CN115730468A - Method, system and device for hybrid control of direct-current side voltage of network-structured type converter - Google Patents
Method, system and device for hybrid control of direct-current side voltage of network-structured type converter Download PDFInfo
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Abstract
The invention discloses a method, a system and a device for hybrid control of direct-current side voltage of a network-forming type converter, belonging to the field of electric power and comprising the steps of providing a direct-current side voltage hybrid control strategy of a network-forming type converter system, and establishing a transient mathematical model of the network-forming type converter containing a direct-current side voltage hybrid control loop under a synchronous and stable scale; analyzing a stability mechanism by using an equal-area rule according to the established mathematical model, and qualitatively analyzing an influence rule of main parameters; solving the critical fault clearing time (CCT) of the system by using a numerical integration principle, and quantitatively analyzing the influence of different parameters; performing parameter optimization design on the voltage hybrid control loop at the direct current side of the network-structured type converter according to the parameter analysis result; the transient state synchronization mechanism of the network-structured converter under the voltage disturbance of the direct current side can be accurately described, and a feasible control strategy and an optimization scheme are provided for improving the transient state stability of the network-structured converter.
Description
Technical Field
The invention relates to the field of electric power, in particular to a method, a system and a device for hybrid control of direct-current side voltage of a network-type converter.
Background
A large amount of renewable energy is connected into a power grid through a converter, so that the inertia and disturbance resistance of the power grid are greatly reduced, and the challenges are brought to large-scale new energy consumption and safe and stable operation of a power system. The power electronic converter has the characteristics of flexible control and the like, and has the capability of actively supporting, stabilizing voltage and frequency when the power grid is disturbed by controlling the converter, so the power electronic converter is called as a network-forming converter. Through a large amount of accesses of the network-structured type converter, the problem of weak disturbance resistance brought by a low-inertia power system can be solved, and the requirements of rotary spare capacity such as firepower and waterpower of the power system can be greatly reduced.
However, the power electronic converter has weak overcurrent capacity and poor robustness for adapting to complex grid conditions. Due to the limited capacity of the direct current side of the network-structured converter, the quick power support is difficult to realize. When the power grid is in extreme working conditions such as short-circuit fault, the voltage fluctuation of the direct current side causes the stability domain degree of the grid-connected converter to be reduced, and the stability problems such as transient step-out and the like are easy to occur, so that a direct current side voltage control strategy with strong stability is urgently needed to be provided, the research of a transient stability optimization design method is developed, and theoretical guidance is provided for engineering design.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method, a system and a device for hybrid control of the direct-current side voltage of a network-type converter.
The purpose of the invention can be realized by the following technical scheme:
a voltage hybrid control method for a direct current side of a network type converter is characterized by comprising the following steps:
establishing a direct-current side voltage hybrid control strategy based on a topological structure and system parameters of the network-structured converter;
constructing a direct-current side equivalent dynamic equation of the network-structured type converter based on the dynamic characteristics of the direct-current side capacitor circuit; constructing a power control loop of the network-building type converter based on each angular frequency output in the topological structure; based on the transmission characteristics of the two-port network, an output active power equation and an output reactive power equation of the converter are established; constructing a transient mathematical model of the network-forming type converter under a synchronous stable scale by combining a direct-current side equivalent dynamic equation, a power control loop of the network-forming type converter and a converter output active power and reactive power equation;
determining a change curve of reference active power through a transient mathematical model of the network-forming type converter, and analyzing the influence of a change curve determination parameter on the transient stability of the network-forming type converter based on an equal area rule;
calculating the critical fault clearing time of the current transformer under different parameter perturbation by a numerical integration method;
aiming at improving the transient stability of the converter, the direct-current side voltage hybrid control strategy is adjusted based on the influence of each parameter on the transient stability of the grid-type converter and the critical fault clearing time of the converter.
Further, the direct current side voltage hybrid control strategy adopts the error-free control on the direct current side voltage deviation value, the output value is fed back to the reference angular frequency value and the reference active power value respectively, the reference angular frequency value is obtained by multiplying the output value by the proportionality coefficient 1-K (K is more than or equal to 0 and less than or equal to 1), and the reference active power value is obtained by multiplying the output value by the proportionality coefficient K and the reference direct current side voltage value.
Further, the construction of the direct-current side equivalent dynamic equation of the network-type converter comprises the following steps:
the mathematical model of the DC side voltage hybrid control link is shown as the following formula:
wherein, the first and the second end of the pipe are connected with each other,
and U dc Respectively a reference DC side voltage and an actually measured voltage, K p1 And K i1 Representing proportional and integral coefficients of PI control loop at DC side, K is mixed coefficient, P 0 The reference active power is output by the direct current side voltage control loop;
considering the dynamic characteristics of the dc-side capacitance circuit, the mathematical model can be established as follows:
wherein i c Is a direct side capacitor current i in And i out Respectively representing input and output currents on the direct current side; i.e. i d Is the current flowing through the DC side crowbar circuit, C dc Is the dc side capacitance;
based on the formula (2), the direct-current side equivalent dynamic equation of the network-type converter can be obtained:
wherein, P in And P out Representing input active power and output active power, P d Is crowbar power loss, generally regardless of crowbar power loss, i.e. P d ＝0；J DC Defined as the equivalent inertia coefficient of the converter, the value of which is equal to C dc U2 dc/P rated And a DC side capacitor U dc And its rated capacity P rated Correlation; neglecting the power loss of the converter switch tube, the input active power of the converter DC side is equal to the output active power of the converter AC side, i.e. P out ＝P em ＝T em ω 0 。
Further, the power control loop of the mesh type converter may be represented as:
wherein ω is 0 Is the reference angular frequency value, ω 1 Is the angular frequency, ω, of the VSG power loop output 2 Is the angular frequency, omega, of the VSG DC side voltage hybrid control output II Is the total angular frequency of the VSG, theta represents the phase angle, T 0 As a reference torque T em Is an electromagnetic torque, J and D p Representing inertia and damping coefficient, respectively.
Further, the construction of the converter output active and reactive power equation comprises the following steps:
using the phase angle of the power grid as a reference coordinate system, defining delta as the phase angle difference between the network-forming type converter and the power grid
Considering that the voltage-current inner loop has a fast response speed, it can be assumed that the dynamic process of the voltage-current inner loop can be ignored, and the relationship between the port voltage and the output current of the grid-type converter is obtained as shown in the following formula
V abc ＝G(s)E abc -Z(s)i abc (6)
Wherein V abc Is the voltage after the filter, G(s) E abc Is the equivalent internal potential of the current transformer, i abc The current value of the converter is output, and Z(s) is equivalent impedance considering inner loop control and line impedance;
according to the transmission characteristics of the two-port network, the converter outputs active power and reactive power
Wherein G is eq ＝R eq /(R2 eq+X2 eq)，B eq ＝-X eq /(R2 eq+X2 eq)；X eq And R eq Is an equivalent impedance Z eq Conductance and susceptance.
Further, the reference active power may be expressed as:
further, the method for calculating the critical fault clearing time of the converter under different parameter perturbations by using a numerical integration method comprises the following steps:
the condition for the calculation of the critical fault clearing time is
By substituting formula (9) for formula (10)
The above equation can be solved by a numerical calculation method; when delta max ＝δ u Then, the delta of the current transformer is obtained c Cutting off the angle delta for critical faults cr (ii) a The critical fault removing angle is substituted into formula (4) to obtain the critical fault removing time t cr As shown in the following formula:
the application also provides a network-forming type converter direct-current side voltage hybrid control system, which comprises the following modules:
a control module: establishing a direct-current side voltage hybrid control strategy based on a topological structure and system parameters of the network-structured converter;
the networking type converter transient mathematical model building module comprises: constructing a direct-current side equivalent dynamic equation of the network-structured type converter based on the dynamic characteristics of the direct-current side capacitor circuit; constructing a power control loop of the network-structured type converter based on each angular frequency output in the topological structure; based on the transmission characteristics of the two-port network, an equation of the active power and the reactive power output by the converter is established; constructing a transient mathematical model of the network-forming type converter under a synchronous stable scale by combining a direct-current side equivalent dynamic equation, a power control loop of the network-forming type converter and a converter output active power and reactive power equation;
a parameter analysis module: determining a change curve of reference active power through a transient mathematical model of the network-forming type converter, and analyzing the influence of parameters on the transient stability of the network-forming type converter based on an equal-area rule to determine the influence of parameters;
a fault analysis module: calculating critical fault clearing time of the current transformer under different parameter perturbation through a numerical integration method;
a feedback module: and adjusting a DC side voltage hybrid control strategy in the control module based on parameter analysis results of the parameter analysis module and the fault analysis module.
The present application also proposes a storage medium, in which a computer-executable program is stored, and the computer-executable program is used for implementing the method for hybrid controlling dc-side voltage of a grid-type converter as described in any one of the above.
The present application further proposes a control device comprising:
at least one memory for storing a program;
at least one processor, configured to load the program to execute the method for hybrid control of dc-side voltage of a grid-type converter as described in any one of the above embodiments.
The invention has the beneficial effects that:
according to the method, the voltage deviation of the direct current side is fed back to the reference active power sum, a network-forming type converter transient mathematical model containing a direct current side voltage control link under a synchronous and stable scale is established, and a stability influence mechanism of the direct current side voltage control on a converter is qualitatively analyzed; and then, quantitatively analyzing the influence rules of different parameters by using the critical fault clearing time, and providing reference for the optimization design of the voltage control parameters of the direct current side. The network-building type converter after the optimization design has stronger stability capability, and the safe and stable operation of the converter is ensured.
Drawings
The invention will be further described with reference to the accompanying drawings.
Fig. 1 is a diagram of a dc side control topology of a network-type converter;
FIG. 2 is a block diagram of a hybrid control of the DC side voltage of the network-forming type converter;
fig. 3 is a diagram of analyzing the influence mechanism of the dc side voltage hybrid control on the transient stability of the grid-type converter based on the equal area rule;
FIG. 4 is a result of perturbation influence quantitative analysis of key parameters of a network-forming type converter;
FIG. 5 is a flow chart of the steps performed by the disclosed method;
fig. 6 is a comparison graph of simulation results of the network-forming type converter before and after control parameter optimization design.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description herein, references to the description of "one embodiment," "an example," "a specific example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
For ease of understanding, the present disclosure sets forth the following power electronic converter control architecture to illustrate the concepts of the present disclosure, the hardware architecture and control architecture of the converter involved in electricity is shown in fig. 1. The hardware structure of the converter comprises a direct current micro source and a DC/AC converter for converting electric energy. The direct current micro source includes, but is not limited to, a direct current type power source such as an energy storage battery and a photovoltaic panel. The direct current input is converted into alternating current through a DC/AC converter and is connected to a public bus. The output end of the DC/AC converter is connected with an LC filter inductance capacitor; the power electronic converter control structure mainly comprises a direct current side voltage control module, a power control module, a voltage control module, a current control module and a pulse width modulation/driving module. The voltage stabilization control of the direct current side is realized by collecting the voltage input voltage control loop of the direct current side of the converter; acquiring port voltage and output current of a converter, calculating to obtain input active power and reactive power, and respectively obtaining a control phase angle and a reference voltage amplitude value through an active power loop and a reactive power control loop; the voltage control module realizes no-difference tracking on the reference voltage through the PI control loop and outputs a reference current value; the current control module controls the output current amplitude of the converter, and the no-difference tracking is realized through a given current reference value through a PI control loop; the pulse width modulation and/or driving module generates a modulation signal to drive switching devices such as IGBTs.
Step 1: the embodiment of the disclosure first obtains a topology structure and system parameters of a network-based converter, and a control structure of the network-based converter is shown in fig. 1. For the problem of dynamic control of the dc side voltage, a dc side voltage hybrid control strategy is proposed, and a control block diagram and a topology structure of a power control loop are shown in fig. 2. The direct-current side voltage hybrid control strategy comprises the following steps:
and the direct-current side voltage deviation value is subjected to PI control to realize no-difference control, and the output values are respectively fed back to the reference angular frequency value and the reference active power value. And the reference angular frequency value is the output value multiplied by the proportionality coefficient 1-K (K is more than or equal to 0 and less than or equal to 1), and the reference active power value is the output value multiplied by the proportionality coefficient K and the reference direct current side voltage value, so that the direct current side voltage hybrid control is realized.
Step 2: before establishing a networking type converter transient model under a synchronous stable scale, considering that the transient response of the networking type converter is mainly dynamically determined by a power control loop, the voltage and current control loop can quickly reach a stable state, namely a converter endMouth voltage V abc Is equal to the reference voltage value E q Output current I dq Equal to the converter reference current value I dq . The mathematical model of the DC side voltage hybrid control link is shown as the following formula:
wherein, P 0 A reference active power output by the direct current side voltage control loop;
and U dc Respectively a reference DC side voltage and an actually measured voltage, K p1 And K i1 And K represents the proportional and integral coefficients of the PI control loop on the direct current side, and is a mixed coefficient. Considering the dynamic characteristics of the dc-side capacitance circuit, the mathematical model can be established as follows:
wherein i c Is a direct side capacitor current i in And i out Respectively representing input and output currents on the DC side, C dc Is the dc side capacitance. i.e. i d Is the current flowing through the dc-side crowbar circuit. Based on the formula (2), the direct-current side equivalent dynamic equation of the network-type converter can be obtained:
wherein, P in And P out Representing input active power and output active power, P d Is crowbar power loss, generally regardless of crowbar power loss, i.e. P d ＝0。J DC Defined as the equivalent inertia coefficient of the converter, the value of which is equal to C dc U2 dc/P rated And a DC side capacitor U dc And its rated capacity P rated And (4) correlating. Neglecting power loss of converter switch tubeThe input active power at the DC side of the converter is equal to the output active power at the AC side, i.e. P out ＝P em ＝T em ω 0 。
The power control loop of a network-type converter can be represented as:
wherein ω is 0 Is the reference angular frequency value, ω 1 Is the angular frequency, ω, of the VSG power loop output 2 Is the angular frequency, omega, of the VSG DC side voltage hybrid control output II Is the total angular frequency of the VSG, theta represents the phase angle, T em Is an electromagnetic torque, T 0 Is the reference torque. J and D p Representing inertia and damping coefficient, respectively. Using the phase angle of the power grid as a reference coordinate system, defining delta as the phase angle difference between the network-forming type converter and the power grid
Considering that the voltage-current inner loop has a fast response speed, it can be assumed that the dynamic process of the voltage-current inner loop can be ignored, and the relationship between the port voltage and the output current of the grid-type converter is obtained as shown in the following formula
V abc ＝G(s)E abc -Z(s)i abc (6)
Wherein V abc Is the voltage after the filter, G(s) E abc Is the equivalent internal potential of the current transformer, i abc The current transformer output current value, and Z(s) is equivalent impedance considering inner loop control and line impedance. According to the transmission characteristics of the two-port network, the converter outputs active power and reactive power
Wherein, G eq ＝R eq /(R2 eq+X2 eq)，B eq ＝-X eq /(R2 eq + X2 eq). E is a current transformerEffective value of port voltage, V g Is the equivalent voltage value of the power grid. X eq And R eq Is an equivalent impedance Z eq Conductance and susceptance. The transient mathematical model of the network-type converter under the synchronous stable scale can be obtained according to the formulas (3), (4) and (7)
And 3, step 3: according to the transient mathematical model of the network-structured converter established in the step 2, the transient synchronous stability of the converter is mainly determined by a direct-current side voltage control loop and a power control loop. According to the equation (8), the DC side voltage control loop will output the reference active power P 0 . Therefore, the influence of the dc side voltage control loop on the grid-type converter is mainly reflected in the change of the reference active power, and the mathematical relationship thereof satisfies the formula (9).
When the grid fails, the converter output active power curve changes from curve I to curve II, as shown in fig. 3. Active power P em The reduction of the reference active power will cause the imbalance of the input and output power of the capacitor at the direct current side, and further cause the reference active power P 0 Increasing as shown by the dashed line in fig. 3. An increase in reference active compared to a constant reference active will result in an acceleration area from S 1 Increase to S 1 +S 3 . When the grid fault is clear, the active output curve of the converter is changed from curve II to curve III. At the moment, the converter outputs active power larger than rated active power, the converter enters a speed reduction state, and the speed reduction area of the converter is S 2 +S 4 . From the above analysis, it can be seen that the dc-side voltage control will cause the acceleration area of the grid-type converter to increase when the grid fails, thereby deteriorating the stability of the converter, and the degree of deterioration and the influence of specific parameters are mainly determined by equation (9). The key parameter C in the formula (9) can be corrected by a numerical integration method dc 、K p1 And K i1 Is analyzed for the effect of (A), the analysis result is as followsShown in table 1.
TABLE 1 influence of key parameters on transient stability of network-type converter
And 4, step 4: and (4) calculating the critical fault clearing time of the current transformer under different parameter perturbations by using a numerical integration method according to the conclusion obtained by the qualitative analysis in the step (2). The condition for the calculation of the critical fault clearing time is
By substituting formula (9) for formula (10)
The above equation can be solved by numerical calculation. When delta max ＝δ u Then, the delta of the current transformer is obtained c Cutting off the angle delta for critical faults cr . The critical failure cutting angle is substituted for the formula (4) to obtain the critical failure cutting time t cr The following formula is shown below.
And 5: according to the quantitative analysis result based on the critical fault clearing time in the step 3, K is known p And K i The increase of the parameter will deteriorate the stability of the system, and the increase of the size of the DC side capacitor is beneficial to the stability of the system. And optimally designing the voltage control parameters of the direct current side of the network-structured type converter according to the analysis result, and enhancing the transient stability of the converter.
Fig. 6 is a comparison graph of phase plane simulation results of different control parameters of the grid-type converter when the grid voltage of 1s drops to 30% and the fault is removed in 1.3s according to the embodiment. It can be known from the observation of the figure that the network-forming type converter after parameter optimization can return to a stable operation state after the fault is removed, and the converter under the control of the direct-current side voltage feedback active power or feedback reference angular frequency has the transient synchronous instability problem, so that the effectiveness and the accuracy of the provided direct-current side voltage hybrid control strategy and the optimization design method thereof are verified.
The embodiment of the invention also discloses a voltage hybrid control system at the direct current side of the network-structured type converter, which comprises the following modules:
a control module: establishing a direct-current side voltage hybrid control strategy based on a topological structure and system parameters of the network-structured converter;
the networking type converter transient mathematical model building module comprises: constructing a direct-current side equivalent dynamic equation of the network-type converter based on the dynamic characteristics of the direct-current side capacitor circuit; constructing a power control loop of the network-structured type converter based on each angular frequency output in the topological structure; based on the transmission characteristics of the two-port network, an equation of the active power and the reactive power output by the converter is established; constructing a transient mathematical model of the network-forming type converter under a synchronous stable scale by combining a direct-current side equivalent dynamic equation, a power control loop of the network-forming type converter and a converter output active power and reactive power equation;
a parameter analysis module: determining a change curve of reference active power through a transient mathematical model of the network-forming type converter, and analyzing the influence of parameters on the transient stability of the network-forming type converter based on an equal-area rule to determine the influence of parameters;
a fault analysis module: calculating critical fault clearing time of the current transformer under different parameter perturbation through a numerical integration method;
a feedback module: and adjusting a DC side voltage hybrid control strategy in the control module based on parameter analysis results of the parameter analysis module and the fault analysis module.
The embodiment of the invention also discloses a control device, which is used for operating the database storage process, wherein the method for controlling the voltage mixing of the direct current side of the network-type converter is implemented when the database storage process is operated.
The embodiment of the invention also discloses a computer storage medium, which comprises a storage database storage process, wherein when the storage database storage process runs, the equipment where the storage medium is located is controlled to execute the method for controlling the voltage mixing at the direct current side of the network-structured converter.
In the context of this disclosure, a computer storage medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The foregoing shows and describes the general principles, principal features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.
Claims (10)
1. A voltage hybrid control method for a direct current side of a network-structured converter is characterized by comprising the following steps:
establishing a direct-current side voltage hybrid control strategy based on a topological structure and system parameters of the network-structured converter;
constructing a direct-current side equivalent dynamic equation of the network-type converter based on the dynamic characteristics of the direct-current side capacitor circuit; constructing a power control loop of the network-building type converter based on each angular frequency output in the topological structure; based on the transmission characteristics of the two-port network, an equation of the active power and the reactive power output by the converter is established; constructing a transient mathematical model of the network-forming type converter under a synchronous stable scale by combining a direct-current side equivalent dynamic equation, a power control loop of the network-forming type converter and a converter output active power and reactive power equation;
determining a change curve of reference active power through a transient mathematical model of the network-forming type converter, and analyzing the influence of a change curve determination parameter on the transient stability of the network-forming type converter based on an equal area rule;
calculating critical fault clearing time of the current transformer under different parameter perturbation through a numerical integration method;
aiming at improving the transient stability of the converter, the direct-current side voltage hybrid control strategy is adjusted based on the influence of each parameter on the transient stability of the grid-type converter and the critical fault clearing time of the converter.
2. The method as claimed in claim 1, wherein the dc-side voltage hybrid control strategy adopts a direct-side voltage deviation value with a homodyne control, the output values are fed back to a reference angular frequency value and a reference active power value respectively, the reference angular frequency value is the output value multiplied by a scaling factor 1-K (0 ≤ K ≤ 1), and the reference active power value is the output value multiplied by a scaling factor K and a reference dc-side voltage value.
3. The method for hybrid control of the direct current side voltage of the grid-structured type converter according to claim 1, wherein the construction of the direct current side equivalent dynamic equation of the grid-structured type converter comprises the following steps:
the mathematical model of the DC side voltage hybrid control link is shown as the following formula:
wherein the content of the first and second substances,
and U dc Respectively a reference DC side voltage and an actually measured voltage, K p1 And K i1 Representing proportional and integral coefficients of PI control loop at DC side, K is mixed coefficient, P 0 The reference active power is output by the direct current side voltage control loop;
considering the dynamic characteristics of the dc-side capacitance circuit, the mathematical model can be established as follows:
wherein i c Is a direct side capacitor current i in And i out Respectively representing input and output currents on the direct current side; i.e. i d Is a current flowing through a DC side crowbar circuit, C dc Is the dc side capacitance;
based on the formula (2), the direct-current side equivalent dynamic equation of the network-type converter can be obtained:
wherein, P in And P out Representing input active power and output active power, P d Is crowbar power loss, generally regardless of crowbar power loss, i.e. P d ＝0；J DC Defined as the equivalent inertia coefficient of the converter, the value of which is equal to C dc U2 dc/P rated And a DC side capacitor U dc And its rated capacity P rated Correlation; neglecting the power loss of the converter switch tube, the input active power of the converter DC side is equal to the output active power of the converter AC side, i.e. P out ＝P em ＝T em ω 0 。
4. The method of claim 3, wherein the power control loop of the grid type converter is represented by:
wherein ω is 0 Is the reference angular frequency value, ω 1 Is the angular frequency, ω, of the VSG power loop output 2 Is the angular frequency, omega, of the VSG DC side voltage hybrid control output II Is the total angular frequency of the VSG, theta represents the phase angle, T 0 As a reference torque T em Is an electromagnetic torque, J and D p Representing inertia and damping coefficient, respectively.
5. The method for hybrid control of the direct current side voltage of the grid-structured converter according to claim 4, wherein the construction of the converter output active and reactive power equation comprises the following steps:
using the phase angle of the power grid as a reference coordinate system, defining delta as the phase angle difference between the network-forming type converter and the power grid
Considering that the voltage-current inner loop has a fast response speed, it can be assumed that the dynamic process of the voltage-current inner loop can be ignored, and the relationship between the port voltage and the output current of the grid-type converter is obtained as shown in the following formula
V abc ＝G(s)E abc -Z(s)i abc (6)
Wherein V abc Is the voltage after the filter, G(s) E abc Is the equivalent internal potential of the current transformer, i abc The current value of the converter is output, and Z(s) is equivalent impedance considering inner loop control and line impedance;
according to the transmission characteristics of the two-port network, the converter outputs active power and reactive power
Wherein G is eq ＝R eq /(R2 eq+X2 eq)，B eq ＝-X eq /(R2 eq+X2 eq)；X eq And R eq Is an equivalent impedance Z eq Conductance and susceptance.
6. The method for hybrid control of the dc-side voltage of the grid-type converter according to claim 5, wherein the reference active power is represented by:
7. the method for controlling the voltage on the direct current side of the grid-type converter in a hybrid manner according to claim 6, wherein the method for calculating the critical fault clearing time of the converter under different parameter perturbation conditions through a numerical integration method comprises the following steps:
the condition for the calculation of the critical fault clearing time is
By substituting formula (9) for formula (10)
The above equation can be solved by a numerical calculation method; when delta max ＝δ u Then, the delta of the current transformer is obtained c Cutting off the angle delta for critical faults cr (ii) a The critical fault removing angle is substituted into formula (4) to obtain the critical fault removing time t cr As shown in the following formula:
8. a grid-type converter direct-current side voltage hybrid control system is characterized by comprising the following modules:
a control module: establishing a direct-current side voltage hybrid control strategy based on a topological structure and system parameters of the network-structured converter;
the networking type converter transient mathematical model building module comprises: constructing a direct-current side equivalent dynamic equation of the network-type converter based on the dynamic characteristics of the direct-current side capacitor circuit; constructing a power control loop of the network-structured type converter based on each angular frequency output in the topological structure; based on the transmission characteristics of the two-port network, an output active power equation and an output reactive power equation of the converter are established; constructing a transient mathematical model of the network-forming type converter under a synchronous and stable scale by combining a direct-current side equivalent dynamic equation, a power control loop of the network-forming type converter and a converter output active and reactive power equation;
a parameter analysis module: determining a change curve of reference active power through a transient mathematical model of the network-forming type converter, and analyzing the influence of parameters on the transient stability of the network-forming type converter based on an equal-area rule to determine the influence of parameters;
a fault analysis module: calculating critical fault clearing time of the current transformer under different parameter perturbation through a numerical integration method;
a feedback module: and adjusting a DC side voltage hybrid control strategy in the control module based on parameter analysis results of the parameter analysis module and the fault analysis module.
9. A storage medium having stored therein a computer-executable program which, when executed by a processor, is configured to implement the method of hybrid dc-side voltage control of a network type converter according to any one of claims 1 to 7.
10. A control device, comprising:
at least one memory for storing a program;
at least one processor configured to load the program to perform the method of hybrid control of dc-side voltage of a grid-type converter according to any one of claims 1 to 7.
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| CN117239776A (en) * | 2023-08-25 | 2023-12-15 | 国网湖北省电力有限公司电力科学研究院 | Target area voltage sag control method, device, system and medium |
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| CN117239776A (en) * | 2023-08-25 | 2023-12-15 | 国网湖北省电力有限公司电力科学研究院 | Target area voltage sag control method, device, system and medium |
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