High-reliability intelligent extra-high voltage isolation switch servo driving mechanism

Abstract

The invention discloses a high-reliability intelligent extra-high voltage isolation switch servo driving mechanism, and relates to the field of isolation switch servo, the high-reliability intelligent extra-high voltage isolation switch servo driving mechanism comprises an interface board, a control board and a driving board, the interface board is provided with six high-voltage input units, six high-voltage output units and input and output terminals, a control unit, an input and output terminal, two groups of RS485 units, a power supply conversion unit, a current sampling processing unit and an encoder signal processing unit are arranged on the control panel. According to the motor-driven operating mechanism based on the servo drive control technology, the overload performance of the operating mechanism is improved due to the fact that the overload capacity of a servo motor is high, and the service life of the operating mechanism is prolonged. Due to the adoption of the modular design, the structural design of the operating mechanism of the high-voltage switchgear is simplified, and due to the adoption of the servo drive control technology, the rotation of the motor is accurately controlled, and the switching-on and switching-off control precision of the operating mechanism is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of isolating switch servo technology, and in particular to a high-reliability intelligent ultra-high voltage isolating switch servo drive mechanism. Background Art

[0002] The isolating switch is a necessary component of the combined electrical appliance. The world's first high-voltage gas-insulated switchgear was designed in the 1920s, using oil as the insulating medium. Compared with the air-insulated switchgear equipped with gas-blown circuit breakers, these oil-insulated switchgear have higher opening and closing capabilities. As the current rating increases, the risk of fire also increases, which has a great impact on substations. Oil is highly flammable, so switchgear began to develop in the direction of gas insulation. In 1968, the world's first batch of SF6 gas-insulated high-voltage switchgear that used SF6 as the insulating and arc-extinguishing medium was put on the market, which was the origin of the later gas-insulated combined electrical appliance GIS.

[0003] In the existing technology, it is urgent to carry out research on the above-mentioned problems to improve the reliability and intelligence level of the disconnector operating mechanism. In order to meet the needs of accurate evaluation and reliability of the switch position of the disconnector operating mechanism, a high-reliability intelligent disconnector servo drive technology is studied, which mainly includes servo controller, servo motor, reducer and other modules. The servo controller receives the opening and closing instructions and controls the motor, and then drives the primary equipment through the high-reliability reducer transmission structure. Therefore, a high-reliability intelligent UHV disconnector servo drive mechanism is needed to meet people's needs. Summary of the invention

[0004] The object of the present invention is to provide a high-reliability intelligent UHV isolating switch servo drive mechanism to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a high-reliability intelligent ultra-high voltage isolating switch servo drive mechanism, comprising an interface board, a control board, and a drive board. The interface board is provided with 6 high-voltage input units, 6 high-voltage output units, and input and output terminals. The control board is provided with a control unit, input and output terminals, two groups of RS485 units, a power conversion unit, a current sampling processing unit, and an encoder signal processing unit. The drive board is provided with a switching power supply, a bus voltage and current sampling unit, a gate drive signal unit, an output current sampling unit, a PFC filter circuit unit, a rectifier bridge unit, a DC bus capacitor unit, and a three-phase inverter bridge unit. The drive board is provided with an AC power supply, a permanent magnet synchronous motor, and an encoder / 485 communication unit.

[0006] Preferably, the input and output terminals of the interface board are connected to the input and output terminals of the control board, the input and output terminals of the control board are connected to the control unit, the AC power supply, PFC filter circuit unit, rectifier bridge unit, DC bus capacitor unit, three-phase inverter bridge unit, permanent magnet synchronous motor, encoder / 485 communication unit, encoder signal processing unit and control unit are connected in sequence, the DC bus capacitor unit, bus voltage and current sampling unit, and control unit are connected in sequence, the three-phase inverter bridge unit and gate drive signal unit are connected to the control unit, and the output current sampling unit and current sampling processing unit are connected to the control unit.

[0007] Preferably, the rectifier bridge unit and the rectifier device system adopt a rectifier bridge module, and the system is protected by a soft start circuit composed of a resistor and a relay. When the system is powered on, the switch is disconnected, and the resistor plays a role in suppressing excessive charging current. When the main circuit voltage rises to a certain value, the switch is closed, and the resistor is cut off from the main circuit to achieve soft start.

[0008] Preferably, the DC bus capacitor unit, the rectifier bridge outputs a pulsating DC voltage. In order to generate a stable DC voltage, a large-capacity electrolytic capacitor is required for voltage stabilization and filtering. Since the input mains power is a 50Hz sinusoidal AC, only the voltage of the wave head part is greater than the voltage across the capacitor, and the capacitor is charged. When the motor is running at high speed with heavy load, without considering the loss, the energy consumed in each charge and discharge cycle satisfies the formula:

[0009]

[0010] It can be obtained that the heavier the load and the smaller the capacitance value, the greater the voltage drop across the capacitor. To ensure that the output power remains unchanged, a larger current needs to be output, which will directly threaten the safety of the power module and increase the loss. In addition, from the perspective of PMSM vector control principle, excessive bus voltage fluctuations will lead to excessive current loop disturbances, poor current loop regulation, and large overshoot or even oscillation in the actual torque current. The specific selection of the energy storage capacitor capacitance can be obtained based on engineering experience, that is, roughly 1800μF is configured according to 1.8kW. In order to suppress the high-frequency oscillation of the DC bus voltage, a non-inductive absorption capacitor is connected in parallel at both ends of the DC input of the module. Based on experience, a non-inductive absorption capacitor of 0.68μF / 850V is selected.

[0011] Preferably, the three-phase inverter bridge unit is internally provided with upper and lower bridge arm control power supply undervoltage locking circuits and a lower bridge arm short-circuit protection circuit, and is also provided with lower bridge arm short-circuit protection and control power supply undervoltage protection fault signal outputs.

[0012] Preferably, the current sampling processing unit and the resistance sampling circuit obtain a DC bus voltage sampling value, and compare it with a set value provided by a reference circuit through a comparator. When the system brakes the DC bus voltage to a certain value, the comparator outputs a braking enable signal to the DSP. The DSP sends a signal to connect the braking resistors at both ends of the bus in parallel to the DC bus to consume excess energy until the DC bus voltage drops to a safe value and the braking resistors are cut off.

[0013] Preferably, the bus voltage and current sampling unit and the output current sampling unit, the current sampling voltage value U obtained by sampling the sampling resistor enters the HCPL-7840 through a filtering circuit, and the HCPL-7840 plays a role of linear amplification and isolation. The obtained differential signal is then processed by the subsequent DC bias and voltage follower circuit, and finally sent to the A / D input pin of the DSP, and the sampling and conversion is performed by the A / D on the DSP chip.

[0014] Preferably, the 6-way high-voltage input unit and the 6-way high-voltage output unit need to design a high-voltage interface circuit for the servo mechanism driver to meet the high-voltage input signal of AC220V / DC220V / DC110V according to the voltage environment of the high-voltage isolation grounding switch. The signal is rectified, stabilized, filtered and isolated by optical coupling, and the high-voltage signal is converted into a low-voltage signal. Then, it is finally sent to the input pin of the DSP through signal processing, and the signal is processed and calculated by the DSP chip. The DO signal of the DSP drives the isolation optical coupling, and the signal drives the relay after passing through the isolation optical coupling. The relay is externally connected to the high-voltage signal to realize the control output of the external high-voltage signal by the DSP output signal.

[0015] Preferably, the encoder / 485 communication unit communicates with the 485 data outside the system through a 485 chip and a high-speed optical coupler. The RS485 bus adopts a balanced transmission and differential reception mode, and isolates the system power supply and the power supply of the RS-485 transceiver through DC-DC, and isolates the signal through an isolation device.

[0016] The beneficial effects of the present invention are:

[0017] 1. In the present invention, the motor-driven operating mechanism based on the servo drive control technology has improved overload performance of the operating mechanism due to the strong overload capacity of the servo motor. The modular design simplifies the structural design of the operating mechanism of the high-voltage switchgear. The servo drive control technology is used to accurately control the rotation of the motor and improve the opening and closing control accuracy of the operating mechanism. The drive control system can obtain mechanical, electrical and control status information in real time, thereby improving the system status perception capability.

[0018] 2. In the present invention, the motor-driven operating mechanism based on servo control can push the opening and closing stroke action of the existing high-voltage switchgear from the open-loop control of the traditional hydraulic spring system to a more advanced and reliable intelligent closed-loop control, which will be conducive to promoting the high-quality, reliable and intelligent application of high-voltage switchgear. By monitoring key parameters such as mechanical state, electrical state and control state, the operating reliability of the equipment is comprehensively evaluated, and the maintenance of high-voltage switchgear is transformed from "periodic maintenance" to "condition maintenance", thereby improving equipment safety, reducing maintenance costs, and bringing huge economic benefits. The research and development results can be widely used in the construction of new power systems to improve the intelligence level of smart grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The control principle diagram of the isolating switch servo mechanism driver proposed by the present invention;

[0020] Figure 2 The overall structural block diagram of the servo mechanism driver proposed by the present invention;

[0021] Figure 3 The phasor diagram of the field oriented control proposed by the present invention;

[0022] Figure 4 The present invention proposes a method based on i d =0 vector control structure diagram;

[0023] Figure 5 A vector diagram of the three-phase voltage proposed by the present invention;

[0024] Figure 6 The schematic diagram of the three-phase voltage-source inverter proposed by the present invention;

[0025] Figure 7 Schematic diagram of the voltage space vector and the corresponding (abc) proposed by the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Reference Figure 1-Figure 7A high-reliability intelligent UHV isolating switch servo drive mechanism comprises three parts: an interface board, a control board and a drive board. The interface board is provided with 6 high-voltage input units, 6 high-voltage output units and input and output terminals. The control board is provided with a control unit, input and output terminals, two groups of RS485 units, a power conversion unit, a current sampling processing unit and an encoder signal processing unit. The drive board is provided with a switching power supply, a bus voltage and current sampling unit, a gate drive signal unit, an output current sampling unit, a PFC filter circuit unit, a rectifier bridge unit, a DC bus capacitor unit and a three-phase inverter bridge unit. The drive board is provided with an AC power supply, a permanent magnet synchronous motor and an encoder / 485 communication unit.

[0028] Furthermore, the input and output terminals of the interface board are connected to the input and output terminals of the control board, the input and output terminals of the control board are connected to the control unit, the AC power supply, PFC filter circuit unit, rectifier bridge unit, DC bus capacitor unit, three-phase inverter bridge unit, permanent magnet synchronous motor, encoder / 485 communication unit, encoder signal processing unit and control unit are connected in sequence, the DC bus capacitor unit, bus voltage and current sampling unit, and control unit are connected in sequence, the three-phase inverter bridge unit and gate drive signal unit are connected to the control unit, and the output current sampling unit and current sampling processing unit are connected to the control unit.

[0029] Furthermore, the rectifier bridge unit and the rectifier device system use a rectifier bridge module. When the system is powered on for the first time, due to the large capacitance of the filter capacitor, the instantaneous charging current will be very large. If it is not protected, the rectifier bridge will burn out. The system uses a soft start circuit composed of a resistor and a relay for protection. When the system is powered on, the switch is disconnected, and the resistor plays a role in suppressing excessive charging current. When the main circuit voltage rises to a certain value, the switch is closed, and the resistor is removed from the main circuit to achieve soft start.

[0030] Furthermore, the DC bus capacitor unit, the rectifier bridge outputs a pulsating DC voltage. In order to generate a stable DC voltage, a large-capacity electrolytic capacitor is required for voltage stabilization and filtering. Since the input mains power is a 50Hz sinusoidal AC, only the voltage at the wave head is greater than the voltage across the capacitor to charge the capacitor. When the motor is running at high speed with heavy load, without considering the loss, the energy consumed in each charge and discharge cycle satisfies the formula:

[0031]

[0032] It can be obtained that the heavier the load and the smaller the capacitance value, the greater the voltage drop across the capacitor. To ensure that the output power remains unchanged, a larger current needs to be output, which will directly threaten the safety of the power module and increase the loss. In addition, from the perspective of PMSM vector control principle, excessive bus voltage fluctuations will lead to excessive current loop disturbances, poor current loop regulation, and large overshoot or even oscillation in the actual torque current. The specific selection of the energy storage capacitor capacitance can be obtained based on engineering experience, that is, roughly 1800μF is configured according to 1.8kW. In order to suppress the high-frequency oscillation of the DC bus voltage, a non-inductive absorption capacitor is connected in parallel at both ends of the DC input of the module. Based on experience, a non-inductive absorption capacitor of 0.68μF / 850V is selected.

[0033] Furthermore, the three-phase inverter bridge unit is internally provided with upper and lower bridge arm control power supply undervoltage locking circuits and a lower bridge arm short-circuit protection circuit, and is also provided with lower bridge arm short-circuit protection and control power supply undervoltage protection fault signal outputs.

[0034] Furthermore, the current sampling processing unit and the resistor sampling circuit obtain a DC bus voltage sampling value, and compare it with a set value provided by a reference circuit through a comparator. When the system brakes the DC bus voltage to a certain value, the comparator outputs a braking enable signal to the DSP. The DSP sends a signal to connect the braking resistors at both ends of the bus in parallel to the DC bus to consume excess energy until the DC bus voltage drops to a safe value and the braking resistors are cut off.

[0035] Furthermore, the bus voltage and current sampling unit and the output current sampling unit, the current sampling voltage value U obtained by sampling the sampling resistor enters the HCPL-7840 through the filtering circuit, and the HCPL-7840 plays the role of linear amplification and isolation. The obtained differential signal is then processed by the subsequent DC bias and voltage follower circuit, and finally sent to the A / D input pin of the DSP, and the A / D on the DSP chip performs sampling and conversion.

[0036] Furthermore, the 6-way high-voltage input unit and the 6-way high-voltage output unit need to design a high-voltage interface circuit for the servo mechanism driver to meet the high-voltage input signal of AC220V / DC220V / DC110V according to the voltage environment of the high-voltage isolation grounding switch. The signal is rectified, stabilized, filtered and isolated by optical coupling, and the high-voltage signal is converted into a low-voltage signal. Then, it is finally sent to the input pin of the DSP through signal processing, and the signal is processed and calculated by the DSP chip. The DO signal of the DSP drives the isolation optical coupling, and the signal drives the relay after passing through the isolation optical coupling. The relay is externally connected to the high-voltage signal to realize the control output of the DSP output signal to the external high-voltage signal.

[0037] Furthermore, the encoder / 485 communication unit communicates with the 485 data outside the system through the 485 chip and high-speed optical coupler. RS485 bus is a common serial bus standard, which adopts balanced transmission and differential reception, so it has the ability to suppress common-mode interference. Because the on-site situation is very complicated, there is a very high common-mode voltage between each node. Although the RS-485 interface adopts a differential transmission method and has a certain ability to resist common-mode interference, when the common-mode voltage exceeds the limit receiving voltage of the RS-485 receiver, that is, greater than +12V or less than -7V, the receiver can no longer work normally, and in severe cases, it may even burn the chip and instruments. The solution to this problem is to isolate the system power supply and the power supply of the RS-485 transceiver through DC-DC; isolate the signal through an isolation device to completely eliminate the influence of the common-mode voltage.

[0038] Working principle of the present invention:

[0039] The servo drive drives the motor to operate the isolating switch, which is mainly composed of an AC power supply, a rectifier circuit, a bus capacitor, an inverter circuit, a control circuit, a communication circuit, a permanent magnet synchronous motor, and an isolating switch. The servo drive drives the motor to rotate, and the motor drives the isolating switch contacts to move, and the isolating switch performs opening and closing actions.

[0040] The rectifier circuit of the servo drive is composed of a rectifier bridge. Its function is to rectify the industrial frequency power supply, and provide the required DC power supply for the inverter circuit and the control circuit after smoothing through the intermediate DC link. The AC power supply generally needs to be introduced into the input end of the rectifier bridge through an absorption capacitor and a varistor network. The function of the network is to absorb the high-frequency harmonic signals and surge overvoltage of the AC power grid, thereby avoiding damage to the inverter.

[0041] The bus capacitor of the servo drive plays a filtering role. Its function is to smooth the output voltage of the rectifier circuit and reduce the AC component to a minimum. It provides "pure DC voltage" for the inverter behind it to reduce the AC voltage waveform distortion output by the inverter. The capacitors of the shared DC bus are generally connected in parallel for energy storage and filtering.

[0042] The inverter circuit is composed of an intelligent power module (IPM). The motor current signal is measured by a current sensor and fed back to the control circuit. The motor speed and rotor position are measured by an encoder installed on the shaft, and the travel of the isolating switch contact can be indirectly obtained from the motor rotor position.

[0043] The servo drive software uses a vector control algorithm, in which the permanent magnet synchronous motor control principle is as follows:

[0044] 1. Mathematical model of permanent magnet synchronous motor (PMSM) in synchronous rotating coordinate system

[0045] The permanent magnet synchronous motor is actually a nonlinear, multivariable system. In order to describe its physical characteristics by simply using a mathematical model, the following assumptions need to be made:

[0046] ① The magnetic saturation effect, eddy current and hysteresis loss of the core are negligible, and the magnetic field can be synthesized using the superposition principle;

[0047] ② The three-phase stator windings are symmetrically distributed in space;

[0048] ③The air gap magnetic field is sinusoidally distributed and higher harmonics are negligible.

[0049] The d-axis of the synchronous rotating dq coordinate system is defined in the direction of the permanent magnet magnetic field, while the q-axis is defined in the direction 90° ahead of the d-axis. The entire coordinate system rotates synchronously with the rotor, so it is called a synchronous rotating coordinate system. The mathematical model of the permanent magnet synchronous motor in this coordinate system is established as follows:

[0050] a. Motor flux equation:

[0051]

[0052] b. Stator voltage equation:

[0053]

[0054] c. Torque equation:

[0055]

[0056] d. Motor flux equation:

[0057]

[0058] In the above formula, P is the differential operator, P n is the number of magnetic pole pairs, T L is the load torque, J is the moment of inertia, ω r is the electrical angular velocity, and its relationship with the motor mechanical angular velocity is: ω r =P n ×ω m .

[0059] 2. Vector control principle

[0060] For a surface mounted permanent magnet synchronous motor (SPMSM for short), since the dq axis inductance is equal, the electromagnetic torque equation shows that i d= 0, the electromagnetic torque generated by the current can reach the maximum value, and the control form at this time is similar to that of a DC motor. Due to the magnetic field orientation, the direction of the rotor permanent magnet flux is the same as the d-axis, and the stator current all acts on the q-axis, so the direction of the stator flux is the same as the q-axis direction. At this time, the stator current is all used to generate electromagnetic torque. d = 0, the permanent magnet synchronous motor is equivalent to a separately excited DC motor, and only needs to control the torque current i q , the electromagnetic torque can be controlled, thereby achieving speed control.

[0061] i d =0 control strategy time phasor diagram as shown Figure 3 At this time, the stator current phase I1 is in the q-axis direction. Since the rotor flux is in the d-axis direction, the generated back electromotive force leads the rotor flux by 90 degrees and is also in the q-axis direction. At this time, only the minimum stator current is needed to achieve the required torque, thereby reducing the copper loss of the motor and improving efficiency.

[0062] Figure 4 The figure shows the control structure diagram of the AC servo system constructed according to the vector control principle. From the perspective of the control object, there are three loop structures, from the inside to the outside, which are the current loop, speed loop and position loop. The only quantities that need to be actually detected by the entire system are: two-phase current and the motor position information and speed information obtained through the encoder. The system forms a closed-loop control through coordinate changes to achieve precise control of the motor current, electromagnetic torque, speed and position.

[0063] 3.SVPWM technology

[0064] Space Vector Pulse Width Modulation (SVPWM) is actually a special switch triggering sequence and pulse width combination corresponding to the three-phase voltage source inverter power device in the AC induction motor or permanent magnet synchronous motor. This switch triggering sequence and combination will produce a three-phase 120° electrical angle difference and a small distortion sinusoidal current waveform in the stator coil. Practice and theory have proved that compared with direct sinusoidal pulse width modulation (SPWM) technology, SVPWM has the following advantages:

[0065] ①SVPWM has a higher degree of harmonic optimization and better harmonic elimination effect than SPWM. It is easy to implement and can improve voltage utilization.

[0066] ②SVPWM is more suitable for digital control systems.

[0067] At present, digital control systems with microcontrollers as the core are the development trend, so the use of SVPWM in inverters should be the preferred choice.

[0068] The instantaneous value of the three-phase sinusoidal voltage of the symmetrical voltage can be expressed as:

[0069]

[0070] Among them U m is the amplitude of the phase voltage, ω=2πf is the angular frequency of the phase voltage. Figure 5 is the vector diagram of the three-phase voltage. A complex plane is formed on this plane. The real axis of the complex plane coincides with the A-phase voltage vector, and the imaginary axis leads the real axis by 90°. They are marked as R e ,I m On this complex plane, the three-phase phase voltage u is defined as a 、u b 、u c The resulting voltage space vector for:

[0071]

[0072] The schematic diagram of the three-phase voltage inverter circuit is as follows Figure 6 As shown. Define the switch quantities a, b, c and a', b', c' to represent the switch states of the six power switch tubes. When a, b or c is 1, the upper arm switch tube of the inverter bridge is turned on, and its lower arm switch tube is turned off (i.e. a', b' or c' is 0); conversely, when a, b or c is 0, the upper arm switch tube is turned off and the lower arm switch tube is turned on (i.e. a', b' or c' is 1). Since the upper and lower switches of the same bridge arm cannot be turned on at the same time, there are a total of 8 configurations of the three-way inverter bridge of the above-mentioned inverter. For different switch state combinations (abc), 8 basic voltage space vectors can be obtained. The vectors are:

[0073]

[0074] Then the phase voltage V an 、V bn 、V cn , line voltage V ab 、V bc 、V ca as well as The values ​​are shown in Table 1 below (where U dc is the DC bus voltage):

[0075] Table 1 Relationship between switch configuration and voltage

[0076]

[0077] It can be seen that among the 8 combined voltage space vectors, there are 2 zero voltage space vectors and 6 non-zero voltage space vectors. The 8 combined basic space voltage vectors are mapped to Figure 3-4The complex plane shown in Figure 1 can be obtained as Figure 7 The voltage space vector diagram is shown in Figure 1. They divide the complex plane into 6 regions, called sectors.

[0078] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A high-reliability intelligent UHV isolating switch servo drive mechanism, characterized by: It includes three parts: an interface board, a control board, and a drive board. The interface board is provided with 6 high-voltage input units, 6 high-voltage output units, and input and output terminals. The control board is provided with a control unit, input and output terminals, two groups of RS485 units, a power conversion unit, a current sampling processing unit, and an encoder signal processing unit. The drive board is provided with a switching power supply, a bus voltage and current sampling unit, a gate drive signal unit, an output current sampling unit, a PFC filter circuit unit, a rectifier bridge unit, a DC bus capacitor unit, and a three-phase inverter bridge unit. The drive board is provided with an AC power supply, a permanent magnet synchronous motor, and an encoder / 485 communication unit.

2. A high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The input and output terminals of the interface board are connected to the input and output terminals of the control board, the input and output terminals of the control board are connected to the control unit, the AC power supply, the PFC filter circuit unit, the rectifier bridge unit, the DC bus capacitor unit, the three-phase inverter bridge unit, the permanent magnet synchronous motor, the encoder / 485 communication unit, the encoder signal processing unit and the control unit are connected in sequence, the DC bus capacitor unit, the bus voltage and current sampling unit, and the control unit are connected in sequence, the three-phase inverter bridge unit and the gate drive signal unit are connected to the control unit, and the output current sampling unit and the current sampling processing unit are connected to the control unit.

3. A high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The rectifier bridge unit and the rectifier device system adopt a rectifier bridge module. The system is protected by a soft start circuit composed of a resistor and a relay. When the system is powered on, the switch is disconnected, and the resistor plays a role in suppressing excessive charging current. When the main circuit voltage rises to a certain value, the switch is closed, and the resistor is cut off from the main circuit to achieve soft start.

4. A high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The DC bus capacitor unit, the rectifier bridge outputs a pulsating DC voltage. In order to generate a stable DC voltage, a large-capacity electrolytic capacitor is required for voltage stabilization and filtering. Since the input mains power is a 50Hz sinusoidal AC, only the voltage at the wave head is greater than the voltage across the capacitor to charge the capacitor. When the motor is running at high speed with heavy load, without considering the loss, the energy consumed in each charge and discharge cycle satisfies the formula: It can be obtained that the heavier the load and the smaller the capacitance value, the greater the voltage drop across the capacitor. To ensure that the output power remains unchanged, a larger current needs to be output, which will directly threaten the safety of the power module and increase the loss. In addition, from the perspective of PMSM vector control principle, excessive bus voltage fluctuations will lead to excessive current loop disturbances, poor current loop regulation, and large overshoot or even oscillation in the actual torque current. The specific selection of the energy storage capacitor capacitance can be obtained based on engineering experience, that is, roughly 1800μF is configured according to 1.8kW. In order to suppress the high-frequency oscillation of the DC bus voltage, a non-inductive absorption capacitor is connected in parallel at both ends of the DC input of the module. Based on experience, a non-inductive absorption capacitor of 0.68μF / 850V is selected.

5. The high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The three-phase inverter bridge unit is internally provided with upper and lower bridge arm control power supply undervoltage locking circuits and a lower bridge arm short-circuit protection circuit, and is also provided with lower bridge arm short-circuit protection and control power supply undervoltage protection fault signal outputs.

6. A high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The current sampling processing unit and the resistor sampling circuit obtain a DC bus voltage sampling value, and compare it with a set value provided by a reference circuit through a comparator. When the system brakes and causes the DC bus voltage to rise to a certain value, the comparator outputs a braking enable signal to the DSP, and the DSP sends a signal to connect the braking resistors at both ends of the bus in parallel to the DC bus to consume excess energy until the DC bus voltage drops to a safe value and the braking resistors are cut off.

7. The high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The bus voltage and current sampling unit and the output current sampling unit, the current sampling voltage value U obtained by sampling the sampling resistor enters the HCPL-7840 through the filtering circuit. The HCPL-7840 plays the role of linear amplification and isolation. The obtained differential signal is then processed by the post-stage DC bias and voltage follower circuit, and finally sent to the A / D input pin of the DSP, and the A / D on the DSP chip performs sampling and conversion.

8. The high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The 6-way high-voltage input unit and the 6-way high-voltage output unit require a high-voltage interface circuit to be designed for the servo mechanism driver to meet the high-voltage input signal of AC220V / DC220V / DC110V according to the voltage environment of the high-voltage isolation grounding switch. The signal is converted from a high-voltage signal to a low-voltage signal through rectification, voltage stabilization, filtering and optocoupler isolation, and then is finally sent to the input pin of the DSP through signal processing. The signal is processed and calculated on the DSP chip, and the DO signal of the DSP drives the isolation optocoupler. The signal drives the relay after passing through the isolation optocoupler. The relay is externally connected to the high-voltage signal to realize the control output of the DSP output signal to the external high-voltage signal.

9. The high-reliability intelligent UHV isolating switch servo drive mechanism according to claim 1, characterized in that: The encoder / 485 communication unit communicates with the 485 data outside the system through the 485 chip and high-speed optical coupler. The RS485 bus adopts balanced transmission and differential reception. The system power supply and the power supply of the RS-485 transceiver are isolated through DC-DC, and the signal is isolated through an isolation device.

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