阅读说明：本技术 一种极低频大功率发射系统 (Extremely-low-frequency high-power transmitting system ) 是由 刘勇 刘庆 饶斯韬 李纵 王亚维 于 2021-03-16 设计创作，主要内容包括：本发明公开了一种极低频大功率发射系统,所述系统包括高精度激励器、信号处理单元、发射主机、转换开关、调谐装置、假负载；调谐装置与发射天线连接；发射主机包括双频段双功率桥级联设置的两个功放单元,用以在同一发射主机的功放电路上对极低频和超低频双频段进行大功率信号合成。本发明实现了通过设计极/超低频双频段双功率桥级联功率合成的大功率极低频发射主机,在同一主功率电路上实现极低频和超低频(0.1Hz～300Hz)双频段500kW大功率信号的高效合成。且设计了直接耦合、电容调谐和匹配调谐的组合调谐方法,与长达上百公里的水平低架发射天线进行匹配调谐,实现0.1Hz～300Hz宽频率范围内全频点水平低架发射天线阻抗匹配调谐和大功率极/超低频信号的高效辐射。(The invention discloses a very low frequency high power transmitting system, which comprises a high precision exciter, a signal processing unit, a transmitting host, a change-over switch, a tuning device and a dummy load; the tuning device is connected with the transmitting antenna; the transmitting host comprises two power amplification units which are arranged in a dual-band dual-power bridge cascade mode and are used for carrying out high-power signal synthesis on an extremely low frequency and an ultra-low frequency dual-band on a power amplification circuit of the same transmitting host. The invention realizes the high-power extremely-low frequency transmitting host machine which realizes the high-efficiency synthesis of the extremely-low frequency and ultra-low frequency (0.1 Hz-300 Hz) dual-band 500kW high-power signals on the same main power circuit by designing the extremely/ultra-low frequency dual-band dual-power bridge cascaded power synthesis. And a combined tuning method of direct coupling, capacitance tuning and matching tuning is designed, and the antenna is matched and tuned with a horizontal low-frame transmitting antenna which is hundreds of kilometers long, so that impedance matching tuning of the full-frequency-point horizontal low-frame transmitting antenna in a wide frequency range of 0.1Hz-300Hz and efficient radiation of high-power ultra-low frequency signals are realized.)

1. A very low frequency high power transmission system, said system comprising: the high-precision exciter, the signal processing unit, the transmitting host, the change-over switch, the tuning device and the dummy load; the tuning device is connected with the transmitting antenna; the transmitting host comprises two power amplification units which are arranged in a dual-band dual-power bridge cascade mode and are used for carrying out high-power signal synthesis on an extremely low frequency and an ultra-low frequency dual-band on a power amplification circuit of the same transmitting host;

the high-precision exciter is used for generating an excitation signal of 0.1-300Hz to be emitted;

the signal processing unit is used for detecting, processing, protecting and shunting the excitation signal input by the high-precision exciter and outputting the excitation signal to the transmitting host;

the transmitting host is used for converting the direct current electric energy provided by the high-voltage rectification power supply into high-power extremely-low frequency and/or ultra-low frequency signals according to the received excitation signals;

the change-over switch is used for controlling the switching between the transmitting host and different loads, and the loads comprise transmitting antenna loads and dummy loads;

the tuning device is used for realizing the optimal impedance matching between the transmitting host and the transmitting antenna load under different transmitting antennas and working frequencies;

the dummy load is used for replacing the transmitting antenna to absorb energy output by the transmitting host when the transmitting host is debugged.

2. The system of claim 1, further comprising: the system comprises a low-voltage power supply system, a high-voltage rectification power supply, a control detection system and a cooling system;

the high-voltage rectification power supply is used for providing high-power direct-current electric energy for the transmitting host;

the control detection system is used for providing a human-computer operation interface;

the cooling system is used for carrying out pure water cooling on a power device in the emission host;

the low-voltage power supply system is used for providing low alternating voltage and direct current power supplies required by all equipment of the transmitting system.

3. The system of claim 1, wherein the tuning means comprises a matching transformer, a series capacitor, a tuning capacitor, and the antenna access switch; the antenna access switch is used for controlling the transmitting antenna to switch between the access matching tuning circuit and the ground; the matching transformer and the series capacitor are respectively connected with the antenna access switch, and a tuning capacitor is further arranged between the matching transformer and the antenna access switch.

4. The system of claim 1, wherein the high-precision exciter comprises a radio frequency module, a first digital signal processing module, and a first main control module, the first digital signal processing module and the first main control module can perform signal transmission with each other, the first main control module is configured to control a display screen to display an image and receive an operation signal corresponding to a key operation, the first digital signal processing module performs digital signal processing on the received operation signal and then sends the operation signal to the radio frequency module, so that the radio frequency module outputs a SPWM (sinusoidal pulse width modulation) signal at 0.1Hz to 30Hz and outputs a three-level driving signal at 30Hz to 300 Hz.

5. The system according to claim 1, wherein the signal processing unit includes a signal receiving module, a signal driving module, an optical fiber output module, a second digital signal processing module, and a second main control module, the second main control module and the second digital signal processing module can perform signal transmission with each other, the signal receiving module is configured to receive the excitation signal sent by the high-precision exciter, the signal driving module is configured to receive the excitation signal sent by the second digital signal processing module and send the excitation signal to the optical fiber output module, and the optical fiber output module is configured to send the excitation signal to the transmitting host.

6. The system of claim 1, wherein the power amplifier unit comprises an interface circuit, a driving circuit, a power amplifier circuit, a detection protection circuit, a touch industrial control screen, an electronic switch, a dc LRCD absorption circuit, a bridge RCD absorption circuit, and a water cooling module, and the interface circuit is configured to receive an excitation signal sent by the signal processing unit and perform photoelectric conversion on the excitation signal; the driving circuit is used for enhancing the excitation signal to perform high-low voltage isolation; the power amplification circuit is used for carrying out power amplification on the excitation signal; the detection protection circuit is used for monitoring signals in the transmitter host and controlling the electronic switch to perform protection action when a fault signal is detected; the touch industrial control screen is used for displaying and operating local parameters of the power amplification unit; the water cooling assembly is used for cooling and radiating the power amplifier circuit.

7. The system of claim 1, wherein the tuning mechanism comprises an east-west tuning mechanism and a north-south tuning mechanism, the east-west tuning mechanism coupled to an east-west antenna of the transmit antenna, the north-south tuning mechanism coupled to a north-south antenna of the transmit antenna.

Technical Field

The application relates to the technical field of low-frequency signals, in particular to a very low-frequency high-power transmitting system.

Background

The low-frequency signals are transmitted to the world in a waveguide mode between the earth and an ionized layer, the frequency range of the extremely low-frequency signals is 3 Hz-30Hz according to the international power connection, the extremely low-frequency signals can penetrate through seawater and stratums with large depth, the transmission loss of the extremely low-frequency electromagnetic waves is small, and the attenuation in the atmosphere is less than 1 dB/kilokilometer. The extremely-low frequency electromagnetic wave is a low-frequency electromagnetic wave (0.1 Hz-300 Hz) which is artificially generated and has a radiation range of thousands of kilometers and a high signal-to-noise ratio. At present, an electromagnetic detection mode of a very low frequency signal transmitting system is poor in anti-interference capability, large in measurement error, short in detection distance and shallow in detection depth, so that the detection effect in practical application is not ideal.

Disclosure of Invention

In order to solve the above problem, an embodiment of the present application provides a very low frequency high power transmission system. The method can be used for large-depth resource exploration, seismic prediction and large-depth latent-to-latent communication.

In a first aspect, an embodiment of the present application provides a very low frequency high power transmission system, where the system includes: the high-precision exciter, the signal processing unit, the transmitting host, the change-over switch, the tuning device and the dummy load; the tuning device is connected with the transmitting antenna; the transmitting host comprises two power amplification units which are arranged in a dual-band dual-power bridge cascade mode and are used for carrying out high-power signal synthesis on an extremely low frequency and an ultra-low frequency dual-band on a power amplification circuit of the same transmitting host;

the high-precision exciter is used for generating an excitation signal of 0.1-300Hz to be emitted;

the signal processing unit is used for detecting, processing, protecting and shunting the excitation signal input by the high-precision exciter and outputting the excitation signal to the transmitting host;

the transmitting host is used for converting the direct current electric energy provided by the high-voltage rectification power supply into high-power extremely-low frequency and/or ultra-low frequency signals according to the received excitation signals;

the change-over switch is used for controlling the switching between the transmitting host and different loads, and the loads comprise transmitting antenna loads and dummy loads;

the tuning device is used for realizing the optimal impedance matching between the transmitting host and the transmitting antenna load under different transmitting antennas and working frequencies;

the dummy load is used for replacing the transmitting antenna to absorb energy output by the transmitting host when the transmitting host is debugged.

Preferably, the system further comprises: the system comprises a low-voltage power supply system, a high-voltage rectification power supply, a control detection system and a cooling system;

the high-voltage rectification power supply is used for providing high-power direct-current electric energy for the transmitting host;

the control detection system is used for providing a human-computer operation interface;

the cooling system is used for carrying out pure water cooling on a power device in the emission host;

the low-voltage power supply system is used for providing low alternating voltage and direct current power supplies required by all equipment of the transmitting system.

Preferably, the tuning device comprises a matching transformer, a series capacitor, a tuning capacitor and the antenna access switch; the antenna access switch is used for controlling the transmitting antenna to switch between the access matching tuning circuit and the ground; the matching transformer and the series capacitor are respectively connected with the antenna access switch, and a tuning capacitor is further arranged between the matching transformer and the antenna access switch.

Preferably, the high-precision exciter comprises a radio frequency module, a first digital signal processing module and a first main control module, wherein the first digital signal processing module and the first main control module can perform signal transmission with each other, the first main control module is used for controlling a display screen to display images and receiving operation signals corresponding to key operation, and the first digital signal processing module performs digital signal processing on the received operation signals and then sends the operation signals to the radio frequency module so that the radio frequency module outputs SPWM signals under 0.1Hz-30 Hz and outputs three-level driving signals under 30 Hz-300 Hz.

Preferably, the signal processing unit includes a signal receiving module, a signal driving module, an optical fiber output module, a second digital signal processing module, and a second main control module, where the second main control module and the second digital signal processing module can perform signal transmission with each other, the signal receiving module is configured to receive an excitation signal sent by the high-precision exciter, the signal driving module is configured to receive the excitation signal sent by the second digital signal processing module and send the excitation signal to the optical fiber output module, and the optical fiber output module is configured to send the excitation signal to the transmitting host.

Preferably, the power amplifier unit comprises an interface circuit, a driving circuit, a power amplifier circuit, a detection protection circuit, a touch industrial control screen, an electronic switch, a direct current LRCD absorption circuit, a bridge RCD absorption circuit, and a water cooling module, wherein the interface circuit is used for receiving an excitation signal sent by the signal processing unit and performing photoelectric conversion on the excitation signal; the driving circuit is used for enhancing the excitation signal to perform high-low voltage isolation; the power amplification circuit is used for carrying out power amplification on the excitation signal; the detection protection circuit is used for monitoring signals in the transmitter host and controlling the electronic switch to perform protection action when a fault signal is detected; the touch industrial control screen is used for displaying and operating local parameters of the power amplification unit; the water cooling assembly is used for cooling and radiating the power amplifier circuit.

Preferably, the tuning device includes an east-west tuning device and a north-south tuning device, the east-west tuning device is connected with an east-west antenna of the transmitting antenna, and the north-south tuning device is connected with a north-south antenna of the transmitting antenna.

The invention has the beneficial effects that: 1. by designing a high-power extremely-low frequency transmitting host for the cascade power synthesis of an extremely/ultra-low frequency dual-band dual-power bridge, the high-efficiency synthesis of an extremely-low frequency and ultra-low frequency (0.1 Hz-300 Hz) dual-band 500kW high-power signal is realized on the same main power circuit. And a combined tuning method of direct coupling, capacitance tuning and matching tuning is designed, and the antenna is matched and tuned with a horizontal low-frame transmitting antenna which is hundreds of kilometers long, so that impedance matching tuning of the full-frequency-point horizontal low-frame transmitting antenna in a wide frequency range of 0.1Hz-300Hz and efficient radiation of high-power ultra-low frequency signals are realized.

2. The system is used for electromagnetic detection, and has the advantages of strong anti-interference capability, small measurement error, long detection distance, large detection depth, suitability for large-area networking reception and the like. And the extremely low frequency signal generated by the system can penetrate deep sea water of hundreds of meters, and is suitable for long-distance large-depth submarine communication.

3. The extremely-low-frequency high-power transmitting system can provide 500kW of extremely/ultra-low-frequency signal transmitting capacity, the output power of a transmitter is effectively loaded on an antenna through matching and tuning, the signal-to-noise ratio of a radiation signal is 10 dB-20 dB higher than that of a natural source signal, tens of kilometers of stratum and hundreds of meters of deep sea water can be penetrated, a new means is provided for the fields of resource exploration, earthquake monitoring and the like, and a large-depth communication means of thousands of kilometers and hundreds of meters in a long distance can be provided.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic diagram illustrating an exemplary structure of a very low frequency high power transmitting system according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of a high-precision actuator according to an embodiment of the present application;

FIG. 3 is a schematic diagram illustrating an example of the SPWM waveform principle provided by the present application;

FIG. 4 is a schematic diagram illustrating an example control principle of SPWM signal generation according to the embodiment of the present application;

FIG. 5 is a schematic diagram illustrating an exemplary timing sequence of an excitation signal in a frequency range of 30 Hz-300Hz according to an embodiment of the present disclosure;

FIG. 6 is a schematic diagram illustrating an example of a stepped waveform output by the transmission host in a frequency range of 30Hz to 300Hz according to the embodiment of the present application;

fig. 7 is a schematic diagram illustrating a structural configuration of a signal processing unit according to an embodiment of the present application;

fig. 8 is a schematic block diagram illustrating an example structure of a second master control module according to an embodiment of the present application;

fig. 9 is a schematic block diagram illustrating an example structure of a signal receiving and processing unit module according to an embodiment of the present application;

fig. 10 is a schematic block diagram illustrating an example structure of a signal driving module according to an embodiment of the present application;

fig. 11 is a schematic diagram illustrating an exemplary structure of a transmitting host according to an embodiment of the present disclosure;

fig. 12 is a schematic diagram illustrating an example structure of a power amplifier unit according to an embodiment of the present application;

fig. 13 is a schematic diagram illustrating a principle of a power amplifier circuit according to an embodiment of the present disclosure;

FIG. 14 is a schematic diagram illustrating four exemplary operating states of a single H-bridge circuit according to an embodiment of the present disclosure;

fig. 15 is a schematic diagram illustrating a principle of a complete power amplifier circuit of a transmitter host according to an embodiment of the present application;

fig. 16 is a schematic diagram illustrating a principle of a tuning apparatus according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

In the following description, the terms "first" and "second" are used for descriptive purposes only and are not intended to indicate or imply relative importance. The following description provides embodiments of the invention, which may be combined with or substituted for various embodiments, and the invention is thus to be construed as embracing all possible combinations of the same and/or different embodiments described. Thus, if one embodiment includes feature A, B, C and another embodiment includes feature B, D, then the invention should also be construed as including embodiments that include one or more of all other possible combinations of A, B, C, D, even though such embodiments may not be explicitly recited in the following text.

The following description provides examples, and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements described without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For example, the described methods may be performed in an order different than the order described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

Referring to fig. 1, fig. 1 is a schematic diagram illustrating an exemplary structure of a very low frequency high power transmitting system according to an embodiment of the present disclosure. In an embodiment of the present application, the system includes: the device comprises a high-precision exciter, a signal processing unit, a transmitting host, a change-over switch, a tuning device, a dummy load, a low-voltage power supply system, a high-voltage rectification power supply, a control detection system and a cooling system; the tuning device is connected with the transmitting antenna; the transmitting host comprises two power amplification units which are arranged in a dual-band dual-power bridge cascade mode and are used for carrying out high-power signal synthesis on an extremely low frequency and an ultra-low frequency dual-band on a power amplification circuit of the same transmitting host;

the high-precision exciter is used for generating an excitation signal of 0.1-300Hz to be emitted;

the signal processing unit is used for detecting, processing, protecting and shunting the excitation signal input by the high-precision exciter and outputting the excitation signal to the transmitting host;

the transmitting host is used for converting the direct current electric energy provided by the high-voltage rectification power supply into high-power extremely-low frequency and/or ultra-low frequency signals according to the received excitation signals;

the change-over switch is used for controlling the switching between the transmitting host and different loads, and the loads comprise transmitting antenna loads and dummy loads;

the tuning device is used for realizing the optimal impedance matching between the transmitting host and the transmitting antenna load under different transmitting antennas and working frequencies;

the dummy load is used for replacing the transmitting antenna to absorb energy output by the transmitting host when the transmitting host is debugged;

the high-voltage rectification power supply is used for providing high-power direct-current electric energy for the transmitting host;

the control detection system is used for providing a human-computer operation interface;

the cooling system is used for carrying out pure water cooling on a power device in the emission host;

the low-voltage power supply system is used for providing low alternating voltage and direct current power supplies required by all equipment of the transmitting system.

Specifically, the extremely-low-frequency high-power transmitting system is provided with two transmitting hosts, the two transmitting hosts can be connected with the east-west antenna and the south-north antenna to work independently, and the two transmitting hosts can work simultaneously to realize space synthesis of high-power signals. The normal default working state is that the No. 1 transmitting host machine works with the east-west transmitting antenna, and the No. 2 transmitting host machine works with the south-north transmitting antenna. When the local equipment or part is in a failure state, the two transmitting hosts or the signal processing units can be mutually standby, so that the scheduled transmission plan or the timely execution of an emergency task is not influenced.

In an implementation manner, an exemplary structure of the high-precision exciter is shown in fig. 2, and the high-precision exciter mainly includes a radio frequency module, a first digital signal processing module, a first main control module, a first power module, a keyboard, and a display. The high-precision exciter can realize the following functions: a) when the working frequency is 0.1Hz-30 Hz (29.9999Hz), the exciter outputs SPWM signals; b) when the working frequency is 30 Hz-300Hz, the exciter outputs a three-level driving signal; c) when the device is used for debugging equipment, the exciter outputs a standard sinusoidal signal of 0.1Hz-300 Hz; d) the device has the functions of frequency setting and conversion, keyboard data processing, control display and the like.

Specifically, when the output frequency is 0.1Hz-30 Hz (29.9999Hz), the emission host adopts the working mode of SPWM modulation, and the exciter generates an SPWM sequence.

As shown in fig. 3, Sinusoidal Pulse Width Modulation (SPWM) is a modulation method in which a sine wave is used as a modulation wave and a triangular wave is used as a carrier wave. Generally, SPWM waveform generation is performed by modulating a signal wave using a waveform desired to be output as a modulation signal and a signal subjected to modulation as a carrier wave to obtain a desired SPWM waveform. The duty cycle of the pulse width varies according to a sinusoidal law, the width of the pulse being the largest and the interval of the pulse being the smallest near the maximum value of the sine value, the width of the pulse being smaller and the interval of the pulse being larger when the sine value is smaller.

The carrier triangular wave adopts a bipolar isosceles triangular wave as a carrier, because the horizontal width and the height of any point on the isosceles triangular wave are in a linear relation and are bilaterally symmetrical, when the carrier triangular wave is intersected with any one sine modulation wave which changes slowly, if the on-off of a switching device in the circuit is controlled at the intersection point moment, a pulse with the width being in direct proportion to the amplitude value of a signal wave can be obtained, and the requirement of SPWM control is exactly met. In addition, in the bipolar carrier modulation method, the SPWM wave has both positive and negative outputs in the corresponding half periods, and the output PWM wave has only positive and negative levels in one modulated wave period, unlike unipolar control, which has zero level. When a triangular wave is modulated by a sinusoidal signal wave, the obtained SPWM wave does not contain lower harmonics but only higher harmonics related to the carrier frequency as long as the carrier ratio is sufficiently high. The harmonic wave contained in the output waveform is a basic mark for measuring the quality of the SPWM control method.

The SPWM modulation scheme is classified into synchronous modulation and asynchronous modulation. Asynchronous modulation refers to fixing the triangular wave frequency over the entire frequency range. Synchronous modulation means that the ratio of the triangular wave frequency to the sinusoidal wave frequency is fixed, i.e., the carrier ratio is fixed, over the entire frequency range. Synchronous modulation is generally used for a three-phase inverter circuit and the condition of high working frequency, and when the frequency is low, the harmonic wave of an output waveform can be obviously increased; asynchronous modulation can still output better current waveform when the working frequency is lower.

Because the working frequency range of the transmitting system is large, the low-end frequency is close to 0Hz, and the asynchronous modulation mode is more suitable, namely the frequency of the triangular wave is fixed. Synchronous modulation is not suitable because it leads to significant harmonic increase in the low frequency band, especially at frequencies below 1 Hz.

Therefore, when the output frequency is 0.1Hz to 30Hz (29.9999Hz), the control schematic diagram of the driver generating the SPWM sequence is shown in fig. 4, the sine wave generator generates sine modulation, the bipolar triangular carrier is generated by the triangular wave generator, and as two H-bridges are adopted for cascade connection, the four paths of carriers have phase differences of 90 degrees in sequence: u shape_c1The initial phase angle of (1) is zero DEG, then U_c2Is 180 ° (and U)_c1Reverse), U_c3Has an initial phase angle of 90 DEG and U_c4Has an initial phase angle of 270 ° (to U)_c3Reverse). The carrier wave and the modulation wave generate a pulse sequence wave after passing through a comparator, and then the pulse sequence wave passes through a phase inverter to obtain two opposite upper and lower pulses to drive two upper and lower power tubes of the same bridge arm. The sequence number S in the figure corresponds to eight switching devices of two cascaded H-bridge power amplifier circuits, wherein S₁And S₁Is a complementary waveform, S₂And S₂′、S₃，S₃′、S₄And S₄' also complementary waveform outputs, and dead time is required to be left for the above four pairs of signals in order to work safely and avoid direct connection of bridge arms.

For the frequency band of 30 Hz-300Hz, the excitation signal timing and the step wave waveform output by the emission host are respectively shown in FIG. 5 and FIG. 6. The functional expression of the output step wave can be listed as follows:

specifically, the signal processing unit is used for detecting, processing, protecting and shunting an excitation signal input by an excitation signal source, namely a high-precision exciter, and outputting a driving signal to the emission host. As shown in fig. 7, the signal processing unit mainly includes a signal receiving module, a signal driving module, an optical fiber output module, a second digital signal processing (DSP + FPGA) module, a second main control module, a second power supply module, a keyboard, a display, and so on. The main functions realized by the signal processing unit are as follows: a) excitation signal switching and grouping output; b) setting and converting frequency; c) excitation signal detection: detecting the SPWM signal when the frequency of the excitation signal is 0.1Hz-30 Hz; detecting a three-level driving signal when the frequency of the excitation signal is 30 Hz-300 Hz; d) the protection device has the functions of direct connection protection, dead zone protection, deviation protection and protection alarm output; e) the equipment receives a control command transmitted by the control system and switches channels between signals input by the two exciters and two groups of output signals; f) electricity/light conversion is performed, and the anti-interference capability is enhanced; g) ethernet interfaces and networking functions.

The second main control module is composed of a microprocessor with an ARM9 CPU as a core, an ARM9 clock rate of 200MHz, 64Mflash and 64MSDRAM, and has 3 UARTs, 2 SPIs, displays, keyboards, networks and other interfaces, so as to implement the following functions: a) the state of each module is controlled to complete the functions of keyboard, display and the like; b) communicating with the DSP; c) and the communication control detection system and the emission control detection system are communicated through a network port. The signal processing unit is arranged between the exciter and the emission host, is used for accessing, shunting and forwarding the excitation signal, judges the waveform of the excitation signal, has the functions of direct connection protection, dead zone protection and frequency deviation protection, and cuts off the output of the excitation signal when detecting that the excitation signal is abnormal. The excitation signal output adopts optical transmission, and the anti-interference capability of the system is improved. The equipment is provided with a network interface, follows a system protocol, receives the remote control of an operation terminal, completes parameter setting according to an instruction, realizes the access and the switching of an excitation signal, and uploads a fault type when a fault is detected.

The second digital signal processing module and the signal receiving module constitute a signal receiving and processing unit module, as shown in fig. 9, which mainly receives an excitation signal input to realize photoelectric isolation of an input signal. Meanwhile, the system detects the signal frequency, the phase and the protection area, gives an alarm and protects in real time, is a universal digital signal processing platform, and has main chips of DSP and FPGA.

As shown in fig. 10, the signal driving module divides and drives a group (eight paths) of excitation signals output by the signal processing module, each branch driving module divides one group into two groups, and finally four groups of electric pulse excitation signals are formed by driving and provided to the following optical fiber output module.

The optical fiber output module consists of eight paths, and the optical transmitter converts the electric pulse excitation signal into an optical pulse excitation signal which is supplied to each power amplification unit through an optical fiber. The signal processing unit has four optical fiber output modules corresponding to the four power amplifier units, and each optical fiber corresponds to the IGCT on the inverter bridge of the power amplifier unit one by one.

Specifically, as shown in fig. 11, a single transmitting host is composed of 2 power amplifier units, and cascade power synthesis is performed by using the 2 power amplifier units. In order to facilitate the mutual backup of the 2 transmitting hosts, the design parameters of the 2 transmitting hosts need to be kept consistent. In order to achieve the aim of 500kW of output power and leave certain margins for the working voltage and current of equipment, the maximum output voltage effective value of the designed emission host is 3800V and the maximum output current effective value is 300A.

The power amplifier units are core units of the transmitting host, and each power amplifier unit is composed of an interface circuit, a driving circuit, a power amplifier circuit, a detection protection circuit, a touch industrial control screen, an electronic switch, a direct current LRCD absorption circuit, a bridge RCD absorption circuit, a water cooling assembly and the like, and is specifically shown in fig. 12. The signal of the signal processing unit is transmitted to the interface circuit and is transmitted to the power amplifier circuit through the driving circuit; the high-voltage rectification power supply is connected with the electronic switch, and a signal of the electronic switch is transmitted to the power amplification circuit through the direct current LRCD absorption circuit; the detection protection circuit and the touch industrial control screen can be in bidirectional transmission with the control detection system and can receive signals transmitted by the power amplification circuit; after the detection protection circuit detects the received signals, the detection protection circuit can send signals to the driving circuit and the electronic switch based on the detection result; the cooling system is connected with the power amplifier circuit through the water cooling assembly; after the power amplification circuit performs power amplification on the signals, the signals can be transmitted to the bridge RCD absorption circuit and the change-over switch.

In a single power amplifier unit circuit, overcurrent detection and direct connection detection protection are designed, and a high-voltage fuse and an IGBT electronic switch are designed at the input end to be used as protection. The overvoltage absorption loop adopts a double RLCD absorption loop at a direct current end, the power device adopts an RC absorption loop and an RCD absorption loop, and the voltage and current detection is acquired by adopting a high-speed Hall sensor.

The corresponding relation between the excitation signal of the power amplification unit and the power device is as follows: when the working frequency is lower than 30Hz, an excitation signal is generated by adopting a Sinusoidal Pulse Width Modulation (SPWM) mode. When the working frequency is higher than 30Hz, the excitation signal is generated by adopting a three-level superposition mode, the duty ratio of the input eight excitation signals is 5/12, and each power tube is conducted for 150 degrees in one period.

The interface circuit receives the excitation signal sent by the signal processing unit and realizes photoelectric conversion; the driving circuit mainly enhances the driving capability of the excitation signal and realizes high-voltage and low-voltage isolation; the power amplifier circuit is a main circuit for realizing power amplification, and the excitation signal can be amplified to specified power by utilizing the energy transmitted by the high-voltage direct-current power supply; the detection protection circuit completes monitoring of various state signals inside the transmitter, and controls the electronic switch to implement protection action in time once a fault signal is found, so that the high-voltage direct-current power supply is cut off, and the safety of the transmitting host is ensured; the touch industrial control screen is used for displaying and operating local parameters of the power amplification unit; the water cooling component is used for cooling and radiating the power amplifier circuit.

The power amplifier circuit can be formed by a single H bridge in an SPWM control mode, as shown in FIG. 13, S1 and S1 'form a half bridge and cannot be conducted simultaneously, S2 and S2' form a half bridge and cannot be conducted simultaneously, otherwise, direct connection occurs and a power tube is damaged. Therefore, in one modulation period, as shown in fig. 14, the circuit has four operating states, namely, forward conduction, reverse conduction, forward bypass and reverse bypass.

The double-bridge cascade power synthesis scheme forms a complete power amplifier circuit of the transmitting host by the power amplifier circuit formed by cascading and overlapping two H-bridge power amplifier units, thereby realizing high-power synthesis, such asAs shown in fig. 15, the two power amplifier units are electrically identical, and the input end of each power amplifier unit is powered by an independent dc power supply, and the cascade operation is realized by the series connection of the output ends. Eight power devices S provided for power amplification unit by exciter₁，S₁′，S₂，S₂′，S₃，S₃′，S₄，S₄' eight switching signals.

Fig. 16 shows a schematic diagram of a tuning apparatus, which mainly includes a matching transformer, a series capacitor, a tuning capacitor, and an antenna access switch. Because the impedance characteristic of the long-distance horizontal low-frame transmitting antenna is inductive in an extremely low frequency band, the working frequency point of a transmitting system is nearly hundreds, the span range is from 0.1Hz to 300Hz, the reactance component difference of the antenna when working at different frequencies is very large, from a few zero ohms to a thousand ohms, a plurality of groups of capacitors are adopted to tune the whole working frequency band in a segmented mode, namely, capacitors are required to be connected in series in an antenna tuning loop to offset the inductive reactance component of the antenna, so that the impedance of an output port of a transmitting host is represented by the characteristic of pure resistance, the maximum current matrix can be obtained under the condition of limited power, and the optimal radiation effect can be achieved. Once tuning is completed, the loop is in series resonance at the working frequency point and shows a band-pass characteristic.

Aiming at the difficult problem of large impedance change of 0.1Hz-300Hz antenna, a series capacitor is used as a branch, a matching transformer is connected with a tuning capacitor to form a branch, and then the reactance component of the antenna is offset by a direct antenna, capacitance tuning and matching tuning combined tuning mode, so that the maximum radiation power is obtained. Namely 0.1Hz-4/8Hz frequency transmission host is directly connected with the transmission antenna. The frequency below 4/8Hz-30Hz is without transformer, and is directly connected with the transmitting antenna through capacitance tuning. The frequency above 30Hz is matched through a transformer, and then is connected with a transmitting antenna through tuning capacitance tuning.

When the transmitting host works at a high frequency end, namely the working frequency is above 30Hz, the matching transformer is adopted for coupling, the matching transformer needs to meet the working requirement of multiple transformation ratios, and the leakage inductance of the matching transformer participates in a tuning loop and influences tuning parameters, so that the transformer designed is required to be low in leakage inductance in the full frequency band. And because the secondary output voltage is higher and the lightning protection characteristic is considered, the transformer has higher insulation level. The east-west antenna is close to a natural resonance point at 311Hz, so that the impedance change is severe, and the east-west antenna does not work when the frequency is higher than 300 Hz.

When the transmitter works at the low end of the frequency, namely the frequency is less than 30Hz, a series capacitor needs to be added to reduce the output voltage of the power amplification unit, so that the aim of reducing the working voltage of the transmitting host is fulfilled. The design principle is the same as that of a tuning capacitor, and the composition form of a capacitor bank is determined according to the capacitance value of the capacitor, the voltage on the capacitor and the current flowing through the capacitor (related to the output voltage and the output current of a transmitter) at different frequencies. The value of the series capacitor is selected to ensure that the range of transmitter output voltages does not exceed 3800V.

Specifically, the control detection equipment completes the functions of monitoring the working state, detecting faults and protecting the extremely low frequency transmitting system, realizes the whole-process automatic and graphical operation of the extremely low frequency transmitting system equipment, and realizes the remote operation and the real-time parameter and equipment state display on CPC and GOT touch screens of operation terminals in a centralized operation mode; in addition, a system control cabinet and manual control switches of all the devices are arranged on the device field, so that the function of manual control on the device field is realized, and the control detection system enables the extremely-low frequency transmitting system to have higher reliability and stronger task execution capacity through dynamic combination and switching of the devices, thereby providing guarantee for the positive point rate of executing tasks.

The control detection system is composed of two operation terminals (1 of which is a cold standby), a main control unit and a system control cabinet (5), realizes the function of communicating with equipment such as an exciter, a signal processing unit and the like, completes the functions of reliable control, operation management, state display, fault prompt, log query and the like of the transmitting system equipment, and ensures the punctual and reliable execution of a transmitting task. The core equipment of the control detection system is composed of a ruggedized computer and a PLC (programmable logic controller), wherein the ruggedized computer is used as a hardware platform of an operation terminal, and the PLC is used as an execution device on site. The PLC is an electronic device which is specially designed for digital operation in industrial environment and has the characteristics of high reliability, severe environment adaptation, easy operability, flexibility and the like. The control detection branch comprises an Ethernet and a control layer network secondary network, the Ethernet is provided with an operation terminal CPC, a main control unit and other equipment, the operation terminal CPC displays the running state information of the emission subsystem equipment in real time through a graphical interface, and the Ethernet sends an instruction to the main control unit to implement the control of the emission subsystem equipment. The main control unit obtains and recognizes the command from the operation terminal CPC, and calls the software control modules of the system control cabinets according to the current equipment state corresponding to the command and according to a certain sequence, and the system control cabinets are used as action execution mechanisms to control the operation of the transmitting subsystem equipment, so that the remote control of the transmitting equipment on the control detection system is realized.

The high-voltage rectification power supply comprises a 10kV power distribution cabinet, a rectifier transformer, a controllable rectification power supply and the like. The 10kV power distribution cabinet is three-phase 10kV power distribution universal equipment and is used for a three-phase 10kV commercial power access system. The rectifier transformer is specially designed for a controllable rectifier power supply and is used for reducing the voltage of a three-phase 10kV mains supply, and the three-phase 10kV mains supply is output in three voltage gears in two connection modes. The controllable rectifying power supply is used for rectifying the three-phase alternating current input by the rectifying transformer into high-voltage direct current, and harmonic components are filtered by the filter to obtain a smoother high-voltage direct current power supply for the transmitting host. According to the requirement of the transmitting host, two sets of high-voltage power supply equipment are required. Each set of high-voltage power supply equipment comprises 1 set of 10kV power distribution cabinet, 1 secondary double-winding three-phase rectifier transformer and 2 controllable rectifier power supplies. Wherein, 2 controllable rectification power supplies bind the power supply with 2 power amplifier units of the transmitting host computer respectively. The corresponding working modes are as follows: the first set of high-voltage power supply equipment supplies power to the first set of emission host; and the second set of high-voltage power supply equipment supplies power to the second set of transmitting host machine.

The transfer switch adopts a customized high-voltage switch cabinet group with related connection and switching relation, and is used for switching between the transmitting host and different types of loads. The antenna access equipment adopts a 35kV or 110kV high-voltage isolating switch with a grounding knife and is used for switching the transmitting antenna between an access matching tuning circuit and grounding. The dummy load is a resistive load, the bearing power is not less than 500kW, the working frequency range is DC-500Hz, the resistance value is 32 omega, the insulation voltage of the resistor body to the shell is not less than 20kVac, and the cooling mode adopts forced air cooling and is used for replacing a transmitting antenna to absorb energy output by a transmitting host when the transmitting host is tuned. The low-voltage power supply equipment is divided into a low-voltage power distribution cabinet, a direct-current screen and a UPS power supply. The low-voltage power distribution cabinet is used for accessing and distributing mains supply alternating current 380V power supply, the direct-current screen is used for supplying power to a 10kV high-voltage switch cabinet and a direct-current 220V operating mechanism in the 10kV power distribution cabinet, and the UPS is used for supplying power to key equipment such as a transmitting host, a high-voltage rectification power supply, a signal processing unit and control detection equipment by uninterrupted alternating current 380V/220V. The cooling equipment comprises reverse osmosis water making equipment, a pure water tank, a water pump, a water supply pipeline (including flow, pressure, temperature and other monitoring), and the like, and is used for pure water cooling of power devices in the transmitting host.