Synchronous phase modifier control system

Abstract

The invention provides a synchronous phase modifier control system, which comprises a synchronous phase modifier, an alternating current motor and a system controller, and is characterized in that the synchronous phase modifier is used for being coaxially and mechanically connected with the alternating current motor through a coupler; the alternating current motor is used for providing an electromagnetic torque to the synchronous phase modifier when receiving a control signal, so that the synchronous phase modifier executes a power control action on a power grid; and the system controller is used for receiving the voltage and current information of the power grid and the operation data information, and sending the control signal to the alternating current motor when detecting the frequency change of the power grid so as to maintain the stability of the power grid. Through cooperation of the synchronous phase modifier and the AC motor, power grid frequency change is responded in real time, power grid stability is maintained, and power grid operation efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of electrical engineering technology, and in particular to a synchronous phase condenser control system. Background Art

[0002] With the rapid increase in the proportion of renewable energy generation, distributed generation systems represented by wind power and photovoltaics are gradually replacing the grid-connected capacity of traditional synchronous generators. This energy structure transformation has led to new stability challenges for the power system: on the one hand, when new energy units are connected to the grid through power electronic converters, they cannot provide the system with natural rotational inertia like synchronous generators; on the other hand, when extreme weather causes new energy units to be disconnected from the grid, the system will face the dual threats of a sudden drop in equivalent rotational inertia and insufficient frequency regulation capacity, which may cause systemic risks such as frequency collapse in severe cases.

[0003] The main technical means of maintaining grid inertia support currently have the following limitations:

[0004] (1) Synchronous condenser technology: By configuring a dedicated synchronous condenser to provide short-term inertia support, it relies on the release of rotor kinetic energy to achieve inertia response. However, due to the physical size of the equipment, the condenser can store a limited amount of rotational inertia, and the continuous support time is usually no more than 10 seconds. In addition, the dynamic response speed is difficult to meet the rapid frequency regulation requirements of a high-proportion new energy grid.

[0005] (2) Mechanical flywheel energy storage technology: using the kinetic energy storage and release of high-speed rotating flywheels to provide inertia support. Although it has a millisecond response speed, there are significant technical bottlenecks: ① The energy density is low, and a large volume flywheel group is required to achieve effective inertia support, resulting in a large footprint and high construction costs; ② Mechanical bearing loss causes high self-energy consumption, and there are safety hazards under high speed conditions; ③ Due to material strength limitations, the continuous energy release time is low. Summary of the invention

[0006] In view of this, an object of the present application is to provide a synchronous phase condenser control system to overcome at least one of the above-mentioned defects.

[0007] In a first aspect, an embodiment of the present application provides a synchronous condenser control system, the control system comprising a synchronous condenser, an AC motor and a system controller, wherein the synchronous condenser is used to be coaxially mechanically connected to the AC motor through a coupling; the AC motor is used to provide electromagnetic torque to the synchronous condenser when receiving a control signal, so that the synchronous condenser performs power control actions on a power grid; the system controller is used to receive power grid voltage, current information and operating data information, and when a change in power grid frequency is detected, sends the control signal to the AC motor to maintain power grid stability.

[0008] In an optional embodiment of the present application, the control system also includes energy storage equipment and an inverter, wherein the inverter is connected to the AC motor to control the electromagnetic torque of the AC motor; the energy storage equipment is used to store and release electrical energy, and is connected to the inverter corresponding to the AC motor through a DC bus to convert electrical energy and mechanical energy with the AC motor.

[0009] In an optional embodiment of the present application, the control system also includes an excitation controller, wherein the excitation controller is connected to a first three-phase AC power supply to obtain electrical energy from the first three-phase AC power supply, and the excitation controller outputs DC power to excite the excitation winding of the synchronous condenser, so as to control the strength and direction of the magnetic field inside the synchronous condenser by adjusting the magnitude and direction of the output DC power.

[0010] In an optional embodiment of the present application, the control system also includes a parallel device, wherein the parallel device is used to monitor the amplitude, frequency and phase of the synchronous phase condenser machine terminal voltage and the low-voltage end voltage of the step-up transformer, and when it is monitored that the amplitude, frequency and phase of the synchronous phase condenser machine terminal voltage and the low-voltage end voltage of the step-up transformer meet the parallel conditions, the synchronous phase condenser is controlled to be connected to the power grid through the step-up transformer.

[0011] In an optional embodiment of the present application, the control system also includes a step-up transformer, wherein the step-up transformer includes a three-phase low-voltage side port of the step-up transformer and a three-phase high-voltage side port of the step-up transformer, the three-phase winding of the stator of the synchronous phase regulator is connected to the three-phase low-voltage side port of the step-up transformer through the parallel device, and is connected to the power grid in parallel through the three-phase high-voltage side port of the step-up transformer.

[0012] In an optional embodiment of the present application, the control system also includes a rectifier, wherein the DC end of the rectifier, the DC end of the inverter and the DC end of the energy storage equipment are connected to the same DC bus, and the AC end of the rectifier is connected to a second three-phase AC power supply, and the rectifier is used to rectify the electric energy obtained from the second three-phase AC power supply into DC power, and to transmit the DC power to the energy storage equipment for charging and to provide energy for the parallel process of the synchronous phase regulator and the power grid.

[0013] In an optional embodiment of the present application, the control system also includes a voltage transformer and a current transformer, wherein the voltage transformer is arranged between the power grid and the system controller to transmit the three-phase voltage information of the power grid to the system controller, and the current transformer is arranged between the power grid and the system controller to transmit the three-phase current information of the power grid to the system controller.

[0014] In an optional embodiment of the present application, the system controller is configured to: receive three-phase voltage information detected by a voltage transformer and three-phase current information detected by a current transformer; and send corresponding control signals to the excitation controller, the inverter and the energy storage equipment respectively according to the three-phase voltage information, the three-phase current information and the operating data information of the excitation controller, the inverter and the energy storage equipment, so as to coordinately control the reactive power output, active power output and grid frequency stability of the synchronous phase regulator.

[0015] In an optional embodiment of the present application, the control system is configured as follows: when the electromagnetic torque of the AC motor controlled by the inverter is consistent with the rotation direction of the rotor of the AC motor, it indicates that the electromagnetic torque on the rotor of the AC motor is the driving torque, and the AC motor is controlled to enter the motor operation state and the synchronous condenser is switched to the generator operation state; the inverter absorbs electrical energy from the DC bus side and converts it into mechanical energy output by the AC motor and transmits it to the rotor of the synchronous condenser; through the interaction of the magnetic field between the stator of the synchronous condenser and the rotor of the synchronous condenser, the synchronous condenser converts the mechanical energy on the rotor into electrical energy in the three-phase winding of the stator of the synchronous condenser, so as to release the electrical energy to the power grid through the step-up transformer, emit active power to the power grid, and maintain the stability of the power grid.

[0016] In an optional embodiment of the present application, the control system is further configured as follows: when the inverter controls the electromagnetic torque of the AC motor to be opposite to the rotation direction of the rotor of the AC motor, it indicates that the electromagnetic torque on the rotor of the AC motor is a braking torque, and the AC motor is controlled to enter a generator operation state and the synchronous condenser is switched to a motor operation state; the power grid inputs electric energy into the three-phase winding of the stator of the synchronous condenser through the low-voltage end of the step-up transformer, and through the magnetic field interaction between the stator of the synchronous condenser and the rotor of the synchronous condenser, the rotor of the synchronous condenser obtains mechanical energy and transmits it to the rotor of the AC motor; according to the magnetic field interaction between the stator of the AC motor and the rotor of the AC motor, the AC motor converts the mechanical energy on the rotor of the AC motor into electric energy in the three-phase winding of the stator of the AC motor; the inverter outputs the electric energy in the three-phase winding of the stator of the AC motor to the DC bus, and inputs the electric energy into the energy storage equipment through the DC bus for storage.

[0017] The synchronous condenser control system provided in the embodiment of the present application integrates a synchronous condenser, an AC motor and a system controller. The synchronous condenser is coaxially connected to the AC motor through a coupling, so that the AC motor can drive the synchronous condenser; when the system controller detects a change in the power grid frequency, it sends a control signal to the AC motor, and the AC motor immediately generates an electromagnetic torque to drive the synchronous condenser to perform power control actions on the power grid; in this way, the synchronous condenser and the AC motor work together to respond to changes in the power grid frequency in real time, effectively maintain the stability of the power grid, and thus improve the operating efficiency of the power grid.

[0018] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of the structure of a synchronous condenser control system provided in an embodiment of the present application;

[0021] Figure 2 One of the flow charts of the synchronous condenser control system provided in the embodiment of the present application;

[0022] Figure 3 This is the second flow chart of the synchronous phase condenser control system provided in the embodiment of the present application. DETAILED DESCRIPTION

[0023] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application usually described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, each other embodiment obtained by those skilled in the art without making creative work belongs to the scope of protection of the present application.

[0024] First, the application scenarios to which the present application is applicable are introduced. The present application can be applied in the field of electrical engineering technology.

[0025] Research has found that with the surge in renewable energy using power electronics technology, the number of high-inertia generators is decreasing in both actual number and share of total power generation, especially in distributed local power grids such as wind and solar farms. However, in bad weather, photovoltaic or wind power grid systems are prone to failure. At this time, the grid system's equivalent moment of inertia is small, and its voltage support and frequency regulation capabilities are seriously insufficient. When a serious fault occurs in the grid, there is insufficient capacity to provide effective support to the grid, which seriously threatens the stable operation of the power system.

[0026] For power systems in areas with a high proportion of new energy transmission, using small phase regulators to provide voltage support and inertia support for distributed energy is a solution. Using high-inertia phase regulators based on coaxial flywheels is one of the development directions. However, when high-inertia phase regulators provide inertial power proportional to the rate of change of the grid frequency, the speed of the synchronous phase regulators is basically consistent with the grid frequency, resulting in a small change in its mechanical energy during the frequency change. In order to improve the inertia support, the volume and weight of the flywheel will be large, the loss of the flywheel will also be large, and the economic efficiency will be poor.

[0027] Based on this, the embodiment of the present application provides a synchronous condenser control system, the control system includes a synchronous condenser, an AC motor and a system controller, the synchronous condenser is used to be coaxially mechanically connected with the AC motor through a coupling; the AC motor is used to provide electromagnetic torque to the synchronous condenser when receiving a control signal, so that the synchronous condenser performs power control actions on the power grid; the system controller is used to receive power grid voltage, current information and operation data information, and when a change in power grid frequency is detected, a control signal is sent to the AC motor to maintain power grid stability. Through this application, the synchronous condenser and the AC motor work together to respond to changes in power grid frequency in real time, maintain power grid stability, and improve power grid operation efficiency.

[0028] A traditional synchronous condenser is a synchronous motor running at no load. However, when the synchronous condenser is connected in parallel with the power grid (the synchronous motor in this special operating state of the synchronous condenser is connected to the power grid to form an overall system with the power grid to operate together), an AC motor with speed regulation capability controlled by an inverter is needed to replace the small-power induction motor that was originally used only for starting and paralleling the synchronous condenser. The AC motor is coaxially mechanically connected to the synchronous condenser, and the smaller-power induction motor with the same number of poles as the synchronous condenser is started from zero speed.

[0029] Synchronous condenser starting refers to the process in which the synchronous condenser starts to rotate from a stationary state, gradually accelerates to the synchronous speed, and finally runs in parallel with the power grid.

[0030] The present application replaces the low-power induction motor that was originally coaxially mechanically connected to the phase regulator and used to drag the stationary phase regulator to a speed close to the synchronous speed and parallel to the power grid quasi-synchronously, with an AC motor with a power lower than the capacity of the synchronous phase regulator and controlled by an inverter.

[0031] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of the synchronous condenser control system provided in the embodiment of the present application. Figure 1 As shown in the figure, the synchronous phase condenser control system provided in the embodiment of the present application includes a synchronous phase condenser 1, an AC motor 2, a system controller 3, an energy storage device 4, an inverter 5, an excitation controller 6, a parallel device 7, a step-up transformer 8, a rectifier 9, a voltage transformer 10, a current transformer 11, a first three-phase AC power supply 12, a second three-phase AC power supply 13, a coupling 14 and a DC bus 15.

[0032] Wherein, the synchronous condenser 1 is used to be coaxially mechanically connected with the AC motor 2 through a coupling 14;

[0033] Here, the synchronous condenser is a special generator designed to provide reactive power support in the power system to maintain voltage stability. In this system, the synchronous condenser 1 is coaxially mechanically connected to the AC motor 2 through a coupling 14, which means that they share the same rotating shaft, thereby achieving the transmission of mechanical energy.

[0034] In an optional embodiment, the AC motor may be an induction motor, a permanent magnet synchronous motor, a switched reluctance motor, or any other AC motor capable of adjusting speed through inverter control.

[0035] Here, in addition to being still used for starting and paralleling synchronous phase regulators, the AC motor has a new function: when the grid frequency decreases or increases, the AC motor applies a controllable drag torque or braking torque to the phase regulator rotor, providing "virtual inertia" for the phase regulator, stabilizing the grid frequency, and exchanging the electric energy input or feedback from the speed regulating AC motor stator with the energy storage equipment, realizing primary frequency regulation of the grid and improving the fault ride-through capability of the new energy grid.

[0036] The AC motor 2 is used to provide electromagnetic torque to the synchronous condenser 1 when receiving the control signal, so that the synchronous condenser 1 performs power control on the power grid 16;

[0037] An AC motor is a device that can convert electrical energy into mechanical energy. In this system, when the AC motor 2 receives a control signal from the system controller 3, it will provide an electromagnetic torque to the synchronous phase condenser 1. The electromagnetic torque is the force generated by the AC motor to drive the synchronous phase condenser 1 to rotate.

[0038] Here, the power of the AC motor is the same as the maximum frequency modulation power of the energy storage type synchronous condenser of the present invention to achieve the primary frequency modulation of the new energy power station grid. That is to say, the rated power of the AC motor (or the output power under certain specific conditions) and the maximum frequency modulation power that can be achieved by a new type of energy storage type synchronous condenser when participating in the primary frequency modulation of the new energy power station grid are numerically equal. Since the frequency drop of the power grid is very low, it can be considered that the rated power of the AC motor is equal to the product of the rated electromagnetic torque required by the synchronous condenser during the primary frequency modulation and the synchronous mechanical angular velocity of the motor.

[0039] The system controller 3 is used to receive grid voltage, current information and operation data information, and when a grid frequency change is detected, sends a control signal to the AC motor 2 to maintain the stability of the grid 16.

[0040] The system controller 3 is the core control unit of the power system, responsible for monitoring the grid status and sending control signals to maintain grid stability. In this system, the system controller 3 receives grid voltage, current information and operating data information. When a grid frequency change is detected, the system controller 3 sends a control signal to the AC motor 2 to adjust its output electromagnetic torque, thereby performing power control actions on the grid 16 through the synchronous phase regulator 1.

[0041] Through the coordinated work of the synchronous phase condenser 1 and the AC motor 2, the system can respond quickly when the grid frequency fluctuates and stabilize the grid frequency by adjusting the electromagnetic torque; the synchronous phase condenser 1 can provide the necessary reactive power, which helps to maintain the stability of the grid voltage and reduce voltage fluctuations and flicker; since the system controller 3 can monitor the grid status in real time and send control signals, the system has a high degree of flexibility and a fast response speed and can adapt to different grid conditions; by precisely controlling the electromagnetic torque of the AC motor 2, the system can optimize the use of energy, reduce unnecessary energy waste, and improve the energy efficiency of the entire power system.

[0042] Specifically, the inverter 5 is connected to the AC motor 2 to control the electromagnetic torque of the AC motor 2;

[0043] Here, the inverter 5 is a power electronic device that can convert direct current (DC) into alternating current (AC). In this power system, the inverter 5 is connected to the AC motor 2, and its main function is to control the electromagnetic torque of the AC motor 2. The inverter 5 can accurately control the electromagnetic torque of the AC motor 2 by adjusting the amplitude, frequency and phase of its output voltage. This control is an important link in the electric traction system, which enables the AC motor to quickly and accurately adjust its output torque according to system requirements.

[0044] Furthermore, the inverter 5 has a fast response characteristic and can quickly adjust its output voltage after detecting the command from the power grid or the system controller 3 , thereby achieving instant control of the electromagnetic torque of the AC motor 2 .

[0045] The energy storage device 4 is used to store and release electric energy, and is connected to the inverter 5 corresponding to the AC motor 2 via the DC bus 15 , so as to perform conversion between electric energy and mechanical energy with the AC motor 2 .

[0046] For example, the energy storage equipment may be flywheel energy storage equipment, superconducting energy storage equipment, supercapacitor energy storage equipment, battery energy storage equipment, and other energy storage equipment with large instantaneous power and fast response speed.

[0047] The energy storage device 4 is a device capable of storing and releasing electric energy, and is connected to the inverter 5 corresponding to the AC motor 2 in this power system through the DC bus 15. The main function of the energy storage device 4 is to convert electric energy into mechanical energy with the AC motor 2, and to provide backup electric energy for the system.

[0048] In the power system, the energy storage device 4 can store the excess electric energy generated by the AC motor 2, or release electric energy when needed to drive the AC motor 2. This conversion is an important part of energy management in the power system, which helps to achieve optimal utilization of electric energy and stable operation of the system.

[0049] In case of an emergency such as a grid failure or a grid frequency change detected by the system controller 3, the energy storage device 4 can quickly release its stored electric energy to maintain the stable operation of the system or provide necessary power support. This backup power function is of great significance to improving the reliability and stability of the power system.

[0050] The energy storage device 4 stores energy and exchanges energy with the AC motor 2 through the DC bus 15 and the inverter 5. The energy storage device 4 converts a certain form of energy stored in itself into electrical energy and releases it to the AC motor 2 through the DC bus 15 and the inverter 5. The energy storage device 4 absorbs the electrical energy fed back by the AC motor 2 and transmitted through the inverter 5 and the DC bus 15 and converts it into a certain form of energy inside itself for storage.

[0051] Specifically, the excitation controller 6 is connected to the first three-phase AC power supply 12 to obtain electrical energy from the first three-phase AC power supply 12. The excitation controller 6 outputs DC power to excite the excitation winding of the synchronous condenser 1 to control the strength and direction of the magnetic field inside the synchronous condenser 1 by adjusting the size and direction of the output DC power.

[0052] Preferably, the first three-phase AC power source 12 and the second three-phase AC power source 13 can be the low-voltage end of the step-up transformer in the system, or can be powered by the power grid through their own step-down transformers, or can share the same step-down transformer to be powered by the power grid, or can be other independent power sources.

[0053] Here, the excitation controller 6 is responsible for providing the excitation current to the excitation winding of the synchronous condenser 1. The excitation current is the key to generating the internal magnetic field of the synchronous condenser, and the strength and direction of the magnetic field determine the reactive power output and voltage regulation capability of the synchronous condenser in the power grid.

[0054] The excitation controller 6 is connected to the first three-phase AC power supply 12 and obtains electric energy from the power supply. The first three-phase AC power supply 12 is usually a stable power supply that can provide the electric energy required by the excitation controller 6; the excitation controller 6 converts the obtained AC electric energy into DC power and outputs it to the excitation winding of the synchronous condenser 1. DC power is the current form required by the excitation winding because it can generate a constant magnetic field; by adjusting the size and direction of the output DC power, the excitation controller 6 can control the strength and direction of the magnetic field inside the synchronous condenser 1. The strength of the magnetic field determines the size of the reactive power that the synchronous condenser can generate, while the direction of the magnetic field determines the nature of the reactive power (inductive or capacitive).

[0055] The main power conversion circuit of the excitation controller 6 of the synchronous condenser 1 is a three-phase thyristor half-controlled or fully-controlled rectifier bridge. The DC voltage output by the three-phase thyristor controlled rectifier bridge is changed by controlling the thyristor trigger angle, thereby changing the excitation current flowing into the synchronous condenser excitation winding through the carbon brush and slip ring. The terminal voltage of the synchronous condenser or the output reactive current is adjusted by controlling the magnitude of the excitation current. The main power conversion circuit of the excitation controller 6 can also use various AC / DC converters.

[0056] Excitation control process: the excitation controller 6 is connected to the first three-phase AC power supply 12 to ensure stable AC power; the rectifier circuit inside the excitation controller 6 converts the AC power into DC power; the converted DC power is output to the excitation winding of the synchronous condenser 1; by adjusting the magnitude and direction of the output current of the excitation controller 6, the strength and direction of the magnetic field inside the synchronous condenser 1 can be accurately controlled; as the strength and direction of the magnetic field change, the reactive power output of the synchronous condenser 1 in the power grid will also be adjusted accordingly, thereby achieving regulation and stabilization of the power grid voltage.

[0057] Through the precise control of the excitation controller 6, the synchronous phase condenser 1 can accurately output reactive power according to the needs of the power grid, which helps to maintain the stability of the power grid voltage; by adjusting the excitation current, the synchronous phase condenser 1 can quickly respond to changes in the power grid voltage and provide necessary voltage support; the precise control of the excitation controller 6 enables the synchronous phase condenser 1 to better operate in synchronization with the power grid, thereby improving the stability of the entire power system.

[0058] Specifically, the parallel device 7 is used to monitor the amplitude, frequency and phase of the terminal voltage of the synchronous phase condenser 1 and the low-voltage terminal voltage of the step-up transformer 8, and when it is monitored that the amplitude, frequency and phase of the terminal voltage of the synchronous phase condenser 1 and the low-voltage terminal voltage of the step-up transformer 8 meet the parallel conditions, the synchronous phase condenser 1 is controlled to be connected to the power grid 16 through the step-up transformer 8.

[0059] Here, the parallel device 7 is used to monitor the amplitude, frequency and phase of the voltage at the machine end of the synchronous condenser 1 and the voltage at the low voltage end of the step-up transformer 8. The parallel device 7 can monitor the amplitude, frequency and phase of the voltage at the machine end of the synchronous condenser 1 and the voltage at the low voltage end of the step-up transformer 8 in real time. These parameters reflect the voltage and current status in the power system and the synchronization status between the synchronous condenser 1 and the power grid 16.

[0060] When it is monitored that the amplitude, frequency and phase of the voltage at the machine end of the synchronous phase condenser 1 and the voltage at the low voltage end of the step-up transformer 8 meet the parallel conditions, the parallel device 7 will send a control signal. The parallel conditions usually include equal or similar voltage amplitudes, the same or similar frequencies, and a phase difference within an allowable range.

[0061] Once the paralleling conditions are met, the quasi-synchronous paralleling operation is completed through the paralleling device 7 (quasi-synchronous paralleling operation means that the synchronous condenser is excited before the parallel closing, and the voltage, frequency and phase of the generator are adjusted to be close to the system voltage, frequency and phase, and the generator circuit breaker is closed to complete the paralleling process), and the synchronous condenser 1 is connected to the power grid 16 through the step-up transformer 8. This usually involves adjusting the excitation current and mechanical torque of the synchronous condenser 1 to ensure that it can smoothly operate in synchronization with the power grid 16.

[0062] The process of connecting to the power grid: the parallel device 7 continuously monitors the amplitude, frequency and phase of the terminal voltage of the synchronous phase condenser 1 and the low-voltage terminal voltage of the step-up transformer 8; when the monitored parameters meet the parallel conditions, the parallel device 7 will make a judgment and prepare to send a control signal; the parallel device 7 sends a control signal to adjust the excitation current and mechanical torque of the synchronous phase condenser 1 to match the voltage, frequency and phase of the power grid 16; after confirming that the synchronization between the synchronous phase condenser 1 and the power grid 16 is good, the parallel device 7 will control the synchronous phase condenser 1 to connect to the power grid 16 through the step-up transformer 8 and start to provide reactive power support for the power grid.

[0063] When the synchronous condensers 1 are connected in parallel, the parallel device 7 simultaneously monitors the amplitude, frequency and phase of the terminal voltage of the synchronous condenser 1 and the low-voltage terminal voltage of the step-up transformer 8. The parallel device 7 sends an excitation control signal to the excitation controller 6 based on the monitoring information, and sends an AC motor speed control signal to the inverter 5; the excitation controller 6 adjusts and controls the excitation current of the synchronous condenser 1 according to the received excitation control signal, and adjusts the terminal voltage of the synchronous condenser 1 to be close to the amplitude of the low-voltage terminal voltage of the step-up transformer 8; the inverter 5 adjusts and controls the speed of the AC motor to speed up or slow down according to the received speed control signal, and adjusts the speed of the synchronous condenser 1 to be close to the synchronous speed; when the terminal voltage amplitude, frequency and phase of the synchronous condenser 1 meet the parallel conditions, the parallel device 7 is activated, and the synchronous condenser 1 is connected to the power grid through the step-up transformer 8.

[0064] After the synchronous condensers 1 are connected in parallel, the energy storage type synchronous condenser 1 based on the speed regulation of the AC motor 2 starts to regulate and control the reactive power and active power of the power grid; the voltage transformer 10 and the current transformer 11 detect the three-phase voltage and three-phase current of the power grid and input them into the system controller 3, and the system controller 3 also receives the real-time operation data information transmitted by the excitation controller 6, the inverter 5 and the energy storage equipment 7 respectively; the system controller 3 performs real-time regulation and control according to the received power grid voltage and current information, as well as the operation data information of the excitation controller 6, the inverter 5 and the energy storage equipment 4, and transmits control signals to the excitation controller 6, the AC motor 1, the inverter 5 and the energy storage equipment 4 respectively.

[0065] The excitation controller 6 controls the magnitude of the rotor excitation current of the synchronous phase condenser 1 according to the received excitation control signal, thereby realizing the control of the reactive power and voltage of the power grid; the inverter 5 controls the strength of the drag torque or braking torque applied by the rotor of the AC motor 2 to the rotor of the coaxially connected phase condenser 1 according to the received speed (or torque) control signal of the AC motor 2, controls the magnitude of the active power output or absorption by the synchronous phase condenser 1 to the power grid 16, realizes the regulation and control of the power grid frequency, provides "virtual inertia" for the synchronous phase condenser 1, and stabilizes the power grid frequency.

[0066] The electric energy input or fed back by the stator of the AC motor 2 is released or absorbed by the energy storage equipment 4 via the inverter 5 and the DC bus 15; the energy storage equipment 4 realizes coordinated control with the speed control signal of the inverter 5 according to the received energy control information, controls the energy storage equipment 4 to release or absorb energy via the DC bus 15, maintains the stability of the voltage and frequency of the DC bus 15, increases the short-circuit capacity and "virtual rotational inertia" of the power system in areas with a high proportion of new energy transmission, and enhances the ability of the power grid to resist risks.

[0067] Through the monitoring and control functions of the paralleling device 7, it is possible to ensure that the synchronous phase condenser 1 is safely and stably connected to the power grid 16 when the paralleling conditions are met, thereby avoiding impact or damage to the power grid; by accurately controlling the excitation current and mechanical torque of the synchronous phase condenser 1, it is possible to keep it in synchronous operation with the power grid 16, thereby improving the stability and reliability of the power system; after the synchronous phase condenser 1 is connected to the power grid, it can provide the necessary reactive power support for the power grid, which helps to maintain the stability of the power grid voltage.

[0068] Specifically, the step-up transformer 8 includes a three-phase low-voltage side port of the step-up transformer and a three-phase high-voltage side port of the step-up transformer. The three-phase winding of the stator of the synchronous phase modulator 1 is connected to the three-phase low-voltage side port of the step-up transformer 8 through the parallel device 7, and is connected to the power grid 16 in parallel through the three-phase high-voltage side port of the step-up transformer 8.

[0069] Here, the step-up transformer 8 can convert lower voltage electric energy into higher voltage electric energy. In the power system, the step-up transformer is usually used to step up the electric energy generated by the generator (such as a synchronous phase regulator) and then send it into the power grid to reduce the power loss during the transmission process.

[0070] Three-phase low-voltage side port of the step-up transformer: The input port of the step-up transformer is usually connected to the output port of the generator (such as the three-phase winding of the stator of the synchronous condenser 1). At this port, the step-up transformer receives lower voltage electric energy from the generator.

[0071] Three-phase high-voltage side port of step-up transformer: The output port of step-up transformer is usually connected to the power grid. At this port, the step-up transformer converts the input lower voltage electrical energy into higher voltage electrical energy and then feeds it into the power grid.

[0072] The connection between the synchronous condenser 1 and the step-up transformer 8: The three-phase winding of the stator of the synchronous condenser 1 is connected to the three-phase low-voltage side port of the step-up transformer 8 through the parallel device 7. The parallel device 7 plays a key role here, which ensures the synchronous connection between the synchronous condenser 1 and the step-up transformer 8, thereby avoiding the current shock caused by the phase difference or voltage mismatch.

[0073] Connection between the boost transformer 8 and the grid 16: The three-phase high-voltage side port of the boost transformer 8 is connected in parallel to the grid 16. This means that the boost transformer boosts the electric energy generated by the synchronous condenser 1 and transmits it in parallel with other electric energy in the grid. This connection method helps to improve the reliability and stability of the grid, because even if a generator or transformer fails, the grid can still obtain electric energy from other sources.

[0074] Through the configuration and connection method of the step-up transformer 8, the step-up transformer can convert the lower voltage electric energy generated by the synchronous phase condenser into higher voltage electric energy, reducing the power loss in the transmission process and improving the transmission efficiency; by connecting the synchronous phase condenser in parallel with the power grid through the step-up transformer, the system can better cope with load fluctuations and fault conditions in the power grid, improving the stability and reliability of the power grid; the step-up transformer enables the synchronous phase condenser to more efficiently utilize the electric energy it generates, providing more reactive power support for the power grid, and helping to maintain the stability of the power grid voltage.

[0075] Specifically, the DC end of the rectifier 9, the DC end of the inverter and the DC end of the energy storage equipment are connected to the same DC bus 15, and the AC end of the rectifier 9 is connected to the second three-phase AC power supply 13. The rectifier 9 is used to rectify the electric energy obtained from the second three-phase AC power supply 13 into DC power, and to transmit the DC power to the energy storage equipment 4 for charging and to provide energy for the parallel process of the synchronous phase regulator 1 and the power grid 16.

[0076] The rectifier 9 can convert alternating current (AC) into direct current (DC). In the power system, the rectifier 9 is usually used to obtain electrical energy from an alternating current power source and convert it into direct current for use by other devices.

[0077] Connection between DC terminal and AC terminal: The rectifier 9 has a DC terminal and an AC terminal. The DC terminal is connected to the same DC bus 15, which is also connected to the DC terminal of the inverter 5 and the DC terminal of the energy storage device 4. The AC terminal is connected to the second three-phase AC power source 13 to obtain electrical energy from the power source.

[0078] The main function of the rectifier 9 is to rectify the electric energy obtained from the second three-phase AC power supply 13 into DC power. This process is realized by the rectifier circuit inside the rectifier 9, which can convert the waveform of AC power into the waveform of DC power; the DC power rectified by the rectifier 9 is not only used to charge the energy storage equipment 4, but also to provide energy for the parallel process of the synchronous condenser 1 and the power grid 16. When the energy storage equipment 4 needs to be charged, the rectifier 9 transmits the DC power to the energy storage equipment 7; when the synchronous condenser 1 needs to be paralleled with the power grid 16, the DC power provided by the rectifier 9 can be used as a temporary energy source in the parallel process.

[0079] The second three-phase AC power source 13 is the power supply of the rectifier 9. The rectifier 9 can adopt a three-phase uncontrolled diode rectifier bridge or a three-phase controlled rectifier bridge. When the rectifier 9 adopts a three-phase uncontrolled diode rectifier bridge, the three-phase uncontrolled diode rectifier bridge can only rectify the second three-phase AC power source 13 into DC power, and energy can only be transmitted in one direction from the AC side to the DC side.

[0080] The DC side of the rectifier bridge is connected to the common DC bus of the inverter and the energy storage equipment after connecting the necessary soft start and filter components. When the energy storage type synchronous condenser system starts working, the rectifier 9 charges the energy storage equipment 4 with the necessary energy before the system starts working, and charges the energy consumed in the process of dragging the static synchronous condenser 1 from static starting to a speed close to synchronous speed to complete the parallel connection with the power grid 16;

[0081] After the synchronous condensers 1 are connected in parallel, the rectifier 9 can allow it to continue working or stop working; thereafter, the energy storage type synchronous condenser 1 based on the speed regulation of the AC motor 2 starts to regulate and control the reactive power and active power of the power grid.

[0082] When the rectifier 9 adopts a three-phase controllable rectifier bridge, energy can be transmitted in both directions between the AC side and the DC side. The rectifier 9 not only charges the energy storage equipment with the necessary energy before the energy storage type synchronous phase condenser system starts working, and consumes the energy consumed in the process of dragging the static synchronous phase condenser from static starting to a speed close to the synchronous speed to complete the parallel connection with the power grid, but also transmits energy to the AC motor 2 side when the system is working, thereby improving the dynamic performance of the system when working.

[0083] The DC ends of the rectifier 9, the inverter 5 and the energy storage device 4 are all connected to the same DC bus 15. This connection method enables the DC power in the system to be efficiently transmitted and distributed among the various components.

[0084] In the power system, energy can flow from the second three-phase AC power source 13 into the DC bus 15 through the rectifier 9, and then be transmitted to the energy storage device 4 for charging, or be converted into AC power through the inverter 5 and then supplied to other devices. At the same time, when the synchronous condenser 1 needs to be paralleled with the power grid, the DC power provided by the rectifier can be used as energy support in the paralleling process.

[0085] The configuration and connection method of the rectifier 9 improves the stability and flexibility of the system. By converting AC power into DC power through the rectifier 9, the system can use electric energy more efficiently and reduce energy waste. At the same time, the rectifier 9 also provides the necessary energy support for the operation of the energy storage equipment 4 and the synchronous condenser 1, so that the system can better cope with load fluctuations and faults in the power grid 16.

[0086] Specifically, the voltage transformer 10 is arranged between the power grid 16 and the system controller 3 to transmit the three-phase voltage information of the power grid 16 to the system controller 3, and the current transformer 11 is arranged between the power grid 16 and the system controller 3 to transmit the three-phase current information of the power grid 16 to the system controller 3.

[0087] Here, voltage transformer (PT) and current transformer (CT) are commonly used measurement and protection devices in power systems.

[0088] The voltage transformer 10 is arranged between the power grid 16 and the system controller 3, and its main function is to proportionally reduce the high voltage of the power grid 16 to a safe measurement range, and then transmit the reduced voltage signal to the system controller 3. The system controller 3 can obtain the three-phase voltage information of the power grid 16 through this voltage signal for monitoring, control and protection of the power system.

[0089] The current transformer 11 is also arranged between the power grid 16 and the system controller 3, and its function is to proportionally reduce the large current in the power grid 16 to a measurable range, and transmit the reduced current signal to the system controller 3. The system controller 3 can obtain the three-phase current information of the power grid 16 through this current signal, which is very important for load management, fault detection and location of the power system.

[0090] The voltage transformer 10 and the current transformer 11 respectively convert the three-phase voltage and three-phase current information of the power grid 16 into a signal form acceptable to the system controller 3, and transmit it to the system controller 3. This process ensures that the system controller 3 can obtain the state information of the power grid in real time and accurately;

[0091] The system controller 3 uses the information obtained from the voltage transformer 10 and the current transformer 11 to monitor and control the power system in real time. For example, when the voltage or current of the power grid is abnormal, the system controller 3 can quickly take measures, such as adjusting the excitation current of the synchronous phase regulator, cutting off the fault line, etc., to maintain the stable operation of the power system; when a fault occurs in the power grid, they can send a fault signal to the system controller 3 in time to help the system controller 3 quickly locate the fault point and take corresponding protection measures, such as tripping to isolate the fault area, to prevent the fault from expanding and causing greater damage to the power system.

[0092] Specifically, the system controller 3 is configured as follows:

[0093] Receiving three-phase voltage information detected by the voltage transformer 10 and three-phase current information detected by the current transformer 11;

[0094] Here, the system controller 3 first receives the three-phase voltage information detected by the voltage transformer 10 and the three-phase current information detected by the current transformer 11. These information reflect the current voltage and current status of the power grid 16 and are the basis for the system controller 3 to perform subsequent calculations and controls.

[0095] The system controller 3 also receives operation data information from the excitation controller 6, the inverter 5 and the energy storage equipment 4. These data include the excitation current of the synchronous condenser 1, the output power of the inverter, the charge and discharge status of the energy storage equipment, etc. The system controller 3 processes and analyzes these data to evaluate the overall operation status of the power system.

[0096] According to the three-phase voltage information, three-phase current information and the operating data information of the excitation controller 6, the inverter 5 and the energy storage equipment 4, corresponding control signals are sent to the excitation controller 6, the inverter 5 and the energy storage equipment 4 respectively to coordinately control the reactive power output, active power output and grid frequency stability of the synchronous phase regulator 1.

[0097] Based on the received information and data analysis results, the system controller 3 sends corresponding control signals to the excitation controller 6, the inverter 5 and the energy storage device 4. These control signals are intended to coordinately control the reactive power output, active power output and grid frequency stability of the synchronous condenser 1.

[0098] The system controller 3 can control the excitation current of the synchronous condenser 1 by adjusting the output of the excitation controller 6, thereby adjusting its reactive power output, which is crucial to maintaining the stability of the grid voltage.

[0099] The system controller 3 can adjust the active power output of the synchronous condenser 1 or other distributed energy sources by controlling the output power of the inverter 5. This helps to balance the active power demand in the power grid and maintain the stability of the power grid frequency.

[0100] The system controller 3 can also control the charging and discharging state of the energy storage equipment 4 according to the grid state and demand. The energy storage equipment 4 can discharge when the grid load is peak to provide additional active power; and charge when the load is low to absorb excess active power.

[0101] The magnitude and direction of the electromagnetic torque of the AC motor are controlled by the inverter, and the capacity of the inverter matches the capacity of the AC motor.

[0102] In an alternative embodiment, see Figure 2 , Figure 2 This is one of the flow charts of the synchronous condenser control system provided in the embodiment of the present application.

[0103] S101. When the electromagnetic torque of the AC motor controlled by the inverter is consistent with the rotation direction of the rotor of the AC motor, it means that the electromagnetic torque on the rotor of the AC motor is the driving torque, and the AC motor is controlled to enter the motor operation state and the synchronous condenser is switched to the generator operation state.

[0104] In this step, when the electromagnetic torque of the AC motor controlled by the inverter is consistent with the rotation direction of the rotor of the AC motor, it means that the electromagnetic torque acting on the rotor of the AC motor is the driving torque.

[0105] In this case, the AC motor is driven into motor operation, i.e. it starts drawing energy from electrical energy and converting it into mechanical energy.

[0106] At the same time, the synchronous condenser switches from motor mode (if it was previously in that mode) to generator mode. In generator mode, the synchronous condenser starts to generate electrical energy instead of consuming it.

[0107] S102, the inverter absorbs electrical energy from the DC bus side, converts it into mechanical energy output by the AC motor and transmits it to the rotor of the synchronous phase regulator.

[0108] The electric energy absorbed from the DC bus side is first converted into AC energy by the inverter, and then this AC energy is transmitted to the AC motor.

[0109] The AC motor uses this electrical energy to generate mechanical energy, which is then transferred to the rotor of the synchronous condenser. In this process, the inverter can efficiently convert DC power into AC power to meet the operating requirements of the AC motor.

[0110] S103. The mechanical energy on the rotor of the synchronous condenser is converted into electrical energy in the three-phase winding of the stator of the synchronous condenser through the magnetic field interaction between the stator of the synchronous condenser and the rotor of the synchronous condenser, so as to release the electrical energy to the power grid through the step-up transformer, generate active power to the power grid, and maintain the stability of the power grid.

[0111] In this step, the mechanical energy on the rotor of the synchronous condenser is converted into electrical energy through the magnetic field interaction between the stator and the rotor of the synchronous condenser, and the electrical energy is stored in the three-phase winding of the stator of the synchronous condenser.

[0112] Subsequently, the electric energy is boosted by the step-up transformer and released into the power grid. In this process, the synchronous condenser acts as a generator to send active power to the power grid. In this process, even if the motor speed is constantly decreasing, the electromagnetic torque is still the driving torque. The AC motor provides mechanical power to the synchronous condenser rotor, slowing down the speed of the motor speed and the frequency of the power grid, which helps to maintain the stable operation of the power grid. The function of the step-up transformer is to increase the voltage level of the electric energy so as to reduce the power loss during long-distance power transmission.

[0113] In another alternative embodiment, see Figure 3 , Figure 3 This is the second flow chart of the synchronous phase condenser control system provided in the embodiment of the present application.

[0114] S201, when the electromagnetic torque of the AC motor controlled by the inverter is opposite to the rotation direction of the rotor of the AC motor, it means that the electromagnetic torque on the rotor of the AC motor is a braking torque, and the AC motor is controlled to enter a generator operation state and the synchronous condenser is switched to a motor operation state;

[0115] In this step, when the inverter controls the electromagnetic torque of the AC motor to be opposite to the rotation direction of the rotor of the AC motor, it means that the electromagnetic torque acting on the rotor of the AC motor is a braking torque.

[0116] In this case, the AC machine no longer operates as a motor, but enters generator operation, i.e. it starts converting mechanical energy into electrical energy.

[0117] At the same time, the synchronous condenser switches from generator mode (if it was previously in that mode) to motor mode, i.e. it starts drawing electrical energy from the grid and converting it into mechanical energy.

[0118] S202, the power grid inputs electric energy into the three-phase winding of the stator of the synchronous condenser through the low-voltage end of the step-up transformer, and through the magnetic field interaction between the stator of the synchronous condenser and the rotor of the synchronous condenser, the rotor of the synchronous condenser obtains mechanical energy and transmits it to the rotor of the AC motor;

[0119] Here, the electric energy in the power grid is first stepped down by the low-voltage end of the step-up transformer, and then input into the three-phase winding of the stator of the synchronous condenser. Through the magnetic field interaction between the stator and rotor of the synchronous condenser, the electric energy is converted into mechanical energy and transmitted to the rotor of the AC motor.

[0120] S203, according to the magnetic field interaction between the stator of the AC motor and the rotor of the AC motor, the AC motor converts the mechanical energy on the rotor of the AC motor into electrical energy in the three-phase winding of the stator of the AC motor;

[0121] Among them, the mechanical energy obtained on the rotor of the AC motor is converted into electrical energy through the magnetic field interaction between the stator and rotor of the AC motor. The electrical energy is stored in the three-phase winding of the stator of the AC motor, ready to be extracted and output by the inverter.

[0122] S204, the inverter outputs the electric energy in the three-phase winding of the stator of the AC motor to the DC bus, and inputs the electric energy into the energy storage device through the DC bus for storage.

[0123] The inverter extracts the electrical energy from the three-phase winding of the stator of the AC motor and outputs it to the DC bus.

[0124] Then, this electrical energy is input into the energy storage equipment (such as battery packs, supercapacitors, etc.) through the DC bus for storage. During this process, even if the motor speed is increasing, the electromagnetic torque is still the driving torque. The synchronous phase regulator provides mechanical power to the AC motor rotor to slow down the increase in motor speed and grid frequency. This process achieves the purpose of converting the electrical energy generated by the AC motor into DC energy and storing it.

[0125] Here, the system controller controls the operation of the synchronous phase condenser based on AC motor speed regulation, realizes coordinated control among the synchronous phase condenser, inverter, and energy storage equipment, and the system controller receives in real time the three-phase voltage information and three-phase current information detected by the voltage transformer and current transformer, as well as the operating data information of the excitation controller, inverter, and energy storage equipment.

[0126] The system controller performs real-time adjustment and control based on the received grid voltage and current information, as well as the operating data information of the excitation controller, inverter and energy storage equipment, and then sends control signals to the excitation controller, AC motor control inverter and energy storage equipment respectively; the excitation controller controls the magnitude of the synchronous condenser rotor excitation current according to the received excitation control signal, thereby controlling the output of reactive power and the terminal voltage of the synchronous condenser; the inverter controls the drag torque or braking torque applied by the AC motor rotor to the coaxially connected condenser rotor according to the received speed (or torque) control signal, and the synchronous condenser outputs or absorbs active power to the grid, providing "virtual inertia" for the condenser, realizing the regulation and control of the grid frequency and stabilizing the grid frequency; the electric energy input or feedback from the AC motor stator is released or absorbed by the energy storage equipment through the inverter and the DC bus; the energy storage equipment realizes coordinated control with the inverter speed control signal according to the received energy control information, controls the energy storage equipment to release or absorb through the DC bus, and keeps the DC bus voltage stable.

[0127] In the present application, when the synchronous condensers are connected in parallel, the parallel device simultaneously monitors the amplitude and frequency of the voltage at the machine end of the synchronous condenser and the voltage at the low voltage end of the step-up transformer. The parallel device sends an excitation control signal to the excitation controller based on the monitoring information, and sends an AC motor acceleration and deceleration signal to the inverter. At this time, the excitation controller adjusts and controls the excitation of the synchronous condenser according to the received excitation control signal to increase or decrease the voltage at the machine end of the synchronous condenser, and the inverter controls the AC motor speed to slowly increase or reduce the AC motor acceleration and deceleration signal according to the received AC motor acceleration and deceleration signal. At the moment when the amplitude, frequency and phase of the voltage at the machine end of the synchronous condenser meet the parallel conditions, the parallel device operates to connect the synchronous condenser to the power grid through the step-up transformer.

[0128] When the synchronous phase regulators of the present application are in normal operation after being connected in parallel, the voltage transformer and the current transformer will detect the three-phase voltage information and the three-phase current information and input them into the system controller. The system controller will also receive the real-time operation data information transmitted by the excitation controller, the inverter and the energy storage equipment respectively. The system controller will perform real-time adjustment and control based on the received information, and transmit the corresponding control signals to the excitation controller, the AC motor control inverter and the energy storage equipment respectively, so as to control the excitation controller, the inverter and the energy storage equipment to operate in the expected direction of their adjustment and control.

[0129] When the synchronous condenser is not needed to participate in regulating the grid voltage and the grid voltage is normal, normal excitation current flows through the synchronous condenser excitation winding, the amplitude of the excitation electromotive force inside the synchronous condenser is basically the same as the amplitude of the low-voltage end voltage of the step-up transformer, and the stator winding current of the synchronous condenser is basically zero.

[0130] When the grid voltage is lower than the normal voltage, the system controller sends an excitation control signal to the excitation controller to increase the excitation current. The excitation current of the synchronous condenser controlled by the excitation controller increases, the inductive reactive current emitted by the synchronous condenser increases, and the inductive reactive power emitted by the synchronous condenser to the grid increases (it is also possible that the capacitive reactive current emitted by the synchronous condenser decreases, reducing the capacitive reactive power emitted by the synchronous condenser to the grid), and the grid voltage gradually returns to normal voltage.

[0131] When the grid voltage is higher than the normal voltage, the system controller sends an excitation control signal to the excitation controller to weaken the excitation current. The excitation current of the synchronous condenser controlled by the excitation controller is reduced, the inductive reactive current emitted by the synchronous condenser is reduced, and the inductive reactive power emitted by the synchronous condenser to the grid is reduced (it is also possible that the capacitive reactive current emitted by the synchronous condenser increases, increasing the capacitive reactive power emitted by the synchronous condenser to the grid), and the grid voltage gradually returns to normal voltage.

[0132] When a short circuit occurs in the power grid and the grid voltage plummets, due to the existence of the damping winding on the synchronous condenser rotor, the direct-axis super transient reactance of the synchronous condenser is small, and the direct-axis of the condenser forcibly increases the excitation current, which can greatly improve the output of the synchronous condenser's instantaneous inductive reactive power and improve the low voltage ride-through capability of the power grid. In this way, the synchronous condenser plays the role of grid voltage support and reactive power compensation, enhancing the dynamic stability of the power system.

[0133] When the power grid operates normally and the load increases suddenly, the voltage and frequency will drop. The system controller sends control signals such as increasing the excitation current, increasing the AC motor driving electromagnetic torque and increasing the energy released by the energy storage equipment to the excitation controller, inverter and energy storage equipment respectively. After receiving their corresponding control signals, they immediately start to adjust and control their respective operating states. The excitation current of the synchronous condenser controlled by the excitation controller increases, the inductive reactive current emitted by the synchronous condenser increases, the inductive reactive power emitted by the synchronous condenser to the power grid increases, and the grid voltage is increased. The inverter control increases the driving electromagnetic torque of the AC motor, increases the driving torque on the rotor of the synchronous condenser, increases the active power output by the synchronous condenser to the power grid, and slows down the speed at which the grid frequency decreases.

[0134] At the same time, the energy storage equipment controls and increases the energy released to the DC bus. Most of the energy released by the energy storage equipment is converted into electrical energy through various energy conversions on the path of energy storage equipment, DC bus, inverter, AC motor, synchronous phase regulator and step-up transformer, and input into the power grid, thereby realizing the regulation and control of the grid frequency, stabilizing the grid frequency and providing "virtual inertia" for the phase regulator.

[0135] When the power grid is operating normally and the load suddenly decreases, the electric energy fed into the power grid by the new energy power generation equipment has not been reduced in time, and the voltage and frequency will increase. The system controller sends control signals such as reducing the excitation current, increasing the braking electromagnetic torque of the AC motor, and increasing the energy absorption of the energy storage equipment to the excitation controller, inverter and energy storage equipment respectively. After receiving their corresponding control signals, they immediately start to adjust and control their respective operating states; the excitation current of the synchronous condenser controlled by the excitation controller is reduced, the inductive reactive current emitted by the synchronous condenser is reduced, the inductive reactive power emitted by the synchronous condenser to the power grid is reduced, and the grid voltage is reduced; the inverter control increases the braking electromagnetic torque of the AC motor, increases the braking torque on the rotor of the synchronous condenser, increases the active power absorbed by the machine end of the synchronous condenser from the power grid, and slows down the rate of increase in the grid frequency.

[0136] At the same time, the energy storage equipment controls and increases the electric energy absorbed by the DC bus. Most of the electric energy input from the power grid to the synchronous condenser is converted into a certain form of energy and stored in the energy storage equipment through various energy conversions on the path of synchronous condenser, AC motor, inverter, DC bus and energy storage equipment, so as to adjust and control the grid frequency, stabilize the grid frequency and provide "virtual inertia" for the condenser. In this way, the primary frequency regulation of the grid is realized, and the dynamic stability of the power system is enhanced.

[0137] After each frequency modulation control of the synchronous phase condenser during the process of grid frequency drop or frequency increase, it is also necessary to control the electromagnetic torque of the AC motor to supplement the energy released or absorbed by the energy storage equipment at an appropriate time.

[0138] Moreover, during the period when the synchronous condenser is not performing primary frequency modulation control, the AC motor is controlled to be in a feedback braking state. The electric energy absorbed by the synchronous condenser from the power grid is used to compensate for the energy consumption in the synchronous condenser except the stator and rotor copper loss during the same operation, as well as all energy consumption generated in the AC motor, inverter and energy storage equipment, to maintain a high energy level stored in the energy storage equipment. It can not only release huge energy when the grid frequency drops, provide the condenser with strong "virtual inertia", but also absorb a certain amount of grid electricity when the grid frequency increases.

[0139] The synchronous condenser control system provided in the embodiment of the present application includes a synchronous condenser, an AC motor and a system controller. The synchronous condenser is used to be coaxially mechanically connected to the AC motor through a coupling; the AC motor is used to provide electromagnetic torque to the synchronous condenser when receiving a control signal, so that the synchronous condenser performs power control actions on the power grid; the system controller is used to receive power grid voltage, current information and operation data information, and send a control signal to the AC motor when a change in power grid frequency is detected to maintain power grid stability. Through this application, the synchronous condenser and the AC motor work together to respond to changes in power grid frequency in real time, maintain power grid stability, and improve power grid operation efficiency.

[0140] The synchronous condenser control system is suitable for use with wind power and photovoltaic power stations, and can mainly solve the following problems:

[0141] Rapid power replenishment capability: When clouds pass by and cause a sudden drop in photovoltaic power generation, the synchronous phase regulator can quickly provide reactive power to make up for the power shortage caused by the reduction in photovoltaic power generation and ensure the stable operation of the power grid.

[0142] Absorbing excess electricity: When wind power encounters gusts and causes a sudden increase in power generation, synchronous phase regulators can absorb excess reactive power, prevent the grid voltage from being too high or the frequency from fluctuating, and maintain the voltage and frequency stability of microgrids in remote areas.

[0143] In summary, the synchronous phase condenser control system can cope with the sudden drop in photovoltaic power generation and the sudden increase in wind power by quickly adjusting reactive power, effectively maintaining the stable operation of the power system. It is particularly suitable for use with wind power and photovoltaic power stations, especially in microgrids in remote areas, and can significantly improve the stability and reliability of the power grid.

[0144] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0145] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0146] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0147] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0148] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application can essentially be embodied in the form of a software product, or in other words, the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0149] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above-mentioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A synchronous phase condenser control system, characterized in that: The control system includes a synchronous condenser, an AC motor and a system controller. Wherein, the synchronous condenser is used to be coaxially mechanically connected to the AC motor through a coupling; The AC motor is used to provide electromagnetic torque to the synchronous condenser when receiving a control signal, so that the synchronous condenser performs power control on the power grid; The system controller is used to receive grid voltage, current information and operation data information, and when a grid frequency change is detected, sends the control signal to the AC motor to maintain grid stability.

2. The system according to claim 1, characterized in that The control system also includes energy storage equipment and an inverter. Wherein, the inverter is connected to the AC motor to control the electromagnetic torque of the AC motor; The energy storage device is used to store and release electric energy, and is connected to an inverter corresponding to the AC motor via a DC bus, so as to convert electric energy into mechanical energy with the AC motor.

3. The system according to claim 2, characterized in that The control system also includes an excitation controller, Among them, the excitation controller is connected to a first three-phase AC power supply to obtain electrical energy from the first three-phase AC power supply, and the excitation controller outputs DC power to excite the excitation winding of the synchronous condenser, so as to control the strength and direction of the magnetic field inside the synchronous condenser by adjusting the size and direction of the output DC power.

4. The system according to claim 3, characterized in that The control system also includes a parallel device, Among them, the parallel device is used to monitor the amplitude, frequency and phase of the synchronous phase condenser machine terminal voltage and the low-voltage end voltage of the step-up transformer, and when it is monitored that the amplitude, frequency and phase of the synchronous phase condenser machine terminal voltage and the low-voltage end voltage of the step-up transformer meet the parallel conditions, the synchronous phase condenser is controlled to be connected to the power grid through the step-up transformer.

5. The system according to claim 4, characterized in that The control system also includes a step-up transformer, Among them, the step-up transformer includes a three-phase low-voltage side port of the step-up transformer and a three-phase high-voltage side port of the step-up transformer. The three-phase winding of the stator of the synchronous phase regulator is connected to the three-phase low-voltage side port of the step-up transformer through the parallel device, and is connected to the power grid in parallel through the three-phase high-voltage side port of the step-up transformer.

6. The system according to claim 5, characterized in that The control system further includes a rectifier, The DC end of the rectifier, the DC end of the inverter and the DC end of the energy storage equipment are connected to the same DC bus, the AC end of the rectifier is connected to a second three-phase AC power supply, and the rectifier is used to rectify the electric energy obtained from the second three-phase AC power supply into DC power, and to transmit the DC power to the energy storage equipment for charging and to provide energy for the parallel process of the synchronous phase regulator and the power grid.

7. The system according to claim 6, characterized in that The control system also includes a voltage transformer and a current transformer, The voltage transformer is arranged between the power grid and the system controller to transmit the three-phase voltage information of the power grid to the system controller, and the current transformer is arranged between the power grid and the system controller to transmit the three-phase current information of the power grid to the system controller.

8. The system according to claim 7, characterized in that The system controller is configured to: Receiving three-phase voltage information detected by a voltage transformer and three-phase current information detected by a current transformer; According to the three-phase voltage information, three-phase current information and the operating data information of the excitation controller, the inverter and the energy storage equipment, corresponding control signals are sent to the excitation controller, the inverter and the energy storage equipment respectively to coordinately control the reactive power output, active power output and grid frequency stability of the synchronous phase regulator.

9. The system according to claim 5, characterized in that The control system is configured to: When the electromagnetic torque of the AC motor controlled by the inverter is consistent with the rotation direction of the rotor of the AC motor, it means that the electromagnetic torque on the rotor of the AC motor is the driving torque, and the AC motor is controlled to enter the motor operation state and the synchronous condenser is switched to the generator operation state; The inverter absorbs electrical energy from the DC bus side, converts it into mechanical energy output by the AC motor, and transmits it to the rotor of the synchronous condenser; Through the magnetic field interaction between the stator of the synchronous condenser and the rotor of the synchronous condenser, the synchronous condenser converts the mechanical energy on the rotor into electrical energy in the three-phase winding of the stator of the synchronous condenser, so as to release the electrical energy to the power grid through the step-up transformer, generate active power to the power grid, and maintain the stability of the power grid.

10. The system according to claim 9, characterized in that The control system is also configured to: When the electromagnetic torque of the AC motor controlled by the inverter is opposite to the rotation direction of the rotor of the AC motor, it means that the electromagnetic torque on the rotor of the AC motor is a braking torque, and the AC motor is controlled to enter the generator operation state and the synchronous condenser is switched to the motor operation state; The power grid inputs electric energy into the three-phase winding of the stator of the synchronous condenser through the low-voltage end of the step-up transformer, and through the magnetic field interaction between the stator of the synchronous condenser and the rotor of the synchronous condenser, the rotor of the synchronous condenser obtains mechanical energy and transmits it to the rotor of the AC motor; According to the magnetic field interaction between the stator of the AC motor and the rotor of the AC motor, the AC motor converts the mechanical energy on the rotor of the AC motor into electrical energy in the three-phase winding of the stator of the AC motor; The inverter outputs the electric energy in the three-phase winding of the stator of the AC motor to the DC bus, and inputs the electric energy into the energy storage device through the DC bus for storage.

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