CN110391674B - Transformer area special for transformer area and control method thereof - Google Patents
Transformer area special for transformer area and control method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00001—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by the display of information or by user interaction, e.g. supervisory control and data acquisition systems [SCADA] or graphical user interfaces [GUI]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/12—Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
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Abstract
The invention provides a transformer area special current transformer and a control method thereof, wherein the transformer area special current transformer comprises a power module, a starting module, an isolation transformer, a detection module, a filtering module, a direct current capacitor, a control module, a display control module, a direct current interface, a communication module and an auxiliary part; on the basis of the structure function of the converter, the control method is provided as follows: the distribution transformer outputs three-phase voltage and current in real time, the working state or the standby state of the converter is determined by the detection module and the control module, and the working state comprises a stage of providing reactive compensation only by the converter, or a stage of providing reactive compensation and active compensation by the converter and the energy storage battery, or only serving as a rectifying device to charge the energy storage battery. The invention solves the problem of heavy load of the distribution transformer area, effectively reduces the three-phase unbalance, reduces the capacity configuration requirement of the energy storage battery of the distribution transformer area, and saves the occupied area of the converter and the whole system.
Description
Technical Field
The invention relates to the technical field of power distribution transformer area management, in particular to a transformer special for a transformer area and a control method thereof.
Background
Along with the continuous improvement of the urban and rural electrification level, the economic quantity of urban and rural enterprises is continuously enlarged, the distribution network load is continuously increased, the daily load peak valley difference is gradually increased, the distribution transformer of a transformer area directly supplies power to a terminal power load, and the distribution transformer of a low-voltage transformer area is influenced by the power load, so that the low-voltage transformer area is overloaded, and the tripping phenomenon caused by voltage out-of-limit is frequent. Practice and research show that the phenomenon of heavy load or overload of a power distribution area is mostly accompanied with three-phase unbalance, wherein one phase has a serious overload condition, so that neutral point voltage deviation is caused, the neutral line flows over large current, and the three-phase voltage is asymmetric to cause distribution transformer tripping.
At present, the heavy load overload condition of distribution transformer in a transformer area can be effectively solved by upgrading the distribution transformer capacity and modifying a circuit, but the modification period is long, the problem of three-phase unbalance of the circuit load cannot be solved, the equipment utilization rate is low, and even the line loss is increased; only reactive power can be compensated by additionally arranging a capacitor bank, the static var generator SVG reactive power compensation device can control three-phase unbalance to a certain degree, and can offset negative sequence current and zero sequence current generated during unbalance, but cannot provide active power, so that the overload problem of the distribution transformer is solved; the power is adjusted through manual line changing and relative load network, the processing mode is difficult to meet the requirement of transient stability, and the effect is poor.
Patent 201620102238.X discloses a three-phase imbalance intelligent device, which adopts multiple sets of inductance-capacitance triangle and star compensation networks, a compensation controller determines an index balance combination compensation network, and a network loss minimization scheme is provided by using residual inductance-capacitance, which can maximize the utilization of elements, but the real-time response capability of the device is limited due to the energy storage characteristic of capacitance and inductance, and active support cannot be provided;
patent 201710036893.9 discloses a multi-converter type unbalanced three-phase load comprehensive regulation system structure and control strategy, a plurality of converters are connected in parallel in a three-phase four-wire system power grid system, the multi-module high/low performance complementary coordination converter is connected to the grid, the traditional comprehensive compensation control strategy is replaced by distribution compensation, the first converter close to the low-voltage side of the transformer is a high-performance converter, the three-phase unbalanced harmonic current of the power grid is filtered, and the rest low-performance converters averagely distribute and control unbalanced three-phase active current and reactive current. The invention achieves the distribution control purpose of balancing the three-phase active, reactive compensation and harmonic suppression functions, improves the electric energy quality, improves the power factor of the distribution transformer, and further improves the service life and the efficiency of the transformer.
The problems of heavy load overload, three-phase imbalance, reactive compensation and the like of distribution transformer in a comprehensive management distribution area provide higher requirements for power companies, and the management capacity, occupied area, cost, construction period and other aspects of configuration equipment need to be comprehensively considered. The existing reactive power compensation device has limited treatment capability; the purpose of treating three-phase imbalance and providing active power can be achieved through the parallel energy storage converters, but the system occupies a large area, and the cost is higher than the matching range of a transformer area.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a transformer special for a transformer area and a control method thereof, and in order to achieve the aim, the invention adopts the technical scheme that:
a transformer special for transformer areas comprises a direct current capacitor, a power module, a starting module, a filtering module, an isolation transformer, a detection module, a control module, a display control module, a direct current interface, a communication module and an auxiliary part; the system comprises a direct current interface, a direct current capacitor, a power module, a starting module, a filtering module and an isolation transformer, wherein the direct current interface, the direct current capacitor, the power module, the starting module, the filtering module and the isolation transformer are sequentially connected, an auxiliary part and a control module are connected with the power module, a detection module is connected with the control module and a low-voltage power distribution cabinet of a load, the detection module is also connected with the isolation transformer, the direct current interface is connected with an energy storage battery, and a display control module is used for displaying results; the detection module is used for detecting the current and voltage information of the output side of the low-voltage power distribution cabinet of the load and calculating the current and voltage information, and controlling the power module to send or absorb reactive current in real time according to the calculation result so as to eliminate heavy-load overload caused by three-phase unbalance of distribution transformer in a distribution area and send or absorb active power by means of an energy storage battery connected with a direct current interface.
According to the scheme, the control module comprises a core control processor which is used for calculating the sampling signal, and transmitting a modulation waveform to drive the power device to transmit and absorb active power and reactive power through logic judgment, closed-loop control, protection control and pulse width modulation control; the communication module is used for the communication between converter inside and outside, and communication interface contains ethernet, serial ports 485, CAN bus, and the communication protocol contains modbus and 104 agreement.
According to the scheme, the display control module is provided with an external man-machine control touch screen and is divided into a local mode and a remote control mode; the local mode is to control and output active power and reactive power through a touch screen; the remote control mode comprises an unattended operation mode and a receiving superior scheduling control mode; in addition, the touch screen displays the operation parameters, alarm information and event records of the converter output current, voltage, power grid current, voltage, a lower-level energy storage battery and other systems, and meanwhile, the charging and discharging start-stop control is carried out.
According to the scheme, the detection module detects the output voltage and current of the low-voltage side of the distribution transformer or directly reads the current and voltage information of the CT and PT of the low-voltage side of the distribution transformer, and simultaneously acquires the output current and voltage information of the converter as the input quantity of the control module.
According to the scheme, the power module is a bridge type bidirectional converter circuit based on a full-control device IGBT, the amplitude of output voltage at an alternating current side is adjusted to be compared with the amplitude at a power grid side by controlling the on-off of the IGBT, and reactive power is absorbed or emitted; or active power is sent out or absorbed to the power grid, and bidirectional circulation of power grid energy and energy of a lower-level energy storage battery is realized; the filtering module is composed of an LC filtering device or an LCL filtering device and is used for eliminating higher harmonic components contained in the output current.
According to the scheme, the direct current capacitor is used as an energy storage element of the bridge type converter, and on one hand, the direct current voltage is output and is inverted into the alternating current voltage through the inverter bridge; on the other hand, the direct-current bus voltage is stabilized, the energy is stored, and ripple current transformation required by the bidirectional current transformer is provided; the starting module comprises a starting resistor and a bypass switch, the bypass switch is connected with the starting resistor in series and in parallel, and the starting resistor is used for preventing a direct current capacitor and a power device from being burnt out at the starting moment and pre-charging the capacitor; after the starting, the starting resistor is bypassed through the bypass switch, and the active loss is reduced.
According to the scheme, the isolation transformer is a low-voltage isolation transformer, one end of the isolation transformer is connected with a power grid, the other end of the isolation transformer is connected with the starting module, and the isolation transformer has the functions of electrical insulation, restraining high-frequency harmonic waves from being connected in a control loop in series and reducing the secondary side voltage input requirement; the direct current interface is a direct current electrical interface for accessing the energy storage battery; the auxiliary part comprises an alternating current and direct current breaker, a contactor, a 220V power interface and an auxiliary UPS power interface.
A control method of a transformer area special-purpose converter is used for controlling the transformer area special-purpose converter in the technical scheme, and comprises the following steps:
the output three-phase voltage and current of the distribution transformer are monitored in real time through a converter detection module, and a control module respectively judges whether the load rate of the three phases of the distribution transformer reaches a threshold value D1 according to detection data;
if one phase of the current reaches, the converter enters a stage of regulation state, and the reactive current of the three phases to be compensated is calculated through the control module;
the control module records reactive current of the current transformer in one-stage regulation state compensation, calculates the load rate of the three phases of the distribution transformer in a simulation mode and judges whether the load rate reaches a threshold value D1; if not, the converter is in a one-stage compensation state and only provides three-phase reactive compensation until the three-phase load rate is lower than a threshold value D2; if the current transformer enters a two-stage compensation state, active power and reactive power are compensated simultaneously, a compensation value is determined through the control module, the power switch device is driven to be switched on and switched off, and corresponding active power and reactive power are output until the three-phase load factor is lower than a threshold value D2;
and when the three-phase load rate of the distribution transformer does not reach the threshold value D1, judging whether the electric quantity of the energy storage battery needs to be compensated, if so, actively controlling the battery to be charged by the converter until the electric quantity of the energy storage battery is recovered to a set value.
According to the scheme, the converter is subjected to reactive compensation in one-stage compensation, the amplitude of the output voltage at the alternating current side of the bridge converter is adjusted to be compared with the amplitude at the power grid side, and reactive power is absorbed or emitted under the action of connecting an isolation transformer, so that the aim of solving the problem of single-phase heavy load overload of distribution transformer through dynamic reactive compensation is fulfilled; the converter compensates active power and reactive power at two stages, negative sequence and zero sequence currents generated by three-phase unbalance are offset by rated reactive output preferentially in a reactive power compensation mode, and residual active power is provided by the energy storage battery in an inversion mode.
According to the scheme, the load rate threshold is the ratio of the load to the capacity of the distribution transformer, wherein D1 is greater than D2; the energy storage battery capacity is characterized by a cell voltage or an energy storage battery state of charge (SOC).
The invention has the beneficial effects that:
the invention provides a transformer area special converter and a control method thereof, which adopt a staged compensation mode and a mode of preferentially compensating reactive power, solve the problem of distribution transformer heavy load overload caused by large single-phase load capacity and serious three-phase unbalance, and control the converter to simultaneously output active power and reactive power when the reactive power compensation can not solve the problem of distribution transformer heavy load overload, and the converter design and control method can dynamically and smoothly compensate the reactive power and the active power in real time, realize the capacitive and inductive reactive power and the two-way compensation of the active power, and effectively reduce the three-phase unbalance while solving the problem of the distribution transformer area heavy load; meanwhile, the capacity configuration requirement of the energy storage battery in the power distribution area is effectively reduced, the occupied area of the converter and the whole system is saved, the economy is improved, and the popularization value is higher.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a block diagram of a zone specific converter apparatus of the present invention;
FIG. 2 is a control module current direct control method;
FIG. 3 is a control module current indirect control method;
FIG. 4 is a power module two-level topology;
fig. 5 is a power module three-level topology.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Fig. 1 is a structural diagram of a transformer area-specific converter apparatus of the present invention, which includes a dc capacitor, a power module, a start module, a filter module, an isolation transformer, a detection module, a control module, a display control module, a dc interface, a communication module, and an auxiliary part; the system comprises a direct current interface, a direct current capacitor, a power module, a starting module, a filtering module and an isolation transformer, wherein the direct current interface, the direct current capacitor, the power module, the starting module, the filtering module and the isolation transformer are sequentially connected, an auxiliary part and a control module are connected with the power module, a detection module is connected with the control module and a low-voltage power distribution cabinet of a load, the detection module is also connected with the isolation transformer, the direct current interface is connected with an energy storage battery, and a display control module is used for displaying results; the detection module is used for detecting the current and voltage information of the output side of the low-voltage power distribution cabinet of the load and calculating the current and voltage information, and controlling the power module to send or absorb reactive current in real time according to the calculation result so as to eliminate heavy-load overload caused by three-phase unbalance of distribution transformer in a distribution area and send or absorb active power by means of an energy storage battery connected with a direct current interface.
According to the scheme, the control module comprises a core control processor which is used for calculating the sampling signal, and transmitting a modulation waveform to drive the power device to transmit and absorb active power and reactive power through logic judgment, closed-loop control, protection control and pulse width modulation control; the communication module is used for the communication between converter inside and outside, and communication interface contains ethernet, serial ports 485, CAN bus, and the communication protocol contains modbus and 104 agreement.
According to the scheme, the display control module is provided with an external man-machine control touch screen and is divided into a local mode and a remote control mode; the local mode is to control and output active power and reactive power through a touch screen; the remote control mode comprises an unattended operation mode and a receiving superior scheduling control mode; in addition, the touch screen displays the operation parameters, alarm information and event records of the converter output current, voltage, power grid current, voltage, a lower-level energy storage battery and other systems, and meanwhile, the charging and discharging start-stop control is carried out.
According to the scheme, the detection module is used for detecting the output voltage and current of the low-voltage side of the distribution transformer or directly reading the current and voltage information of the CT and PT of the low-voltage side of the distribution transformer, and simultaneously acquiring the output current and voltage information of the converter, the temperature of the power module and the information of an external energy storage battery as the input quantity of the control module.
According to the scheme, the power module is a bridge type bidirectional converter circuit based on a full-control device IGBT, the amplitude of output voltage at an alternating current side is adjusted to be compared with the amplitude at a power grid side by controlling the on-off of the IGBT, and reactive power is absorbed or emitted; or active power is sent out or absorbed to the power grid, and bidirectional circulation of power grid energy and energy of a lower-level energy storage battery is realized; the filtering module is composed of an LC filtering device or an LCL filtering device and is used for eliminating higher harmonic components contained in the output current.
According to the scheme, the direct current capacitor is used as an energy storage element of the bridge type converter, and on one hand, the direct current voltage is output and is inverted into the alternating current voltage through the inverter bridge; on the other hand, the direct-current bus voltage is stabilized, the energy is stored, and ripple current transformation required by the bidirectional current transformer is provided; the starting module comprises a starting resistor and a bypass switch, the bypass switch is connected with the starting resistor in series and in parallel, and the starting resistor is used for preventing a direct current capacitor and a power device from being burnt out at the starting moment and pre-charging the capacitor; after the starting, the starting resistor is bypassed through the bypass switch, and the active loss is reduced.
According to the scheme, the isolation transformer is a low-voltage isolation transformer, one end of the isolation transformer is connected with a power grid, the other end of the isolation transformer is connected with the current transformer filtering module, and the isolation transformer has the functions of electrical insulation, suppression of high-frequency harmonic waves from entering a control loop in series and reduction of secondary side voltage input requirements; the direct current interface is a direct current electrical interface for accessing the energy storage battery; the auxiliary part comprises an alternating current and direct current breaker, a contactor, a 220V power interface and an auxiliary UPS power interface.
The control module comprises a high-speed industrial DSP core processor and a powerful FPGA chip, and the calculation and logic processing adopts a full digitalization technology to realize closed-loop control and protect logic control so as to finish the output and absorption control of reactive power and active power; the closed loop control may be a direct current control, as shown in FIG. 2; or current indirect control, as shown in figure 3.
The communication module is connected with the display control module in a serial port communication mode, and is in information intercommunication with a superior monitoring and subordinate energy storage battery in a serial port or Ethernet mode, and a communication protocol adopts a modbus or 104 protocol.
The power module is a bidirectional converter circuit of a full-control device IGBT, the bidirectional converter circuit can be a two-level structure as shown in fig. 4 or a three-level structure as shown in fig. 5, and even a serial (multi-level) or parallel (multiple) chain type topological structure, the two-level structure is suitable for a small-dosage low-voltage grade, and the multi-level or chain type topological structure can meet the requirements of higher voltage grade and capacity.
The invention provides a control method of a transformer area special-purpose converter, which is used for controlling the transformer area special-purpose converter in the technical scheme and comprises the following steps:
1) the output voltage and current of the distribution transformer are monitored in real time through the converter detection module, and the control module respectively judges whether the three-phase load rate of the distribution transformer reaches a converter starting threshold D1 according to detection data.
2) And if the load rate of one phase reaches the starting threshold of the converter, the converter enters a stage of regulation state, and the reactive current of the three phases to be compensated is calculated through the control module.
3) The control module records reactive current of the converter in one-stage regulation state compensation, calculates the three-phase load rate of the distribution transformer in a simulation mode and judges whether the three-phase load rate is higher than a threshold value D1; if not, the converter performs one-stage compensation and only provides reactive compensation until the three-phase load rate is lower than a threshold value D2; if the current transformer enters a two-stage compensation state, active power and reactive power are compensated simultaneously, a compensation value is determined through the control module, the power switch device is driven to be switched on and switched off, and corresponding active power and reactive power are output until the three-phase load factor is lower than a threshold value D2; if the distribution transformer is overloaded, judging that the three phases of the distribution transformer all reach the calculation requirement active value, and controlling the energy storage system to discharge;
5) and when the distribution transformation three-phase load rate does not reach the threshold value D1, judging whether the energy storage battery needs to compensate the electric quantity, if so, actively controlling the battery to be charged by the converter until the SOC of the energy storage battery is recovered to the set value.
The first-stage compensation of the converter is reactive compensation, namely, the amplitude of the output voltage at the alternating current side of the bridge converter is adjusted to be compared with the amplitude at the power grid side, and reactive power is absorbed or emitted under the action of connecting an isolation transformer, so that the aim of dynamic reactive compensation is fulfilled;
the converter compensates active power and reactive power at two stages, negative sequence and zero sequence currents generated by three-phase unbalance are offset by rated reactive output preferentially in a reactive power compensation mode, and residual active power is provided by an energy storage battery in an inversion mode.
The load rate threshold is the ratio of the load to the capacity of the distribution transformer, wherein D1 is greater than D2; the energy storage battery capacity is characterized by a cell voltage or an energy storage battery state of charge (SOC).
The invention provides a transformer area special converter and a control method thereof, which adopt a staged compensation mode and a mode of preferentially compensating reactive power, solve the problem of distribution transformer heavy load overload caused by large single-phase load capacity and serious three-phase unbalance, and control the converter to simultaneously output active power and reactive power when the reactive power compensation can not solve the problem of distribution transformer heavy load overload, and the converter design and control method can dynamically and smoothly compensate the reactive power and the active power in real time, realize the capacitive and inductive reactive power and the two-way compensation of the active power, and effectively reduce the three-phase unbalance while solving the problem of the distribution transformer area heavy load; meanwhile, the capacity configuration requirement of the energy storage battery in the power distribution area is effectively reduced, the occupied area of the converter and the whole system is saved, the economy is improved, and the popularization value is higher.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. A control method of a zone-specific converter is used for controlling the zone-specific converter, and the zone-specific converter comprises the following steps:
the device comprises a direct current capacitor, a power module, a starting module, a filtering module, an isolation transformer, a detection module, a control module, a display control module, a direct current interface, a communication module and an auxiliary part; the system comprises a direct current interface, a direct current capacitor, a power module, a starting module, a filtering module and an isolation transformer, wherein the direct current interface, the direct current capacitor, the power module, the starting module, the filtering module and the isolation transformer are sequentially connected; the communication module is connected with the display control module in a serial port communication mode, and the display control module is used for displaying results; the current and voltage information of the output side of the low-voltage power distribution cabinet of the load is detected through the detection module and calculated, the power module is controlled to send or absorb reactive current in real time according to the calculation result so as to eliminate heavy-load overload caused by three-phase unbalance of distribution transformer in a transformer area, and meanwhile, active power is sent or absorbed by means of an energy storage battery connected with a direct-current interface;
the method is characterized by comprising the following steps:
the output three-phase voltage and current of the distribution transformer are monitored in real time through a converter detection module, and a control module respectively judges whether the load rate of the three phases of the distribution transformer reaches a converter starting threshold D1 according to detection data;
if one phase reaches D1, the converter enters a first-stage regulation state, and reactive current of the three phases to be compensated is calculated through the control module;
the control module records reactive current of the current transformer in one-stage regulation state compensation, calculates the load rate of the three phases of the distribution transformer in a simulation mode and judges whether the load rate reaches a threshold value D1; if not, the converter is in a first-stage compensation state, only three-phase reactive compensation is provided until the three-phase load rate is lower than a preset threshold value D2 of the converter; if the current transformer enters a two-stage compensation state, active power and reactive power are compensated simultaneously, a compensation value is determined through the control module, the power switch device is driven to be switched on and switched off, and corresponding active power and reactive power are output until the three-phase load factor is lower than a threshold value D2;
and when the three-phase load rate of the distribution transformer does not reach the threshold value D1, judging whether the electric quantity of the energy storage battery needs to be compensated, if so, actively controlling the battery to be charged by the converter until the electric quantity of the energy storage battery is recovered to a set value.
2. The method for controlling the transformer area dedicated to the transformer area according to claim 1, wherein the transformer is compensated to reactive compensation in one stage, and reactive power is absorbed or emitted by adjusting the amplitude of the output voltage at the ac side of the bridge type transformer to be compared with the amplitude at the grid side under the action of the isolation transformer, so as to achieve the purpose of dynamic reactive compensation to solve the problem of single-phase overload of the distribution transformer; the converter compensates active power and reactive power at two stages, preferably compensates reactive power, counteracts negative sequence and zero sequence current generated by three-phase unbalance through rated reactive power output in a reactive power compensation mode, and provides residual active power through an energy storage battery in an inversion mode.
3. The method of claim 1, wherein the load factor threshold is a ratio of load to capacity of the distribution transformer, wherein D1 > D2; the energy storage battery capacity is characterized by a cell voltage or an energy storage battery state of charge (SOC).
4. The method as claimed in claim 1, wherein the control module comprises a core control processor for calculating the sampling signal, and sending out the modulated waveform to drive the power device to send out and absorb active and reactive power through logic judgment, closed-loop control, protection control, and pulse width modulation control; communication module is used for the communication between converter inside and the outside, and communication interface contains ethernet, serial ports 485, CAN bus, and the communication protocol contains modbus and 104 agreement.
5. The control method of the transformer special for the transformer district as claimed in claim 1, wherein the display control module is in communication connection with the control module, and has an external man-machine control touch screen which is divided into a local mode and a remote control mode; the local mode is to control and output active power and reactive power through a touch screen; the remote control mode comprises an unattended operation mode and a receiving superior scheduling control mode; in addition, the touch screen displays the operation parameters, alarm information and event records of the converter output current, voltage, power grid current, voltage, a lower-level energy storage battery and other systems, and meanwhile, the charging and discharging start-stop control is carried out.
6. The method as claimed in claim 1, wherein the detection module detects the output voltage and current of the low voltage side of the distribution transformer or directly reads the current and voltage information of the CT and PT at the low voltage side of the distribution transformer, and collects the output current and voltage information of the converter as the input of the control module.
7. The control method of the transformer special for the transformer area according to claim 1, wherein the power module is a bridge type bidirectional converter circuit based on a full-control device IGBT, and the amplitude of the output voltage at the alternating current side is adjusted to be compared with the amplitude at the power grid side by controlling the on and off of the IGBT to absorb or emit reactive power; or active power is sent out or absorbed to the power grid, and bidirectional circulation of power grid energy and energy of a lower-level energy storage battery is realized; the filtering module is composed of an LC filtering device or an LCL filtering device and is used for eliminating higher harmonic components contained in the output current.
8. The method for controlling the transformer special for the transformer district as claimed in claim 7, wherein the dc capacitor is used as an energy storage element of the bridge type transformer, on one hand, the dc voltage is outputted and inverted into the ac voltage by the inverter bridge; on the other hand, the direct-current bus voltage is stabilized, the energy is stored, and ripple current transformation required by the bidirectional current transformer is provided; the starting module comprises a starting resistor and a bypass switch, the bypass switch is connected with the starting resistor in series and in parallel, and the starting resistor is used for preventing the direct current capacitor and the power device from being burnt out at the starting moment and pre-charging the capacitor; after the starting, the starting resistor is bypassed through the bypass switch, and the active loss is reduced.
9. The method for controlling the transformer special for the transformer district as claimed in claim 1, wherein the isolation transformer is a low voltage isolation transformer, one end of the isolation transformer is connected with the power grid, and the other end of the isolation transformer is connected with the starting module, and the isolation transformer has the functions of electrical insulation, suppression of high frequency harmonic waves from entering the control loop and reduction of the secondary side voltage input requirement; the direct current interface is a direct current electrical interface for accessing the energy storage battery; the auxiliary part comprises an alternating current and direct current breaker, a contactor, a 220V power interface and an auxiliary UPS power interface.
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| CN111431200B (en) * | 2020-04-28 | 2022-05-24 | 蜂巢能源科技有限公司 | Outdoor cabinet type energy storage system |
| CN112366724B (en) * | 2020-11-10 | 2024-03-26 | 上海电气工程设计有限公司 | Reactive compensation method and system based on storage battery |
| CN114188939A (en) * | 2021-11-29 | 2022-03-15 | 深圳供电局有限公司 | Method for regulating and controlling power distribution network |
| CN114552608B (en) * | 2022-04-13 | 2023-10-13 | 南方电网电力科技股份有限公司 | Three-phase imbalance treatment method and related device based on charge and discharge of energy storage system |
| CN115764920B (en) * | 2023-01-09 | 2023-05-23 | 杭州得诚电力科技股份有限公司 | Static var generator, control method and control module of static var generator |
| CN117748518B (en) * | 2024-02-21 | 2024-05-07 | 上海派能能源科技股份有限公司 | Treatment method for terminal voltage of low-voltage power grid and energy storage equipment |
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