CN105098829A - Distributed power supply switching control method based on current transformer output current - Google Patents
Distributed power supply switching control method based on current transformer output current Download PDFInfo
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- CN105098829A CN105098829A CN201510189487.7A CN201510189487A CN105098829A CN 105098829 A CN105098829 A CN 105098829A CN 201510189487 A CN201510189487 A CN 201510189487A CN 105098829 A CN105098829 A CN 105098829A
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Abstract
The invention belongs to the field of electric and electronic equipment control, and particularly relates to a distributed power supply switching control method based on current transformer output current. A feedforward votlage ring and a voltage outer ring are additionally arranged on the basis of the control of an inductance current inner ring of a distributed current transformer, and the switching control from the current source control to the voltage source control and the switching control from the voltage source control to the current source control of a distributed power supply through a voltage limiter. When a unintentional islanding phenomenon occurs, the output current of the current transformer suddenly changes, the reference value and the actual value of the output current of the current transformer generate a difference value, the voltage limiter is started after the difference value is amplified by a PI controller, and the switching from the current source control to the voltage source control is realized. When a power grid recovers the power supply, the voltage limiter is out of action, and the switching from the voltage source control to the current source control is realized. From the simulation results, the method can better realize the smooth transition of PCC node voltage and is only related to the parameters of the distributed power supply itself.
Description
Technical field
The invention belongs to power electronic equipment control field, particularly relate to a kind of distributed power source method for handover control based on output current of converter.
Background technology
When the grid collapses, cause electrical network circuit breaker trip, the former distributed power supply system be incorporated into the power networks is in island operation state, forms the situation that the local load of distributed power source band works alone, this situation has sudden and randomness, is called unplanned isolated island.Due to the uncertainty of unplanned isolated island, how to ensure that the stable power-supplying in unplanned isolated island handoff procedure seems very important.
When isolated island occurs, distributed power source controls the switching controlled to voltage source from current source, proof load supply power voltage is constant; When power system restoration is powered, distributed power source controls the switching controls controlled to current source from voltage source, realize being incorporated into the power networks.
The idle imbalance that under unplanned isolated island, grid cut-off causes, can limit its frequency distortion caused by improved PLL; The meritorious imbalance that under unplanned isolated island, grid cut-off causes, can be gained merit by the output of change inverter and limit its voltage distortion caused.Change inverter output power, a kind of method directly changes reference current value, and the another kind of method then voltage of collateral security powering load does not distort and sets out, and controls reference voltage.
Under conventional situation, the current transformer of distributed power source can adopt droop control when being incorporated into the power networks, and constant voltage constant frequency (V/F) can be adopted when isolated power grid to control.Grid-connected/isolated island to be carried out when island phenomenon occurs and power system restoration is powered to switch.At present in unplanned isolated island situation, existing two kinds of methods realize the seamless switching of grid-connected turn of lonely net: prior art [1], see " IndirectCurrentControlAlgorithmforUtilityInteractiveInve rtersinDistributedGenerationSystems " that IEEETRANSACTIONSONPOWERELECTRONICS the 23rd volume the 3rd phase publishes, according to the LCL filter vector correlation of single-phase distributed power source, propose the indirect control strategy controlling to flow into power network current with control capacitance voltage, when grid-connected turn of lonely net by the amplitude limit to capacitance voltage, ensure that points of common connection (PCC point) voltage is in certain scope, prior art [2], see " IndirectCurrentControlBasedSeamlessTransferofThree-phase InverterinDistributedGeneration " that IEEETRANSACTIONSONPOWERELECTRONICS the 29th volume the 7th phase publishes, this technical method does not rely on LCL filter vector correlation, when completing switching by the amplitude limit exported current controller, PCC point voltage controls, and belongs to the current indirect control method of three-phase, prior art [1] and [2] all can be described as current indirect control.But current indirect control depends on proposed single-phase topology and LCL filter vector correlation [1].[2] can rapid starting resistor amplitude limiter based on the control of power network current during grid-connected turn of distributed power source orphan net in, apply electric network impedance parameter to carry out uneoupled control, and realize switching controls by the instruction current formation current closed-loop flowing into electrical network, apply when known inflow power network current instruction.
Summary of the invention
The object of the invention is to, a kind of distributed power source method for handover control based on output current of converter is proposed, the problem of distributed power source seamless switching during for solving distributed power source seamless switching and power system restoration when unplanned isolated island occurs, when realizing switching, PCC point voltage seamlessly transits.
To achieve these goals, the technical scheme that the present invention proposes does not distort to realize supply power voltage in handoff procedure by carrying out starting resistor amplitude limiter to the control of output current of converter.It is characterized in that the basis that controls in the inductive current inner ring of distributed power source current transformer increases outer voltage, feed-forward voltage ring and inductive current outer shroud, and applied voltage amplitude limiter realizes distributed power source controls from current source the switching controls that controls to voltage source and control the switching controls that controls to current source from voltage source; When unplanned isolated island occurs, output current of converter produces sudden change, and the reference value of output current of converter compares generation difference with actual value, and this difference is starting resistor amplitude limiter after PI controller amplifies, and realizes the switching that current source controls to control to voltage source; After power system restoration is powered, voltage clipper is ineffective, realizes the switching that voltage source controls to control to current source; Feed-forward voltage ring directly acts on modulating wave, improves the response speed of switching controls.
Wherein, described output current of converter reference value compares with actual value and produces difference and amplify through PI controller, and PI controller parameter can require modify according to the requirement of supply power voltage quality before and after switching and the response speed of Voltage loop.
Described feed-forward voltage ring directly acts on modulating wave and improves switch speed, and feed-forward voltage ring PI controller parameter is determined by the requirement of switch speed, can be different from the PI controller parameter of outer voltage.
Described synchronous rotating frame voltage clipper design considerations IEEEStd_15472003 standard.
The present invention has following beneficial effect: the present invention controls the PCC point voltage of distributed power supply system by the indirect starting resistor amplitude limiter of difference of output current of converter reference value and actual value, the seamless switching that current source controls to control to voltage source is realized during isolated island, power system restoration realizes the seamless switching that voltage source controls to control to current source after powering, ensure the quality of voltage of load supplying; This control method is only relevant with distributed power source current transformer inherent parameters, and control method is not by the impact of electrical network parameter.
Accompanying drawing explanation
Fig. 1 is distributed power source converter system schematic diagram of the present invention;
Fig. 2 is control structure schematic diagram of the present invention;
Fig. 3 is the overall control block diagram containing electric current loop and Voltage loop of the present invention;
Fig. 4 is startup ring control system block diagram of the present invention;
Fig. 5 is the PCC point voltage analogous diagram based on currents combination seamless switching.
Embodiment
Below in conjunction with accompanying drawing, the present invention will be further described.
Fig. 1 is distributed power source converter system schematic diagram of the present invention.Current transformer is the voltage constant of three-phase voltage type current transformer, DC side, and 6 IGBT adopt PWM to control, by current transformer output AC voltage.Time grid-connected, the power part supply load that current transformer exports, a part returns electrical network; During lonely net, the whole supply load of power that current transformer exports.Select LC filter, to be inductive current be the electric current that three-phase grid type current transformer flows out
i la
,
i lb
,
i lc
, filter capacitor electric current is
i ca,
i cb,
i cc, load current is
i lLa
,
i lLb
,
i lLc
, time grid-connected, power network current is
i ga
,
i gb,
i gc, PCC point voltage is called points of common connection voltage simultaneously, and its value also equals filter capacitor both end voltage.
Fig. 2 is control structure schematic diagram of the present invention.Converted three-phase symmetrical rest frame with electrical network fundamental frequency synchronous rotating frame transverse axis (d axle) and the synchronous rotating frame longitudinal axis (q axle) to by coordinate transform, wherein inductive current reference value (output current of converter reference value), inductive current are respectively under rotating coordinate system transverse axis
i refLd ,
i ld , be respectively under the longitudinal axis
i refLq ,
i lq , PCC point voltage is under rotating coordinate system transverse axis
u pCCd , under the longitudinal axis be
u pCCq , in inductive current, ring controller is
pI 1, outer voltage controller is
pI 2, feed-forward voltage ring controller is
pI 3.When being incorporated into the power networks, current transformer controls as current source, and now voltage clipper is inoperative, difference identically vanishing when grid-connected of output current of converter reference value and actual value; And output current of converter actual value diminishes when orphan nets, now output current of converter reference value and actual value produce difference, this difference through controller (
pI 0) starting amplitude limiter after amplification, voltage instruction reaches rapidly the amplitude limiter upper limit or lower limit, and then starting resistor outer shroud.Meanwhile, according to IEEEStd_15472003 standard, design voltage amplitude limiter (
d v ), carry out clamper PCC point voltage with this.
Fig. 3 is the overall control block diagram containing electric current loop and Voltage loop of the present invention.Inductive current inner ring PI controller is
g 1(
s), with the outer voltage PI controller of current inner loop cascade be
g 2(
s), the feed-forward voltage ring PI controller in parallel with current inner loop is
g 3(
s), wherein
k pWM for current transformer equivalent gain,
,
,
,
,
,
for the parameter of pi regulator,
r f for filter inductance internal resistance,
l f for filter inductance,
c f for filter capacitor,
i lL for load current,
i g for power network current.
Obtain inductive current open-loop transfer function such as formula (1) by Fig. 3, inductive current closed loop transfer function, is such as formula (2), and the open-loop transfer function of outer voltage is such as formula (3), and the voltage open-loop transfer function containing feed-forward voltage ring as the formula (4).
G 1(
s)=
（1）
G 2(
s)=
（2）
G 3(
s)=
（3）
G 4(
s)=
（4）
Fig. 4 is startup ring control system block diagram of the present invention.Wherein
g 4(
s) for starting ring controller,
g 5(
s) be closed loop transfer function, formula corresponding to Fig. 3, as the formula (5).
G 5(
s)=
（5）
Wherein A
, B
, C
+ 1
D
，E
。
Startup ring is released by Fig. 4
i * l arrive
u * c open-loop transfer function
g 6(
s), there is formula (6) to set up.
G 6(
s)=
G 4(
s)
G 5(
s)
s（6）
Determine according to cut-off frequency in the transfer function expression formula in formula (1), (2), (3), (4), (5), (6) and switching effect
,
,
,
,
,
value.
When unplanned isolated island occurs there is Spline smoothing in the difference of output current of converter reference value and actual value, start ring and amplify this change by with the speed of large especially multiple, until reach voltage clipper limit value, PI controller parameter can require to design according to the response speed of the requirement and Voltage loop that switch front and back supply power voltage quality.
Fig. 5 is in main circuit parameter setting situation, based on the seamless switching control method simulation result that output current of converter controls.Wherein switching time is 0.225s.As we can see from the figure, method based on output current of converter control can meet the seamless switching under unplanned isolated island, PCC point voltage only has less distortion, PCC point voltage can be tried one's best transition smoothly, still can normally work to meet electric network power-fail back loading.
Claims (4)
1. the distributed power source method for handover control based on output current of converter, it is characterized in that the basis that controls in the inductive current inner ring of distributed power source current transformer increases outer voltage, feed-forward voltage ring and inductive current outer shroud, and applied voltage amplitude limiter realizes distributed power source controls from current source the switching controls that controls to voltage source and control the switching controls that controls to current source from voltage source; When unplanned isolated island occurs, output current of converter produces sudden change, and the reference value of output current of converter and actual value produce difference, and this difference is starting resistor amplitude limiter after PI controller amplifies, and realizes the switching that current source controls to control to voltage source; After power system restoration is powered, voltage clipper is ineffective, realizes the switching that voltage source controls to control to current source; Feed-forward voltage ring directly acts on modulating wave, improves the response speed of switching controls.
2. a kind of distributed power source method for handover control based on output current of converter according to claim 1, output current of converter reference value compares with actual value and produces difference and amplify through PI controller, and PI controller parameter can require modify according to the requirement of supply power voltage quality before and after switching and the response speed of Voltage loop.
3. a kind of distributed power source method for handover control based on output current of converter according to claim 1, feed-forward voltage ring directly acts on modulating wave and improves switch speed, feed-forward voltage ring PI controller parameter is determined by the requirement of switch speed, can be different from the PI controller parameter of outer voltage.
4. a kind of distributed power source method for handover control based on output current of converter according to claim 1, synchronous rotating frame voltage clipper design considerations IEEEStd_15472003 standard.
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| CN201510189487.7A CN105098829A (en) | 2015-04-21 | 2015-04-21 | Distributed power supply switching control method based on current transformer output current |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106410769A (en) * | 2016-09-14 | 2017-02-15 | 上海电力学院 | Current limiting method for droop control microgrid based on reference filtering inductive current |
| CN110601221A (en) * | 2019-06-17 | 2019-12-20 | 湖南大学 | Voltage stability control method for connecting multi-voltage source type converter to medium-voltage direct-current system |
| CN112260315A (en) * | 2020-10-16 | 2021-01-22 | 成都英格利科技有限公司 | Seamless switching control system and strategy based on improved droop control |
| CN114189007A (en) * | 2021-11-15 | 2022-03-15 | 阳光电源股份有限公司 | Vehicle-mounted charger working mode switching control method and device and vehicle-mounted charger |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101902146A (en) * | 2010-08-06 | 2010-12-01 | 西安交通大学 | Current type control method of three-phase inverter in distributed generation system |
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2015
- 2015-04-21 CN CN201510189487.7A patent/CN105098829A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101902146A (en) * | 2010-08-06 | 2010-12-01 | 西安交通大学 | Current type control method of three-phase inverter in distributed generation system |
Non-Patent Citations (2)
| Title |
|---|
| ZENG LIU等: "Indirect Current Control Based Seamless Transfer of Three-phase Inverter in Distributed Generation", 《IEEE TRANSACTIONS ON POWER ELECTRONICS》 * |
| 刘增等: "一种可实现分布式发电系统平滑切换的三相逆变器控制方法", 《电工技术学报》 * |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106410769A (en) * | 2016-09-14 | 2017-02-15 | 上海电力学院 | Current limiting method for droop control microgrid based on reference filtering inductive current |
| CN110601221A (en) * | 2019-06-17 | 2019-12-20 | 湖南大学 | Voltage stability control method for connecting multi-voltage source type converter to medium-voltage direct-current system |
| CN110601221B (en) * | 2019-06-17 | 2021-04-02 | 湖南大学 | Voltage stability control method for connecting multi-voltage source type converter to medium-voltage direct-current system |
| CN112260315A (en) * | 2020-10-16 | 2021-01-22 | 成都英格利科技有限公司 | Seamless switching control system and strategy based on improved droop control |
| CN114189007A (en) * | 2021-11-15 | 2022-03-15 | 阳光电源股份有限公司 | Vehicle-mounted charger working mode switching control method and device and vehicle-mounted charger |
| CN114189007B (en) * | 2021-11-15 | 2024-04-12 | 阳光电源股份有限公司 | Vehicle-mounted charger working mode switching control method and device and vehicle-mounted charger |
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Application publication date: 20151125 |
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