Superconducting phase modifier excitation power unit with adjustable top value voltage and control method thereof

Abstract

The invention discloses a superconductive phase modifier excitation power unit with adjustable top value voltage and a control method thereof, and the power unit comprises the following modules which are connected in sequence: the input end of a PWM rectifier module is connected with an excitation power supply, and AC / DC conversion is carried out on the input voltage of the excitation power supply; the DC bus support capacitor module realizes output DC voltage support of the PWM rectifier module; the DC chopper module realizes DC / DC chopping output of the DC bus voltage according to the excitation requirement of the generator; the voltage smoothing module is used for smoothing and filtering the chopping pulse voltage output by the direct current chopper module; and the output end of the voltage commutation module is connected with the superconducting rotor and is used for realizing rectification of rotor excitation current and conversion of an inversion loop. According to the technical scheme, the excitation voltage and the excitation current can be adjusted stably in the steady state, the effect of the high excitation multiple can be exerted in the transient state and the dynamic state to improve the quick response capacity of the system, and meanwhile the excitation inversion capacity is achieved to achieve quick reduction of the excitation current.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical engineering, and particularly relates to a superconducting synchronous condenser excitation power unit with adjustable peak voltage and a control method thereof. Background Art

[0002] With the continuous and rapid development of new energy sources such as wind power and photovoltaic power in China and the continuous expansion of the construction scale of the UHV transmission network, the demand for reactive power in the power system is increasing day by day. To solve the problems of high-proportion new energy consumption and the stability of the UHV AC / DC hybrid power grid, synchronous condensers have been developed and applied rapidly. Compared with reactive power compensation devices such as SVC and STATCOM, synchronous condensers have stronger voltage support capabilities.

[0003] Compared with synchronous condensers using traditional conductors, superconducting synchronous condensers have the characteristics of high current density and low resistance loss, which can greatly improve the efficiency of the motor and simultaneously greatly reduce the volume and weight of the motor. At the same time, the stator of the superconducting motor can adopt a non-magnetic tooth structure, and the physical air gap of the motor is very large. Therefore, the synchronous reactance of the superconducting synchronous condenser is greatly reduced, and the reactive power regulation range is wider, which can better meet the requirements of grid voltage support and dynamic reactive power compensation.

[0004] The rotor winding of the superconducting synchronous condenser operates in a superconducting state with a very small resistance. Compared with conventional units, it has an extremely low rated excitation voltage and an extremely long time constant. Therefore, compared with the excitation system of conventional units, on the one hand, the superconducting synchronous condenser excitation system needs to ensure the control accuracy of the low excitation voltage during steady-state operation. On the other hand, during the voltage regulation process and under the strong excitation condition, in order to reduce the regulation time, it is also necessary to have an excitation voltage boost ratio output capacity of 200 times or more to achieve dynamic and rapid regulation.

[0005] Some related research uses a traditional thyristor excitation system to achieve the output of the boost voltage by raising the secondary voltage of the excitation transformer. The problems brought by this method are that during the steady-state operation of the synchronous condenser, due to the overall gain of the excitation system being too large and the triggering angle of the control excitation system changing within a very small range close to 90°, the overall regulation quality of the system is affected. On the other hand, if the high excitation voltage boost ratio is not properly controlled, it is very easy to have control overshoot.

[0006] To address this issue, some studies have proposed a combined excitation method that switches between a high-voltage and a low-voltage double-set excitation power circuit. During steady-state operation, the low-voltage excitation circuit is used, and when strong excitation is required, it switches to the high-voltage excitation circuit. This solution brings problems such as a complex structure of the excitation power circuit and reduced control reliability. The high-voltage excitation circuit is designed to provide strong excitation voltage using uncontrolled diode rectification, and the strong excitation ability cannot be dynamically adjusted according to the strong excitation requirements of the synchronous condenser. At the same time, this solution cannot achieve the inversion and feedback of excitation energy to the AC side. When the excitation system reduces magnetization, the energy of the superconducting rotor winding is fed back to a large-capacity capacitor or dissipated through a power-consuming resistor, making the system equipment configuration and control complex and reducing the reliability of excitation demagnetization.

[0007] For the application requirements of superconducting synchronous condensers, it is necessary to study an excitation power unit solution with a simple topology structure and control method, which can not only make the regulation of the excitation voltage and current target values stable during steady state, but also play the role of a high strong excitation multiple to improve the fast response ability during transient and dynamic processes. At the same time, it also needs to have the ability of excitation inversion to quickly reduce the excitation current. Summary of the Invention

[0008] The object of the present invention is to provide a superconducting synchronous condenser excitation power unit with adjustable peak voltage and its control method, which can make the excitation voltage and excitation current regulation stable during steady state, and can also play the role of a high strong excitation multiple to improve the fast response ability of the system during transient and dynamic processes. At the same time, it also has the ability of excitation inversion to quickly reduce the excitation current.

[0009] To achieve the above object, the solution of the present invention is:

[0010] A superconducting synchronous condenser excitation power unit with adjustable peak voltage includes a PWM rectifier module, a DC bus support capacitor module, a DC chopper module, a voltage smoothing module, and a voltage commutation module connected in sequence;

[0011] The input end of the PWM rectifier module is connected to the excitation power supply to perform AC / DC conversion on the input voltage of the excitation power supply;

[0012] The DC bus support capacitor module is connected between the PWM rectifier module and the DC chopper module to achieve the support of the DC voltage output by the PWM rectifier module;

[0013] The DC chopper module performs DC / DC chopping output of the DC bus voltage according to the excitation needs of the generator;

[0014] The voltage smoothing module is used to smooth and filter the chopped pulse voltage output by the DC chopper module;

[0015] The output end of the said voltage commutation module is connected to the superconducting rotor, which is used to realize the rectification of the rotor excitation current and the conversion of the inverter circuit.

[0016] The above PWM rectifier module adopts a three-phase voltage source converter based on IGBT.

[0017] The above DC chopper module adopts an H-bridge DC converter based on IGBT.

[0018] The above DC chopper module realizes the DC / DC chopping output of the DC bus voltage according to the excitation needs of the generator, including realizing the positive level, zero level and negative level output through the on-off control of IGBT;

[0019] The normal excitation is realized by adopting the combination mode of positive level and zero level, and the regulation between 0 and the excitation peak voltage is output; the inverter control is carried out by adopting the combination mode of zero level and negative level to realize the fast and strong reduction of excitation.

[0020] The above voltage smoothing module includes a positive series inductor, a negative series inductor and a parallel capacitor. Among them, one end of the positive series inductor is connected to the positive output of the DC chopper module, and the other end is connected to the positive pole of the parallel capacitor; one end of the negative series inductor is connected to the negative output of the DC chopper module, and the other end is connected to the negative pole of the parallel capacitor.

[0021] The above voltage commutation module includes a first switch tube, a second switch tube, a first diode to a fourth diode. Among them, the collector of the first switch tube is connected to the positive output of the voltage smoothing module, and the emitter is connected to the positive pole of the superconducting rotor; the collector of the second switch tube is connected to the negative pole of the superconducting rotor, and the emitter is connected to the negative output of the voltage smoothing module; the first diode and the second diode are respectively reversely connected in parallel at both ends of the first switch tube and the second switch tube; the cathode of the third diode is connected to the positive output of the voltage smoothing module, and the anode is connected to the negative pole of the superconducting rotor; the cathode of the fourth diode is connected to the positive pole of the superconducting rotor, and the anode is connected to the negative output of the voltage smoothing module.

[0022] A control method for the excitation power unit of a superconducting synchronous condenser with adjustable peak voltage as described above includes,

[0023] When the excitation power unit outputs a positive excitation voltage, control the voltage commutation module to be in the rectification working state;

[0024] When the excitation power unit outputs a negative excitation voltage, control the voltage commutation module to be in the inversion working state.

[0025] The above voltage commutation module includes a first switching tube, a second switching tube, a first diode to a fourth diode. Among them, the collector of the first switching tube is connected to the positive output of the voltage smoothing module, and the emitter is connected to the positive pole of the superconducting rotor; the collector of the second switching tube is connected to the negative pole of the superconducting rotor, and the emitter is connected to the negative output of the voltage smoothing module; the first diode and the second diode are respectively reversely connected in parallel at both ends of the first switching tube and the second switching tube; the cathode of the third diode is connected to the positive output of the voltage smoothing module, and the anode is connected to the negative pole of the superconducting rotor; the cathode of the fourth diode is connected to the positive pole of the superconducting rotor, and the anode is connected to the negative output of the voltage smoothing module;

[0026] When the excitation power unit outputs a positive excitation voltage, the first switching tube and the second switching tube are controlled to be in the on state;

[0027] When the excitation power unit outputs a negative excitation voltage, the first switching tube and the second switching tube are controlled to be in the off state.

[0028] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the steps of the control method described above are implemented.

[0029] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the steps of the control method described above are implemented.

[0030] After adopting the above solution, the topological structure of the present invention is simple. By controlling the DC output voltage amplitude of the PWM rectifier module, the adjustable top value voltage of the excitation system is realized. It can achieve high-precision control of the steady-state excitation voltage and excitation current and high excitation multiple output of the excitation voltage during strong excitation; at the same time, it can also realize the fast inversion of the excitation energy to the AC power supply. The steady-state and strong excitation control in the excitation system of the present invention adopt the same loop, and the overall structure of the system is simple, which is beneficial to engineering applications. Finally, it can fully exert the effects of high excitation voltage strong excitation multiple to strongly increase the excitation current and inversion to strongly decrease the excitation current, and improve the fast response ability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a structural block diagram of an excitation power unit of a superconducting synchronous condenser with adjustable top value voltage according to the present invention;

[0032] Figure 2 is a schematic structural diagram of an embodiment of an excitation power unit of a superconducting synchronous condenser with adjustable top value voltage according to the present invention;

[0033] Reference numerals in the figure: 1 - PWM rectifier module; 2 - DC bus support capacitor module; 3 - DC chopper module; 4 - voltage smoothing module; 5 - voltage commutation module; 6 - superconducting rotor. Specific Embodiments

[0034] The technical solutions and beneficial effects of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0035] As Figure 1 shown, the present invention provides a superconducting synchronous condenser excitation power unit with adjustable peak voltage, including a PWM rectifier module, a DC bus support capacitor module, a DC chopper module, a voltage smoothing module, and a voltage commutation module connected in sequence; wherein,

[0036] The PWM rectifier module realizes the AC / DC conversion of the excitation power supply, and the amplitude of the DC output voltage is controllable;

[0037] The DC bus support capacitor module realizes the support of the DC voltage output by the PWM rectifier module;

[0038] The DC chopper module realizes the DC / DC chopped output of the DC bus voltage according to the excitation needs of the generator;

[0039] The voltage smoothing module realizes the smoothing and filtering of the chopped pulse voltage output by the DC chopper;

[0040] The voltage commutation module realizes the conversion of the rectification and inversion circuits of the rotor excitation current.

[0041] As a preferred embodiment of the present invention, as Figure 2 shown, the PWM rectifier module 1 adopts a three-phase voltage source converter based on IGBT to realize the ACDC conversion of the AC excitation voltage and output a DC voltage with controllable amplitude. This DC voltage provides a DC power supply for the DC chopper module 3, and the amplitude of the DC voltage is the peak excitation voltage that the excitation power unit can output. During steady-state operation, by controlling the output DC voltage to a small value, such as 2 times the rated excitation voltage, high-precision control of the excitation voltage can be achieved; during excitation boosting, quickly adjust the target value of the output DC voltage to dynamically increase the peak excitation voltage, such as 200 times the rated excitation voltage, to achieve a significant increase in the excitation boosting multiple.

[0042] The DC chopper module 3 adopts an H-bridge DC converter based on IGBT. By controlling the on-off of IGBT, positive level, zero level, and negative level outputs can be achieved. The normal excitation is realized by combining the positive level and zero level, and the regulation between 0 and the excitation peak voltage is achieved. For example, when the peak excitation voltage is 2 times the rated excitation voltage, the duty cycle of the positive level is controlled to be 50%, and the duty cycle of the zero level is 50%, then the average value of the output excitation voltage is the rated excitation voltage; when the peak excitation voltage is 200 times the rated excitation voltage, the duty cycle of the positive level is controlled to be 100%, then the output excitation voltage is 200 times the rated excitation voltage, realizing the strong excitation output of the excitation voltage. The zero level and negative level are combined for inverter control to achieve rapid strong reduction and extinction of magnetization. For example, when the peak excitation voltage is 200 times the rated excitation voltage, the duty cycle of the negative level is controlled to be 100%, then the excitation energy is rapidly inverted through the negative 200 times the rated excitation voltage.

[0043] The voltage smoothing module 4 includes a positive series inductor L1, a negative series inductor L2, and a parallel capacitor C1. Among them, one end of L1 is connected to the positive output of the DC chopper module 3, and the other end is connected to the positive electrode of C1; one end of L2 is connected to the negative output of the DC chopper module 3, and the other end is connected to the negative electrode of C1. The voltage smoothing module 4 can smooth the pulsed square wave output by the DC chopper module 3 into a stable DC excitation voltage, reducing the excitation voltage ripple applied to the superconducting rotor.

[0044] The voltage commutation module 5 includes switching tubes V1, V2, and diodes D1-D4. Among them, the collector of V1 is connected to the positive electrode of C1, and the emitter is connected to the positive electrode of the superconducting rotor 6; the collector of V2 is connected to the negative electrode of the superconducting rotor 6, and the emitter is connected to the negative electrode of C1; D1 and D2 are respectively reversely connected in parallel at both ends of V1 and V2; the cathode of D3 is connected to the positive electrode of C1, and the anode is connected to the negative electrode of the superconducting rotor 6; the cathode of D4 is connected to the positive electrode of the superconducting rotor 6, and the anode is connected to the negative electrode of C1. By controlling the base voltage of V1 and V2, the switching states of V1 and V2 are controlled. Specifically, when the excitation system operates in rectification mode, the switching tubes V1 and V2 are in the on state, realizing the injection of the excitation current from the excitation system into the superconducting rotor; when operating in inversion mode, the switching tubes V1 and V2 are in the off state, and the transmission direction of the excitation energy is from the superconducting rotor through the voltage commutation module, the voltage smoothing module, the DC chopper module, the DC bus support capacitor module, and the PWM rectifier module to the AC power supply. The excitation current on the superconducting rotor inductor continues to flow through D3 and D4, realizing the flow of the excitation current from the superconducting rotor into the voltage smoothing module. During this process, the capacitor voltage always remains positive.

[0045] The embodiment of the present invention also provides a control method for the superconducting synchronous condenser excitation power unit with adjustable peak voltage as described above, including the following controls respectively according to needs:

[0046] When the excitation power unit outputs a positive excitation voltage, the excitation power unit is controlled to operate in a rectification state. The excitation power unit obtains energy from the AC power supply. Under steady state, the PWM rectifier module controls the output voltage of the DC side to be a low voltage, and the DC chopper module adjusts the corresponding control duty cycle according to the excitation control target. By controlling the switching tubes V1 and V2 of the voltage commutation module to be in the on state, the steady-state high-precision control of the excitation voltage and the excitation current is achieved. During strong excitation, the PWM rectifier module controls the output voltage of the DC side to be a high voltage with a controllable amplitude according to the strong excitation requirement of the unit, and the subsequent connected modules are used to achieve the output of a high strong excitation multiple of the excitation voltage.

[0047] When the excitation power unit outputs a negative excitation voltage, the excitation power unit is controlled to operate in an inversion state. At this time, the energy flows in the reverse direction, and the switching tubes V1 and V2 of the voltage commutation module are controlled to be in the off state. The energy of the excitation winding flows reversely through each module and is sent back to the AC power supply, thereby realizing the shutdown and field suppression with a rapid decrease in the excitation current.

[0048] The embodiment of the present invention also provides another computer device, including a processor and a memory configured to store a computer program that can run on the processor; wherein, when the processor is configured to run the computer program, it executes the method steps in the foregoing embodiments.

[0049] In practical applications, the above-mentioned processor includes a Field-Programmable Gate Array (FPGA). The processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It can be understood that for different devices, the electronic devices used to implement the functions of the above-mentioned processor can also be others, and the embodiments of the present invention do not make specific limitations.

[0050] The above-mentioned memory can be a volatile memory, such as a Random-Access Memory (RAM); or a non-volatile memory, such as a Read-Only Memory (ROM), a flash memory, a Hard Disk Drive (HDD), or a Solid-State Drive (SSD); or a combination of the above types of memories, and provides instructions and data to the processor.

[0051] In an exemplary embodiment, the embodiment of the present invention also provides a computer-readable storage medium for storing a computer program.

[0052] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program enables the computer to execute the corresponding processes implemented by the processor in each of the methods of the embodiments of the present invention. For the sake of brevity, it will not be described in detail here.

[0053] In several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined, or can be integrated into another system, or some features can be ignored, or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed with each other can be through some interfaces. The indirect coupling or communication connection of devices or units can be electrical, mechanical, or other forms.

[0054] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript.

[0055] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, and the combination of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0056] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the processes in Figure 1One or more processes and / or blocks Figure 1 The functions specified in one block or more blocks.

[0057] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one process Figure 1 One or more processes and / or blocks Figure 1 The steps of the functions specified in one block or more blocks.

[0058] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A superconducting synchronous condenser excitation power unit with adjustable peak voltage, characterized in that: It includes a PWM rectifier module, a DC bus support capacitor module, a DC chopper module, a voltage smoothing module, and a voltage commutation module connected in sequence; The input end of the PWM rectifier module is connected to the excitation power supply, and the input voltage of the excitation power supply is subjected to AC / DC conversion; The DC bus support capacitor module is connected between the PWM rectifier module and the DC chopper module to realize the support of the DC voltage output by the PWM rectifier module; The DC chopper module realizes the DC / DC chopping output of the DC bus voltage according to the excitation requirement of the generator; The voltage smoothing module is used to smooth and filter the chopped pulse voltage output by the DC chopper module; The output end of the voltage commutation module is connected to the superconducting rotor, and is used to realize the rectification of the rotor excitation current and the conversion of the rectification and inversion circuits.

2. The superconducting synchronous condenser excitation power unit with adjustable peak voltage according to claim 1, characterized in that: The PWM rectifier module adopts a three-phase voltage source converter based on IGBT.

3. The field excitation power unit of the superconducting synchronous condenser with adjustable peak voltage as described in claim 1, characterized in that: The DC chopper module adopts an H-bridge DC converter based on IGBT.

4. The superconducting synchronous condenser excitation power unit with adjustable peak voltage as described in claim 1, characterized in that: The DC chopper module realizes the DC / DC chopping output of the DC bus voltage according to the excitation requirement of the generator, including realizing the output of positive level, zero level, and negative level through the on-off control of IGBT; The normal excitation is realized by the combination of positive level and zero level, and the adjustment between 0 and the excitation peak voltage is output; the inversion control is carried out by the combination of zero level and negative level to realize the fast and strong reduction of field extinction.

5. The field excitation power unit of the superconducting synchronous condenser with adjustable peak value voltage as claimed in claim 1, characterized in that: The voltage smoothing module includes a positive series inductor, a negative series inductor, and a parallel capacitor. Among them, one end of the positive series inductor is connected to the positive output of the DC chopper module, and the other end is connected to the positive pole of the parallel capacitor; one end of the negative series inductor is connected to the negative output of the DC chopper module, and the other end is connected to the negative pole of the parallel capacitor.

6. The superconducting synchronous condenser excitation power unit with adjustable peak voltage as described in claim 1, characterized in that: The voltage commutation module includes a first switch tube, a second switch tube, a first diode to a fourth diode. Among them, the collector of the first switch tube is connected to the positive output of the voltage smoothing module, and the emitter is connected to the positive pole of the superconducting rotor; the collector of the second switch tube is connected to the negative pole of the superconducting rotor, and the emitter is connected to the negative output of the voltage smoothing module; the first diode and the second diode are respectively reversely connected in parallel at both ends of the first switch tube and the second switch tube; the cathode of the third diode is connected to the positive output of the voltage smoothing module, and the anode is connected to the negative pole of the superconducting rotor; the cathode of the fourth diode is connected to the positive pole of the superconducting rotor, and the anode is connected to the negative output of the voltage smoothing module.

7. The control method of a superconducting synchronous condenser excitation power unit with adjustable peak voltage as described in claim 1, characterized in that: When the excitation power unit outputs a positive excitation voltage, the voltage commutation module is controlled to be in the rectification working state; When the excitation power unit outputs a negative excitation voltage, the voltage commutation module is controlled to be in the inversion working state.

8. The control method according to claim 7, wherein: The voltage commutation module includes a first switching tube, a second switching tube, a first diode to a fourth diode. Among them, the collector of the first switching tube is connected to the positive output of the voltage smoothing module, and the emitter is connected to the positive pole of the superconducting rotor; the collector of the second switching tube is connected to the negative pole of the superconducting rotor, and the emitter is connected to the negative output of the voltage smoothing module; the first diode and the second diode are respectively reversely connected in parallel at both ends of the first switching tube and the second switching tube; the cathode of the third diode is connected to the positive output of the voltage smoothing module, and the anode is connected to the negative pole of the superconducting rotor; the cathode of the fourth diode is connected to the positive pole of the superconducting rotor, and the anode is connected to the negative output of the voltage smoothing module; When the excitation power unit outputs a positive excitation voltage, control the first switching tube and the second switching tube to be in the on state; When the excitation power unit outputs a negative excitation voltage, control the first switching tube and the second switching tube to be in the off state.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the control method described in claim 7 or 8.

10. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the control method described in claim 7 or 8.

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