CN103595052A - Method for stably controlling switchover from micro-grid connection into island state - Google Patents
Method for stably controlling switchover from micro-grid connection into island state Download PDFInfo
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Abstract
The invention relates to a method for stably controlling switchover from micro-grid connection into an island state. When switchover is planned, a micro-grid stability control system collects grid connection point power before the micro-grid is sectionalized from an electric system, a power source and a load are configured to be basically balanced, and meanwhile the grid connection point transmission power before sectionalization is sent to an inverter; a grid connection point breaker is stably cut off, the output power of the inverter is maintained as the grid connection point transmission power before the sectionalization, and power can reach the balance immediately after the micro-grid becomes off-grid. When the switchover is not planned, the micro-grid is sectionalized with the electric system suddenly to form an island, the load or the partial power branch circuit is cut within 10ms according to the difference between currents before the sectionalization of a grid connection point and the maximum output power of an energy storing inverter, and the stability of the system switchover moment is ensured; the energy storing inverter with the maximum capacity is immediately transferred into V/F control, and other power sources are set to be P/Q control. According to the method, the micro-grid connection can be smoothly switched over to the island state.
Description
Technical field
The present invention relates to stable control method when a kind of micro-electrical network is grid-connected to be switched to island state, belong to control technique in power system field.
Background technology
Micro-electrical network has two kinds of operational modes, and under normal circumstances, micro-electrical network is connected and is incorporated into the power networks with power distribution network by PCC point, carries out Power Exchange with power distribution network; When detecting, power distribution network occurs that voltage falls, when fault or interruption maintenance, micro-electrical network initiatively disconnects with power distribution network the islet operation pattern that enters, the independent load power supply in micro-electrical network of micro-power supply.
Accordingly, micro-electrical network has four kinds of running statuses: two kinds of steady operational status: state and islet operation state are incorporated into the power networks; Two kinds of transient state running statuses: grid-connected switching transient state and isolated island switch transient state.
The transient characterisitics of micro-electrical network are comparatively complicated, and the distributed power source characteristic inner with it, part throttle characteristics, energy-storage system characteristic are closely related.For example, the natural energy resources non-scheduling of photovoltaic, this class of wind power generation, and the generating of this class is different from conventional electric generators, and its output is this class power electronic equipment of inverter, this has just determined that wind, light generating micro-grid system lack inertia, are unfavorable for system stable operation.The micro-electrical network of natural energy resources that can independent operating will configure the energy storage of certain capacity.In addition, micro-electrical network, when being incorporated into the power networks with electric power system, also interacts with electric power system, directly affects the stability of micro-electrical network and electric power system.Therefore, the stable operation of micro-electrical network needs perfect stabilizing control system.
Micro-stabilization of power grids is in the past mainly by inverter itself adjusting (calling in the following text from master control), and inverter passes through acquisition system electric parameters, finds that electric parameters changes, and judges micro-network load fluctuation or unexpected and electric power system disconnection.Micro-network load fluctuation or unexpected and electric power system disconnection, there is unplanned isolated island, in order to maintain micro-line voltage, frequency, need to there is the make an immediate response variation of micro-operation of power networks pattern of an energy storage inverter, for micro-grid system provides the reference value of voltage and frequency, and the inner meritorious and idle supply and demand of the micro-electrical network of balance simultaneously.
Shortcoming from master control is:
1, control hysteresis.Inverter by acquisition system electric parameters, judges that when micro-electrical network electric parameters changes, micro-electrical network moves under unbalanced power state, and present P, the parameter such as V, Q, f is to unstable future development, this control lags behind.
2, response speed cannot guarantee micro-grid system stability.From measuring, determine response, the time that inverter is realized output adjustment is approximately 100ms.In the situation that also site Power Exchange is larger, micro-electrical network and electric power system disconnect suddenly, and the imbalance of its power can cause within a few tens of milliseconds, and micro-electrical network just loses stable.
Therefore, only depending on the regulation and control of inverter to maintain micro-stabilization of power grids, is not perfect solution.
Summary of the invention
The technical problem that the present invention solves is: propose a kind of micro-network stability control method, can micro-electric network state be changed and be controlled in real time, realize grid-connected taking over seamlessly to island state.
In order to solve the grid-connected technical problem of switching to plan island state, one of technical scheme that the present invention proposes is, the stable control method that a kind of micro-electrical network is grid-connected while switching to island state plan, comprises the following steps:
A) micro-electrical network, when being incorporated into the power networks state, by the load fluctuation of electric power system tracking balance, is preferentially used micro-electrical network energy;
B) micro-electrical network receives grid-connected after isolated island switching command, before micro-electrical network and electric power system off-the-line, micro-Stability Control System collection site power, configuration generators and loads makes it in a basic balance, before simultaneously sending off-the-line to energy storage inverter and the transmission power of site;
C) steadily cut off grid-connected point breaker, make the power output of described energy storage inverter remain the front also site transmission power of described off-the-line, micro-electrical network reaches balance immediately from the rear power of net, realize the steady off-the-line of micro-electrical network and electric power system, thereby complete the plan of micro-electrical network from the state of being incorporated into the power networks to islet operation state, switch.
The further improvement of one of technique scheme is: in step b), configure generators and loads and make its method in a basic balance be: before microgrid controller sends off-the-line to energy storage inverter and the power of site, it is before described off-the-line and site power that order energy storage inverter increases power, configuration generators and loads, makes both balances; If energy storage inverter has reached maximum power and can not meet that to increase power be before described off-the-line and site power, cut-out load, by reducing load power, makes power supply and load balancing.
The technical problem of switching in order to solve unplanned island state, two of the technical scheme that the present invention proposes is: a kind of micro-electrical network, by grid-connected stable control method while switching to unplanned isolated island, comprises the following steps:
1) micro-electrical network, when being incorporated into the power networks state, by the load fluctuation of electric power system tracking balance, is preferentially used micro-electrical network energy;
2) micro-electrical network suddenly forms isolated island with electric power system off-the-line, according to and site off-the-line before trend and energy storage inverter Maximum Power Output poor, at the inline cutting load of 10ms or cut away part power branch, guarantee the system switching stability of moment;
3) the energy storage inverter that heap(ed) capacity is set transfers V/F immediately to be controlled, and sets up voltage and the frequency of micro-electrical network;
4) other power supplys being set is that P/Q controls, and completes the grid-connected unplanned switching to isolated island of micro-electrical network.
Two further improvement of technique scheme is: after step 4) completing, by regulating energy storage inverter and load power balance, corrective system enters lonely net steady operation.
Two further improve again and be of technique scheme: adopt that isolated island detects, the unplanned isolated island of judgment technology active detecting occurs.
The beneficial effect that the present invention brings is: the present invention passes through micro-electrical network and the also data acquisition and processing (DAP) of site electric parameters, state variation that can the micro-electrical network of anticipation, the real-time control that realization changes micro-electric network state, thus realize grid-connected the taking over seamlessly to isolated island of micro-electrical network.Compared with prior art, fast response time of the present invention, plan can realize real-time power output balance while switching; During unplanned switching, adopt isolated island detection, the unplanned isolated island of judgment technology active detecting to occur, can in 10ms, realize power output balance.
Embodiment
Embodiment mono-
The stable control method of the present embodiment when to be that micro-electrical network is grid-connected switch to island state plan, establishes and the through-put power of site is Pc, and energy storage inverter power output is Ppcs, comprises the following steps:
A) micro-electrical network, when being incorporated into the power networks state, by the load fluctuation of electric power system tracking balance, is preferentially used micro-electrical network energy;
B) micro-electrical network receives grid-connected after isolated island switching command, before micro-electrical network and electric power system off-the-line, micro-Stability Control System collection site power, configuration generators and loads makes it in a basic balance, before simultaneously sending off-the-line to energy storage inverter and the transmission power of site;
In the present embodiment, configuring generators and loads makes its method in a basic balance be: gather and site power P c(establish flow out microgrid on the occasion of, while flowing into microgrid, power is negative value), before microgrid controller sends off-the-line to energy storage inverter and the transmission power Pc of site, order energy storage inverter increases Gong and Shuais ⊿ Ppcs=Pc, configuration generators and loads, makes both balances; If energy storage inverter has reached maximum power and can not meet and increase Gong and Shuai ⊿ Ppcs=Pc, cut-out load, by reducing load power, makes power supply and load balancing;
C) steadily cut off grid-connected point breaker, make the power output of described inverter remain the front also site transmission power of described off-the-line, micro-electrical network reaches balance immediately from the rear power of net, realizes the steady off-the-line of micro-electrical network and electric power system, thereby complete the grid-connected plan to isolated island of micro-electrical network, switches.
Embodiment bis-
The present embodiment is micro-electrical network by grid-connected stable control method while switching to unplanned isolated island, comprises the following steps:
1) micro-electrical network, when being incorporated into the power networks state, by the load fluctuation of electric power system tracking balance, is preferentially used micro-electrical network energy.
2) micro-electrical network suddenly forms isolated island with electric power system off-the-line, according to and site off-the-line before trend and energy storage inverter Maximum Power Output poor, at the inline cutting load of 10ms or cut away part power branch, guarantee the system switching stability of moment.
The present embodiment adopts isolated island detection, the unplanned isolated island of judgment technology active detecting to occur.
3) the energy storage inverter that heap(ed) capacity is set transfers V/F immediately to be controlled, and sets up voltage and the frequency of micro-electrical network.
4) other power supplys being set is that P/Q controls, and completes the grid-connected unplanned switching to isolated island of micro-electrical network.
The present embodiment is in step 4) complete after, by regulating energy storage inverter and load power balance, in 10ms, corrective system enters isolated island steady operation.
Micro-network stability control method of the present invention is not limited to the concrete technical scheme described in above-described embodiment, and the technical scheme that all employings are equal to replacement formation is the protection range that the present invention requires.
Claims (5)
1. the stable control method that micro-electrical network is grid-connected while switching to island state plan, comprises the following steps:
A) micro-electrical network, when being incorporated into the power networks state, is fluctuateed by electric power system tracking, balanced load, preferentially uses micro-electrical network energy;
B) micro-electrical network receives grid-connected after isolated island switching command, before micro-electrical network and electric power system off-the-line, micro-Stability Control System collection site power, configuration generators and loads makes it in a basic balance, before simultaneously sending off-the-line to energy storage inverter and the transmission power of site;
C) steadily cut off grid-connected point breaker, make the power output of described energy storage inverter remain the front also site transmission power of described off-the-line, micro-electrical network reaches balance immediately from the rear power of net, realizes the steady off-the-line of micro-electrical network and electric power system, thereby complete the grid-connected plan to isolated island of micro-electrical network, switches.
2. the stable control method that micro-electrical network according to claim 1 is grid-connected while switching to island state plan, it is characterized in that, in step b), configuring generators and loads makes its method in a basic balance be: before microgrid controller sends off-the-line to energy storage inverter and the power of site, it is before described off-the-line and site power that order energy storage inverter increases power, configuration generators and loads, makes both balances; If energy storage inverter has reached maximum power and can not meet that to increase power be before described off-the-line and site power, cut-out load, by reducing load power, makes power supply and load balancing.
3. the stable control method that micro-electrical network is grid-connected while switching to island state is unplanned, comprises the following steps:
1) micro-electrical network, when being incorporated into the power networks state, by the load fluctuation of electric power system tracking balance, is preferentially used micro-electrical network energy;
2) micro-electrical network suddenly forms isolated island with electric power system off-the-line, according to and site off-the-line before trend and energy storage inverter Maximum Power Output poor, at the inline cutting load of 10ms or cut away part power branch, guarantee the system switching stability of moment;
3) the energy storage inverter that heap(ed) capacity is set transfers V/F immediately to be controlled, and sets up voltage and the frequency of micro-electrical network;
4) other power supplys being set is that P/Q controls, and completes the grid-connected unplanned switching to isolated island of micro-electrical network.
4. the stable control method that micro-electrical network according to claim 3 is grid-connected while switching to island state is unplanned, is characterized in that: step 4) complete after, by regulating energy storage inverter and load power balance, corrective system enters isolated island steady operation.
5. the stable control method that micro-electrical network according to claim 3 is grid-connected while switching to island state is unplanned, is characterized in that: adopt that isolated island detects, the unplanned isolated island of judgment technology active detecting occurs.
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Cited By (8)
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| CN103795084A (en) * | 2014-02-24 | 2014-05-14 | 国电南瑞科技股份有限公司 | Microgrid one-button smooth switching control method from grid connection to off-grid mode |
| CN106786592A (en) * | 2017-01-13 | 2017-05-31 | 全球能源互联网研究院 | A kind of isolated island method for handover control and device suitable for flexible direct current power transmission system |
| US10291024B2 (en) | 2014-11-04 | 2019-05-14 | Abb Schweiz Ag | Control of a microgrid |
| CN109842148A (en) * | 2018-02-01 | 2019-06-04 | 大全集团有限公司 | A kind of micro-grid connection turns the stable control method of isolated operation mode |
| CN110336315A (en) * | 2019-06-04 | 2019-10-15 | 深圳供电局有限公司 | A kind of receiving end city partial electric grid isolated power grid control system |
| CN111628525A (en) * | 2020-05-29 | 2020-09-04 | 辽宁工业大学 | Switching system-based micro-grid dual-mode stable control method |
| CN112165116A (en) * | 2020-09-18 | 2021-01-01 | 广东电网有限责任公司韶关供电局 | Handling method and device for small hydropower system with unplanned island effect |
| CN114123181A (en) * | 2021-11-24 | 2022-03-01 | 许继集团有限公司 | Mode switching control method and device for power distribution network flexible loop closing device |
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Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103795084B (en) * | 2014-02-24 | 2015-11-18 | 国电南瑞科技股份有限公司 | The one-touch grid-connected net that leaves of micro-capacitance sensor takes over seamlessly control method |
| CN103795084A (en) * | 2014-02-24 | 2014-05-14 | 国电南瑞科技股份有限公司 | Microgrid one-button smooth switching control method from grid connection to off-grid mode |
| US10291024B2 (en) | 2014-11-04 | 2019-05-14 | Abb Schweiz Ag | Control of a microgrid |
| CN106786592B (en) * | 2017-01-13 | 2023-01-24 | 全球能源互联网研究院有限公司 | Island switching control method and device suitable for flexible direct current transmission system |
| CN106786592A (en) * | 2017-01-13 | 2017-05-31 | 全球能源互联网研究院 | A kind of isolated island method for handover control and device suitable for flexible direct current power transmission system |
| CN109842148A (en) * | 2018-02-01 | 2019-06-04 | 大全集团有限公司 | A kind of micro-grid connection turns the stable control method of isolated operation mode |
| WO2019148688A1 (en) * | 2018-02-01 | 2019-08-08 | 大全集团有限公司 | Method for controlling stability when microgrid grid connection switches to island operation mode |
| CN110336315A (en) * | 2019-06-04 | 2019-10-15 | 深圳供电局有限公司 | A kind of receiving end city partial electric grid isolated power grid control system |
| CN110336315B (en) * | 2019-06-04 | 2023-03-03 | 深圳供电局有限公司 | Isolated network operation control system for local power grid of receiving-end city |
| CN111628525B (en) * | 2020-05-29 | 2022-03-08 | 辽宁工业大学 | Switching system-based micro-grid dual-mode stable control method |
| CN111628525A (en) * | 2020-05-29 | 2020-09-04 | 辽宁工业大学 | Switching system-based micro-grid dual-mode stable control method |
| CN112165116A (en) * | 2020-09-18 | 2021-01-01 | 广东电网有限责任公司韶关供电局 | Handling method and device for small hydropower system with unplanned island effect |
| CN112165116B (en) * | 2020-09-18 | 2022-06-28 | 广东电网有限责任公司韶关供电局 | Handling method and device for small hydropower system with unplanned island effect |
| CN114123181A (en) * | 2021-11-24 | 2022-03-01 | 许继集团有限公司 | Mode switching control method and device for power distribution network flexible loop closing device |
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