A resonance control method, device and equipment for a multi-valve group flexible direct current transmission system

Abstract

The present invention relates to the technical field of high-voltage direct current transmission, and discloses a resonance control method, device and equipment for a multi-valve group flexible direct current transmission system. The present invention performs delay processing on the controlled voltage quantity of the corresponding converter station according to the execution time of the AC voltage control link of the converter station, and further performs delay processing on the processed controlled voltage quantity obtained by the delay processing according to the execution time of the current reference value distribution link, to obtain a voltage feedforward control quantity, and calculates the corresponding current inner loop PI controller parameters with the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient as 1, and uses the voltage feedforward control quantity and the current inner loop PI controller parameters as the input of the current control link of the corresponding converter, and executes the current control link to obtain a voltage modulation wave. The present invention can avoid conflicts between the AC voltage control targets of each converter and effectively reduce the risk of system resonance.

Description

Technical Field

[0001] The present invention relates to the technical field of high voltage direct current power transmission, and in particular to a resonance control method, device and equipment for a multi-valve group flexible direct current power transmission system. Background Art

[0002] For a multi-valve group flexible DC transmission system, a single converter station contains multiple converters. In the island operation mode, if each converter uses a fixed AC side voltage control, the AC voltage control targets of each converter will conflict. Therefore, special design is required for the fixed AC voltage control target to ensure coordination between different valve groups.

[0003] In addition, in the multi-valve flexible DC transmission system, there is a coupling effect between the AC voltage outer loop and the current inner loop, which is easy to affect the system resonance characteristics. Therefore, it is also necessary to consider the coupling effect between the inner and outer loops, and reduce the risk of system resonance through the coordination between the inner and outer loops. Summary of the invention

[0004] The present invention provides a resonance control method, device and equipment for a multi-valve group flexible direct current transmission system, which solves the technical problems that in the existing multi-valve group flexible direct current transmission system, the AC voltage control targets of each converter conflict under a fixed AC side voltage control strategy and the system resonance risk is easily caused by the coupling between the AC voltage outer loop and the current inner loop.

[0005] A first aspect of the present invention provides a resonance control method for a multi-valve group flexible direct current transmission system, the method comprising:

[0006] Execute the AC voltage control link of the converter station and obtain the corresponding first execution time, and perform delay processing on the controlled voltage of the corresponding converter station input into the AC voltage control link according to the first execution time to obtain the processed controlled voltage; the AC voltage control link obtains the total reference value of the current inner loop according to the voltage outer loop PI controller parameter, the AC voltage reference value and the controlled voltage;

[0007] Execute the current reference value distribution link and obtain the corresponding second execution time, and perform delay processing on the processed controlled voltage amount according to the second execution time to obtain the voltage feedforward control amount; the current reference value distribution link distributes the total reference value of the current inner loop according to the current distribution coefficient of each converter to obtain the current inner loop reference value of each converter;

[0008] The product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient is 1, and the current inner loop PI controller parameters of the corresponding converter are calculated according to the voltage outer loop PI controller parameters and the current distribution coefficient;

[0009] Execute the current control link of each converter; the current control link obtains a voltage modulation wave according to the controlled current of the corresponding converter station, the voltage feedforward control amount, the current inner loop PI controller parameters of the corresponding converter and the current inner loop reference value to modulate the corresponding converter.

[0010] According to an achievable manner of the first aspect of the present invention, the step of executing the AC voltage control link of the converter station includes:

[0011] Collecting the AC bus voltage of the converter station, performing positive-sequence dq-axis transformation on the AC bus voltage to obtain a positive-sequence voltage d-axis component measurement value and a positive-sequence voltage q-axis component measurement value, and performing negative-sequence dq-axis transformation on the AC bus voltage to obtain a negative-sequence voltage d-axis component measurement value and a negative-sequence voltage q-axis component measurement value;

[0012] Acquire an AC voltage reference value and a voltage outer loop PI controller parameter; the AC voltage reference value includes a positive sequence voltage d-axis component reference value, a positive sequence voltage q-axis component reference value, a negative sequence voltage d-axis component reference value, and a negative sequence voltage q-axis component reference value;

[0013] Subtract the positive-sequence voltage d-axis component reference value from the corresponding positive-sequence voltage d-axis component measurement value, and subtract the positive-sequence voltage q-axis component measurement value from the positive-sequence voltage q-axis component reference value, and obtain the positive-sequence current inner-loop total reference value d-axis component and the positive-sequence current inner-loop total reference value q-axis component after passing through the voltage outer-loop PI controller based on the voltage outer-loop PI controller parameters respectively;

[0014] The negative-sequence voltage d-axis component reference value is subtracted from the corresponding negative-sequence voltage d-axis component measurement value, and the negative-sequence voltage q-axis component reference value is subtracted from the corresponding negative-sequence voltage q-axis component measurement value, and after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters, the negative-sequence current inner loop total reference value d-axis component and the negative-sequence current inner loop total reference value q-axis component are obtained.

[0015] According to an achievable manner of the first aspect of the present invention, the step of executing the current reference value allocation includes:

[0016] When the multi-valve group flexible direct current transmission system is in a steady-state operation mode, the current distribution coefficients of the converters are set to be the same.

[0017] According to an achievable manner of the first aspect of the present invention, the method further includes:

[0018] After executing the current control link of each converter, the AC side impedance of the converter is calculated and output according to the following formula:

[0019]

[0020] In the formula, zP / N represents the AC side impedance of the converter, s is the Laplace operator, L is the equivalent reactance on the AC side, K p_AC K is the proportional coefficient of the voltage outer loop PI controller, p_i K is the proportional coefficient of the current inner loop PI controller, n is the current distribution coefficient of converter n, G vd is the link delay of the voltage outer loop control, G id is the link delay of the current inner loop control, G fd is the link delay of voltage feedforward control, G sv is the equivalent transfer function of voltage sampling processing, G si is the equivalent transfer function of current sampling processing, K d is the dq axis decoupling coefficient, and T is the power frequency period.

[0021] A second aspect of the present invention provides a resonance control device for a multi-valve group flexible direct current transmission system, the device comprising:

[0022] A first execution module is used to execute the AC voltage control link of the converter station and obtain the corresponding first execution time, and perform delay processing on the controlled voltage of the corresponding converter station input into the AC voltage control link according to the first execution time to obtain the processed controlled voltage; the AC voltage control link obtains the total reference value of the current inner loop according to the voltage outer loop PI controller parameters, the AC voltage reference value and the controlled voltage;

[0023] A second execution module is used to execute the current reference value distribution link and obtain the corresponding second execution time, and to delay the processed controlled voltage amount according to the second execution time to obtain the voltage feedforward control amount; the current reference value distribution link distributes the total reference value of the current inner loop according to the current distribution coefficient of each converter to obtain the current inner loop reference value of each converter;

[0024] A first calculation module is used to calculate the current inner loop PI controller parameters of the corresponding converter according to the voltage outer loop PI controller parameters and the current distribution coefficient, with the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient being 1;

[0025] The third execution module is used to execute the current control link of each converter; the current control link obtains a voltage modulation wave according to the controlled current of the corresponding converter station, the voltage feedforward control amount, the current inner loop PI controller parameters of the corresponding converter and the current inner loop reference value to modulate the corresponding converter.

[0026] According to an achievable manner of the second aspect of the present invention, the first execution module includes:

[0027] A conversion unit is used to collect the AC bus voltage of the converter station, perform positive sequence dq axis conversion on the AC bus voltage to obtain a positive sequence voltage d axis component measurement value and a positive sequence voltage q axis component measurement value, and perform negative sequence dq axis conversion on the AC bus voltage to obtain a negative sequence voltage d axis component measurement value and a negative sequence voltage q axis component measurement value;

[0028] An acquisition unit, used to acquire an AC voltage reference value and a voltage outer loop PI controller parameter; the AC voltage reference value includes a positive sequence voltage d-axis component reference value, a positive sequence voltage q-axis component reference value, a negative sequence voltage d-axis component reference value, and a negative sequence voltage q-axis component reference value;

[0029] A first voltage outer loop control unit, configured to subtract the positive-sequence voltage d-axis component reference value from the positive-sequence voltage d-axis component measurement value, and subtract the positive-sequence voltage q-axis component measurement value from the positive-sequence voltage q-axis component reference value, and obtain the positive-sequence current inner loop total reference value d-axis component and the positive-sequence current inner loop total reference value q-axis component after passing through a voltage outer loop PI controller based on the voltage outer loop PI controller parameters respectively;

[0030] The second voltage outer loop control unit is used to subtract the corresponding negative-sequence voltage d-axis component measurement value from the negative-sequence voltage d-axis component reference value, and subtract the corresponding negative-sequence voltage q-axis component measurement value from the negative-sequence voltage q-axis component reference value, and obtain the negative-sequence current inner loop total reference value d-axis component and the negative-sequence current inner loop total reference value q-axis component after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters respectively.

[0031] According to an achievable manner of the second aspect of the present invention, the second execution module includes:

[0032] The setting unit is used to set the current distribution coefficients of each converter to be the same when the multi-valve group flexible direct current transmission system is in a steady-state operation mode.

[0033] According to an achievable manner of the second aspect of the present invention, the device further includes:

[0034] The second calculation module is used to calculate and output the AC side impedance of the converter according to the following formula after executing the current control link of each converter:

[0035]

[0036] In the formula, z P / N represents the AC side impedance of the converter, s is the Laplace operator, L is the equivalent reactance on the AC side, K p_AC K is the proportional coefficient of the voltage outer loop PI controller, p_i K is the proportional coefficient of the current inner loop PI controller, n is the current distribution coefficient of converter n, Gvd is the link delay of the voltage outer loop control, G id is the link delay of the current inner loop control, G fd is the link delay of voltage feedforward control, G sv is the equivalent transfer function of voltage sampling processing, G si is the equivalent transfer function of current sampling processing, K d is the dq axis decoupling coefficient, and T is the power frequency period.

[0037] A third aspect of the present invention provides a resonance control device for a multi-valve group flexible direct current transmission system, comprising:

[0038] A memory for storing instructions; wherein the instructions are used to implement the resonance control method of a multi-valve group flexible direct current transmission system as described in any one of the above implementation methods;

[0039] A processor is used to execute instructions in the memory.

[0040] A fourth aspect of the present invention is a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method for controlling resonance of a multi-valve group flexible direct current transmission system as described in any of the above-mentioned embodiments can be implemented.

[0041] It can be seen from the above technical solutions that the present invention has the following advantages:

[0042] The present invention performs delay processing on the controlled voltage quantity of the corresponding converter station according to the execution time of the AC voltage control link of the converter station to obtain the processed controlled voltage quantity, and performs delay processing on the processed controlled voltage quantity according to the execution time of the current reference value distribution link to obtain the voltage feedforward control quantity, and calculates the current inner loop PI controller parameters of the corresponding converter with the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient as 1, and uses the voltage feedforward control quantity and the current inner loop PI controller parameters as the input of the current control link of the corresponding converter, and executes the current control link to output a voltage modulation wave for modulating the corresponding converter; the present invention enables each converter in the converter station to share the AC voltage outer loop by executing the AC voltage control link and the current reference value distribution link. loop, the AC voltage outer loop generates the AC current inner loop reference value of each converter, which can avoid the conflict of the AC voltage control targets of each converter under the fixed AC side voltage control strategy; considering the coupling effect between the AC voltage outer loop and the current inner loop, the present invention performs the above two delay processings so that the controlled voltage of the AC voltage outer loop and the voltage feedforward control quantity of the current inner loop use the same control link channel, ensuring that the link delays of the AC voltage outer loop and the voltage feedforward are the same, and at the same time, coordinately design the proportional coefficient of the voltage outer loop PI controller and the proportional coefficient of the current inner loop PI controller, so that the product of the proportional coefficient of the voltage outer loop PI controller, the current distribution coefficient, and the proportional coefficient of the current inner loop PI controller is 1, thereby offsetting the disturbance introduced by the AC voltage outer loop and the voltage feedforward, improving the impedance characteristics of the converter in the system, and reducing the risk of system resonance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 A flow chart of a resonance control method for a multi-valve group flexible direct current transmission system provided by an optional embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the AC voltage outer loop control principle provided for another optional embodiment of the present invention;

[0046] Figure 3 A schematic diagram of the current inner loop control principle provided by an optional embodiment of the present invention;

[0047] Figure 4A flowchart of a resonance control method for a multi-valve group flexible direct current transmission system provided by another optional embodiment of the present invention;

[0048] Figure 5 A schematic diagram of an impedance characteristic curve of a flexible DC converter that meets the first technical feature but does not meet the second technical feature, provided in an optional embodiment of the present invention;

[0049] Figure 6 A schematic diagram of an impedance characteristic curve of a flexible DC converter that meets the second technical feature but does not meet the first technical feature, provided in an optional embodiment of the present invention;

[0050] Figure 7 A schematic diagram of an impedance characteristic curve of a flexible DC converter that satisfies both the first technical feature and the second technical feature, provided by an optional embodiment of the present invention;

[0051] Figure 8 An alternative embodiment of the present invention provides a method for Figure 1 The waveform diagram of the voltage and current at the AC grid connection point of the converter station after the method shown;

[0052] Fig. 9 An alternative embodiment of the present invention provides a method for Figure 1 Spectrum analysis diagram of the voltage at the AC grid connection point of the converter station before the method shown;

[0053] Fig.10 A structural connection block diagram of a resonance control device for a multi-valve group flexible direct current transmission system provided by an optional embodiment of the present invention;

[0054] Fig.11 A structural connection block diagram of a resonance control device for a multi-valve group flexible DC power transmission system provided in another optional embodiment of the present invention.

[0055] Reference numerals:

[0056] 1-first execution module; 2-second execution module; 3-first calculation module; 4-third execution module; 5-second calculation module. DETAILED DESCRIPTION

[0057] The embodiments of the present invention provide a resonance control method, device and equipment for a multi-valve group flexible direct current transmission system, which are used to solve the technical problems that in the existing multi-valve group flexible direct current transmission system, the AC voltage control targets of each converter conflict under a fixed AC side voltage control strategy and the system resonance risk is easily caused by the coupling between the AC voltage outer loop and the current inner loop.

[0058] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The invention provides a resonance control method for a multi-valve group flexible direct current power transmission system.

[0060] See also Figure 1 , Figure 1 A flow chart of a resonance control method for a multi-valve group flexible direct current transmission system provided by an embodiment of the present invention is shown.

[0061] An embodiment of the present invention provides a resonance control method for a multi-valve group flexible direct current transmission system, comprising steps S1-S4.

[0062] Step S1, execute the AC voltage control link of the converter station and obtain the corresponding first execution time, and delay the controlled voltage of the corresponding converter station input into the AC voltage control link according to the first execution time to obtain the processed controlled voltage; the AC voltage control link obtains the total reference value of the current inner loop according to the voltage outer loop PI controller parameters, the AC voltage reference value and the controlled voltage.

[0063] When implementing it, Figure 2 As shown, the AC voltage control link of the converter station includes:

[0064] Collect the AC bus voltage u of the converter station A ,u B ,u C , the AC bus voltage is transformed into a positive-sequence dq axis to obtain a positive-sequence voltage d-axis component measurement value u dP and the measured value u of the q-axis component of the positive sequence voltage qP , and perform negative sequence dq axis transformation to obtain the negative sequence voltage d axis component measurement value u dN and the measured value u of the negative sequence voltage q-axis component qN ;

[0065] Acquire the AC voltage reference value and the voltage outer loop PI controller parameters; the AC voltage reference value includes the positive sequence voltage d-axis component reference value U * dP , positive sequence voltage q-axis component reference value U * qP , Negative sequence voltage d-axis component reference value U * dNAnd the negative sequence voltage q-axis component reference value U * qN ;

[0066] The positive sequence voltage d-axis component reference value U * dP Subtract the corresponding positive sequence voltage d-axis component measurement value u dP , the positive sequence voltage q-axis component reference value U * qP Subtract the corresponding positive sequence voltage q-axis component measurement value u qP , respectively, after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters, the positive sequence current inner loop total reference value d-axis component i * dP and the total reference value of the positive sequence current inner loop q-axis component i * qP ;

[0067] The negative sequence voltage d-axis component reference value U * dN Subtract the corresponding negative sequence voltage d-axis component measurement value u dN , the negative sequence voltage q-axis component reference value U * qN Subtract the corresponding negative sequence voltage q-axis component measurement value u qN , respectively, after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters, the negative sequence current inner loop total reference value d-axis component i * dN and the total reference value of the negative sequence current inner loop q-axis component i * qN .

[0068] Figure 2 In, G sv is the equivalent transfer function of voltage sampling processing, θ1 is the reference phase angle of dq axis transformation, G sd It is the transfer function of the 1 / 4 power frequency period delay filter.

[0069] Step S2, execute the current reference value distribution link and obtain the corresponding second execution time, delay the processed controlled voltage according to the second execution time to obtain the voltage feedforward control amount; the current reference value distribution link distributes the total reference value of the current inner loop according to the current distribution coefficient of each converter to obtain the current inner loop reference value of each converter.

[0070] like Figure 2 As shown, taking four converters as an example, the total reference value dq axis component of the positive and negative sequence current inner loop is multiplied by the current distribution coefficient K1 to obtain the current inner loop reference value i of the first converter. * dP，1,i * qP，1 ,i * dN，1 ,i * qN，1 , multiplied by the current distribution coefficient K2 to obtain the current inner loop reference value i of the second converter * dP，2 ,i * qP，2 ,i * dN，2 ,i * qN，2 , multiplied by the current distribution coefficient K3 to obtain the current inner loop reference value i of the third converter * dP，3 ,i * qP，3 ,i * dN，3 ,i * qN，3 , multiplied by the current distribution coefficient K4 to obtain the current inner loop reference value i of the fourth converter * dP，4 ,i * qP，4 ,i * dN，4 ,i * qN，4 .

[0071] In one achievable manner, when the multi-valve group flexible direct current transmission system is in a steady-state operation mode, the current distribution coefficients of the converters are set to be the same.

[0072] The current inner loop reference values ​​of each converter obtained in step S3 are respectively used as one of the input quantities of the current control link of the corresponding converter, and the voltage feedforward control quantity obtained is uniformly used as one of the input quantities of the current control link of each converter.

[0073] Step S3, taking the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient as 1, calculating the current inner loop PI controller parameters of the corresponding converter according to the voltage outer loop PI controller parameters and the current distribution coefficient.

[0074] Step S4, executing the current control link of each converter; the current control link obtains a voltage modulation wave according to the controlled current of the corresponding converter station, the voltage feedforward control amount, the current inner loop PI controller parameters of the corresponding converter and the current inner loop reference value to modulate the corresponding converter.

[0075] like Figure 3 As shown, the collected three-phase current i on the flexible DC AC side A ,i B ,iC After the positive and negative sequence dq axis transformation, the positive and negative sequence dq axis current component measurement value i is obtained dP ,i qP ,i dN ,i qN Input current control link, where G si is the equivalent transfer function of current sampling processing, G sd is the 1 / 4 power frequency cycle delay filter transfer function. The current inner loop control link includes the PI control link, the decoupling control link and the voltage feedforward link. By executing each link, a voltage modulation wave for modulating the flexible DC converter is finally generated. The control parameters are designed to meet the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient of 1.

[0076] Figure 3 in,i dP ,i qP are the measured values ​​of the dq axis components of the positive sequence current, i dN ,i qN are respectively the measured values ​​of the dq axis components of the negative sequence current, K d is the dq axis decoupling coefficient, is the positive sequence abc axis reference modulation wave, is the negative sequence abc axis reference modulation wave, It is the reference modulation wave of abc axis.

[0077] In one achievable manner, such as Figure 4 As shown, in Figure 1 Based on the method shown, after executing the current control link of each converter, the method further includes:

[0078] Step S5, calculating and outputting the AC side impedance of the converter.

[0079] Among them, the harmonic linearization method is used to set the calculation formula of the converter AC side impedance as:

[0080]

[0081] In the formula, z P / N represents the AC side impedance of the converter, s is the Laplace operator, L is the equivalent reactance on the AC side, K p_AC K is the proportional coefficient of the voltage outer loop PI controller, p_i K is the proportional coefficient of the current inner loop PI controller, n is the current distribution coefficient of converter n, G vd is the link delay of the voltage outer loop control, G id is the link delay of the current inner loop control, G fd is the link delay of voltage feedforward control, Gsv is the equivalent transfer function of voltage sampling processing, G si is the equivalent transfer function of current sampling processing, K d is the dq axis decoupling coefficient, and T is the power frequency period.

[0082] In the above embodiments of the present application, there are two technical features in optimizing the resonance control of the existing multi-valve group flexible DC power transmission system:

[0083] The first technical feature is that the controlled voltage quantity of the corresponding converter station input into the AC voltage control link is delayed according to the execution time of the AC voltage control link to obtain the processed controlled voltage quantity, and the processed controlled voltage quantity is delayed according to the execution time of the current reference value distribution link to obtain the voltage feedforward control quantity, which can ensure that the link delays of the AC voltage control channel and the feedforward voltage control channel are the same;

[0084] Second technical feature: the product of the proportional coefficient of the voltage outer loop PI controller, the current distribution coefficient and the proportional coefficient of the current inner loop PI controller is 1.

[0085] Combining the above two technical points, the disturbance introduced by the voltage outer loop control and voltage feedforward control in the bipolar flexible DC transmission control system can be offset, thereby improving the equivalent impedance characteristics of the flexible DC converter and reducing the risk of high-frequency resonance in the system.

[0086] Both of these technical features will have an impact on the impedance reshaping measures. If the first technical feature is met, the second technical feature is not met, that is, the control link delay item G of the AC voltage outer loop vd and the control link delay term G of the voltage feedforward fd Equal, but K p_AC , K p_i and K n The product of is not 1. At this time, the disturbance term K introduced by the AC voltage outer loop is p_AC K p_i K n G sv G fd and the disturbance term introduced by voltage feedforward -G vd G sv It cannot be completely offset, resulting in poor impedance characteristics, which can easily cause system resonance. Under this condition, the impedance characteristic curve of the flexible DC converter is as follows Figure 5 As shown, it can be seen that the flexible DC converter impedance phase angle has a large area of ​​negative damping in the range of 2000-4000Hz, and the maximum impedance phase angle is close to 130°. The negative damping is serious, which is not conducive to the resonance stability of the system.

[0087] If the second technical feature is met, but the first technical feature is not met, that is, K p_AC , K p_i and Kn The product of is 1, and the control link delay term G of the AC voltage outer loop vd and the control link delay term G of the voltage feedforward fd are not equal, then the disturbance term G introduced by the AC voltage outer loop sv G fd and the disturbance term introduced by voltage feedforward -G vd G sv It cannot be completely offset, resulting in poor impedance characteristics and easy to cause system resonance. Under this condition, the impedance characteristic curve of the flexible DC converter is as follows Figure 6 As shown, it can be seen that there is a large area of ​​negative damping in the impedance phase angle range of 2250~3750Hz, and the maximum value of the impedance phase angle is close to 180°, and the minimum value of the phase angle is close to 150°. The negative damping of the flexible DC converter is serious, which is not conducive to the resonance stability of the system.

[0088] If the first and second technical features are met at the same time, that is, the control link delay item G of the AC voltage outer loop vd and the control link delay term G of the voltage feedforward fd Equal, K p_AC , K p_i and K n The product of is 1. At this time, the disturbance term G introduced by the AC voltage outer loop is sv G fd and the disturbance term introduced by voltage feedforward -G vd G sv The impedance characteristics are completely offset, thereby improving the impedance characteristics and reducing the risk of resonance. Under this condition, the impedance characteristic curve of the flexible DC converter is as follows Figure 7 As shown, it can be seen that the impedance phase angle is basically within ±90° in the entire frequency band, the negative damping characteristics are effectively suppressed, the impedance characteristics are greatly improved, and the risk of resonance in the system is greatly reduced.

[0089] A simulation model of photovoltaic transmission through a flexible direct current island is built in PSCAD / EMTDC to verify the method proposed in the present invention. The voltage and current waveforms of the AC grid connection point of the flexible direct current converter station are obtained as shown in the figure below. Figure 8 After the system completes startup and enters steady state, it exits the resonance control method described in the above embodiment of the present invention at 3.8s. The conventional control method of the prior art is adopted, and the system has high-frequency resonance, such as Fig. 9 As shown, the resonant frequency is 1325 Hz, and the resonance control method described in the above embodiment of the present invention is put into use again for 4.0 s. The high-frequency resonance gradually decays and is effectively suppressed. In summary, the effectiveness of the method proposed in the present invention is verified.

[0090] The present invention also provides a resonance control device for a multi-valve group flexible DC power transmission system, which can be used to execute the resonance control method for a multi-valve group flexible DC power transmission system described in any one of the above embodiments of the present invention.

[0091] See also Fig.10 , Fig.10 A structural connection block diagram of a resonance control device for a multi-valve group flexible direct current transmission system provided by an embodiment of the present invention is shown.

[0092] An embodiment of the present invention provides a resonance control device for a multi-valve group flexible direct current power transmission system, comprising:

[0093] The first execution module 1 is used to execute the AC voltage control link of the converter station and obtain the corresponding first execution time, and perform delay processing on the controlled voltage of the corresponding converter station input into the AC voltage control link according to the first execution time to obtain the processed controlled voltage; the AC voltage control link obtains the total reference value of the current inner loop according to the voltage outer loop PI controller parameters, the AC voltage reference value and the controlled voltage;

[0094] The second execution module 2 is used to execute the current reference value distribution link and obtain the corresponding second execution time, and perform delay processing on the processed controlled voltage amount according to the second execution time to obtain the voltage feedforward control amount; the current reference value distribution link distributes the total reference value of the current inner loop according to the current distribution coefficient of each converter to obtain the current inner loop reference value of each converter;

[0095] A first calculation module 3 is used to calculate the current inner loop PI controller parameters of the corresponding converter according to the voltage outer loop PI controller parameters and the current distribution coefficient, with the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient being 1;

[0096] The third execution module 4 is used to execute the current control link of each converter; the current control link obtains a voltage modulation wave according to the controlled current of the corresponding converter station, the voltage feedforward control amount, the current inner loop PI controller parameters of the corresponding converter and the current inner loop reference value to modulate the corresponding converter.

[0097] In one achievable manner, the first execution module 1 includes:

[0098] A conversion unit is used to collect the AC bus voltage of the converter station, perform positive sequence dq axis conversion on the AC bus voltage to obtain a positive sequence voltage d axis component measurement value and a positive sequence voltage q axis component measurement value, and perform negative sequence dq axis conversion on the AC bus voltage to obtain a negative sequence voltage d axis component measurement value and a negative sequence voltage q axis component measurement value;

[0099] An acquisition unit, used to acquire an AC voltage reference value and a voltage outer loop PI controller parameter; the AC voltage reference value includes a positive sequence voltage d-axis component reference value, a positive sequence voltage q-axis component reference value, a negative sequence voltage d-axis component reference value, and a negative sequence voltage q-axis component reference value;

[0100] A first voltage outer loop control unit, configured to subtract the positive-sequence voltage d-axis component reference value from the positive-sequence voltage d-axis component measurement value, and subtract the positive-sequence voltage q-axis component measurement value from the positive-sequence voltage q-axis component reference value, and obtain the positive-sequence current inner loop total reference value d-axis component and the positive-sequence current inner loop total reference value q-axis component after passing through a voltage outer loop PI controller based on the voltage outer loop PI controller parameters respectively;

[0101] The second voltage outer loop control unit is used to subtract the corresponding negative-sequence voltage d-axis component measurement value from the negative-sequence voltage d-axis component reference value, and subtract the corresponding negative-sequence voltage q-axis component measurement value from the negative-sequence voltage q-axis component reference value, and obtain the negative-sequence current inner loop total reference value d-axis component and the negative-sequence current inner loop total reference value q-axis component after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters respectively.

[0102] In one achievable manner, the second execution module 2 includes:

[0103] The setting unit is used to set the current distribution coefficients of each converter to be the same when the multi-valve group flexible direct current transmission system is in a steady-state operation mode.

[0104] In one achievable manner, such as Fig.11 As shown, in Fig.10 Based on the device shown, the device also includes:

[0105] The second calculation module 5 is used to calculate and output the AC side impedance of the converter according to the following formula after executing the current control link of each converter:

[0106]

[0107] In the formula, z P / N represents the AC side impedance of the converter, s is the Laplace operator, L is the equivalent reactance on the AC side, K p_AC K is the proportional coefficient of the voltage outer loop PI controller, p_i K is the proportional coefficient of the current inner loop PI controller, n is the current distribution coefficient of converter n, G vd is the link delay of the voltage outer loop control, G id is the link delay of the current inner loop control, G fd is the link delay of voltage feedforward control, G sv is the equivalent transfer function of voltage sampling processing, Gsi is the equivalent transfer function of current sampling processing, K d is the dq axis decoupling coefficient, and T is the power frequency period.

[0108] The present invention also provides a resonance control device for a multi-valve group flexible direct current transmission system, comprising:

[0109] A memory for storing instructions; wherein the instructions are used to implement the resonance control method of a multi-valve group flexible direct current transmission system as described in any one of the above embodiments;

[0110] A processor is used to execute instructions in the memory.

[0111] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the resonance control method of a multi-valve group flexible direct current transmission system as described in any one of the above embodiments is implemented.

[0112] Technical personnel in the relevant field can clearly understand that, for the convenience and conciseness of description, the specific working processes of the above-described devices, equipment and modules can refer to the corresponding processes in the aforementioned method embodiments, and the specific beneficial effects of the above-described devices, equipment and modules can refer to the corresponding beneficial effects in the aforementioned method embodiments, which will not be repeated here.

[0113] In the several embodiments provided in this application, it should be understood that the disclosed devices, equipment and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0114] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0115] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of software functional modules.

[0116] If the integrated module is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0117] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A resonance control method for a multi-valve flexible DC transmission system, characterized in that: The method comprises: Execute the AC voltage control link of the converter station and obtain the corresponding first execution time, and perform delay processing on the controlled voltage of the corresponding converter station input into the AC voltage control link according to the first execution time to obtain the processed controlled voltage; the AC voltage control link obtains the total reference value of the current inner loop according to the voltage outer loop PI controller parameter, the AC voltage reference value and the controlled voltage; Execute the current reference value distribution link and obtain the corresponding second execution time, and perform delay processing on the processed controlled voltage amount according to the second execution time to obtain the voltage feedforward control amount; the current reference value distribution link distributes the total reference value of the current inner loop according to the current distribution coefficient of each converter to obtain the current inner loop reference value of each converter; The product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient is 1, and the current inner loop PI controller parameters of the corresponding converter are calculated according to the voltage outer loop PI controller parameters and the current distribution coefficient; Execute the current control link of each converter; the current control link obtains a voltage modulation wave according to the controlled current of the corresponding converter station, the voltage feedforward control amount, the current inner loop PI controller parameters of the corresponding converter and the current inner loop reference value to modulate the corresponding converter.

2. The resonance control method of a multi-valve flexible DC power transmission system according to claim 1, characterized in that: The AC voltage control link of the converter station includes: Collecting the AC bus voltage of the converter station, performing positive-sequence dq-axis transformation on the AC bus voltage to obtain a positive-sequence voltage d-axis component measurement value and a positive-sequence voltage q-axis component measurement value, and performing negative-sequence dq-axis transformation on the AC bus voltage to obtain a negative-sequence voltage d-axis component measurement value and a negative-sequence voltage q-axis component measurement value; Acquire an AC voltage reference value and a voltage outer loop PI controller parameter; the AC voltage reference value includes a positive sequence voltage d-axis component reference value, a positive sequence voltage q-axis component reference value, a negative sequence voltage d-axis component reference value, and a negative sequence voltage q-axis component reference value; Subtract the positive-sequence voltage d-axis component reference value from the corresponding positive-sequence voltage d-axis component measurement value, and subtract the positive-sequence voltage q-axis component measurement value from the positive-sequence voltage q-axis component reference value, and obtain the positive-sequence current inner-loop total reference value d-axis component and the positive-sequence current inner-loop total reference value q-axis component after passing through the voltage outer-loop PI controller based on the voltage outer-loop PI controller parameters respectively; The negative-sequence voltage d-axis component reference value is subtracted from the corresponding negative-sequence voltage d-axis component measurement value, and the negative-sequence voltage q-axis component reference value is subtracted from the corresponding negative-sequence voltage q-axis component measurement value, and after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters, the negative-sequence current inner loop total reference value d-axis component and the negative-sequence current inner loop total reference value q-axis component are obtained.

3. The resonance control method of a multi-valve flexible DC transmission system according to claim 1, characterized in that: The execution current reference value distribution link includes: When the multi-valve group flexible direct current transmission system is in a steady-state operation mode, the current distribution coefficients of the converters are set to be the same.

4. The resonance control method of a multi-valve flexible DC transmission system according to claim 1, characterized in that: The method further comprises: After executing the current control link of each converter, the AC side impedance of the converter is calculated and output according to the following formula: In the formula, Z P / N represents the AC side impedance of the converter, s is the Laplace operator, L is the equivalent reactance on the AC side, K p_AC K is the proportional coefficient of the voltage outer loop PI controller, p_i K is the proportional coefficient of the current inner loop PI controller, n is the current distribution coefficient of converter n, G vd is the link delay of the voltage outer loop control, G id is the link delay of the current inner loop control, G fd is the link delay of voltage feedforward control, G sv is the equivalent transfer function of voltage sampling processing, G si is the equivalent transfer function of current sampling processing, K d is the dq axis decoupling coefficient, and T is the power frequency period.

5. A resonance control device for a multi-valve flexible DC transmission system, characterized in that: The device comprises: A first execution module is used to execute the AC voltage control link of the converter station and obtain the corresponding first execution time, and perform delay processing on the controlled voltage of the corresponding converter station input into the AC voltage control link according to the first execution time to obtain the processed controlled voltage; the AC voltage control link obtains the total reference value of the current inner loop according to the voltage outer loop PI controller parameters, the AC voltage reference value and the controlled voltage; A second execution module is used to execute the current reference value distribution link and obtain the corresponding second execution time, and to delay the processed controlled voltage amount according to the second execution time to obtain the voltage feedforward control amount; the current reference value distribution link distributes the total reference value of the current inner loop according to the current distribution coefficient of each converter to obtain the current inner loop reference value of each converter; A first calculation module is used to calculate the current inner loop PI controller parameters of the corresponding converter according to the voltage outer loop PI controller parameters and the current distribution coefficient, with the product of the voltage outer loop PI controller proportional coefficient, the current distribution coefficient and the current inner loop PI controller proportional coefficient being 1; The third execution module is used to execute the current control link of each converter; the current control link obtains a voltage modulation wave according to the controlled current of the corresponding converter station, the voltage feedforward control amount, the current inner loop PI controller parameters of the corresponding converter and the current inner loop reference value to modulate the corresponding converter.

6. The resonance control device for a multi-valve flexible DC power transmission system according to claim 5, characterized in that: The first execution module includes: A conversion unit is used to collect the AC bus voltage of the converter station, perform positive sequence dq axis conversion on the AC bus voltage to obtain a positive sequence voltage d axis component measurement value and a positive sequence voltage q axis component measurement value, and perform negative sequence dq axis conversion on the AC bus voltage to obtain a negative sequence voltage d axis component measurement value and a negative sequence voltage q axis component measurement value; An acquisition unit, used to acquire an AC voltage reference value and a voltage outer loop PI controller parameter; the AC voltage reference value includes a positive sequence voltage d-axis component reference value, a positive sequence voltage q-axis component reference value, a negative sequence voltage d-axis component reference value, and a negative sequence voltage q-axis component reference value; A first voltage outer loop control unit, configured to subtract the positive-sequence voltage d-axis component reference value from the positive-sequence voltage d-axis component measurement value, and subtract the positive-sequence voltage q-axis component measurement value from the positive-sequence voltage q-axis component reference value, and obtain the positive-sequence current inner loop total reference value d-axis component and the positive-sequence current inner loop total reference value q-axis component after passing through a voltage outer loop PI controller based on the voltage outer loop PI controller parameters respectively; The second voltage outer loop control unit is used to subtract the corresponding negative-sequence voltage d-axis component measurement value from the negative-sequence voltage d-axis component reference value, and subtract the corresponding negative-sequence voltage q-axis component measurement value from the negative-sequence voltage q-axis component reference value, and obtain the negative-sequence current inner loop total reference value d-axis component and the negative-sequence current inner loop total reference value q-axis component after passing through the voltage outer loop PI controller based on the voltage outer loop PI controller parameters respectively.

7. The resonance control device for a multi-valve flexible DC power transmission system according to claim 5, characterized in that: The second execution module includes: The setting unit is used to set the current distribution coefficients of each converter to be the same when the multi-valve group flexible direct current transmission system is in a steady-state operation mode.

8. The resonance control device for a multi-valve flexible DC power transmission system according to claim 5, characterized in that: The device also includes: The second calculation module is used to calculate and output the AC side impedance of the converter according to the following formula after executing the current control link of each converter: In the formula, Z P / N represents the AC side impedance of the converter, s is the Laplace operator, L is the equivalent reactance on the AC side, K p_AC K is the proportional coefficient of the voltage outer loop PI controller, p_i K is the proportional coefficient of the current inner loop PI controller, n is the current distribution coefficient of converter n, G vd is the link delay of the voltage outer loop control, G id is the link delay of the current inner loop control, G fd is the link delay of voltage feedforward control, G sv is the equivalent transfer function of voltage sampling processing, G si is the equivalent transfer function of current sampling processing, K d is the dq axis decoupling coefficient, and T is the power frequency period.

9. A resonance control device for a multi-valve flexible DC transmission system, characterized in that: include: A memory for storing instructions; wherein the instructions are used to implement the resonance control method of a multi-valve group flexible direct current transmission system according to any one of claims 1 to 4; A processor is used to execute instructions in the memory.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by the processor, the resonance control method for a multi-valve group flexible direct current transmission system according to any one of claims 1 to 4 is implemented.

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