CN117411327A - Energy-feedback split capacitive three-phase power electronic load compatible with various requirements - Google Patents
Energy-feedback split capacitive three-phase power electronic load compatible with various requirements Download PDFInfo
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- CN117411327A CN117411327A CN202311386127.7A CN202311386127A CN117411327A CN 117411327 A CN117411327 A CN 117411327A CN 202311386127 A CN202311386127 A CN 202311386127A CN 117411327 A CN117411327 A CN 117411327A
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- 230000009466 transformation Effects 0.000 claims description 18
- 230000008878 coupling Effects 0.000 claims description 12
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- 238000005859 coupling reaction Methods 0.000 claims description 12
- 230000001939 inductive effect Effects 0.000 claims description 2
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- 230000003068 static effect Effects 0.000 abstract description 2
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- 238000011160 research Methods 0.000 description 5
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- 230000032683 aging Effects 0.000 description 1
- 238000005094 computer simulation Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
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Abstract
An energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, wherein a main circuit adopts an AC/DC/AC two-stage back-to-back structure: the front stage is a three-phase four-wire split capacitor type PWM rectifier bridge for simulating a load; the rear stage is a three-phase three-wire PWM inverter bridge, so that energy feedback is realized; the middle side uses a split capacitor, and voltage equalizing control is carried out on voltages at two ends of the capacitor by adopting a flyback circuit and an SPWM control strategy. The control strategy converts the three-phase alternating current voltage signal under the abc coordinate system into the direct current signal under the dq0 coordinate system through Park conversion and Clark conversion, and under the decoupling condition, a PI controller is adopted to track the signal without static difference. The invention can realize multiple load simulation by using one circuit topology, can maintain the voltage stability of the direct current bus under the special conditions of three-phase unbalanced load, unidirectional load, nonlinear load and the like, realizes the rapid adjustment of current, and feeds electric energy back to a power grid, thereby having great practical value.
Description
Technical Field
The invention belongs to the technical field of power electronic loads, relates to an energy-fed split capacitor type three-phase power electronic load compatible with various requirements, and in particular relates to an energy-fed power electronic load topology and a control method capable of realizing static and dynamic simulation of linear loads and nonlinear loads and considering simulation requirements of single-phase, three-phase three-wire systems and three-phase four-wire systems.
Background
The traditional electric load comprises passive elements such as a resistor, a capacitor, an inductor and the like, but the traditional test load has the pain points of incapability of continuously adjusting the load, single load characteristic, low simulation precision, high energy consumption and the like. If a set of power electronic converter is connected with the tested power supply, the phase and the magnitude of the output current of the power supply are accurately controlled, and then the power supply side is equal to a real load for testing, so that the purpose of simulating the load is achieved, and the power electronic load is the energy feedback type electronic load.
In 1990, a device for testing aging of a UPS has been proposed, and the application scenario of the device is relatively fixed. The active and reactive power adjustment of the three-phase tested power supply is gradually realized in the follow-up process. And then various direct current power supplies are applied, so that various specialists conduct a great deal of research on the power electronic load for testing, and the power electronic load is initially provided with a prototype from the use of a DC/AC converter to be connected with a power grid so as to control the output power of the tested power supply, to the addition of a Boost, buck, cuk converter, and the function of adding feedback energy to the power grid is achieved. In 2012, an AC power electronic load composed of two stages of AC/DC converters is proposed, and the back-to-back structure of the AC power electronic load is gradually accepted, so that the foundation for research on the power electronic load in recent years is laid.
The existing energy-fed alternating current electronic load research is mainly designed aiming at single-phase or three-phase balance working conditions, and is difficult to consider load tests under various working conditions such as three-phase three-wire system, three-phase four-wire system, single-phase and the like, so that further research is needed to develop the energy-fed alternating current electronic load, the input characteristics of the energy-fed alternating current electronic load are completely consistent with various typical load impedances corresponding to the actual working conditions on site, and the steady-state operation and the dynamic change characteristics of the single-phase, three-phase balance and three-phase unbalanced loads during load mutation are flexibly simulated. How to realize a load which flexibly simulates various characteristics so far, the simplification of a circuit is still one of important research contents in the field.
Disclosure of Invention
The invention aims to make up the defects of the traditional technology, and provides an energy-feedback split capacitor type three-phase power electronic load compatible with various requirements.
The energy feedback type split capacitor three-phase power electronic load compatible with various requirements is characterized by comprising a load simulation module, an energy feedback module, a direct current module and a control module; the load simulation module comprises a three-phase filter inductor, six groups of first-stage power switching devices and six groups of first-stage diodes which are respectively connected in inverse parallel, the fourth bridge arm adopts two capacitors, and the load simulation module comprises a three-phase four-wire bridge circuit formed by six groups of first-stage power switching devices and a split capacitor fourth bridge arm; the energy feedback module comprises a three-phase LCL filter, six groups of second-stage power switching devices and six groups of second-stage diodes which are respectively connected in anti-parallel with the six groups of second-stage power switching devices, and the energy feedback module comprises a three-phase bridge circuit formed by the six groups of second-stage power switching devices; the direct current module comprises a direct current capacitor; the control module comprises a phase-locked loop module, a split capacitor voltage equalizing module, a load simulation control module and an energy feedback control module. The power electronic load main circuit uses an AC/DC/AC two-stage back-to-back structure: the front stage is a three-phase four-wire split capacitor type PWM rectifier bridge and is used for simulating loads of various working conditions; the rear stage is a three-phase three-wire PWM inverter bridge, so that energy feedback to a power grid is realized, and energy waste is reduced; the split capacitor structure is used at the middle side, voltage equalizing control is carried out on voltages at two ends of the split capacitor by adopting the flyback circuit structure and the SPWM control strategy, and three-phase unbalanced load, unidirectional load and nonlinear load can be simulated.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the phase-locked loop module comprises a Clark conversion link, a Park conversion link, a PI control link and a phase mutation link.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the split capacitor voltage equalizing module comprises an upper split capacitor, a lower split capacitor, two groups of third-stage power switching devices, two groups of third-stage diodes which are respectively and reversely connected in parallel with the upper split capacitor, a coupling inductor Le1 and a coupling inductor Le2, and the split capacitor voltage equalizing module comprises an upper split capacitor, a lower split capacitor, two groups of third-stage power switching devices, two groups of third-stage diodes which are respectively and reversely connected in parallel with the lower split capacitor, the coupling inductor Le1 and the coupling inductor Le 2.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the first-stage power switching device, the second-stage power switching device and the third-stage power switching device are all insulated gate bipolar transistors.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the load simulation control module comprises a first-stage coordinate transformation link, a first-stage PI control link, a first-stage decoupling link and a first-stage SPWM control link.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the energy feedback control module comprises a second-stage coordinate transformation link, a second-stage PI control link, a second-stage decoupling link and a second-stage SPWM control link.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the first-stage coordinate transformation link and the second-stage coordinate transformation link are both composed of Clark transformation and Park transformation.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the phase mutation link is used for mutating the obtained power grid phase to form phase requirements when simulating resistive, capacitive and inductive loads, and the obtained phase is used for generating three-phase unbalanced given current.
As a preferred solution of the energy-feedback split-capacitor three-phase power electronic load compatible with various requirements, the invention comprises the following steps: the non-linear load simulation current setting circuit comprises six diodes and six resistors respectively connected in parallel, and the non-linear load simulation current setting circuit comprises a three-phase bridge circuit formed by the six diodes.
Compared with the prior art, the invention has the following advantages:
1. aiming at the problems that the traditional three-phase power electronic load can not simulate a single-phase load and a three-phase unbalanced load at the same time, and the simulation effect on a nonlinear load is poor, and the like, the invention provides an energy-fed three-phase four-wire power electronic load using a front-end split capacitor rectifier based on SPWM control and a control mode thereof, and can effectively simulate the load conditions of three-phase balance, three-phase unbalance, nonlinearity, single phase and the like.
2. In the aspect of control, three-phase alternating current quantity is converted into direct current quantity under the dq0 coordinate system through coordinate transformation, the adjusting speed is faster, and the tracking effect is better.
3. The split capacitor is used as a fourth bridge arm, voltage equalizing control is carried out on voltages at two ends of the split capacitor, and stability of direct current bus voltage in load simulation conditions such as three-phase unbalanced load and nonlinear load can be guaranteed.
Drawings
FIG. 1 is a circuit diagram of an energy-fed split capacitor three-phase power electronic load compatible with multiple requirements.
Fig. 2 is a flow chart of a phase-locked loop portion of an energy-fed split-capacitor three-phase power electronic load as a whole that is compatible with multiple requirements.
Fig. 3 is a circuit diagram of a split capacitor voltage equalizing section in an energy-fed split capacitor three-phase power electronic load compatible with multiple requirements.
Fig. 4 is a flow chart of a control portion of a split capacitor voltage equalizing portion in an energy-fed split capacitor three-phase power electronic load compatible with multiple requirements.
FIG. 5 is a flow chart of a load simulation control module in an energy-fed split capacitor type three-phase power electronic load compatible with multiple requirements.
FIG. 6 is a control flow diagram of an energy feedback control module in an energy fed split capacitor type three-phase power electronic load compatible with multiple requirements.
Fig. 7 is a circuit for current setting when a nonlinear load is simulated in an energy-fed split-capacitor three-phase power electronic load compatible with multiple requirements.
Fig. 8 is a circuit diagram of a simulated single-phase load in an energy-fed split-capacitor three-phase power electronic load compatible with multiple requirements.
Fig. 9 is a waveform diagram of dc bus voltage when simulating a three-phase unbalanced load in an energy-fed split capacitor type three-phase power electronic load compatible with various requirements.
Description of the embodiments
The technical scheme of the invention is clearly and completely described below with reference to the attached drawings. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
Example 1
Referring to fig. 1 to 3, a first embodiment of the present invention provides an energy-feedback split capacitor type three-phase power electronic load capable of simulating a three-phase unbalanced load, a unidirectional load, and a nonlinear load, which includes a load simulation module 100, a dc module 200, an energy feedback module 300, and a control module 400. The control module 400 generates control signals to control the on and off of the respective switching devices so as to implement various types of load simulation. The energy is fed back to the power grid through the energy feedback module 300, so that the energy use efficiency is improved.
The load simulation module comprises a three-phase filter inductor 101, six groups of first-stage power switching devices 102 and six groups of first-stage diodes 103 which are respectively connected in inverse parallel, a fourth bridge arm adopts two capacitors 104, and the load simulation module 100 comprises a three-phase four-wire bridge circuit formed by six groups of first-stage power switching devices 102 and a fourth bridge arm of a split capacitor 104; the direct current module 200 comprises a direct current capacitor 201; the energy feedback module comprises a three-phase LCL filter 301, six groups of second-stage power switching devices 302 and six groups of second-stage diodes 303 which are respectively connected in anti-parallel with the three-phase LCL filter, and the energy feedback module 300 comprises a three-phase bridge circuit formed by six groups of second-stage power switching devices 302 and six groups of second-stage diodes 303 which are respectively connected in anti-parallel with the six groups of second-stage power switching devices; the control module 400 includes a phase-locked loop module 401, a split capacitor voltage equalizing module 402, a load simulation control module 403, and an energy feedback control module 404.
The phase-locked loop module 401 includes a Clark conversion link 401.A, a Park conversion link 401.B, a PI control link 401.C, and a phase abrupt change link 401.D.
The first stage power switching device 102, the second stage power switching device 302, and the third stage power switching device 402.C are all insulated gate bipolar transistors.
The split capacitor voltage equalizing module 402 comprises an upper split capacitor 402.A, a lower split capacitor 402.B, two groups of third-stage power switching device switching devices and two groups of third-stage diodes 402.C, a coupling inductor Le1 and a coupling inductor Le 2.D which are respectively and reversely connected in parallel, and the split capacitor voltage equalizing module 402 comprises an upper split capacitor 402.A, a lower split capacitor 402.B, two groups of third-stage power switching devices and two groups of third-stage diodes 402.C, a coupling inductor Le1 and a coupling inductor Le 2.D which are respectively and reversely connected in parallel.
The load simulation control module 403 includes a first-stage coordinate transformation link 403.A, a first-stage PI control link 403.B, a first-stage decoupling link 403.C, and a first-stage SPWM control link 403.D.
The energy feedback control module 404 includes a second level coordinate transformation link 404.A, a second level PI control link 404.B, a second level decoupling link 404.C, and a second level SPWM control link 404.D.
Example 2
Referring to fig. 1 to 9, a second embodiment of the present invention is shown. In the above embodiment, the energy-feedback split capacitor type three-phase power electronic load compatible with multiple load requirements includes a load simulation module 100, an energy feedback module 300, a dc module 200, and a control module 400. The control module 400 generates control signals to control the on and off of the respective switching devices so as to implement various types of load simulation. The energy is fed back to the power grid through the energy feedback module 300, so that the energy use efficiency is improved.
When the three-phase unbalanced load simulation is performed, a given current is generated by the three-phase unbalanced current generation circuit to achieve the three-phase unbalanced load simulation effect, and meanwhile, detection is performed, and a switching signal of the first-stage power switching device is generated by the first-stage coordinate transformation link 403.A, the first-stage PI control link 403.B, the first-stage decoupling link 403.C and the first-stage SPWM control link 403.D, so that the switching state of the switching signal is controlled, and the whole load simulation module 100 can achieve the appointed load requirement simulation. In the whole process, the two switching devices in the split capacitor voltage equalizing link switch the switching states according to the switching signals generated by the voltage requirements of the two ends of the switching devices so as to keep the voltage equalization of the upper capacitor and the lower capacitor and the voltage stability of the direct current bus.
The energy feedback module is a three-phase bridge inverter, when energy feedback is carried out, the phase of a power grid is obtained through a phase-locked loop, the voltage of a direct current bus and the output current of the inverter are sampled, and the current meets the grid connection requirement through the second-stage coordinate transformation link 404.A, the second-stage PI control link 404.B, the second-stage decoupling link 404.C and the second-stage SPWM control link 404.D.
When single-phase load simulation is carried out, any two phases in the three-phase load are disconnected, meanwhile, corresponding two-phase bridge arms are disconnected according to the selected two phases, at the moment, the midpoint of the split capacitor is connected with the midpoint of the power supply, a complete loop is formed by the split capacitor, the one-phase power supply and the bridge arms, and at the moment, the front end structure of the circuit is a single-phase half-bridge rectifier so as to realize the simulation of the single-phase load.
In the case of nonlinear load simulation, the current setting circuit 500 of the nonlinear load simulation includes six diodes 501 and six resistors 502 respectively connected in parallel therewith, and the current setting circuit 500 of the nonlinear load simulation is a three-phase bridge circuit formed by six diodes 501 and six resistors 502 respectively connected in parallel therewith. The three-phase input currents of the circuit are unbalanced, so that the topological structure of the circuit is consistent with the structure of the three-phase unbalanced load, and the front end of the circuit can work in an analog nonlinear load state by modifying a given current waveform into a current waveform corresponding to the nonlinear load. At this time, the sum of the three-phase currents is not 0, i.e. the neutral line has current, and the voltage of the two split capacitors at the direct current side has unbalance phenomenon, which can adversely affect the load simulation performance and the grid-connected performance of the device and the service life of the system, so that the split capacitor voltage equalizing module is still required to act, the voltage difference value on the two split capacitors is reduced, and the simulation performance and the electric energy quality are improved.
When voltage equalizing control of the split capacitors is carried out, the voltage of the split capacitor at one side is differed from the voltage of the direct current bus which is 0.5 times, the difference value is compared with the triangular wave after passing through the PI controller, and then corresponding driving signals are output, so that the two switching tubes are driven to be turned on and off, and the voltage at two ends of the split capacitors is controlled.
Referring to fig. 9, fig. 9 has an abscissa of time t(s) and an ordinate of voltage Udc (v). When the three-phase unbalanced load is simulated, the voltage of the direct current bus rises faster and is stabilized near a given value quickly due to the adoption of the split capacitor voltage-equalizing circuit, and the regulating effect is good. The stable direct current bus voltage is provided for the whole experiment.
Compared with the prior art, the existing power electronic load cannot simulate special load conditions such as three-phase unbalanced load and nonlinear load, and has poor stabilizing effect on the voltage of a direct current bus. Meanwhile, the traditional control method based on the abc coordinate system has a relatively large error and a relatively poor adjusting effect. The invention can simulate various load conditions such as three-phase unbalance, nonlinearity, single phase and the like by using the same circuit topology, and aims at the problem of direct current bus voltage fluctuation existing in unbalanced load, and the split capacitor is adopted as a fourth bridge arm and voltage equalizing control is carried out to maintain the stability of bus voltage. In the aspect of control, the three-intersection flow is converted into the dq0 coordinate system by adopting coordinate transformation for control, so that the adjustment speed is higher, and the tracking effect is better.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made in the above embodiments by those skilled in the art without departing from the spirit and principles of the invention. The protection scope of the present invention is defined by the claims and the equivalents thereof.
Claims (9)
1. An energy-fed split capacitor type three-phase power electronic load compatible with various requirements is characterized by comprising a load simulation module (100), a direct current module (200), an energy feedback module (300) and a control module (400);
the load simulation module comprises a three-phase filter inductor (101), six groups of first-stage power switching devices (102) and six groups of first-stage diodes (103) which are respectively connected in inverse parallel, a fourth bridge arm adopts two capacitors (104), and the load simulation module (100) comprises a three-phase four-wire bridge circuit formed by six groups of first-stage power switching devices (102) and a fourth bridge arm of a split capacitor (104);
the direct current module (200) comprises a direct current capacitor (201);
the energy feedback module comprises a three-phase LCL filter (301), six groups of second-stage power switching devices (302) and six groups of second-stage diodes (303) which are respectively connected in anti-parallel with the six groups of second-stage power switching devices, and the energy feedback module (300) comprises a three-phase bridge circuit formed by six groups of second-stage power switching devices (302) and six groups of second-stage diodes (303) which are respectively connected in anti-parallel with the six groups of second-stage power switching devices;
the control module (400) comprises a phase-locked loop module (401), a split capacitor voltage equalizing module (402), a load simulation control module (403) and an energy feedback control module (404).
2.A power electronic load according to claim 1, characterized in that the phase-locked loop module (401) comprises a Clark conversion stage (401. A), a Park conversion stage (401. B), a PI control stage (401. C) and a phase jump stage (401. D).
3.A power electronic load according to claim 1, characterized in that the split capacitor voltage equalizing module (402) comprises an upper split capacitor (402. A), a lower split capacitor (402. B), two sets of third stage power switching devices and two sets of third stage diodes (402. C), a coupling inductance Le1 and a coupling inductance Le2 (402. D) connected in anti-parallel with each other, the split capacitor voltage equalizing module (402) being constituted by the upper split capacitor (402. A), the lower split capacitor (402. B), the two sets of third stage power switching devices and the two sets of third stage diodes (402. C), the coupling inductance Le1 and the coupling inductance Le2 (402. D) connected in anti-parallel with each other.
4.A power electronic load according to claim 1 or claim 3, wherein the first stage power switching device (102), the second stage power switching device (302) and the third stage power switching device (402. C) are all insulated gate bipolar transistors.
5. The power electronic load according to claim 1, wherein the load simulation control module (403) comprises a first level coordinate transformation link (403. A), a first level PI control link (403. B), a first level decoupling link (403. C) and a first level SPWM control link (403. D).
6. The power electronic load of claim 1, wherein the energy feedback control module (404) comprises a second level coordinate transformation link (404. A), a second level PI control link (404. B), a second level decoupling link (404. C), and a second level SPWM control link (404. D).
7. A power electronic load according to claim 5 or claim 6, characterized in that the first stage coordinate transformation stage (403. A) and the second stage coordinate transformation stage (404. A) consist of a Clark transformation and a Park transformation.
8. A power electronic load according to claim 2, characterized in that the phase jump step (401. D) jumps the resulting grid phase, constructs phase requirements when simulating resistive, capacitive and inductive loads, and uses the resulting phase for generating a three-phase imbalance given current.
9. A power electronic load according to claim 2, further comprising a non-linear load-modeled current-giving circuit (500), the non-linear load-modeled current-giving circuit (500) comprising six diodes (501) and six resistors (502) respectively connected in parallel therewith, the non-linear load-modeled current-giving circuit (500) constituting a three-phase bridge circuit from six diodes (501) and six resistors (502) respectively connected in parallel therewith.
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