CN112054682B - Current sharing control method for flexible direct-current transmission direct-current converter of offshore wind farm - Google Patents
Current sharing control method for flexible direct-current transmission direct-current converter of offshore wind farm Download PDFInfo
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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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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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
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
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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
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
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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
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention relates to a current sharing control method for a flexible direct current transmission direct current converter of an offshore wind farm, and belongs to the technical field of wind power. The control method comprises the following steps: the difference between the voltage reference value of the low-voltage side direct-current bus and the actual value of the voltage reference value is subjected to amplitude limiting after PI to obtain the output current reference value of the preceding-stage converter of each direct-current converter module, the actual value of the output current reference value is subtracted, and the driving signal of the preceding-stage converter is generated through PI, so that the functions of boosting and stabilizing the voltage and the transmission power of the low-voltage side direct-current bus are realized; taking the average value of the high-voltage side currents of all the direct current converter modules as the reference value i of the high-voltage side current of each direct current converter moduleok *Subtract its actual value iokObtaining the current-sharing compensation i through PIcok(ii) a Subtracting the actual value from the reference value of the output voltage of the preceding converter of each module, limiting the amplitude after PI, and icokAdd and subtract iokAnd a driving signal of a post-stage converter is generated through PI, so that the functions of current sharing, voltage boosting, power transmission and grid connection of a high-voltage side are realized.
Description
Technical Field
The invention relates to a control method, in particular to a current sharing control method of a flexible direct current transmission direct current converter of an offshore wind farm, and belongs to the technical field of wind power.
Background
Offshore wind power is the leading-edge field of wind power technology, and is the key field of the development of the international wind power industry at present, and the development of offshore wind power is a great trend. The traditional offshore wind power adopts alternating current grid connection, a wind turbine generator outputs 690V/50Hz alternating current through an alternating current-direct current converter, and the alternating current is boosted by a power frequency transformer and then is converged to an alternating current bus for grid connection through a submarine cable. In recent years, the flexible direct current transmission technology has the advantages of flexible operation control, good power quality and the like, and is applied more and more widely in offshore wind power. The flexible direct current transmission grid-connected technical scheme adopted by the current offshore wind farm power generation system has two types: and the AC bus is controlled in a centralized manner and the DC bus is controlled in a dispersed manner. However, both the problems are the same as the traditional alternating current grid connection, and each wind turbine needs to be provided with a power frequency transformer in a cabin or a tower, so that the problems of heavy cabin, crowded space, difficult construction, operation and maintenance and the like are caused, and the development requirements of offshore wind power cannot be met.
Therefore, the problem can be solved by a brand-new offshore wind farm multi-terminal flexible direct-current power transmission grid-connected system. In the grid-connected system, no matter the double-fed wind turbine generator or the permanent magnet direct-drive wind turbine generator, the converter system comprises a front-end AC/DC part and a rear-end DC/DC direct-current boosting part (called a direct-current grid-side converter GSC), and the direct-current grid-side converter GSC is directly connected with a direct-current high-voltage power grid. The GSC, as one of the key components in the dc transmission system, functions as: when the wind turbine generator works normally, the GSC realizes a direct current boosting function, transmits power generated by the wind driven generator to a direct current power grid, and simultaneously maintains the voltage stability of the low-voltage side of the wind driven generator. Therefore, the GSC can realize direct-current high-gain transformation, so that a power frequency transformer is not needed, the occupied area is small, the loss is low, and the restriction bottleneck of the flexible direct-current transmission system of the offshore wind farm can be effectively solved.
The GSC is a MW-level high-power direct current converter. In order to realize the MW level high power transmission, the GSC must adopt a plurality of direct current converter modules which are connected in parallel. In practical use, however, the parameters of the inductors, capacitors, switching tubes and other devices of each module are not completely consistent due to the manufacturing process, and the switching tubes are not turned on/off synchronously, which causes the problem of non-uniform current. The consequence is: overload occurs to one or some modules, and the modules are damaged due to failure after running for a period of time, so that the whole device is damaged, and the reliability of the system is greatly reduced. Therefore, a current sharing control strategy which is effective and accords with the actual working condition needs to be established.
The current sharing control method is mainly divided into a passive current sharing method and an active current sharing method. The passive current sharing method is also called an output impedance method, realizes current sharing by adjusting the output impedance of the converter, belongs to open-loop control, has the advantages of simple control method and the defect that the method sacrifices the external characteristic of the converter to achieve current sharing and is only suitable for occasions with low load power. The active current sharing method is formed by combining different current sharing control modes and different current sharing bus forming modes, wherein the current sharing control modes are divided into an outer ring adjusting method, an inner ring adjusting method, a double ring adjusting method and an external controller method; from the formation mode of the current-sharing bus, the current-sharing bus can be divided into an averaging method and a master-slave method, and the current-sharing bus has the advantages of higher current-sharing precision and more application occasions, and has the defects of narrower bandwidth of a current-sharing loop, easy instability of a system caused by the existence of the current-sharing bus and higher loss.
Disclosure of Invention
The main purposes of the invention are as follows: aiming at the defects in the prior art, the invention provides a current sharing control method of a flexible direct current transmission direct current converter of an offshore wind farm, which realizes the high-power and high-voltage gain function of the converter by connecting modules in parallel and adopting two-stage cascade boosting for each module; and the automatic current sharing of each module is realized through a high-voltage side current-sharing ring of the direct current converter. The current equalizing scheme does not depend on parameters of all devices in the module, so that the inherent defects of a parallel system can be overcome, and the reliable operation of the system is ensured.
As a Grid Side Converter (GSC) of an offshore wind farm flexible direct current transmission system, the direct current converter provided by the invention has the following functions: 1) when the wind turbine generator normally works, the direct current boosting function is realized; 2) transmitting power generated by the wind driven generator to a direct current power grid, and simultaneously maintaining the voltage of the low-voltage side of the direct current power grid stable; 3) for the DFIG wind turbine generator, in the DFIG starting stage, the GSC also needs to acquire energy from a direct-current power grid, an inverter power supply is provided for a rotor side converter of the DFIG, the rotor is excited, and the GSC is in a voltage reduction state at the moment, so that the GSC must realize energy bidirectional transmission for the DFIG wind turbine generator.
In order to achieve the aim, the flexible direct-current transmission direct-current converter of the offshore wind power plant comprises a plurality of direct-current converter modules, an input-output parallel structure is adopted, and the direct-current converter modules comprise a front-stage converter and a rear-stage converter; one end of the preceding-stage converter is connected with a low-voltage side direct-current bus, and the other end of the preceding-stage converter is connected with the rear-stage converter; the other end of the rear-stage converter is connected with a high-voltage side direct-current bus, and the high-voltage side direct-current bus is connected with a high-voltage direct-current power grid.
The pre-stage converter is a Buck-Boost circuit and comprises a first filter capacitor, a first inductor, a first switch tube, a second switch tube and a second filter capacitor, and the pre-stage converter is used for: 1) stabilizing the voltage of the low-voltage direct current bus; 2) boosting the voltage of the low-voltage side direct current bus; 3) and transmitting the power generated by the wind driven generator to the post-stage converter.
The post converter is also a Buck-Boost circuit, comprises a second inductor, a third switch tube, a fourth switch tube and a third filter capacitor, and has the following functions: 1) current sharing of a high-voltage side is realized; 2) boosting the output voltage of the pre-stage converter; 3) and stabilizing the output voltage of the preceding converter, controlling the current input to a direct current power grid, and transmitting the power generated by the wind driven generator to the direct current power grid to realize direct current grid connection.
The invention relates to a current sharing control method of an offshore wind farm flexible direct current transmission direct current converter, which comprises the following steps of:
In the formula iokThe current on the high-voltage side of the kth direct current converter module is k equal to 1,2, …, n; n is a positive integer;
Compared with the prior art, the invention has the beneficial effects that:
1) the direct current converter module adopts a non-isolated cascade structure, has the advantages of no need of a high-frequency transformer, high voltage gain, low loss, small volume, high power density and the like, and can effectively solve the restriction bottleneck of the flexible direct current transmission system of the offshore wind farm.
2) The current-sharing control method does not need to consider parameter difference of the same devices of each module, does not need a complex current-sharing bus and a current-sharing controller, has simple control and high current-sharing precision, and can realize natural current sharing among the modules of a parallel system.
Drawings
FIG. 1 is a schematic diagram of a topological structure of a flexible direct-current transmission direct-current converter of an offshore wind farm.
Fig. 2 is an illustration of an example of a structure of a multi-terminal flexible direct-current power transmission grid-connected system of an offshore wind farm.
Fig. 3 is a schematic view of a topology structure of the dc converter module according to the present invention.
Fig. 4 is a schematic diagram of a dc converter topology structure formed by two dc converter modules according to the present invention.
Fig. 5 is a block diagram of current sharing control according to the present invention.
Fig. 6 shows the low-side currents of the two dc converter modules without current sharing control.
Fig. 7 shows the high-side currents of the two dc converter modules without current sharing control.
Fig. 8 is a control block diagram of two dc converter modules under the condition of not adding current sharing control.
Fig. 9 shows the high-side currents of the two dc converter modules under the condition of current sharing control.
Fig. 10 shows the low-side currents of two dc converter modules under the condition of current sharing control.
Wherein, 1-a pre-stage converter; 2-a post-stage converter; 3-a first dc converter module; 4-a second dc converter module; 6-low voltage side direct current bus; 8-high voltage side dc bus; 10-a first flow equalizing ring; 20-a second flow equalizing ring; 31-a pre-converter of the first dc converter module 3; 32-the post converter of the first dc converter module 3; 41-pre converter of the second dc converter module 4; 42-the subsequent converter of the second dc converter module 4.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, the flexible dc power transmission dc converter for the offshore wind farm of the present invention includes n dc converter modules (hereinafter referred to as "modules"), a low-voltage side dc bus 6 and a high-voltage side dc bus 8, and adopts an input-output parallel structure (IPOP): the input side of each module is connected in parallel and is connected with a low-voltage side direct current bus 6; the output sides of the two are also connected in parallel and are connected with a high-voltage side direct current bus 8; the high-voltage side direct current bus 8 is connected with a high-voltage direct current power grid. In FIG. 1, VLThe low-voltage side DC bus voltage, V, of the DC converter of the present inventionHThe invention relates to a high-voltage side direct-current bus voltage of a direct-current converter; i.e. i1、i2、…inLow side currents, i, of the 1 st, 2 nd and … th modules, respectivelyo1、io2、…ionThe high side currents of the 1 st, 2 nd and … th modules, respectively.
Fig. 2 shows a brand new multi-terminal DC transmission grid-connected system for an offshore wind farm, in which the DC converter of the present invention is used as a DC grid-side converter (GSC) in the system, the low-voltage side of the DC converter is connected to a front-end AC/DC converter of a wind turbine generator, and the high-voltage side of the DC converter is connected to a DC grid, so as to boost DC voltage and transmit the generated power of the wind turbine generator to the DC grid.
As shown in fig. 3, each dc converter module includes a pre-converter 1 and a post-converter 2. The pre-stage converter 1 is a Buck-Boost circuit and comprises a first filter capacitor Ck0A first inductor Lk1First switching tube VTk1A second switching tube VTk2A second filter capacitor Ck1(k ═ 1,2, …, n). A first filter capacitor Ck0Is connected with the low-voltage side direct current bus 6, and the other end is connected with the first inductor Lk1Connecting; first inductance Lk1The other end of the first switch tube VT and the first switch tube VT respectivelyk1And a second switching tube VTk2One end of the two ends are connected; second switch tube VTk2And the other end of the second filter capacitor Ck1Is connected to a second filter capacitor Ck1And the other end thereof is connected to the low-voltage side of the subsequent-stage converter 2.
The post-converter 2 is also a Buck-Boost circuit, and comprises a second inductor Lk2And a third switching tube VTk3And a fourth switching tube VTk4A third filter capacitor Ck3(k ═ 1,2, …, n). Second inductance Lk2And a second filter capacitor C of the pre-converter 1k1Connected to a second inductor Lk2The other end of the first and second switching tubes VTk3And a fourth switching transistor VTk4One end of the two is connected; fourth switch tube VTk4And the other end of the third filter capacitor Ck3ToEnd-to-end, third filter capacitor Ck3And the other end thereof is connected with a high-voltage side direct current bus 8.
The current-sharing control method of the present invention is described by taking an offshore wind farm flexible dc power transmission dc converter composed of two (n-2) dc converter modules as an example.
As shown in fig. 4, the first dc converter module 3 comprises a pre-converter 31 and a post-converter 32, the pre-converter 31 comprising a first filter capacitor C10A first inductor L11First switching tube VT11A second switching tube VT12A second filter capacitor C11(ii) a The post-converter 32 includes a second inductor L12And a third switching tube VT13And a fourth switching tube VT14A third filter capacitor C13(ii) a The second dc converter module 4 comprises a pre-converter 41 and a post-converter 42, the pre-converter 41 comprising a first filter capacitor C20A first inductor L21First switching tube VT21A second switching tube VT22A second filter capacitor C21(ii) a The post-converter 42 includes a second inductor L22And a third switching tube VT23And a fourth switching tube VT24A third filter capacitor C23。
Neglecting the loss of the switching devices and the line loss of the front-stage and rear-stage converters, the total voltage gain G of each dc converter module is:
in the formula, Vmk(k is 1,2) is the high-side voltage of the pre-converter 31 or 41, i.e., m in fig. 41Point or m2The voltage of the point, which is also the low-side voltage of the subsequent- stage converter 32 or 42; d1And D2The duty cycles of the pre-converter 31 or 41 and the post-converter 32 or 42, respectively.
The current sharing control method for the flexible direct current transmission direct current converter of the offshore wind farm comprises the following steps as shown in fig. 5:
Step 4, the output voltage reference value V of the pre-converter 31 of the first DC converter module 3 is calculatedm1 *With its current actual value Vm1The difference is limited after the PI controller, and the output of the PI controller is equal to the high-voltage side current-sharing compensation quantity i of the first direct current converter module 3 obtained in the step 3co1Adding and subtracting the actual value i of the high-voltage side current of the first DC converter module 3o1The obtained difference is sent to a PWM module through a PI controller to generate a driving signal of a post converter 32; at the same time, the output voltage reference value V of the pre-converter 41 of the second DC converter module 4 is setm2 *With its current actual value Vm2The difference is limited after the PI controller, the output of the PI controller is equal to the high-voltage side current-sharing compensation quantity i of the second direct current converter module 4 obtained in the step 3co2Adding and subtracting the actual value i of the high-voltage side current of the second DC converter module 4o2The obtained difference is sent to the PWM module through the PI controller to generate a driving signal of the post-stage converter 42; the functions of current equalization, voltage boosting, power transmission and grid connection at the high-voltage side are realized.
The invention will be further described below with reference to a preferred embodiment.
In order to verify the effectiveness of the current-sharing control method of the flexible direct-current transmission direct-current converter of the offshore wind farm, the current-sharing control method and the current-sharing control method are respectively adopted for simulation comparison analysis on a direct-current converter with the rated power of 2MW and containing two direct-current converter modules. The rated power of each module is 1MW, and the low-voltage side direct-current bus voltage V of each moduleL1150V, high side DC bus voltage VH10kV, the low-voltage side current i of each module1、i2All should be 870A, and the high-side current io1、io2Are all 100A. Other simulation parameters are shown in table 1.
TABLE 1 DC CONVERTER SIMULATION MODEL PARAMETERS
| Name (R) | Parameter(s) |
| Output voltage reference value V of preceding convertermk *(kV) | 3.4 |
| Average inductor current Δ IL11，ΔIL12(A) | 87，29 |
| Inductor L11，L12，L21，L22(μH) | 50，80，55，88 |
| Capacitor C11，C21(μF) | 15000，16500 |
| Capacitor C12，C22(μF) | 1500，1650 |
| Duty cycle D1，D2 | 0.66 |
| Switching frequency fs(kHz) | 5 |
| Load RL(Ω) | 100 |
From table 1, it can be seen that the inductance L of the pre-converter 3111Inductance L with pre-converter 4121Inductor L of the post-converter 3212L with the subsequent converter 4222The difference between each two is 10%, and the capacitance C of the pre-converter 3111C with pre-converter 4121Capacitor C of the post-converter 3212And a capacitor C of the post-converter 4222Each with a 10% difference, the purpose of which is to simulate the parameter deviations of the actual product.
Fig. 6 and 7 are graphs of simulation results of low-voltage side current and high-voltage side current of two dc converter modules which do not adopt the current sharing control method. From fig. 6, it can be seen that the low side currents of the two modules are 940A and 800A, respectively, while from fig. 7, the high side currents of the two modules are 90A and 110A, respectively. Therefore, under the condition that no current-sharing control measure is taken, the problem of non-uniform current of each module can occur due to the fact that corresponding inductance and capacitance values in the first direct current converter module 3 and the second direct current converter module 4 are deviated.
Fig. 8 is a control block diagram of a current sharing control method that is not used.
Fig. 9 and fig. 10 are simulation result diagrams of high-voltage side current and low-voltage side current of two dc converter modules adopting the current sharing control method of the present invention, respectively. As can be seen from fig. 9, the high-side currents of the two modules are both 100A, while as can be seen from fig. 10, the low-side currents of the two modules are almost 870A, and the current sharing control is realized, thereby verifying the effectiveness of the current sharing control strategy of the present invention.
Claims (1)
1. A current sharing control method for an offshore wind farm flexible direct current transmission direct current converter comprises a plurality of direct current converter modules and a control module, wherein the direct current converter modules adopt an input-output parallel structure and comprise a preceding converter and a following converter; one end of the preceding-stage converter is connected with a low-voltage side direct-current bus, and the other end of the preceding-stage converter is connected with the rear-stage converter; the other end of the rear-stage converter is connected with a high-voltage side direct-current bus, and the high-voltage side direct-current bus is connected with a high-voltage direct-current power grid; the front-stage converter and the rear-stage converter are both Buck-Boost circuits; the method is characterized in that: the method comprises the following steps:
step 1, a voltage reference value V of the low-voltage side direct current bus is obtainedL *With its current actual value VLThe difference is subjected to amplitude limiting after passing through a PI controller, and the output is a reference value i of output current of a preceding converter of each direct current converter modulemk *And then subtracting the current actual value i of the output current of the pre-converter of each DC converter modulemkThen the signals are sent to a PWM module through a PI controller, and driving signals of a preceding stage converter of each direct current converter module are respectively generated, so that the functions of boosting and stabilizing the voltage of a low-voltage side direct current bus and transmitting power are realized;
step 2, solving the average value of the high-voltage side currents of all the direct current converter modules according to the formula (1) to serve as the high-voltage side current reference value i of each direct current converter moduleok *：
In the formula iokThe current on the high-voltage side of the kth direct current converter module is k equal to 1,2, …, n; n is a positive integer;
step 3, referring the high-voltage side current reference value i of the direct current converter moduleok *Respectively corresponding to the current actual value i of the high-voltage side current of each DC converter moduleokThe difference is outputted as the high-voltage side current-sharing compensation i of the DC converter module through the PI controllercok；
Step 4, output voltage reference value V of the pre-stage converter of each direct current converter modulemk *With its current actual value VmkThe difference is limited by a PI controller, and the output of the PI controller is equal to the high-voltage side current-sharing compensation quantity i obtained in the step 3cokAdding and subtracting the actual value i of the high-voltage side current of the DC converter moduleokThe obtained difference is sent to a PWM module through a PI controller to respectively generate driving signals of a post converter of each DC converter module, so that the current equalizing, boosting, power transmission and grid connection functions of a high-voltage side are realized。
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Effective date of registration: 20231126 Address after: Room 316, Zone E, No. 2, Lane 921, Xinshen Road, Xinhe Town, Chongming District, Shanghai, 202150 (Shanghai Fusheng Economic Development Zone) Patentee after: SHANGHAI ELECTRIC POWER NEW ENERGY DEVELOPMENT CO.,LTD. Address before: 230000 floor 1, building 2, phase I, e-commerce Park, Jinggang Road, Shushan Economic Development Zone, Hefei City, Anhui Province Patentee before: Dragon totem Technology (Hefei) Co.,Ltd. Effective date of registration: 20231126 Address after: 230000 floor 1, building 2, phase I, e-commerce Park, Jinggang Road, Shushan Economic Development Zone, Hefei City, Anhui Province Patentee after: Dragon totem Technology (Hefei) Co.,Ltd. Address before: 273165 Jingxuan West Road, Qufu City, Jining, Shandong Province, No. 57 Patentee before: QUFU NORMAL University |