Ice melting device based on low-frequency variable frequency

Abstract

The invention discloses an ice melting device based on low-frequency variable frequency. The ice melting device comprises a power supply circuit, a main power and driving circuit, an overvoltage absorption circuit and a weak current control circuit, the power supply circuit is used for supplying power to the variable-frequency ice melting device and the control current; the main power and driving circuit is used for synthesizing a voltage waveform with required amplitude and frequency by using an input voltage vector to realize three-phase variable-frequency ice melting; the overvoltage absorption circuit is used for absorbing and discharging abnormal high voltage generated when the ice melting device is started, stopped, operated or broken down; and the weak current control circuit is used for controlling, managing and protecting the work of the main power and driving circuit by generating a low-voltage and low-current safety signal. The ice melting current is increased, and quick and efficient ice melting is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric power deicing, and particularly relates to a low-frequency variable-frequency deicing device. BACKGROUND

[0002] With the continuous development of new energy industry and low-carbon economy, the distribution network lines have been greatly expanded in recent years in China. Multi-branch and short-distance distribution network is the main content of the distribution network line laying at present and in the future. With the expansion of the distribution network lines, a large number of distribution network lines inevitably pass through the icing area of micro-topography and micro-climate. These lines are limited by the micro-topography area and show the characteristics of distributed and short-distance icing, which poses a severe challenge to the ice disaster prevention of the distribution network lines.

[0003] At present, a large number of studies are carried out on the distribution network icing prevention technology, which can be divided into mechanical deicing, passive deicing and electric heating deicing according to the type. The mechanical deicing includes external vibration deicing and electromagnetic pulse deicing. The passive deicing includes anti-icing coating, deicing ring and wind skirt. The electric heating deicing is mainly divided into alternating current deicing and direct current deicing. Due to the existence of a large number of distribution transformers and mutual inductors in the distribution network, the workload of full-line removal is too large, which limits the application of the direct current deicing method. The alternating current deicing is divided into power frequency short circuit alternating current deicing, high frequency deicing and load transfer deicing. The load transfer deicing has high requirements for the structure and operation mode of the power grid, and the realization conditions are high. The high frequency deicing is difficult to be widely applied in the distribution network due to the difficulty in obtaining high frequency excitation power supply, excessive reactive power compensation and electromagnetic interference problems.

[0004] The application proposes a low-frequency variable-frequency deicing device for the distribution network to solve the problems of low power factor and difficult continuous voltage adjustment of the existing distribution network alternating current short circuit deicing. The purpose is to increase the deicing current to achieve rapid and efficient deicing. SUMMARY

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the application proposes a low-frequency variable-frequency deicing device to solve the problems of low power factor and difficult continuous voltage adjustment of the existing distribution network alternating current short circuit deicing, and the purpose is to increase the deicing current to achieve rapid and efficient deicing.

[0006] The technical scheme adopted by the application to solve the technical problems is: a low-frequency variable-frequency deicing device, comprising a power supply circuit, a main power and driving circuit, an overvoltage absorption circuit and a weak current control circuit; The output end of the power supply circuit is connected to the main power and driving circuit, the main power and driving circuit is connected to the deicing line; the overvoltage absorption circuit is connected in parallel with the main power and driving circuit, the input end of the overvoltage absorption circuit is connected to the output end of the power supply circuit, and the output end is connected to the deicing line; the weak current control circuit is connected in parallel with the main power and driving circuit, the input end of the weak current control circuit is connected to the output end of the power supply circuit, and the output end is connected to the deicing line; The power supply circuit is used for power supply and control current supply for the variable frequency ice melting device; The main power and driving circuit is used for synthesizing voltage waveforms with required amplitude and frequency by input voltage vectors; through the three-phase output terminal, the ice melting line is connected after three-phase short circuit, the frequency is changed according to the line and ice covering degree, required large current is generated, and three-phase variable frequency ice melting is realized. The overvoltage absorption circuit is used for absorbing and discharging abnormally high voltage generated by the ice melting device during starting, stopping, operation or failure. The weak current control circuit is used for controlling, managing and protecting the work of the main power and driving circuit by generating a safe signal with low voltage and small current; the ice melting line state is monitored and fed back, the main power and driving circuit switching action is remotely controlled, and the frequency is adjusted; and strong and weak current isolation is realized.

[0007] Further, the power supply circuit comprises a 10kV bus, a circuit breaker, a voltage regulating transformer and a filter circuit; the 10kV bus output is connected with the circuit breaker, the circuit breaker output is connected with the voltage regulating transformer, and the voltage regulating transformer output is connected with the filter circuit.

[0008] Further, the main power and driving circuit comprises a main power circuit, an IGBT matrix driving circuit and a protection circuit; the IGBT matrix driving circuit output is connected with the protection circuit input, and the protection circuit output is connected with the main power circuit input.

[0009] Further, the weak current control circuit comprises an external unit, an upper computer and a signal conditioning circuit; the output of the external unit is connected with the input of the signal conditioning circuit, the output of the upper computer is connected with the input of the signal conditioning circuit, and the output of the signal conditioning circuit is connected with the input of the main power and driving circuit.

[0010] Further, the signal conditioning circuit comprises a DSP logic control circuit and a CPLD commutation control circuit.

[0011] Further, the power supply mode used by the power supply circuit comprises 10kV line voltage reduction power supply, power car power supply and generator power supply.

[0012] Further, the variable frequency ice melting device is installed on a three-layer storage structure with length, width and height of 0.5m; the first layer of the storage structure is the weak current control circuit; the second layer of the storage structure is the overvoltage absorption circuit; and the third layer of the storage structure is the main power and driving circuit.

[0013] Further, the technical parameters of the variable frequency ice melting device are as follows: the capacity of the variable frequency ice melting device is 0.5MVA, the input phase voltage is 0-694V, the input phase current is 0-840A, the output phase voltage is 0-694V, the output phase current is 0-840A, and the frequency range is 1-80Hz.

[0014] An ice-melting method based on the above-mentioned variable frequency ice-melting device includes the following steps: Step 1: Selection of de-icing frequency based on non-disconnection of the primary side of the distribution transformer; Step 2: The input power is AC. The bidirectional switch of the main power and drive circuit is composed of two common emitter switches connected in reverse series, which can realize the function of bidirectional conduction of the switch. Step 3: Overvoltage absorption circuit protection prevents damage to core power equipment or device breakdown caused by voltage overshoot when instantaneous shutdown is required under abnormal operating conditions. Step four: Using the modulation strategy of indirect space vector algorithm, the voltage waveform with the required amplitude and frequency is synthesized by input voltage vector; and three-phase frequency conversion ice melting is achieved by connecting the three-phase output to the ice melting circuit after the three phases are shorted at the end.

[0015] How to use and how to work with a variable frequency ice melting device: Phase 1: Preparation Stage: Based on the specific line segment requiring ice melting, obtain the parameters (resistance, inductance) of that segment and estimate the required frequency, current, and duration for ice melting. Power Deactivation: Isolate the target line, ensuring complete disconnection from the operating power grid, and implement safety grounding measures. Short-Circuit Operation: At the opposite end of the line (receiving side), reliably short-circuit and ground the three-phase conductors using a switch or temporary line. Connection Device: At this end (power supply side), connect the output terminal of the frequency converter ice melting device to one or two phases of the line via a cable (forming a loop). The device input terminal is then connected to the station power supply or dedicated power supply, completing the device wiring and isolation. Phase 2: Ice Melting Execution. The device operates, slowly increasing the output current while closely monitoring via a low-voltage control circuit: whether the output current, voltage, and frequency are within the predetermined range; whether the line current is stable; and whether the temperature of the device body and connection points is normal. Phase 3: Ice Melting Completion and Recovery, Shutdown Operation: Confirm that the ice on the line has melted and fallen off. Slowly and smoothly reduce the output current to zero using the main power and drive circuit. Disconnect the power supply to the ice melting device. System Restoration: Disconnect the de-icing device from the power line. Remove the short-circuit wiring at the other end of the power line. Remove temporary grounding and other relevant temporary safety measures. Check the power restoration conditions and restore power. Record all key data from this de-icing operation (time, parameters, energy consumption, effects, etc.) for subsequent analysis and optimization.

[0016] The variable frequency ice melting device utilizes the "skin effect" of alternating current and, through precise control of the output current frequency, efficiently converts electrical energy into the internal energy (heat) of the conductor, thereby melting the ice.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The low-frequency variable-frequency ice melting is essentially to change the impedance by changing the ice melting line reactance, and to realize the regulation of ice melting current under the regulation of ice melting voltage. When the low-frequency variable-frequency ice melting is carried out on the transmission line with a certain working condition, there is a minimum ice melting frequency of the power distribution primary side without removal operation. The frequency increases with the increase of ice melting voltage. The variable-frequency ice melting method provided in the present application realizes stepless regulation of ice melting voltage and current through voltage regulation and frequency conversion. The ice melting power factor can be effectively improved by reducing the ice melting frequency, and the ice melting distance is increased. With the increase of the cross section of the conductor, the effect is more significant.

[0018] Through the ice melting by direct AC-AC frequency conversion, without intermediate bulky DC link, the ice melting voltage and frequency can be continuously regulated, and the maximum output ice melting current is 800A, which meets the actual needs of 5km portable ice melting of distribution network. The method of low-frequency variable-frequency ice melting for distribution network transmission line can solve the problems of high proportion of reactive power in current frequency AC ice melting and inflexible regulation of ice melting range. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description.

[0020] Figure 1 The working principle diagram of the variable-frequency ice melting device based on low-frequency variable-frequency of the embodiment of the present application.

[0021] Figure 2 The circuit diagram of the variable-frequency ice melting device based on low-frequency variable-frequency of the embodiment of the present application. DETAILED DESCRIPTION

[0022] The technical solutions of the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation of the present application.

[0024] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0025] Embodiment one: As shown in Figure 1 , Figure 2 , the present application embodiment is a low-frequency variable frequency ice melting device, which comprises a power supply circuit, a main power and driving circuit, an overvoltage absorption circuit and a weak current control circuit; The output end of the power supply circuit is connected to the main power and driving circuit, and the main power and driving circuit is connected to the ice melting circuit; the overvoltage absorption circuit is connected in parallel with the main power and driving circuit, the input end of the overvoltage absorption circuit is connected with the output end of the power supply circuit, and the output end is connected with the ice melting circuit; the weak current control circuit is connected in parallel with the main power and driving circuit, the input end of the weak current control circuit is connected with the output end of the power supply circuit, and the output end is connected with the ice melting circuit; The power supply circuit is used for power supply of the variable frequency ice melting device and control circuit; the power supply circuit comprises a 10kV bus, a circuit breaker, a voltage regulating transformer and a filter circuit; the 10kV bus output is connected with the circuit breaker, the circuit breaker output is connected with the voltage regulating transformer, and the voltage regulating transformer output is connected with the filter circuit. The power supply mode used by the power supply circuit includes: 10kV line voltage reduction power supply, power supply of power generation vehicle and power supply of generator.

[0026] The main power and driving circuit is used for synthesizing the voltage waveform with the required amplitude and frequency by using the input voltage vector; through the ice melting circuit connected with the three-phase short circuit at the end of the three-phase output, the frequency is changed according to the line and icing degree, the required large current is generated, and three-phase variable frequency ice melting is realized; the main power and driving circuit comprises a main power circuit, an IGBT matrix driving circuit and a protection circuit. The output end of the IGBT matrix driving circuit is connected with the input end of the protection circuit, and the output end of the protection circuit is connected with the input of the main power circuit.

[0027] The overvoltage absorption circuit is used for absorbing and discharging the abnormally high voltage generated by the ice melting device during start-stop, operation or failure, so as to protect the core power equipment and devices from overvoltage breakdown damage; The weak current control circuit is used for controlling, managing and protecting the operation of the main power and driving circuit by generating a low voltage and small current safety signal, monitoring and feeding back the ice melting line state, remotely controlling the switching action of the main power and driving circuit, and adjusting the frequency; and realizing strong current and weak current isolation. The weak current control circuit comprises an external unit, an upper computer and a signal conditioning circuit; the output end of the external unit is connected to the input end of the signal conditioning circuit, the output end of the upper computer is connected to the input end of the signal conditioning circuit, and the output end of the signal conditioning circuit is connected to the input end of the main power and driving circuit. The signal conditioning circuit comprises a DSP logic control circuit and a CPLD commutation control circuit.

[0028] Embodiment two is the above-mentioned low-frequency variable frequency ice melting device, which also comprises a power supply circuit, a main power and driving circuit, an overvoltage absorption circuit and a weak current control circuit. The difference lies in that: The variable frequency ice melting device is installed on a three-layer storage structure with a length, width and height of 0.5 m; the first layer of the storage structure is the weak current control circuit; the second layer of the storage structure is the overvoltage absorption circuit; and the third layer of the storage structure is the main power and driving circuit.

[0029] The technical parameters of the variable frequency ice melting device are as follows: the capacity of the variable frequency ice melting device is 0.5 MVA, the input phase voltage is 0-694 V, the input phase current is 0-840 A, the output phase voltage is 0-694 V, the output phase current is 0-840 A, and the frequency range is 1-80 Hz.

[0030] Embodiment three is an ice melting method based on the low-frequency variable frequency ice melting device of embodiments one and two, comprising the following steps: Step one, ice melting frequency selection based on non-removal of the primary side of the distribution transformer; Step two, the input power is alternating current, and the bidirectional switch of the main power and driving circuit adopts two common-emitter reverse series connection to realize the function of bidirectional conduction of the switch.

[0031] Step three, the overvoltage absorption circuit protects against damage or device breakdown caused by voltage overshoot when instantaneous shutdown is required under abnormal working conditions.

[0032] Step four, an indirect space vector algorithm modulation strategy is adopted to synthesize the required amplitude and frequency voltage waveform using the input voltage vector. Through the ice melting line connected to the three-phase short circuit at the end of the three-phase output, three-phase variable frequency ice melting is realized.

[0033] The use method and working principle of the variable frequency ice melting device are as follows: The first stage is a preparation stage: according to the specific line section of ice melting, the parameters (resistance, inductance) of the line section are obtained, and the frequency, current and duration required for ice melting are estimated. Power-off operation: the target line is powered off and isolated, ensuring complete disconnection from the operating power grid, and safety grounding measures are taken. Short-circuit operation: at the opposite end (power receiving side) of the line, the three-phase conductor is reliably short-circuited and grounded through a switch or a temporary line. Connection device: at the sending end (power sending side), the output of the variable frequency ice melting device is connected to one or two phases of the line through a cable (forming a loop). The input of the device is connected to the station power supply or a dedicated power supply, completing the device wiring and isolation.

[0034] The second stage is to execute ice melting, the device is running, and the output current of the device is slowly increased, while closely monitoring whether the output current, voltage and frequency are within the predetermined range through the weak current control circuit. Whether the line current is stable. Whether the temperature of the device body and the connection point is normal. The third stage is to end and restore ice melting, shutdown operation: confirm that the line ice has melted and fallen off. Slowly and smoothly reduce the output current of the main power and the driving circuit to zero. Disconnect the power supply of the ice melting device. System recovery: remove the connection between the ice melting device and the line. Remove the short-circuit connection at the opposite end of the line. Remove the temporary safety measures such as temporary grounding. Check the line power restoration conditions and restore power supply. Record all key data (time, parameters, energy consumption, effect, etc.) of this ice melting for subsequent analysis and optimization.

[0035] The variable frequency ice melting device utilizes the "skin effect" of alternating current and precisely controls the output current frequency to efficiently convert electrical energy into internal energy (heat) of the conductor, thereby melting the ice.

[0036] Compared with the prior art, the beneficial effects of the present application are: Low-frequency variable frequency ice melting essentially changes the impedance by changing the ice melting line reactance, and adjusts the ice melting current under the ice melting voltage regulation. When low-frequency variable frequency ice melting is performed on a certain working condition of the transmission line, there is a minimum ice melting frequency at which the distribution primary side is not removed from operation. This frequency increases with the increase of ice melting voltage. The variable frequency ice melting method presented in this paper realizes stepless adjustment of ice melting voltage and current through voltage regulation and frequency conversion. By reducing the ice melting frequency, the ice melting power factor can be effectively improved, and the ice melting distance can be increased. With the increase of the cross section of the conductor, the effect is more significant.

[0037] By directly converting ice melting through AC-AC, there is no intermediate bulky DC link, and continuous adjustment of ice melting voltage and frequency can be realized, with a maximum ice melting current of 800A, which meets the actual needs of 5 km portable ice melting of distribution network. By adopting the method of low-frequency variable frequency ice melting for distribution network transmission lines, the problem of high reactive power ratio of current distribution network frequency AC ice melting and inflexible ice melting range adjustment can be solved.

[0038] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A low-frequency variable frequency ice melting device, characterized in that, Includes power supply circuit, main power and drive circuit, overvoltage absorption circuit and low voltage control circuit; The output of the power supply circuit is connected to the main power and drive circuit, which is connected to the de-icing circuit. The overvoltage absorption circuit is connected in parallel with the main power and drive circuit. The input of the overvoltage absorption circuit is connected to the output of the power supply circuit, and the output is connected to the de-icing circuit. The low-voltage control circuit is connected in parallel with the main power and drive circuit. The input of the low-voltage control circuit is connected to the output of the power supply circuit, and the output is connected to the de-icing circuit. The power supply circuit is used to supply power to the variable frequency ice melting device and control the current. The main power and drive circuit is used to synthesize the voltage waveform with the required amplitude and frequency using the input voltage vector; through the three-phase output connected to the de-icing circuit after the three phases are shorted at the end, the frequency is changed according to the circuit and the degree of icing to generate the required large current, thereby realizing three-phase frequency conversion de-icing; Overvoltage absorption circuit is used to absorb and release abnormally high voltages generated during the start-up, shutdown, operation, or malfunction of the de-icing device; Low-voltage control circuits are used to control, manage, and protect the operation of the main power and drive circuits by generating low-voltage, low-current safety signals; to monitor and provide feedback on the status of the de-icing line; to remotely control the switching action of the main power and drive circuits and adjust the frequency; and to achieve isolation between high-voltage and low-voltage circuits.

2. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The power supply circuit includes a 10kV bus, a circuit breaker, a voltage regulating transformer, and a filter circuit; the output of the 10kV bus is connected to the circuit breaker, the output of the circuit breaker is connected to the voltage regulating transformer, and the output of the voltage regulating transformer is connected to the filter circuit.

3. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The main power and drive circuit includes a main power circuit, an IGBT matrix drive circuit, and a protection circuit. The output of the IGBT matrix drive circuit is connected to the input of the protection circuit, and the output of the protection circuit is connected to the input of the main power circuit.

4. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The low-voltage control circuit includes a peripheral unit, a host computer, and a signal conditioning circuit; the output terminal of the peripheral unit is connected to the input terminal of the signal conditioning circuit, the output terminal of the host computer is connected to the input terminal of the signal conditioning circuit, and the output terminal of the signal conditioning circuit is connected to the input terminal of the main power and drive circuit.

5. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The signal conditioning circuit includes a DSP logic control circuit and a CPLD commutation control circuit.

6. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The power supply circuit uses the following power supply methods: 10 kV line step-down power supply, generator vehicle power supply, and generator power supply.

7. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The variable frequency ice melting device is installed on a three-layer storage structure with a length, width and height of 0.5m. The first layer of the storage structure is a low-voltage control circuit; the second layer of the storage structure is an overvoltage absorption circuit; and the third layer of the storage structure is the main power and drive circuit.

8. The low-frequency variable frequency ice melting device according to claim 1, characterized in that, The technical parameters of the variable frequency ice melting device are as follows: the variable frequency ice melting device has a capacity of 0.5MVA, an input phase voltage of 0-694V, an input phase current of 0-840A, an output phase voltage of 0-694V, an output phase current of 0-840A, and a frequency range of 1-80Hz.

9. A method for melting ice based on any one of the variable frequency ice-melting devices according to claims 1-8, comprising the following steps: Step 1: Selection of de-icing frequency based on non-disconnection of the primary side of the distribution transformer; Step 2: The input power is AC. The bidirectional switch of the main power and drive circuit is composed of two common emitter switches connected in reverse series, which can realize the function of bidirectional conduction of the switch. Step 3: Overvoltage absorption circuit protection prevents damage to core power equipment or device breakdown caused by voltage overshoot when instantaneous shutdown is required under abnormal operating conditions. Step four: Using the modulation strategy of indirect space vector algorithm, the voltage waveform with the required amplitude and frequency is synthesized by input voltage vector; and three-phase frequency conversion ice melting is achieved by connecting the three-phase output to the ice melting circuit after the three phases are shorted at the end.

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