Static frequency converter control method and control system of distributed phase modifier unit

Abstract

The invention discloses a static frequency converter control method and a static frequency converter control system for a distributed phase modifier unit. The static frequency converter control method of the distributed phase modifier group comprises the following steps: determining a target phase modifier group and calling a corresponding sequence control constant value according to a starting instruction; according to the sequential control constant value, power loop switches are closed in sequence to establish an excitation power supply path; after an excitation power supply path is established, rotor initial position detection is executed, a correct initial triggering sequence is determined, pulse output is unlocked, and power output is started; dragging the target phase modifier group to start in a forced commutation mode; monitoring the terminal voltage frequency of the target phase modifier unit in real time; and when the terminal voltage frequency is higher than a preset commutation switching threshold, switching the commutation mode from a forced commutation mode to a load commutation mode, and continuing to drag the target phase modifier unit to accelerate to the target rotating speed.

Description

Technical Field

[0001] This invention relates to the technical field of static frequency converters, and more particularly to a static frequency converter control method and control system for a distributed synchronous condenser group. Background Technology

[0002] Static frequency converters (SFCs) are key equipment for starting large synchronous motors and synchronous condenser units. In traditional centralized synchronous condenser stations (single large-capacity unit), the control strategy of SFCs is relatively mature, typically employing fixed control parameters and unified fault protection logic. With the development of power grid structures, the application of distributed synchronous condenser units is becoming increasingly widespread. Distributed synchronous condenser units usually refer to multiple small-to-medium capacity synchronous condensers operating in parallel at the same site.

[0003] However, traditional SFCs use mechanical position sensors such as rotary transformers and photoelectric encoders to detect rotor position, which has problems such as complex installation and maintenance, weak anti-electromagnetic interference capability, and high cost. They are prone to failure in the strong electromagnetic environment of distributed synchronous condensers and cannot flexibly adapt to the different starting parameters of multiple synchronous condensers. Summary of the Invention

[0004] In view of the aforementioned problems with the easy failure of existing distributed synchronous condenser groups, this invention is proposed.

[0005] Therefore, one of the objectives of this invention is to provide a static inverter control method for distributed synchronous condenser groups, which aims to improve reliability and startup efficiency.

[0006] To address the aforementioned technical problems of insufficient reliability and low startup efficiency, this invention provides the following technical solution: a static inverter control method for a distributed synchronous condenser group, comprising the following steps: Based on the start command, the target camera group is determined and the corresponding sequential control setpoint is invoked; According to the sequential control setpoint, the power circuit switches are closed sequentially to establish the excitation power supply path; After establishing the excitation power supply path, the rotor initial position is detected to determine the correct initial trigger sequence, unlock the pulse output, and start outputting power. The target phase-shifting group is started by dragging it using the forced phase-switching mode. Real-time monitoring of the terminal voltage frequency of the target synchronous condenser group; When the terminal voltage frequency is higher than the preset commutation switching threshold, the commutation mode is switched from forced commutation mode to load commutation mode, and the target synchronous condenser group continues to be driven to the target speed.

[0007] As a preferred embodiment of the static inverter control method for the distributed synchronous condenser group of the present invention, the sequential control setpoints include at least the start command waiting time, the stop command waiting time, the target speed, the cooling system start delay, and the excitation input threshold.

[0008] As a preferred embodiment of the static inverter control method for the distributed synchronous condenser group of the present invention, the rotor initial position detection includes: sending an excitation step signal to the excitation system of the target synchronous condenser group; detecting the transient terminal voltage induced by the excitation step signal; calculating the initial electrical position of the rotor based on the phase information of the transient terminal voltage, and determining the initial triggering sequence accordingly.

[0009] As a preferred embodiment of the static inverter control method for the distributed synchronous condenser group described in this invention, the preset commutation switching threshold is 10% of the rated frequency of the target synchronous condenser group.

[0010] As a preferred embodiment of the static inverter control method for the distributed synchronous condenser group of the present invention, it further includes a fault handling step, which involves real-time monitoring of the IP signal and PF signal reported by the thyristor valve group. If the number of IP signals lost simultaneously on a single valve arm exceeds a first set value, or the number of thyristors experiencing power failure (PF) simultaneously exceeds a second set value, the system will be immediately tripped.

[0011] As a preferred embodiment of the static inverter control method for the distributed synchronous condenser group described in this invention, the IP signal is a ready signal issued by the thyristor unit after successfully obtaining power, and the first set value is the maximum number of thyristors on a single valve arm that can simultaneously lose the IP signal; if this number is exceeded, a trip is triggered.

[0012] As a preferred embodiment of the static inverter control method for the distributed synchronous condenser group described in this invention, the PF signal is a protective triggering of the thyristor unit when the positive voltage of the thyristor exceeds its hardware setting value. The second setting value is the maximum number of thyristors that can be simultaneously triggered on a single valve arm. Exceeding this number will trigger a trip.

[0013] Another objective of this invention is to provide a static inverter control system for a distributed synchronous condenser group, comprising: a CPU module for task management, communication, and waveform recording; a DSP module for high-speed sampling and control calculation; an analog signal acquisition module for voltage and current signal sampling; and a digital input / output module for external signal interfaces, wherein the CPU module, DSP module, analog signal acquisition module, and digital input / output module are all mounted on a backplane.

[0014] As a preferred embodiment of the static frequency converter control system for the distributed synchronous condenser group of the present invention, the valve control unit is configured to: count the number of thyristors that simultaneously generate power frequency (PF) signals in each valve arm, and send a trip request to the control unit when the number exceeds a predetermined value; count the number of thyristors that simultaneously lose IP signals in each valve arm, and send a trip request to the control unit when the number exceeds a predetermined value.

[0015] The beneficial effects of this invention are as follows: By inducing the terminal voltage and calculating the phase using an excitation step signal, this invention can quickly and accurately locate the rotor magnetic pole position at extremely low speeds. This provides the correct initial sequence for subsequent thyristor triggering, avoiding the risk of insufficient starting torque, starting failure, or even equipment damage due to incorrect initial trigger angles, greatly improving the reliability of the starting process. By employing a forced commutation mode at low speeds, reliable current cut-off is ensured; when the speed increases to a point where the back electromotive force at the machine terminals is sufficient to support natural commutation, it automatically switches to load commutation mode. This ensures the stability of low-speed starting while utilizing the high efficiency of load commutation during high-speed operation, making the entire acceleration process smooth and continuous. The control system adopts a hierarchical distributed design, with the control unit, valve control unit, and thyristor unit connected through a standard communication interface. This improves the system's scalability and maintainability, and enhances its anti-interference capability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the static frequency converter control system for the distributed synchronous condenser group of the present invention.

[0018] Figure 2 This is a schematic diagram of the power circuit of the static inverter control system for the distributed synchronous condenser group of the present invention.

[0019] Figure 3 This is a schematic diagram of torque control in the static inverter control system of the distributed synchronous condenser group of the present invention.

[0020] Figure 4 This is a connection diagram of the static frequency converter control system for the distributed synchronous condenser group of the present invention.

[0021] Figure 5 This is a schematic diagram of the forced commutation process of the static inverter control system of the distributed synchronous condenser group of the present invention.

[0022] Figure 6This is a schematic diagram of the terminal voltage during the excitation step time of the static inverter control system of the distributed synchronous condenser group of the present invention.

[0023] Figure 7 This is a protective triggering principle diagram of the static frequency converter control system for the distributed synchronous condenser group of the present invention.

[0024] Figure 8 This is a schematic diagram of the installation of the control unit of the static inverter control system of the distributed synchronous condenser group of the present invention.

[0025] Figure 9 This is a schematic diagram of the installation of the valve control unit in the static inverter control system of the distributed synchronous condenser group of the present invention.

[0026] Figure 10 This is a schematic diagram of the interface of the valve control unit of the static frequency converter control system of the distributed synchronous condenser group of the present invention. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0030] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0031] Example 1

[0032] refer to Figures 1-6 This is the first embodiment of the present invention, which provides a static inverter control method for a distributed synchronous condenser group. This method includes the following steps. Based on the start command, the target camera group is determined and the corresponding sequential control setpoint is invoked; According to the sequential control setting, the power circuit 400 switch is closed in sequence to establish the excitation power supply path; After establishing the excitation power supply path, the rotor initial position is detected to determine the correct initial trigger sequence, unlock the pulse output, and start outputting power. The target phase-shifting group is started by dragging it using the forced phase-switching mode. Real-time monitoring of the terminal voltage frequency of the target synchronous condenser group; When the terminal voltage frequency is higher than the preset commutation switching threshold, the commutation mode is switched from forced commutation mode to load commutation mode, and the target synchronous condenser group continues to be driven to the target speed.

[0033] Since distributed synchronous condenser units typically consist of multiple synchronous condensers operating in parallel, and the starting parameters of each unit differ, differentiated control is achieved through sequential control setpoints, which are pre-input values. The power circuit 400 forms a complete path from the grid to the grid-side converter 401, then to the smoothing reactor 403, then to the generator-side converter 402, and finally to the synchronous condenser stator, providing frequency conversion drive power to the synchronous condenser stator windings. The control unit 100 sends an excitation current reference signal to the excitation system through an analog output channel to control the rotor magnetic field. The switches of the power circuit 400 must be closed in the following sequence: isolating switch to grid-side circuit breaker to generator-side circuit breaker. First, the isolating switch is closed to achieve physical isolation; then the grid-side circuit breaker is closed to connect to the grid; finally, the generator-side circuit breaker is closed to connect to the synchronous condenser stator, avoiding closing inrush current.

[0034] The control unit 100 receives the start command from the remote monitoring system via hardwiring or a communication interface. The command includes the target camera group number. The control unit 100 retrieves the corresponding preset parameters for the unit from its built-in sequential control setpoint library. The sequential control setpoints include at least the start command waiting time (for waiting for external equipment to be ready); the stop command waiting time (for delayed confirmation in case of a fault); the target speed (corresponding to the 50Hz rated frequency); the cooling system start delay (to ensure that the fan / pump reaches a stable operating state); and the excitation activation threshold (to determine that the excitation system is ready).

[0035] After the excitation power supply path is established, the rotor is stationary before the synchronous condenser starts. The rotor magnetic pole position must be clearly defined; otherwise, an incorrect triggering sequence of the thyristor 301 will lead to startup failure or equipment damage. Once the excitation power supply path is established in the power circuit 400, the cooling system is also activated to ensure that the power devices do not overheat during the testing process.

[0036] Once the initial rotor position is determined, the control unit 100 sends a pulse unlock command to the valve control unit 200. The valve control unit 200 then extends the trigger pulse and drives the thyristor 301 to conduct through the thyristor unit 300, and the machine-side converter 402 begins to output power. Each pulse drives one thyristor 301.

[0037] refer to Figure 5 During the low-speed phase of the generator unit, the internal electromotive force of the motor is very low and cannot meet the load commutation requirements of the thyristors. At this time, other methods should be used to assist the thyristor turn-off and commutation of the generator-side converter. First, control the grid-side converter to invert, forcing the loop current to zero and maintaining it for a period of time Δt, which is sufficient to ensure that the thyristors recover their blocking capability. Second, trigger the thyristors that should be conducting after commutation, and simultaneously control the grid-side converter to re-establish the loop current, thereby achieving a jump-like migration of the stator magnetic field in space. When the motor speed increases to 10% of its rated speed, the generator-side AC voltage will be sufficient to meet the load commutation requirements of the thyristors, and the system can switch to the load commutation control mode.

[0038] The real-time speed of the target synchronous condenser is calculated using the terminal voltage frequency, with the formula n = 60f / p, where p is the number of pole pairs, f is the terminal voltage frequency, and n is the speed. When the target synchronous condenser operates at low speed, the back EMF is insufficient to naturally turn off the thyristor 301, meaning the load commutation condition is not met. In this case, the grid-side converter 401 actively turns off the current, i.e., forced commutation. The preset commutation switching threshold is 10% of the rated frequency of the synchronous condenser. When the speed is ≥ 10% of the rated speed, the back EMF of the synchronous condenser is sufficient to turn off the thyristor 301, resulting in higher load commutation efficiency, i.e., switching to load commutation. The inverter operation of the grid-side converter 401 is stopped, and the conducting thyristor 301 is naturally turned off using the back EMF of the synchronous condenser. Based on the rotor position detection results, the next set of thyristors 301 is triggered at the zero-crossing point of the back EMF, achieving impact-free commutation.

[0039] Example 2

[0040] The second embodiment of the present invention differs from the first embodiment in that: the rotor initial position detection includes sending an excitation step signal to the excitation system of the target synchronous condenser group; detecting the transient terminal voltage induced by the excitation step signal; calculating the initial electrical position of the rotor based on the phase information of the transient terminal voltage, and determining the initial triggering sequence accordingly.

[0041] Before the unit starts, the rotor is in a stationary or near-stationary state. To determine the rotor position of the motor G, a transient terminal voltage needs to be induced. The control unit 100 sends a rapidly changing excitation step signal to the excitation system, which induces a detectable transient terminal voltage in the stator windings. By analyzing the phase information of the three-phase transient voltage, the initial electrical position of the rotor can be calculated. The analog signal acquisition module 103 samples the three-phase terminal voltage in real time, filters out harmonic interference through a filtering algorithm, and extracts the phase information of the transient voltage. Using the synchronous motor electromagnetic coupling model, the initial electrical position of the rotor is calculated, the initial triggering sequence of the thyristors 301 is determined, and each thyristor 301 is triggered sequentially according to the calculation results.

[0042] The remaining structure is the same as that in Example 1.

[0043] Example 3

[0044] Reference Figure 4 This is the third embodiment of the present invention, which differs from the second embodiment in that it further includes a fault handling step, which involves real-time monitoring of the IP signal and PF signal reported by the thyristor 301 valve group. If the number of IP signals lost simultaneously on a single valve arm exceeds the first set value, or the number of thyristors 301 that simultaneously experience power failure exceeds the second set value, the system will be immediately tripped.

[0045] Furthermore, the IP signal is a ready signal issued by the thyristor unit 300 after successfully obtaining power. It allows a maximum number of thyristors 301 on a single valve arm to simultaneously lose the IP signal. Exceeding this number will trigger a trip.

[0046] The PF signal is triggered when the positive voltage across the thyristor 301 exceeds its hardware setting value. The thyristor unit 300 will forcibly trigger the thyristor 301 for protection. The second setting value allows the maximum number of thyristors 301 that can be triggered for protection on a single valve arm at the same time. Exceeding this number will trigger a trip.

[0047] The thyristor unit 300 obtains power through local coupling, and after successful power acquisition, it sends an IP signal to the valve control unit 200. When the forward voltage of thyristor 301 exceeds the hardware threshold, thyristor unit 300 triggers protective triggering and feeds back the PF signal to valve control unit 200.

[0048] The valve control unit 200 counts the number of lost IP signals and the number of protective triggers for each valve arm. If the number of lost IP signals for a single valve arm is greater than or equal to a first set value, or the number of protective triggers is greater than or equal to a second set value, it immediately sends a trip request to the control unit 100. After receiving the request, the control unit 100 executes the interlocking pulse output, that is, cuts off the power output; disconnects the power circuit 400 circuit breaker; starts fault recording, and records the current, voltage, and signal status 2 seconds before and 3 seconds after the fault; and sends a fault trip alarm to the monitoring system.

[0049] The remaining structure is the same as that in Example 2.

[0050] Example 4

[0051] Reference Figures 1-10 In a fourth embodiment of the present invention, a static frequency converter control system for a distributed synchronous condenser group is also provided. This device includes a control unit 100, which is configured to execute a control method and contains a sequential control setpoint library. The valve control unit 200 is communicatively connected to the control unit 100 and is used to receive trigger commands and send trigger pulses. Several thyristor units 300 are communicatively connected to the valve control unit 200 and are used to drive the thyristor 301 valve group. The power circuit 400 is electrically connected to the control unit 100 to control the operation of the converter; The output terminal of the control unit 100 is connected to the power circuit 400 via a cable for outputting opening and closing commands. The control unit 100 uses a 4U high chassis, and its backplane slots are arranged according to functional zones. The various modules are connected via a backplane bus to achieve data exchange and power distribution. The valve control unit 200 uses a 6U chassis, and its core function is to distribute trigger pulses and monitor their status. The power circuit 400 includes at least a grid-side converter 401, a generator-side converter 402, and a smoothing reactor 403.

[0052] refer to Figures 1-3 , Figure 3 The medium-voltage power supply voltage (fixed frequency) is the fixed-frequency voltage of the medium-voltage starting power supply, while the generator terminal voltage (variable frequency) is the variable-frequency voltage on the stator side of the motor that varies with the speed. Both are connected by current transformers and voltage transformers to collect electrical data, providing a basis for control. The control and protection system receives current and voltage signals collected by the current and voltage transformers and outputs three control commands: control current Id, control flux ψ, and control inverter bridge β angle. These three commands work together to power the grid-side and generator-side converters. The converters adjust the thyristor triggering logic according to the control commands, changing the current and magnetic field state of the stator windings. Through the interaction between the stator rotating magnetic field and the rotor magnetic field, a stable and controllable drive torque is ultimately output to drive the unit to accelerate or operate stably. Figure 3 The DC voltage components output by the grid-side converters Udr and Udi, respectively, are the d-axis and i-axis, and are key parameters of the DC-side voltage in torque control. The +A / +C / +B and -A / -C / -B on both sides are the three-phase terminals of the motor stator windings, corresponding to the three-phase current input terminals of the SFC output. The entire left side of the converter is the rectifier bridge, and the right side is the inverter bridge. The ICB on the left is the input circuit breaker, used to connect the SFC device to the power frequency grid and provide short-circuit protection. The right side of the ICB is the transformer. CT and PT are the current transformer and voltage transformer, respectively. DS on the right side of the figure is the output circuit breaker. G is the generator. The excitation system is a system that provides adjustable DC current to the rotor of the synchronous motor G to establish the magnetic field (i.e., magnetic flux ψ) inside the motor.

[0053] The control unit uses the formula ,in The electromagnetic torque output by SFC This is a motor constant, a fixed value based on the motor's structural parameters. For the control current output by the control system, For stator flux, The cosine function of the power factor angle. It is the actual operating angle after taking into account various factors such as the commutation overlap angle. It represents the phase relationship between current and voltage (or magnetic flux) and directly affects the effective component of torque.

[0054] Increased capacity is required when starting the unit. To overcome static resistance, dynamic adjustments are required during acceleration. To avoid speed fluctuations, reduce speed when stopping the machine. In conjunction with braking, the control and protection system changes the trigger angle of the grid-side converter. amplitude, The larger the current, the larger the electromagnetic torque base, and vice versa. The real-time electromagnetic torque is obtained by collecting the grid-side current signal from the current transformer and performing calculations. Numerically, SFC adjusts the rotor excitation current by sending a reference signal to the excitation system, thereby changing the stator flux. The strength or weakness, As the magnetic field increases, the magnetic force strengthens, and the torque increases accordingly. It needs to be matched with the motor speed. At low speeds, it maintains a constant magnetic flux, and at high speeds, it enters the weak magnetic field region to avoid over-magnetic flux damaging the motor. DC current The corresponding current vector and stator flux The phase difference between the vectors is equivalent to βm in the diagram. By adjusting the trigger delay angle β of the machine-side converter, the phase difference is changed. Angle size, =0 =1, the torque reaches its maximum value; When it increases As the torque decreases, the torque also decreases synchronously.

[0055] During the unit startup phase, To maintain a constant magnetic flux, by increasing And Angle locked at the optimal value ≈1, quickly generates large torque to overcome the unit's static resistance; as the speed increases, the control unit gradually decreases. Entering the weak magnetic region, while fine-tuning and The angle ensures smooth torque and avoids speed overshoot. If overcurrent is detected, the control unit quickly reduces the speed. Decrease when passing through magnetic flux Adjustment when commutation is abnormal The angle is used to correct the torque in real time using a formula.

[0056] This system adopts a hierarchical distributed architecture, with the control unit 100 as the core. It forms a complete control and protection system with components such as valve control unit 200 and power circuit 400 through hard wiring and optical fiber. The control unit 100 and valve control unit 200 are installed in a standard cabinet. The control unit 100 and valve control unit 200 are embedded. The power circuit 400 devices are connected through copper busbars and power cables.

[0057] The control unit 100 includes a CPU plug-in 101 for task management, communication and waveform recording; a DSP plug-in 102 for high-speed sampling and control calculation; an analog signal acquisition plug-in 103 for voltage and current signal sampling; and a digital input / output plug-in 104 for external signal interface.

[0058] refer to Figure 6 The CPU module 101, DSP module 102, analog signal acquisition module 103, and digital input / output module 104 are all mounted on the backplane of the control unit 100. The CPU module 101, as the management core, exchanges data at high speed with the DSP module 102 via the backplane PCIe bus. The DSP module 102 receives sampled data from the analog signal acquisition module 103 via the backplane parallel bus. The optocoupler output of the digital input module 104a is sent to the DSP module 102 via the backplane digital I / O bus. The drive signal of the digital output module 104b is controlled by the DSP module 102 via the backplane bus.

[0059] CPU Plug-in 101 can use a dual-core ARM Cortex-A9 processor with an integrated hardware floating-point unit, supporting multi-task parallel processing. Tasks are managed through the operating system. CPU Plug-in 101 has a built-in configurable setpoint table, supporting the storage of differentiated parameters for four synchronous condenser groups. Each group contains 32 setpoints, such as start-up command waiting time and commutation threshold, forming a sequential control setpoint library. Furthermore, in the event of a fault, data storage is initiated within 10ms, recording 8 analog signals and 32 digital signals. The recorded data can be uploaded to the backend via Ethernet or exported via USB.

[0060] DSP plug-in 102 can use TI TMS320F28377D floating-point DSP, which integrates CLA (control law accelerator) and supports parallel computing. DSP plug-in 102 receives voltage / current signals from analog acquisition plug-in 103, performs FIR digital filtering with a cutoff frequency of 500Hz to suppress harmonics, and calculates characteristic quantities such as RMS value, phase, and frequency.

[0061] DSP plug-in 102 also calculates the rotor position and implements the excitation step induction method through a detection algorithm. First, an excitation current step of 5A / ms is applied; then, the transient voltage at the generator terminal is collected; and then the rotor position angle θ is extracted through Park transformation with an accuracy of ≤±3°.

[0062] Furthermore, the DSP plug-in 102 switches the commutation mode in real time according to the rotational speed through the commutation control logic. At low speeds (<10% of rated speed), it calculates the inverter angle (β angle) of the grid-side converter 401 to achieve forced commutation, with the current returning to zero time ≤5ms. At high speeds (≥10% of rated speed), it tracks the phase of the generator terminal voltage through a phase-locked loop (PLL) to determine the load commutation time, with a tracking error ≤0.1Hz.

[0063] The DSP plug-in 102 can also realize closed-loop speed control, using a PI regulator with an adjustable proportional coefficient of 0.5~2.0 and an adjustable integral time of 0.1~1s. The output frequency is adjusted according to the deviation between the target speed and the actual speed, and the speed control accuracy is ≤±2r / min.

[0064] The analog signal acquisition module 103 includes 12 voltage input channels and 8 current input channels, each independently isolated. It features a 16-bit AD converter (AD7606 can be used, with a conversion rate of 1 MSPS). Each channel is connected in series with an RC low-pass filter and a limiting circuit. It acquires grid-side voltage, generator-side voltage, DC-side voltage, magnetizing voltage, grid-side current, generator-side current, magnetizing current, and cooling current. Finally, the sampled data is sent to the DSP module 102 via the backplane bus and simultaneously buffered in the CPU module 101.

[0065] The digital input / output module 104 is divided into digital input module 104a and digital output module 104b. The digital input module has 24 passive contact inputs with optocoupler isolation, an isolation voltage ≥2.5kV, and a response time ≤1ms. The digital output module has 16 relay outputs, supporting pulse and level outputs. The digital inputs are used to receive external device status, such as circuit breaker open / close positions, cooling fan operation signals, remote start / stop commands, and excitation ready signals. The digital outputs control the opening and closing of power switches, the start / stop of the cooling system, and pulse interlocking.

[0066] The backplane adopts a 32-bit VME bus architecture, supports hot-swapping of plug-ins, and has a bus transmission rate of ≥100Mbps. Each plug-in communicates with other plug-ins through the backplane. An external power supply is also connected for power.

[0067] refer to Figure 7 and Figure 8The valve control unit 200 is configured to count the number of thyristors 301 that simultaneously trigger protective signals in each valve arm. When the number exceeds a set value, it sends a trip request to the control unit 100. The valve control unit 200 also includes a DSP plug-in 102 and an optical interface plug-in 201 for communication with the thyristor unit 300. The valve control unit 200 counts the number of thyristors 301 that simultaneously lose IP signals in each valve arm, and sends a trip request to the control unit 100 when the number exceeds a set value. The SFP optical module of the DSP plug-in 102 is directly connected to the optical port of the optical interface plug-in 201 of the valve control unit 200 via a 50 / 125μm multimode fiber. The triggering system for each valve arm adopts a star topology. Each optical interface plug-in 201 drives one phase bridge arm, and each phase bridge arm contains two valve arms. Each optical port is connected to one thyristor unit 300 via a 62.5 / 125μm multimode fiber.

[0068] The thyristor unit 300 can be model NR1653, employing power circuit 400 coupling power extraction technology, eliminating the need for an external auxiliary power supply. Energy is obtained from the power circuit 400 through a coupling capacitor assembly connected in parallel with the thyristor 301. This coupling capacitor assembly consists of two 0.1μF / 2500V CBB capacitors connected in series, with a total withstand voltage ≥5000V. When the voltage of the power circuit 400 is ≥500V, the coupling capacitor charges to a stable voltage, which is then output as a stable 5V / 100mA DC power supply via a rectifier bridge and a linear regulator chip to power the internal circuitry of the TCU. The rectifier bridge can be model KBU808, and the linear regulator chip can be model LM7805.

[0069] The thyristor unit 300 also has a built-in energy storage capacitor with parameters of 100μF / 16V, which ensures that the thyristor unit 300 can maintain a stable power supply for ≥20ms when the voltage of the power circuit 400 fluctuates briefly, thus avoiding triggering an interruption.

[0070] The core chip of the thyristor unit 300 can be an 8-bit microcontroller, model PIC16F877A, which is responsible for receiving instructions from the valve control unit 200, detecting the status of the thyristor 301 and outputting a trigger signal. After receiving the 5V / 10μs trigger pulse output by the control unit 100, it is isolated and amplified by a high-frequency pulse transformer to output a 2A / 15μs trigger current, which directly drives the gate-cathode circuit of the thyristor 301 to conduct.

[0071] The valve control unit 200 monitors the status of the thyristor units 300 of each valve arm in real time. If ≥2 thyristor units 300 of a single valve arm, such as the upper bridge arm of phase A, stop sending IP signals, the valve control unit 200 determines that there is an IP signal loss fault and immediately sends a trip request to the control unit 100. If ≥2 thyristor units 300 of a single valve arm send PF signals within one power frequency cycle, the valve control unit 200 determines that there is an overvoltage fault in the valve arm, triggers the system to trip and blocks the pulse output.

[0072] refer to Figure 5 During the operation of the static inverter, if the forward voltage of a certain thyristor 301 rises and exceeds the second set value, the sampling circuit 304 detects the high voltage, uses a voltage divider resistor to reduce the voltage and inputs it into the calculation period, comparing it with the reference voltage V. Once the detected voltage is greater than the reference voltage V, the drive chip 303 outputs a signal to the thyristor 301 and sends a PF signal, turning on the thyristor 301 to release the overvoltage energy and prevent the thyristor 301 from being broken down.

[0073] The power circuit 400 adopts a modular design. The input terminal of the grid-side converter 401 is connected to the lower port of the input circuit breaker through a rectangular copper busbar. The DC bus adopts a double copper busbar structure with a smoothing reactor 403 connected in series in the middle. The output terminal of the machine-side converter 402 is connected to the output isolating switch through a flexible cable.

[0074] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise changed, and the nature or number or position of discrete elements may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. Therefore, the invention is not limited to the particular embodiments but extends to a variety of modifications that still fall within the scope of the appended claims.

[0075] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A static frequency converter control method for a distributed synchronous condenser group, characterized in that: Includes the following steps, Based on the start command, the target camera group is determined and the corresponding sequential control setpoint is invoked; According to the sequential control setpoint, the power circuit (400) switch is closed sequentially to establish the excitation power supply path; After establishing the excitation power supply path, the rotor initial position is detected to determine the correct initial trigger sequence, unlock the pulse output, and start outputting power. The target phase-shifting group is started by dragging it using the forced phase-switching mode. Real-time monitoring of the terminal voltage frequency of the target synchronous condenser group; When the terminal voltage frequency is higher than the preset commutation switching threshold, the commutation mode is switched from forced commutation mode to load commutation mode, and the target synchronous condenser group continues to be driven to the target speed.

2. The static inverter control method for a distributed synchronous condenser group according to claim 1, characterized in that: The sequential control setpoints include at least the start command waiting time, stop command waiting time, target speed, cooling system start delay, and excitation input threshold.

3. The static inverter control method for a distributed synchronous condenser group according to claim 1 or 2, characterized in that: The rotor initial position detection includes sending an excitation step signal to the excitation system of the target synchronous condenser group; detecting the transient terminal voltage induced by the excitation step signal; calculating the initial electrical position of the rotor based on the phase information of the transient terminal voltage; and determining the initial triggering sequence accordingly.

4. The static inverter control method for a distributed synchronous condenser group according to claim 3, characterized in that: The preset commutation switching threshold is 10% of the rated frequency of the target phase shifter group.

5. The static inverter control method for a distributed synchronous condenser group according to claim 1 or 4, characterized in that: It also includes troubleshooting steps. Real-time monitoring of the IP and PF signals reported by the thyristor (301) valve group; If the number of IP signals lost simultaneously on a single valve arm exceeds the first set value, or the number of thyristors (301) that simultaneously experience power failure exceeds the second set value, the system trips immediately.

6. The static inverter control method for a distributed synchronous condenser group according to claim 5, characterized in that: The IP signal is a ready signal issued by the thyristor unit (300) after successfully obtaining power. The first set value is the maximum number of thyristors (301) on a single valve arm that are allowed to lose the IP signal at the same time. If this number is exceeded, a trip will be triggered.

7. The static inverter control method for a distributed synchronous condenser group according to claim 6, characterized in that: The PF signal is that when the positive voltage of the thyristor (301) exceeds its hardware setting value, the thyristor unit (300) will forcibly trigger the thyristor (301) for protection. The second setting value is the maximum number of thyristors (301) that can be triggered for protection on a single valve arm at the same time. If this number is exceeded, the trip will be triggered.

8. A static frequency converter control system for a distributed synchronous condenser group, applicable to the static frequency converter control method for any of claims 1 to 7, characterized in that: include, A control unit (100) is configured to execute a control method and contains a sequential control setpoint library; The valve control unit (200) is communicatively connected to the control unit (100) and is used to receive trigger commands and extend trigger pulses; Several thyristor units (300) are communicatively connected to the valve control unit (200) and are used to drive the thyristor (301) valve group; The power circuit (400) includes at least a grid-side converter (401), a machine-side converter (402), and a smoothing reactor (403). The output end of the control unit (100) is connected to the power circuit (400) via a cable for outputting opening and closing commands. The control unit uses the formula... Torque calculation is performed, where The output electromagnetic torque, This is a motor constant, a fixed value based on the motor's structural parameters. For the control current output by the control system, For stator flux, The cosine function of the power factor angle. It is the actual working angle after taking into account various factors such as the commutation overlap angle.

9. The static frequency converter control system for a distributed synchronous condenser group according to claim 8, characterized in that: The control unit (100) includes, CPU plugin (101) is used for task management, communication, and waveform recording; DSP plug-in (102) is used for high-speed sampling and control calculations; Analog signal acquisition module (103) is used for voltage and current signal sampling; Digital input / output module (104) for external signal interface; The CPU plug-in (101), DSP plug-in (102), analog signal acquisition plug-in (103), and digital input / output plug-in (104) are all installed on the back panel.

10. The static frequency converter control system for a distributed synchronous condenser group according to claim 9, characterized in that: The valve control unit (200) is configured to count the number of thyristors (301) that simultaneously cause power tripping in each valve arm, and send a tripping request to the control unit (100) when the number exceeds a set value. The number of thyristors (301) that simultaneously lose IP signals in each valve arm is counted. When the number exceeds a certain value, a tripping request is sent to the control unit (100).

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