the field of direct current (DC) transmission technology, and in particular to a SLCC control method and system based on quasi-grid SVF assistance. Background Art

[0002] LCC-HVDC (Line-Commutated Converter High-Voltage Direct Current) is a high-voltage direct current (HVDC) transmission technology based on grid-commutated converters (CCCs). LCC-HVDC is widely used in long-distance power transmission due to its high capacity and low losses. However, traditional LCC (Line-Commutated Converter) systems face the risk of commutation failure during operation. The root cause is the converter's strong dependence on the AC system voltage. When a short-circuit fault in the receiving AC grid causes a voltage drop, the commutation voltage cannot be maintained between the valve arms during the commutation process, resulting in discontinuous commutation current and ultimately commutation failure. Statistics show that over 70% of commutation failures are directly related to the dynamic characteristics of the AC system voltage. Therefore, LCC systems require a large amount of reactive power compensation equipment to maintain voltage during normal operation.

[0003] To address this issue, existing technologies have proposed an improved solution by connecting an SVG (Static Var Generator) or SVF (Static Var Generator and Filter) in parallel with the LCC system. The rapid reactive power compensation capabilities of the SVG / SVF theoretically support AC bus voltage stability. However, traditional SVGs employ a current source control strategy, and their dynamic response speed (typically 50-100ms) is insufficient to match the transient voltage fluctuations (microsecond timescale) during the LCC commutation process. This increases the risk of commutation failure and reduces system voltage stability, severely limiting the operational stability and reliability of the self-adaptive statcom and line commutation converter (SLCC). Therefore, there is an urgent need to develop a grid-like SVF control strategy suitable for SLCCs to improve their operational stability. Summary of the Invention

[0004] The purpose of the present invention is to provide a SLCC control method and system based on a quasi-network SVF assisted SLCC, so that the SVF in the SLCC can maintain stable and independent operation by relying on its own adjustment capability.

[0005] The present invention adopts the following technical solution: a SLCC control method based on quasi-network SVF assistance, comprising the following steps:

[0006] S1. Based on the control strategy of constant current on the rectifier side and constant voltage on the inverter side, the LCC is controlled to operate under rated conditions.

[0007] S2. Obtain the reactive power shortage on the inverter side of the LCC based on the relevant electrical quantities when the LCC is operating under rated conditions.

[0008] S3. Based on the active power transmission requirement of the LCC and the reactive power shortage on the inverter side of the LCC, a first SVF voltage command value is generated through the active power and reactive power outer loops.

[0009] S4. Based on the first SVF voltage command value, obtain the d-axis and q-axis components of the fundamental frequency reactive compensation current, and use the q-axis component of the fundamental frequency reactive compensation current as the fundamental frequency reactive compensation current command value.

[0010] S5. Process the LCC output current using a multi-synchronous rotating coordinate method to obtain a harmonic compensation current reference value.

[0011] S6. Superimpose the fundamental frequency reactive compensation current command value and the harmonic compensation current reference value to obtain the SVF current command value. Based on the current inner loop controller, obtain the second SVF voltage command value. Use the voltage equalization control strategy and the carrier phase shift modulation strategy to process the second SVF voltage command value to obtain the switching signal for controlling the SVF, thereby realizing the control of the SLCC.

[0012] Furthermore, in step S1, controlling the LCC to operate under rated conditions includes the following:

[0013] Set the current command value on the rectifier side according to the SLCC load demand and the power transmission requirements of the DC transmission system ,Will Compared with the measured DC current on the rectifier side Compare and get the current deviation , , use the proportional-integral controller to get the complementary angle, get the trigger angle adjustment signal, use the phase shift link to get the thyristor trigger pulse, and control the difference between the DC current on the rectifier side and the set current command value to be within 5%.

[0014] Set the voltage command value on the inverter side according to the voltage level of the inverter station AC bus and the reactive power demand of the SLCC ,Will Compared with the measured DC voltage on the inverter side Compare and get the voltage deviation , The proportional-integral controller is used to obtain the advance trigger angle adjustment signal, and the phase-shift link is used to obtain the thyristor trigger pulse, so as to control the difference between the DC voltage on the inverter side and the set voltage command value to be within 5%.

[0015] Furthermore, in step S2, obtaining the reactive power shortage on the LCC inverter side includes the following:

[0016] The SVF is set on the inverter side, and the electrical quantity of the LCC when operating under rated conditions is expressed as:

[0017] ;

[0018] ;

[0019] ;

[0020] ;

[0021] ;

[0022] ;

[0023] in, Indicates the no-load DC voltage of the inverter station. Indicates the total number of 6-pulse converters per pole in the SLCC converter station, Indicates the effective value of the equivalent no-load line voltage on the valve side of the inverter station. represents the actual DC voltage of the countercurrent station, Indicates the arc extinction angle of the inverter station. Indicates the equivalent commutation reactance on the valve side of the inverter station, Indicates the DC current of the inverter station, Indicates the leading trigger angle of the inverter station. Indicates the commutation angle of the inverter station, Indicates the power factor angle of the inverter station, Indicates the actual DC voltage of the rectifier station, represents the resistance of the DC transmission line, Indicates the reactive power consumed by the inverter station.

[0024] LCC inverter side reactive power shortage The calculation formula is:

[0025] ;

[0026] in, Indicates the reactive power consumed during the commutation process, Indicates the reactive power consumed by the commutation transformer, Indicates the active power transmitted between the AC system and the converter station, Represents the reactive power transmitted between the AC system and the converter station, Indicates the voltage on the commutation transformer side, Indicates the short-circuit voltage percentage, Indicates the voltage on the converter valve side. represents the commutation transformer capacity, Represents the commutation reactance.

[0027] Furthermore, in step S3, generating the first SVF voltage command value includes the following:

[0028] During the SLCC startup phase, the active power command value is set to 0. During the SLCC rated operating phase, the actual SVF capacitor voltage value is subtracted from the SVF capacitor voltage rated value, and the difference is input into the proportional-integral controller to obtain the active power command value.

[0029] The SVF active power transmission is adjusted using the droop control method to obtain the SVF command voltage angular frequency , the specific formula is:

[0030] ;

[0031] in, represents the inertia coefficient, represents the damping coefficient, represents the grid voltage angular frequency reference value, t represents the tth moment, Indicates the active power command value, Indicates the measured value of active power.

[0032] The SVF reactive power transmission is adjusted using the droop control method to obtain the SVF command voltage amplitude E. The specific formula is:

[0033] ;

[0034] in, Represents the reactive integral coefficient, Indicates the reactive power command value, using the reactive power shortage on the LCC inverter side as the reactive power command value. represents the reactive droop coefficient, Indicates the voltage rating, Indicates the measured voltage value. Indicates the measured value of reactive power.

[0035] Set the SVF instruction voltage angular frequency The frequency and amplitude of the parallel virtual synchronous generator voltage used to maintain the operation of the SLCC are used to generate the first SVF voltage command value. The specific formula is:

[0036] ;

[0037] in, 、 、 Indicates the first SVF voltage command values for phases a, b, and c, respectively.

[0038] Perform Park transformation on the first SVF voltage command values of phases a, b, and c to obtain the d and q axis components of the first voltage command values of the SVF in the dq coordinate system. .

[0039] Furthermore, in step S4, the d-axis and q-axis components of the fundamental frequency reactive compensation current are calculated as follows:

[0040] ;

[0041] in, Represents the d-axis component of the fundamental frequency reactive compensation current, represents the voltage outer loop integral coefficient, Represents the voltage outer loop proportional coefficient, represents a pull transformation, represents the d-axis component of the compensation point voltage, represents the SVF bridge arm capacitance, represents the q-axis component of the compensation point voltage, Represents the q-axis component of the fundamental frequency reactive compensation current.

[0042] Furthermore, in step S5, obtaining the harmonic compensation current includes the following:

[0043] The output current and voltage waveforms of the converter station are collected in real time. The order of the corresponding harmonic component to be filtered out is obtained according to the order of the LCC characteristic harmonic using the multi-synchronous rotating coordinate method. Based on this order, the LCC output current is converted into the sum of the DC component obtained by transforming the characteristic harmonic and the AC component obtained by transforming other components in the rotating coordinate system. After filtering the sum component, it is inversely transformed into an AC quantity to obtain the subharmonic component in the characteristic subharmonic of the LCC output current. The specific expression is:

[0044] ;

[0045] in, represents the d-axis component of the current, represents the q-axis component of the current, represents the Parker transformation matrix, represents the current a-phase component, represents the b-phase component of the current, represents the c-phase component of the current, Indicates the angular frequency of the rotating coordinate system corresponding to the order harmonic of the harmonic component to be filtered out.

[0046] All harmonic components are added together to obtain the total harmonic component, which is used as the reference value of the harmonic compensation current.

[0047] Among them, the order of LCC characteristic harmonics is , , Indicates the index of the 6-pulse converter per pole in the SLCC converter station.

[0048] Furthermore, in step S6, the d-axis component of the fundamental frequency reactive compensation current is used as the d-axis component command value of the total compensation current, and the fundamental frequency reactive compensation current command value is superimposed with the harmonic compensation current reference value to obtain the SVF current command value, which is input into the current inner loop controller to obtain the second SVF voltage command value d and q-axis components. The specific formula is:

[0049] ;

[0050] in, represents the d-axis component of the second SVF voltage command value, represents the q-axis component of the second SVF voltage command value, represents the integral coefficient of the inner current loop, Indicates the current inner loop proportional coefficient, Indicates the d-axis component of the SVF current command value, represents the q-axis component of the SVF current command value, represents the d-axis component of the measured value of the SVF bridge arm current, represents the q-axis component of the measured value of the SVF bridge arm current, represents the SVF bridge arm inductance.

[0051] Will 、 After phase-to-phase voltage equalization control, a modulated wave is obtained. Using the carrier phase-shift modulation strategy, the switching signals of each SVF submodule are output according to the modulated wave to control the on and off of the SVF submodule.

[0052] Furthermore, the present invention also proposes a SLCC control system based on a quasi-network SVF auxiliary, comprising:

[0053] The LCC operation control module is used to control the LCC to operate under rated conditions based on the control strategy of constant current on the rectifier side and constant voltage on the inverter side.

[0054] The SVF voltage command value generation module is used to obtain the reactive power shortage on the LCC inverter side based on the relevant electrical quantities when the LCC is operating under rated operating conditions; based on the active power transmission requirements of the LCC and the reactive power shortage on the LCC inverter side, the first SVF voltage command value is generated through the active and reactive outer loops.

[0055] The harmonic compensation current reference value acquisition module is used to process the LCC output current using a multi-synchronous rotating coordinate method to obtain a harmonic compensation current reference value.

[0056] The SLCC control module is used to obtain the d-axis and q-axis components of the fundamental frequency reactive compensation current based on the first SVF voltage command value, and use the q-axis component of the fundamental frequency reactive compensation current as the fundamental frequency reactive compensation current command value. The fundamental frequency reactive compensation current command value and the harmonic compensation current reference value are superimposed to obtain the SVF current command value. Based on the current inner loop controller, the second SVF voltage command value is obtained. The second SVF voltage command value is processed using the voltage equalization control strategy to obtain the switching signal for controlling the SVF, thereby realizing control of the SLCC.

[0057] Furthermore, the present invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and runnable on the processor. When the processor executes the computer program, the steps of the SLCC control method based on the assisted SVF of the class network are implemented.

[0058] Furthermore, the present invention also proposes a computer-readable storage medium, which stores a computer program. When the computer program is run by a processor, it executes the SLCC control method based on the SVF-assisted SLCC control method.

[0059] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0060] 1. The present invention enables the SVF to autonomously regulate voltage and reactive power. Through dual closed-loop control of the active and reactive power outer loop and the current inner loop, the SVF's dependence on the AC system is reduced, and the SVF can maintain stable and independent operation in the SLCC by relying on its own regulation capabilities.

[0061] 2. The present invention reduces the SVF failure rate through voltage balancing control, significantly improving the reliability and stability of LCC operation in weak systems when facing AC system failures or voltage fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is an overall implementation flow chart of the present invention.

[0063] Figure 2 This is a flow chart of generating the first SVF voltage command value according to the present invention.

[0064] Figure 3 It is a flow chart of generating a modulated wave according to the present invention.

[0065] Figure 4 This is a topological diagram of the SLCC inverter side of the present invention.

[0066] Figure 5 1 is a graph showing the DC voltage and current results of the SLCC in an embodiment of the present invention.

[0067] Figure 6 1 is a diagram showing the active and reactive exchange results on the SLCC inverter side in an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0069] To achieve the above objectives, the present invention proposes a SLCC control method based on the assisted SVF of the quasi-network type, such as Figure 1 The specific steps are as follows:

[0070] S1. Based on the control strategy of constant current on the rectifier side and constant voltage on the inverter side, the LCC is controlled to operate under rated conditions; specifically:

[0071] Set the current command value on the rectifier side according to the SLCC load demand and the power transmission requirements of the DC transmission system ,Will Compared with the measured DC current on the rectifier side Compare and get the current deviation , , use the proportional-integral controller to get the complementary angle, get the trigger angle adjustment signal, use the phase shift link to get the thyristor trigger pulse, and control the difference between the DC current on the rectifier side and the set current command value to be within 5%.

[0072] Set the voltage command value on the inverter side according to the voltage level of the inverter station AC bus and the reactive power demand of the SLCC ,Will Compared with the measured DC voltage on the inverter side Compare and get the voltage deviation , The proportional-integral controller is used to obtain the advance trigger angle adjustment signal, and the phase-shift link is used to obtain the thyristor trigger pulse, so as to control the difference between the DC voltage on the inverter side and the set voltage command value to be within 5%.

[0073] S2. Obtain the reactive power shortage on the inverter side of the LCC based on the relevant electrical quantities when the LCC is operating under rated conditions; specifically:

[0074] The SVF is set on the inverter side, and the electrical quantity of the LCC when operating under rated conditions is expressed as:

[0075] ;

[0076] ;

[0077] ;

[0078] ;

[0079] ;

[0080] ;

[0081] in, Indicates the no-load DC voltage of the inverter station. Indicates the total number of 6-pulse converters per pole in the SLCC converter station, Indicates the effective value of the equivalent no-load line voltage on the valve side of the inverter station. represents the actual DC voltage of the countercurrent station, Indicates the arc extinction angle of the inverter station. Indicates the equivalent commutation reactance on the valve side of the inverter station, Indicates the DC current of the inverter station, Indicates the leading trigger angle of the inverter station. Indicates the commutation angle of the inverter station, Indicates the power factor angle of the inverter station, Indicates the actual DC voltage of the rectifier station, represents the resistance of the DC transmission line, Indicates the reactive power consumed by the inverter station.

[0082] The equivalent commutation reactance obtained after parallel connection of SVF According to the calculation formula of the commutation overlap angle, adding SVF can reduce the commutation overlap angle, accelerate the LCC commutation process, and thus reduce the risk of commutation failure.

[0083] LCC inverter side reactive power shortage The calculation formula is:

[0084] ;

[0085] in, Indicates the reactive power consumed during the commutation process, Indicates the reactive power consumed by the commutation transformer, Indicates the active power transmitted between the AC system and the converter station, Represents the reactive power transmitted between the AC system and the converter station, Indicates the voltage on the grid side of the commutation transformer. Indicates the short-circuit voltage percentage, Indicates the voltage on the converter valve side. represents the commutation transformer capacity, Represents the commutation reactance.

[0086] S3, such as Figure 2 As shown, based on the active power transmission requirement of the LCC and the reactive power shortage on the inverter side of the LCC, the first SVF voltage command value is generated through the active power and reactive power outer loops; specifically:

[0087] The SVF active power transmission command value is obtained differently during the SLCC startup phase and the stable operation phase. During the SLCC startup phase (i.e., when the DC voltage and DC current gradually increase but have not stabilized at the command values), the active power command value is set to 0. During the SLCC stable operation phase (i.e., when the DC voltage and DC current stabilize near the command values, with an error within 5%), the actual SVF capacitor voltage is subtracted from the rated SVF capacitor voltage and this difference is input into the proportional-integral controller to obtain the active power command value. This ensures that the active power in the SLCC is primarily provided by the LCC while maintaining overall capacitor voltage balance within the SVF. This approach allows the SVF to quickly adjust active power distribution in response to SLCC load changes or disturbances, preventing SLCC instability caused by voltage fluctuations.

[0088] The SVF active power transmission is adjusted using the droop control method to obtain the SVF command voltage angular frequency , the specific formula is:

[0089] ;

[0090] in, Indicates the inertia coefficient, which simulates the virtual mechanical torque output to adjust the frequency; Represents the damping coefficient, which describes the change in output power when the frequency changes by one unit; represents the grid voltage angular frequency reference value; t represents the tth moment; Indicates the active power command value; Indicates the measured value of active power.

[0091] Figure 2 middle, .

[0092] The SVF reactive power transmission is adjusted using the droop control method to obtain the SVF command voltage amplitude E. The specific formula is:

[0093] ;

[0094] in, Indicates the reactive integral coefficient, ensuring that the SLCC voltage remains stable in the long term; Indicates the reactive power command value, using the reactive power shortage on the LCC inverter side as the reactive power command value; Represents the reactive power droop coefficient, which is used to enable SLCC to respond faster to reactive power changes; Indicates voltage rating; Indicates the measured voltage value; Indicates the measured value of reactive power.

[0095] Set the SVF instruction voltage angular frequency The frequency and amplitude of the parallel virtual synchronous generator voltage used to maintain the operation of the SLCC are used to generate the first SVF voltage command value. The specific formula is:

[0096] ;

[0097] in, 、 、 Indicates the first SVF voltage command values for phases a, b, and c, respectively.

[0098] Perform Park transformation on the first SVF voltage command values of phases a, b, and c to obtain the d and q axis components of the first voltage command values of the SVF in the dq coordinate system. .

[0099] S4, such as Figure 3 As shown, based on the first SVF voltage command value, the d-axis and q-axis components of the fundamental frequency reactive compensation current are obtained, and the q-axis component of the fundamental frequency reactive compensation current is used as the fundamental frequency reactive compensation current command value; specifically:

[0100] The calculation method of the d-axis and q-axis components of the fundamental frequency reactive compensation current is:

[0101] ;

[0102] in, Represents the d-axis component of the fundamental frequency reactive compensation current, represents the voltage outer loop integral coefficient, Represents the voltage outer loop proportional coefficient, represents a pull transformation, represents the d-axis component of the compensation point voltage, represents the SVF bridge arm capacitance, represents the q-axis component of the compensation point voltage, Represents the q-axis component of the fundamental frequency reactive compensation current.

[0103] S5. Use the multi-synchronous rotating coordinate method to process the LCC output current to obtain the harmonic compensation current reference value; specifically:

[0104] The output current and voltage waveforms of the converter station are collected in real time. The order of the corresponding harmonic component to be filtered out is obtained according to the order of the LCC characteristic harmonic using the multi-synchronous rotating coordinate method. Based on this order, the LCC output current is converted into the sum of the DC component obtained by transforming the characteristic harmonic and the AC component obtained by transforming other components in the rotating coordinate system. After filtering the sum component, it is inversely transformed into an AC quantity to obtain the subharmonic component in the characteristic subharmonic of the LCC output current. The specific expression is:

[0105] ;

[0106] in, represents the d-axis component of the current, represents the q-axis component of the current, represents the Parker transformation matrix, represents the current a-phase component, represents the b-phase component of the current, represents the c-phase component of the current, Indicates the angular frequency of the rotating coordinate system corresponding to the order harmonic of the harmonic component to be filtered out.

[0107] All harmonic components are added together to obtain the total harmonic component, which is used as the reference value of the harmonic compensation current.

[0108] Among them, the order of LCC characteristic harmonics is , , Indicates the index of the 6-pulse converter per pole in the SLCC converter station. Indicates the mth harmonic component that needs to be filtered out, and n indicates the harmonic order of the highest harmonic component that needs to be filtered out.

[0109] Since the harmonic compensation current is used as part of the current loop command current in subsequent steps, each harmonic component needs to be converted to the dq axis in the rotating coordinate system of the fundamental frequency.

[0110] S6. Superimpose the fundamental frequency reactive power compensation current command value and the harmonic compensation current reference value to obtain the SVF current command value. Based on the current inner loop controller, obtain the second SVF voltage command value. Use the voltage balancing control strategy and the carrier phase shift modulation strategy to process the second SVF voltage command value to obtain the switching signal for controlling the SVF, thereby achieving precise control of the active and reactive power of the SLCC and ensuring stable operation. Specifically:

[0111] The d-axis component of the fundamental frequency reactive compensation current is used as the d-axis component command value of the total compensation current. The fundamental frequency reactive compensation current command value is superimposed on the harmonic compensation current reference value to obtain the SVF current command value. This value is input into the current inner loop controller to obtain the d-axis and q-axis components of the second SVF voltage command value. The specific formula is:

[0112] ;

[0113] in, represents the d-axis component of the second SVF voltage command value, represents the q-axis component of the second SVF voltage command value, represents the current inner loop integral coefficient, Indicates the current inner loop proportional coefficient, Indicates the d-axis component of the SVF current command value, represents the q-axis component of the SVF current command value, represents the d-axis component of the measured value of the SVF bridge arm current, represents the q-axis component of the measured value of the SVF bridge arm current, represents the SVF bridge arm inductance.

[0114] SVF is composed of cascaded submodules using fully controlled devices. 、 After phase-to-phase voltage equalization control, a modulated wave is obtained. Using the carrier phase-shift modulation strategy, the switching signals of each SVF submodule are output according to the modulated wave to control the on and off of the SVF submodule.

[0115] Example:

[0116] Since each converter station consists of a single six-pulsation converter valve, .

[0117] The parameters of the LCC and SLCC are obtained, as shown in Table 1. Among them, the DC current, DC voltage, and grid voltage frequency determine the operation of the SLCC, while the SVF bridge arm inductance, SVF submodule capacitance, number of submodules, and SVF submodule rated voltage determine the SVF structural parameters.

[0118] Table 1 Parameters of LCC and SLCC

[0119]

[0120] The topology structure of SLCC inverter side is as follows: Figure 4 As shown, it is running at full load under rated conditions. Figure 4 As can be seen in the figure, the inverter station uses a single set of six-pulsation converter valves, and the SVF is installed on the inverter side. The operating goal of the SVF is to reduce the reactive exchange between the inverter side AC system and the converter valve and reduce the inverter side harmonics.

[0121] SLCC operation status Figure 5 、 Figure 6 As shown, the DC voltage and current are both operating at rated values, the active power transmission is 600MW, and the reactive power exchange between the inverter side network and valves is basically 0, which meets the requirements.

[0122] Figure 5 The voltage and current diagram of the SLCC DC line is shown in Figure 2. Figure 5 As can be seen from the figure, the DC voltage and DC current are stable at 200kV and 3kA respectively, which are consistent with the rated values and have almost no overshoot. Figure 5 It can be seen from the figure that the method proposed in the present invention enables the SLCC to operate at full load under rated conditions.

[0123] Figure 6 This is the active and reactive exchange diagram on the SLCC inverter side. Figure 6 As can be seen from the figure, the active power is stable at 600MW, which is consistent with the required active power transmission, while the reactive power exchange is almost 0. Figure 6 It can be seen from the figure that the method proposed in the present invention realizes the requirements of LCC transmitting active power and SVF providing reactive power in SLCC, and successfully reduces the dependence of the converter station on the AC system.

[0124] The present invention also proposes an SLCC control system based on a quasi-grid SVF, comprising an LCC operation control module, an SVF voltage command value generation module, a harmonic compensation current reference value acquisition module, an SLCC control module, and a computer program executable on a processor. It should be noted that each module in the above system corresponds to the specific steps of the method provided in the present invention, and has the corresponding functional modules and beneficial effects of the method. For technical details not fully described in this embodiment, please refer to the method provided in the present invention.

[0125] An embodiment of the present invention further provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor. It should be noted that when the processor executes the computer program, it corresponds to the specific steps of the method provided in the embodiment of the present invention and has the corresponding functional modules and beneficial effects of the method. For technical details not fully described in this embodiment, please refer to the method provided in the embodiment of the present invention.

[0126] The present invention also provides a computer-readable storage medium storing a computer program. It should be noted that when executed by a processor, the computer program corresponds to the specific steps of the method provided in the present invention and has the corresponding functional modules and beneficial effects. For technical details not fully described in this embodiment, please refer to the method provided in the present invention.

[0127] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A SLCC control method based on quasi-network SVF assistance, characterized in that: include: S1, based on the control strategy of constant current on the rectifier side and constant voltage on the inverter side, controls the LCC to operate under rated conditions; S2. Obtain the reactive power shortage on the inverter side of the LCC based on the electrical quantity when the LCC is operating under rated conditions; S3. Based on the active power transmission requirement of the LCC and the reactive power shortage on the inverter side of the LCC, a first SVF voltage command value is generated through the active power and reactive power outer loops. S4. Based on the first SVF voltage command value, obtain the d-axis and q-axis components of the fundamental frequency reactive compensation current, and use the q-axis component of the fundamental frequency reactive compensation current as the fundamental frequency reactive compensation current command value; S5. Process the LCC output current using a multi-synchronous rotating coordinate method to obtain a harmonic compensation current reference value; S6. Superimpose the fundamental frequency reactive compensation current command value and the harmonic compensation current reference value to obtain the SVF current command value. Based on the current inner loop controller, obtain the second SVF voltage command value. Use the voltage equalization control strategy and the carrier phase shift modulation strategy to process the second SVF voltage command value to obtain the switching signal for controlling the SVF, thereby realizing the control of the SLCC.

2. The SLCC control method based on the quasi-network SVF assistance according to claim 1 is characterized in that: In step S1, controlling the LCC to operate under rated conditions includes the following: Set the current command value on the rectifier side according to the SLCC load demand and the power transmission requirements of the DC transmission system ,Will Compared with the measured DC current on the rectifier side Compare and get the current deviation , , using the proportional-integral controller to obtain the supplementary angle, obtain the trigger angle adjustment signal, and use the phase shift link to obtain the thyristor trigger pulse, controlling the difference between the DC current on the rectifier side and the set current command value to be within 5%; Set the voltage command value on the inverter side according to the voltage level of the inverter station AC bus and the reactive power demand of the SLCC ,Will Compared with the measured DC voltage on the inverter side Compare and get the voltage deviation , The proportional-integral controller is used to obtain the advance trigger angle adjustment signal, and the phase-shift link is used to obtain the thyristor trigger pulse, so as to control the difference between the DC voltage on the inverter side and the set voltage command value to be within 5%.

3. The SLCC control method based on the quasi-network SVF assistance according to claim 1 is characterized in that: In step S2, obtaining the reactive power shortage on the LCC inverter side includes the following contents: The SVF is set on the inverter side, and the electrical quantity of the LCC when operating under rated conditions is expressed as: ； ； ； ； ； ； in, Indicates the no-load DC voltage of the inverter station. Indicates the total number of 6-pulse converters per pole in the SLCC converter station, Indicates the effective value of the equivalent no-load line voltage on the valve side of the inverter station. represents the actual DC voltage of the countercurrent station, Indicates the arc extinction angle of the inverter station. Indicates the equivalent commutation reactance on the valve side of the inverter station, Indicates the DC current of the inverter station, Indicates the commutation angle of the inverter station, Indicates the power factor angle of the inverter station, Indicates the actual DC voltage of the rectifier station, represents the resistance of the DC transmission line, Indicates the reactive power consumed by the inverter station; LCC inverter side reactive power shortage The calculation formula is: ； in, Indicates the active power transmitted between the AC system and the converter station, Represents the reactive power transmitted between the AC system and the converter station, Indicates the voltage on the commutation transformer side, Indicates the short-circuit voltage percentage, Indicates the voltage on the converter valve side. represents the commutation transformer capacity, Represents the commutation reactance.

4. The SLCC control method based on the quasi-network SVF assistance according to claim 1 is characterized in that: In step S3, generating the first SVF voltage command value includes the following: During the SLCC startup phase, the active power command value is set to 0. During the SLCC rated operating phase, the actual SVF capacitor voltage value is subtracted from the SVF capacitor voltage rated value, and the difference is input into the proportional-integral controller to obtain the active power command value. The SVF active power transmission is adjusted using the droop control method to obtain the SVF command voltage angular frequency , the specific formula is: ； in, represents the inertia coefficient, represents the damping coefficient, represents the grid voltage angular frequency reference value, t represents the tth moment, Indicates the active power command value, Indicates the measured value of active power; The SVF reactive power transmission is adjusted using the droop control method to obtain the SVF command voltage amplitude E. The specific formula is: ； in, Represents the reactive integral coefficient, Indicates the reactive power command value, represents the reactive droop coefficient, Indicates the voltage rating, Indicates the measured voltage value. Indicates the measured value of reactive power; Use the reactive power shortage on the LCC inverter side as the reactive power command value; Based on SVF instruction voltage angular frequency and the SVF command voltage amplitude E to generate the first SVF voltage command value. The specific formula is: ； in, 、 、 Represent the first SVF voltage command values of phases a, b, and c respectively; Perform Park transformation on the first SVF voltage command values of phases a, b, and c to obtain the d and q axis components of the first voltage command values of the SVF in the dq coordinate system. .

5. The SLCC control method based on the assisted quasi-network SVF according to claim 4 is characterized in that: In step S4, the d-axis and q-axis components of the fundamental frequency reactive compensation current are calculated as follows: ； in, Represents the d-axis component of the fundamental frequency reactive compensation current, represents the voltage outer loop integral coefficient, represents a pull transformation, Represents the voltage outer loop proportional coefficient, represents the d-axis component of the compensation point voltage, represents the SVF bridge arm capacitance, represents the q-axis component of the compensation point voltage, Represents the q-axis component of the fundamental frequency reactive compensation current.

6. The SLCC control method based on the quasi-network SVF assistance according to claim 1 is characterized in that: In step S5, obtaining the harmonic compensation current includes the following: The output current and voltage waveforms of the converter station are collected in real time. The order of the corresponding harmonic component to be filtered out is obtained according to the order of the LCC characteristic harmonic using the multi-synchronous rotating coordinate method. Based on this order, the LCC output current is converted into the sum of the DC component obtained by transforming the characteristic harmonic and the AC component obtained by transforming other components in the rotating coordinate system. After filtering the sum component, it is inversely transformed into an AC quantity to obtain the subharmonic component in the characteristic subharmonic of the LCC output current. The specific expression is: ； in, represents the d-axis component of the current, represents the q-axis component of the current, represents the current a-phase component, represents the b-phase component of the current, represents the c-phase component of the current, Indicates the angular frequency of the rotating coordinate system corresponding to the harmonic order of the harmonic component to be filtered out, and t represents the tth moment; Add up all harmonic components to get the total harmonic component, which is used as the reference value of harmonic compensation current; Among them, the order of LCC characteristic harmonics is , , Indicates the index of the 6-pulse converter per pole in the SLCC converter station. Indicates the total number of 6-pulse converters per pole in the SLCC converter station.

7. The SLCC control method based on the quasi-network SVF assistance according to claim 1 is characterized in that: In step S6, the d-axis component of the fundamental frequency reactive compensation current is used as the d-axis component command value of the total compensation current, and the fundamental frequency reactive compensation current command value is superimposed with the harmonic compensation current reference value to obtain the SVF current command value. This value is input into the current inner loop controller to obtain the second SVF voltage command value d and q-axis components. The specific formula is: ； in, represents the d-axis component of the second SVF voltage command value, represents the q-axis component of the second SVF voltage command value, represents the d-axis component of the compensation point voltage, represents the q-axis component of the compensation point voltage, represents the integral coefficient of the inner current loop, Indicates the current inner loop proportional coefficient, Indicates the d-axis component of the SVF current command value, represents the q-axis component of the SVF current command value, represents the d-axis component of the measured value of the SVF bridge arm current, represents the q-axis component of the measured value of the SVF bridge arm current, Indicates the SVF command voltage angular frequency, represents a pull transformation, represents the SVF bridge arm inductance; Will 、 After phase-to-phase voltage equalization control, a modulated wave is obtained. Using the carrier phase-shift modulation strategy, the switching signals of each SVF submodule are output according to the modulated wave to control the on and off of the SVF submodule.

8. A system for the SLCC control method based on the quasi-network SVF auxiliary according to claim 1, characterized in that: include: The LCC operation control module is used to control the LCC to operate under rated conditions based on the control strategy of constant current on the rectifier side and constant voltage on the inverter side; The SVF voltage command value generation module is used to obtain the reactive power shortage on the LCC inverter side based on the electrical quantity when the LCC is operating under rated conditions; based on the active power transmission requirements of the LCC and the reactive power shortage on the LCC inverter side, the module generates a first SVF voltage command value through the active and reactive outer loops; The harmonic compensation current reference value acquisition module is used to process the LCC output current using the multi-synchronous rotating coordinate method to obtain the harmonic compensation current reference value; The SLCC control module is used to obtain the d-axis and q-axis components of the fundamental frequency reactive compensation current based on the first SVF voltage command value, and use the q-axis component of the fundamental frequency reactive compensation current as the fundamental frequency reactive compensation current command value. The fundamental frequency reactive compensation current command value and the harmonic compensation current reference value are superimposed to obtain the SVF current command value. Based on the current inner loop controller, the second SVF voltage command value is obtained. The second SVF voltage command value is processed using the voltage equalization control strategy to obtain the switching signal for controlling the SVF, thereby realizing control of the SLCC.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the SLCC control method based on the quasi-mesh SVF assistance according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the SLCC control method based on the quasi-mesh SVF assistance according to any one of claims 1 to 7 is executed.

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