CN113064096A - Shore power test system based on medium-high voltage alternating current - Google Patents
Shore power test system based on medium-high voltage alternating current Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/40—Testing power supplies
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/28—Provision in measuring instruments for reference values, e.g. standard voltage, standard waveform
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/40—Testing power supplies
- G01R31/42—AC power supplies
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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
- H02M5/02—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 without intermediate conversion into dc
- H02M5/04—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 without intermediate conversion into dc by static converters
- H02M5/10—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 without intermediate conversion into dc by static converters using transformers
- H02M5/12—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 without intermediate conversion into dc by static converters using transformers for conversion of voltage or current amplitude only
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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
- 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
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with 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
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with 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
Abstract
The invention discloses a shore power test system based on medium-high voltage alternating current, which comprises a phase-shifting transformer, a voltage disturbance source subsystem, a man-machine interaction module and a voltage output module, wherein the voltage disturbance source subsystem comprises three power units, a rectification control module and an inversion control module, each power unit comprises N rectification subunits and N inversion subunits, the phase-shifting transformer is used for converting three-phase medium-high voltage alternating current into three-phase low-voltage alternating current, and each phase of low-voltage alternating current is output to the corresponding N rectification subunits after phase shifting in sequence; the rectification control module is used for controlling the active power of the rectification subunit and maintaining the voltage stability of the rectification subunit; the inversion control module is used for acquiring feedback current of the inversion subunit and adjusting the output of the inversion subunit by comparing the feedback current with preset instruction current; the voltage output module is used for superposing the outputs of the three-phase medium-high voltage alternating current and voltage disturbance source subsystem and then outputting the superposed outputs to the shore power supply module to be tested so as to ensure that the test system outputs disturbance test waveforms with different electric energy qualities.
Description
Technical Field
The invention belongs to the technical field of shore power tests, and particularly relates to a shore power test system based on medium-high voltage alternating current.
Background
According to the disturbance source of the traditional medium-high voltage alternating current shore power system, a transformer is used for realizing power disturbance in a manual switching mode, the method can only realize voltage sag or rise disturbance, the circuit is simple and easy to realize, disturbance can be generated in a short time, and the defects of limited simulation disturbance mode, poor controllability and the like exist. At present, the mainstream multi-module cascade type inverter comprises a Modular Multilevel Converter (MMC), an inverter based on a cascade H bridge and a disturbance test platform combined by a digital-physical hybrid simulation technology based on a real-time digital simulation device.
However, with the MMC scheme, the number of submodules used is large, the size is large, and the problem of balancing of capacitor voltage of the submodules needs to be considered besides the control of the stability of direct-current voltage.
The inverter based on the cascade H bridge comprises input multi-winding isolation transformers, a plurality of back-to-back power units and a filter LC loop, wherein the secondary winding of each input isolation transformer is connected with the input end of one back-to-back power unit, and the back-to-back power units are cascaded to form a 10kV voltage output end and connected with the filter LC loop to serve as a test power supply of a medium-high voltage alternating current shore power system. In order to achieve 10kV disturbance level, the number of back-to-back power units is required to be 10-16. Therefore, the topological structure has the advantages of more used power units, larger volume, complex control and higher cost.
In addition, the electric energy quality disturbance generating device of the full-control device can be combined with a digital-physical hybrid simulation technology based on a real-time digital simulation device to realize the electric energy quality disturbance test of high-voltage high-power equipment under laboratory conditions.
Disclosure of Invention
Aiming at least one defect or improvement requirement in the prior art, the invention provides a shore power test system based on medium-high voltage alternating current, so as to ensure that the test system outputs disturbance test waveforms with different electric energy qualities, and the shore power test system is flexible, controllable, low in cost, few in power devices and small in size.
In order to achieve the above object, according to one aspect of the present invention, a shore power test system based on medium-high voltage alternating current is provided, the shore power test system includes a phase-shifting transformer, a voltage disturbance source subsystem, a human-computer interaction module and a voltage output module, the voltage disturbance source subsystem includes three power units, a rectification control module and an inversion control module, the three power units are respectively connected with an output end of the phase-shifting transformer, each power unit includes N rectifier sub-units and N inverter sub-units, the N inverter sub-units are cascaded back to back and then output to the voltage output module, the rectification control module is respectively connected with all the rectifier sub-units, the inversion control module is respectively connected with all the inverter sub-units, and the voltage output module is connected with a shore power module to be tested;
the phase-shifting transformer is used for converting three-phase medium-high voltage alternating current into three-phase low-voltage alternating current, and each phase of low-voltage alternating current is output to the corresponding N rectifier sub-units after phase shifting in sequence;
the rectification control module is used for controlling the active power of the rectification subunit and maintaining the voltage stability of the rectification subunit;
the inversion control module is used for acquiring feedback current of the inversion subunit and adjusting the output of the inversion subunit by comparing the feedback current with preset instruction current;
and the voltage output module is used for superposing the outputs of the three-phase medium-high voltage alternating current and voltage disturbance source subsystem and then outputting the superposed outputs to the shore power supply module to be tested.
As a further improvement of the present invention, the rectification control module includes a first PI regulator, a first current tracking control submodule, a second current tracking control submodule, and a third current tracking control submodule, an output end of the first PI regulator is respectively connected to the first current tracking control submodule, the second current tracking control submodule, and the third current tracking control submodule, the rectification submodule includes a rectification side IGBT, and the first current tracking control submodule, the second current tracking control submodule, and the third current tracking control submodule are respectively connected to the rectification side IGBTs of the three power units.
As a further improvement of the invention, the rectification control module obtains the total voltage U at the rectification side by obtainingdAccording to the total voltage U of the rectifying sidedAnd a rectified side voltage reference value Ud*The output of the first PI regulator is regulated by the difference value, and the output of the IGBT at the rectifying side is regulated by the first current tracking control submodule, the second current tracking control submodule and the third current tracking control submodule so as to realize the voltage stable output of the rectifying subunit.
As a further development of the invention, the first PI regulator utilizes the total voltage U on the rectifying sidedAnd a rectified side voltage reference value Ud*The difference value of (a) generates an active current instruction IpThe first current tracking submodule, the second current tracking control submodule and the third current tracking control submodule are respectively multiplied with the phase locking phase of the power grid, and the multiplication result is used as an active current instruction and is multiplied with three input currents i at the rectifying sideaf、ibf、icfComparing to obtain error value, and tracking and controlling the error value by current tracking submodule to form positive sequence component u of output voltage of each phasea1、ub1、uc1Is then connected to the feed forward voltage UfAdding to obtain output voltage u of each phasea2、ub2，uc2Signal as modulated wave passing carrier ratioAnd the comparison module generates a PWM driving signal to control the IGBT at the rectification side.
As a further improvement of the present invention, the inverter control module includes a second PI regulator, a first instruction current control submodule, a second instruction current control submodule, and a third instruction current control submodule, an output end of the second PI regulator is respectively connected to the first instruction current control submodule, the second instruction current control submodule, and the third instruction current control submodule, the inverter submodule includes an inverter side H-bridge, and the first instruction current control submodule, the second instruction current control submodule, and the third instruction current control submodule are respectively connected to the inverter side H-bridge of the three power units.
As a further improvement of the invention, the inversion control module acquires a power grid synchronous phase obtained by power grid phase locking, PI controls a d-axis voltage and a preset instruction amplitude output by a voltage disturbance source and a q-axis voltage and a preset instruction amplitude output by the voltage disturbance source respectively through a second PI regulator, and performs inverse transformation on the acquired direct current quantity to acquire an instruction current iLa*，iLb*，iLc*And comparing the inverter side inductive current serving as feedback current with the instruction current, performing PI control to obtain a three-phase modulation wave, further obtaining each phase of PWM signals, and driving the corresponding IGBT of the inverter side H bridge by using each phase of PWM signals after the triangular carrier of each phase of H bridge on the inverter side is subjected to carrier phase shift.
As a further improvement of the invention, the inversion control module obtains the unbalance degree and converts the unbalance degree into the real part and the imaginary part of the given negative sequence voltage, the real part and the imaginary part of the given negative sequence voltage are subjected to IDFT to obtain a modulation wave, and the modulation wave is compared with the triangular carrier wave to generate a PWM signal to drive the IGBT of the H bridge on the inversion side.
The inverter control module is used for generating a three-phase harmonic voltage modulation wave after IDFT conversion of a real part and an imaginary part of 2-25 th harmonic waves and comparing the three-phase harmonic voltage modulation wave with a triangular carrier to generate a PWM signal to drive an IGBT of an H bridge on an inverter side.
As a further improvement of the invention, the shore power test system further comprises a voltage generator, wherein the voltage generator is connected with the voltage output module and is used for testing the tolerance degree of the electrical equipment to voltage sag and the open-phase protection function.
As a further improvement of the shore power supply testing system, the shore power supply testing system further comprises a current generator, wherein the current generator is connected with the voltage output module and is used for verifying the over-current and short-circuit protection of the shore power supply.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
the shore power test system based on the medium-high voltage alternating current provided by the invention adopts a structure of cascading a multi-winding transformer and back-to-back power units, wherein after being cascaded, a plurality of modules output disturbance voltage which is superposed to 10kV, various disturbance sources are generated, including voltage harmonics, voltage deviation, voltage sag and voltage three-phase imbalance, and the disturbance sources act on the medium-high voltage alternating current shore power system to test the electric energy quality tolerance of the medium-high voltage alternating current shore power system. This patent adopts the topology and the control technique of optimization, when promoting equipment capacity, adopts the power module cascade that the quantity is less, produces the voltage disturbance of 10kV level, guarantees that test system outputs the disturbance test waveform of different electric energy quality and nimble, controllable, with low costs, power device is few, small.
According to the shore power test system based on the medium-high voltage alternating current, the rectifying side and the inverting side of the shore power test system adopt full-control rectification, and bidirectional flow of energy can be realized. The rectification side adopts a three-level rectification topological structure, and compared with a common half-bridge circuit, the three-level circuit has the capability of neutral-point follow current, has good effects on improving output ripples and reducing loss, and meanwhile, the IGBT voltage resistance is lower than that of two levels, and the loss is low.
According to the shore power test system based on the medium-high voltage alternating current, 3 power modules are cascaded on the inversion side, and the output disturbance voltage is superposed to 10 kV. High-voltage large-capacity wide-bandwidth power quality waveform output realized by using low-voltage low-bandwidth power electronic device
Drawings
Fig. 1 is a schematic diagram of a shore power test system based on medium-high voltage alternating current provided by an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a voltage disturbance source subsystem according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a rectifier control module and a rectifier sub-module connection provided by an embodiment of the invention;
fig. 4 is a schematic diagram of an inverter control module according to an embodiment of the present invention to achieve a specified voltage output;
fig. 5 is a schematic diagram of an inverter control module according to an embodiment of the present invention to implement unbalanced voltage output control;
fig. 6 is a schematic diagram of an inverter control module according to an embodiment of the present invention to implement harmonic voltage output control;
fig. 7 is a schematic diagram of a carrier modulation process provided by an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 1 is a schematic diagram of a shore power test system based on medium-high voltage alternating current provided by an embodiment of the invention. As shown in fig. 1, a shore power test system based on medium-high voltage alternating current comprises a phase-shifting transformer, a voltage disturbance source subsystem, a man-machine interaction module and a voltage output module, wherein the voltage disturbance source subsystem comprises three power units, a rectification control module and an inversion control module, the three power units are respectively and correspondingly connected with the output end of the phase-shifting transformer, each power unit comprises N rectifier sub-units and N inverter sub-units, the N inverter sub-units are cascaded back to back and output the cascaded voltage to the voltage output module, the rectification control module is respectively connected with all the rectifier sub-units, the inversion control module is respectively connected with all the inverter sub-units, and the voltage output module is connected with a shore power supply module to be tested;
the phase-shifting transformer is used for converting three-phase medium-high voltage alternating current into three-phase low-voltage alternating current, and each phase of low-voltage alternating current is output to the corresponding N rectifier sub-units after being subjected to phase shifting in sequence;
the rectification control module is used for controlling the active power of the rectification subunit and maintaining the voltage stability of the rectification subunit;
the inversion control module is used for acquiring feedback current of the inversion subunit and adjusting the output of the inversion subunit by comparing the feedback current with preset instruction current;
and the voltage output module is used for superposing the outputs of the three-phase medium-high voltage alternating current and voltage disturbance source subsystem and then outputting the superposed outputs to the shore power supply module to be tested.
Fig. 2 is a schematic structural diagram of a voltage disturbance source subsystem according to an embodiment of the present invention. As shown in fig. 2, the voltage disturbance source subsystem is a core part of the test platform, is connected in series to a 10kV main loop, and includes three power units, a rectification control module and an inversion control module, and is mainly responsible for analog quantity sampling, disturbance source switching control, switching contact feedback sampling, power unit disturbance output control, and communication with an industrial personal computer and a background upper computer. The power unit comprises a multi-winding transformer, a back-to-back power unit, a circuit breaker, a contactor and the like, mainly executes power output and outputs various disturbance voltage waveforms. As an example, the voltage disturbance source employs 3 back-to-back power cells cascaded together for each phase, and 9 modules in total. Each module can be divided into a rectification side and an inversion side according to functions, the rectification side is connected with the secondary side of the transformer through a connecting reactor, and the output of the inversion side adopts an alternating current side cascade structure.
Fig. 3 is a schematic diagram of a rectifier control module and a rectifier sub-module according to an embodiment of the present invention. As shown in fig. 3, preferably, the rectification control module includes a first PI regulator, a first current tracking control submodule, a second current tracking control submodule, and a third current tracking control submodule, wherein an output end of the first PI regulator is respectively connected to the first current tracking control submodule, the second current tracking control submodule, and the third current tracking control submodule, the rectification submodule includes a rectification side IGBT, and the first current tracking control submodule, the second current tracking control submodule, and the third current tracking control submodule are connected to the first current tracking control submodule, the second current tracking control submodule, and the third current tracking control submodule, respectivelyAre respectively correspondingly connected with the IGBT on the rectification side of the three power units, and the rectification control module obtains the total voltage U on the rectification sidedAccording to the total voltage U of the rectifying sidedAnd a rectified side voltage reference value Ud*The output of the first PI regulator is regulated by the difference value, and the output of the IGBT at the rectifying side is regulated by the first current tracking control submodule, the second current tracking control submodule and the third current tracking control submodule so as to realize the voltage stable output of the rectifying subunit. In particular, the total voltage U on the rectifying sidedAnd a rectified side voltage reference value Ud*Comparing, the error generates an active flow instruction I through a first PI regulatorpThe current tracking sub-modules are respectively multiplied by the phase locking phases of the power grid to serve as active current instructions and three input currents i at the rectifying sidesaf、ibf、icfComparing, and forming positive sequence component u of output voltage of each phase by tracking control of current tracking submodulea1、ub1、uc1Is then connected to the feed forward voltage UfAdding to obtain output voltage u of each phasea2、ub2，uc2And the signal is used as a modulation wave to generate a PWM driving signal through a carrier comparison module to control the rectification side IGBT.
Fig. 4 is a schematic diagram of the inverter control module according to the embodiment of the present invention for realizing a specific voltage output. As shown in fig. 4, the inversion control module includes a second PI regulator, a first instruction current control submodule, a second instruction current control submodule, and a third instruction current control submodule, wherein an output end of the second PI regulator is respectively connected to the first instruction current control submodule, the second instruction current control submodule, and the third instruction current control submodule, the inversion submodule includes an inversion side H bridge, the first instruction current control submodule, the second instruction current control submodule, and the third instruction current control submodule are respectively connected to the inversion side H bridges of the three power units, the inversion control module obtains a power grid synchronous phase obtained by power grid phase locking, and performs abc-dq change on the voltage disturbance source output voltage, that is, the second PI regulator respectively performs PI control on the d-axis voltage and the preset instruction amplitude value output by the voltage disturbance source, and performs PI control on the q-axis voltage and the preset instruction amplitude value output by the voltage disturbance source, is obtained byThe direct current value is inversely transformed to obtain a command current iLa*，iLb*，iLc*And comparing the inverter side inductive current serving as feedback current with the instruction current, performing PI control to obtain a three-phase modulation wave, further obtaining each phase of PWM signals, and driving the corresponding IGBT of the inverter side H bridge by using each phase of PWM signals after the triangular carrier of each phase of H bridge on the inverter side is subjected to carrier phase shift.
Fig. 5 is a schematic diagram of an inverter control module according to an embodiment of the present invention for implementing unbalanced voltage output control. As shown in fig. 5, the inversion control module obtains the imbalance and converts the imbalance into the real part and the imaginary part of the given negative sequence voltage, the real part and the imaginary part of the given negative sequence voltage are subjected to IDFT conversion to obtain a modulation wave, and the modulation wave is compared with the triangular carrier wave to generate a PWM signal to drive the IGBT of the H bridge on the inversion side.
Fig. 6 is a schematic diagram of the inverter control module according to the embodiment of the present invention for implementing harmonic voltage output control. As shown in fig. 6, the inversion control module performs IDFT conversion on the real part and the imaginary part of the harmonic wave of 2 to 25 th order to generate a three-phase harmonic voltage modulation wave, and compares the three-phase harmonic voltage modulation wave with a triangular carrier to generate a PWM signal to drive the IGBT of the H bridge on the inversion side.
Preferably, the test system further comprises a voltage generator, the voltage generator is connected with the voltage output module and is used for simulating and generating voltage sag and voltage open phase so as to test the tolerance degree of the electrical equipment to the voltage sag and the open phase protection function. As an example, the voltage generator outputs three-phase voltage of 0-120V.
Preferably, the test system further comprises a current generator, wherein the current generator is connected with the voltage output module and is used for simulating faults such as overcurrent and short circuit and verifying overcurrent and short circuit protection of the shore power supply. As an example, the current generator outputs three-phase voltages of 0-10A.
Fig. 7 is a schematic diagram of a carrier modulation process provided by an embodiment of the present invention. As shown in fig. 7, in the test system, in the cascade inverter having the number of modules N, a common modulated wave signal is used for each module inversion side of each phase, the modulated wave signal is composed of a voltage command, a harmonic command, and an unbalanced voltage command which specify disturbance, the phases of the respective triangular carriers are shifted by 1/N of a half of the period of the triangular carrier, and the outputs of the respective inverter modules are superimposed, whereby the total output voltage of the cascade inverter having the number of levels (2N +1) can be obtained. The total output waveform of the cascade inverter modulated by the single-pole frequency multiplication CPS-SPWM is more in level number, closer to a sine wave, smaller in harmonic component and better in waveform than the output waveform modulated by the bipolar CPS-SPWM. The voltage type PWM inverter is output as PWM waves with the same frequency as sinusoidal modulation waves after being modulated by SPWM, the lowest harmonic wave after Fourier decomposition is related to a carrier ratio k, the lowest harmonic frequency of a bipolar SPWM waveform is k, the lowest harmonic frequency of a unipolar frequency doubling SPWM waveform is 2k, fundamental waves and the modulation waves have the same frequency and the same phase, the amplitude is M times of the modulation waves, and M is the modulation ratio. Because the frequency of the lowest harmonic wave can be adjusted by changing the carrier ratio, the frequency of the lowest harmonic wave can be increased as much as possible, so that the filtering is easier, and the voltage and the current with low harmonic wave content are output. After 2 modules are cascaded, through carrier phase shift, when N cascaded inverter modules are modulated by using a carrier phase shift bipolar CPS-SPWM method, the lowest subcarrier harmonic wave of the output bipolar CPS-SPWM waveform is Nk, if a modulation method of unipolar frequency multiplication CPS-SPWM is adopted, the lowest subcarrier harmonic wave of the output unipolar frequency multiplication CPS-SPWM waveform appears near 2Nk, when a single module is compared, the cascaded harmonic wave has better characteristic, perfect harmonic-free output can be realized after filtering, and the amplitude, the frequency and the phase of output voltage can be adjusted. Through the analysis, the disturbance source can be equivalent to a controllable voltage source with adjustable amplitude, frequency and phase, and the output can realize the following waveform, single combination of fundamental waves to 25 harmonics, and superposition of different harmonics. The tested object is connected with the output end, and the experimental requirement can be met.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A shore power test system based on medium-high voltage alternating current is characterized by comprising a phase-shifting transformer, a voltage disturbance source subsystem, a man-machine interaction module and a voltage output module, wherein the voltage disturbance source subsystem comprises three power units, a rectification control module and an inversion control module, the three power units are respectively and correspondingly connected with the output end of the phase-shifting transformer, each power unit comprises N rectification subunits and N inversion subunits, the N inversion subunits are cascaded back to back and then output to the voltage output module, the rectification control module is respectively connected with all the rectification subunits, the inversion control module is respectively connected with all the inversion subunits, and the voltage output module is connected with a shore power supply module to be tested;
the phase-shifting transformer is used for converting three-phase medium-high voltage alternating current into three-phase low-voltage alternating current, and each phase of low-voltage alternating current is output to the corresponding N rectifier sub-units after phase shifting in sequence;
the rectification control module is used for controlling the active power of the rectification subunit and maintaining the voltage stability of the rectification subunit;
the inversion control module is used for acquiring feedback current of the inversion subunit and adjusting the output of the inversion subunit by comparing the feedback current with preset instruction current;
and the voltage output module is used for superposing the outputs of the three-phase medium-high voltage alternating current and voltage disturbance source subsystem and then outputting the superposed outputs to the shore power supply module to be tested.
2. The shore power test system based on medium-high voltage alternating current of claim 1, wherein the rectification control module comprises a first PI regulator, a first current tracking control submodule, a second current tracking control submodule and a third current tracking control submodule, an output end of the first PI regulator is respectively connected with the first current tracking control submodule, the second current tracking control submodule and the third current tracking control submodule, the rectifier submodule comprises a rectification side IGBT, and the first current tracking control submodule, the second current tracking control submodule and the third current tracking control submodule are respectively correspondingly connected with the rectification side IGBTs of the three power units.
3. The shore power test system based on medium-high voltage alternating current of claim 2, wherein the rectification control module obtains the total rectification side voltage UdAccording to the total voltage U of the rectifying sidedAnd a rectified side voltage reference value Ud*The output of the first PI regulator is regulated by the difference value, and the output of the IGBT at the rectifying side is regulated by the first current tracking control submodule, the second current tracking control submodule and the third current tracking control submodule so as to realize the voltage stable output of the rectifying subunit.
4. The middle-high voltage alternating current-based shore power test system of claim 3, wherein said first PI regulator utilizes a rectified side total voltage UdAnd a rectified side voltage reference value Ud*The difference value of (a) generates an active current instruction IpThe first current tracking submodule, the second current tracking control submodule and the third current tracking control submodule are respectively multiplied with the phase locking phase of the power grid, and the multiplication result is used as an active current instruction and is multiplied with three input currents i at the rectifying sideaf、ibf、icfComparing to obtain error value, and tracking and controlling the error value by current tracking submodule to form positive sequence component u of output voltage of each phasea1、ub1、uc1Is then connected to the feed forward voltage UfAdding to obtain output voltage u of each phasea2、ub2，uc2And the signal is used as a modulation wave to generate a PWM driving signal through a carrier comparison module to control the rectification side IGBT.
5. The shore power test system based on medium-high voltage alternating current of claim 1, wherein the inversion control module comprises a second PI regulator, a first command current control submodule, a second command current control submodule and a third command current control submodule, an output end of the second PI regulator is respectively connected with the first command current control submodule, the second command current control submodule and the third command current control submodule, the inversion submodule comprises an inversion side H-bridge, and the first command current control submodule, the second command current control submodule and the third command current control submodule are respectively connected with the inversion side H-bridge of the three power units correspondingly.
6. The shore power test system based on medium-high voltage alternating current of claim 5, wherein the inversion control module obtains a grid synchronous phase obtained by grid phase locking, PI controls a d-axis voltage and a preset instruction amplitude output by the voltage disturbance source and a q-axis voltage and a preset instruction amplitude output by the voltage disturbance source through a second PI regulator, and performs inverse transformation on the obtained direct current to obtain an instruction current iLa*，iLb*，iLc*And comparing the inverter side inductive current serving as feedback current with the instruction current, performing PI control to obtain a three-phase modulation wave, further obtaining each phase of PWM signals, and driving the corresponding IGBT of the inverter side H bridge by using each phase of PWM signals after the triangular carrier of each phase of H bridge on the inverter side is subjected to carrier phase shift.
7. The shore power test system based on the medium-high voltage alternating current as claimed in claim 5, wherein the inversion control module obtains the degree of unbalance and converts the degree of unbalance into a real part and an imaginary part of the given negative sequence voltage, the real part and the imaginary part of the given negative sequence voltage are subjected to IDFT to obtain a modulation wave, and the modulation wave is compared with the triangular carrier to generate a PWM signal to drive the IGBT of the H bridge on the inversion side.
8. The middle-high voltage alternating current-based shore power test system as claimed in claim 5, wherein the inversion control module generates three-phase harmonic voltage modulation waves after IDFT conversion is carried out on the real part and the imaginary part of 2-25 harmonics, and the three-phase harmonic voltage modulation waves are compared with a triangular carrier wave to generate PWM signals to drive the IGBT of the inversion side H bridge.
9. The shore power test system based on medium-high voltage alternating current of claim 1, wherein the shore power test system further comprises a voltage generator, the voltage generator is connected with the voltage output module, and the voltage generator is used for testing the tolerance degree of the electrical equipment on voltage sag and the open-phase protection function.
10. The shore power test system based on the medium-high voltage alternating current of claim 1, wherein the shore power test system further comprises a current generator, the current generator is connected with the voltage output module, and the current generator is used for verifying the shore power supply overcurrent and short-circuit protection.
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