CN107086611A - Control method of substation AC-DC hybrid microsite power consumption system - Google Patents

Abstract

The present invention provides a kind of control method of transformer station's alternating current-direct current mixing microgrid station power use system, including：Under normal circumstances, alternating current-direct current mixing microgrid station power use system is incorporated into the power networks, and the voltage of AC network, frequency are supported by power network；Photovoltaic cell is controlled using MPPT maximum power point tracking；When storage battery charge state is less than given threshold, energy storage two way convertor is exerted oneself carry out charge control according to the photovoltaic of photovoltaic cell；Alternating current-direct current two way convertor works in rectification mode by control targe of DC bus-bar voltage；Under accident conditions, control platform cuts off alternating current-direct current two way convertor；Photovoltaic cell is still using MPPT maximum power point tracking control；Energy storage two way convertor is exerted oneself according to photovoltaic, switches to electric discharge or charge mode to maintain DC bus-bar voltage to stabilize to target.The present invention combines the service requirement of transformer station, disclosure satisfy that power demands of each type load under normal and accident conditions.

Description

Control method of substation AC-DC hybrid microsite power consumption system

technical field

The invention relates to the technical field of electric power automation, in particular to a control method for a substation AC/DC hybrid microsite power consumption system.

Background technique

With the popularization of intelligent substations, the DC load in the substations is increasing, and the capacity of batteries that need to be configured is also increasing. The DC network power supply of the station power system has a single form and is not reliable enough. The rectifier, inverter and storage battery of the power consumption system of the station are fully equipped, and the idle space on the top of the station is sufficient, which fully meets the requirements of introducing photovoltaic power supply and building an AC-DC hybrid micro-grid.

The substation AC-DC hybrid microgrid power consumption system has the advantages of AC-DC hybrid microgrid reducing power electronic conversion links and simple control. Different control strategies are required to meet different control objectives under the grid-connected and isolated operating states of the microgrid. After the AC/DC hybrid microgrid is applied to the power consumption system of the substation, it is necessary to develop a control strategy to meet the operation requirements of the substation.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a control method for a substation AC-DC hybrid micro-grid power system, to control the operation status of the AC-DC hybrid micro-grid power system in grid-connected and island states, To meet the operation requirements of the substation under normal and accident conditions. The technical scheme adopted in the present invention is:

A control method for a substation AC-DC hybrid microsite power consumption system, comprising:

Under normal circumstances, the AC-DC hybrid microsite power consumption system is connected to the grid, and the voltage and frequency of the AC network are supported by the grid; the photovoltaic battery adopts maximum power point tracking control; when the state of charge of the battery is less than the set threshold, the energy storage bidirectional The converter performs charging control according to the photovoltaic output of the photovoltaic cell; the AC-DC bidirectional converter operates in the rectification mode with the DC bus voltage as the control target;

When the state of charge of the battery is greater than the set threshold, the energy storage bidirectional converter is on standby to protect the battery; the AC-DC bidirectional converter is based on the photovoltaic output, and when the photovoltaic output is less than the DC network load, it works at Rectification mode, when the photovoltaic output is greater than the load of the DC network, it works in the inverter mode, and inverts the excess electric energy of the DC network to the AC network;

In the event of an accident, the control platform cuts off the AC-DC bidirectional converter; the photovoltaic battery still adopts maximum power point tracking control; the energy storage bidirectional converter switches to discharge or charge according to the photovoltaic output to maintain the stability of the DC bus voltage model.

Further, under normal circumstances, when the state of charge of the battery is less than the set threshold, the energy storage bidirectional converter performs charging control according to the photovoltaic output of the photovoltaic cell, specifically:

The charging power of the energy storage bidirectional converter changes correspondingly according to the variation of the photovoltaic output of the photovoltaic cell to stabilize the fluctuation of the photovoltaic output.

Further, in the event of an accident, the energy storage bidirectional converter is switched to a discharge or charge mode aimed at maintaining the stability of the DC bus voltage according to the photovoltaic output, specifically:

When the photovoltaic output is less than the DC network load, the energy storage bidirectional converter works in discharge mode; when the photovoltaic output is greater than the DC network load, the energy storage bidirectional converter is on standby or charging the battery. .

Further, the set threshold value of the battery state of charge is 95%.

The advantages of the present invention are: the control strategy of the substation AC-DC hybrid micro-grid power system effectively utilizes the advantages of the AC-DC hybrid micro-grid, reduces energy conversion links, and reduces energy conversion losses. The control target does not need to consider reactive power and frequency. Focus on voltage stability and simplify the control process. Considering the operation requirements of the substation under normal and accidental conditions, it can meet the power supply demand of different loads, improve the reliability of the power consumption system of the station, and adapt to the needs of the increasing DC load of the smart substation, which is conducive to the stable operation of the system and reduces the cost of promotion. The difficulty of application ensures the safe and stable operation of substations.

Description of drawings

Fig. 1 is a schematic diagram of the power system of the substation AC-DC hybrid microsite of the present invention.

Fig. 2 is a flow chart of the control method of the present invention.

detailed description

The present invention will be further described below in conjunction with specific drawings and embodiments.

The substation AC-DC hybrid microsite power system, as shown in Figure 1, includes DC network, AC network, photovoltaic cells, batteries, photovoltaic converters, energy storage bidirectional converters, communication converters, UPS power supplies, AC DC bidirectional converter, information collection module and control platform; the control platform can be a background server or computer; DC bus L1 is set in the DC network, and AC bus L2 is set in the AC network;

There are DC loads, communication loads, AC loads, and UPS loads in the power system of the station; the UPS loads are mainly equipment loads that need to switch power supply immediately when the power supply is abnormal, and the UPS loads are connected to the UPS power supply;

The AC network is powered by the station transformer to meet the power demand of AC load and UPS load under normal conditions; the DC network is powered by AC power rectification and photovoltaic cells under normal conditions to meet the power demand of DC load and communication load. Under normal circumstances, the photovoltaic cell and the storage battery are jointly powered to meet the power demand of the UPS load, communication load and DC load connected to the UPS power supply.

The AC bus L2 takes power from the station transformer; in Figure 1, the outputs of the 1# station transformer and the 2# station transformer are respectively connected to the two input terminals of the automatic switcher ATS, and the output terminal of the automatic switcher ATS is connected to the AC bus L2 ; Two station transformers that can switch automatically can provide better AC power supply security;

The AC input terminal of the UPS power supply is connected to the AC bus L2 through the circuit breaker JK1, and the DC input terminal is connected to the DC bus L1 through the circuit breaker JK2. The power supply terminal of the UPS power supply is used to connect the UPS load (the UPS load is not marked in Figure 1 due to limited space) ;

The AC bus L2 is connected to one end of the circuit breaker JK3, and the other end of the circuit breaker JK3 is used to connect the AC load; only one AC load circuit breaker JK3 is drawn in Figure 1, and there are actually one or more AC load circuit breakers;

One end of the AC-DC bidirectional converter is connected to the DC bus L1, and the other end is connected to the AC bus L2;

The photovoltaic cell is connected to the input terminal of the photovoltaic converter through the circuit breaker DK1, and the output terminal of the photovoltaic converter is connected to the DC bus L1 through the circuit breaker DK4; the photovoltaic converter converts the output voltage of the photovoltaic cell into a DC voltage on the DC bus L1 220v DC, and has a certain voltage stabilizing ability; the photovoltaic battery can use the idle space on the top of the substation, which can block the sun in summer and reduce the temperature of the high and low voltage chambers in the station;

The battery is connected to one end of the energy storage bidirectional converter through the circuit breaker DK2, and the other end of the energy storage bidirectional converter is connected to the DC bus L1 through the circuit breaker DK5;

One end of the DC bus L1 is connected to the circuit breaker DK3, and the other end of the circuit breaker DK3 is used to connect the DC load; only one DC load circuit breaker DK3 is drawn in Figure 1, but there are actually one or more DC load circuit breakers;

The DC bus L1 is connected to the input terminal of the communication converter, and the output terminal of the communication converter is used to connect the communication load; the communication converter can convert 220v DC to 48v DC voltage;

The information collection module is connected to the photovoltaic cell, storage battery and DC bus L1, responsible for collecting photovoltaic cell output, DC bus voltage and storage battery related parameters, and sending the collected parameters to the control platform;

The control platform connects and controls photovoltaic converters, energy storage bidirectional converters, communication converters and AC/DC bidirectional converters;

The AC-DC hybrid microsite power consumption system is comprehensively controlled by the control platform; the control strategy is as follows:

Under normal circumstances, the AC-DC hybrid microsite power consumption system is connected to the grid, and the voltage and frequency of the AC network are supported by the large power grid; photovoltaic cells adopt maximum power point tracking control (MTTP) to maximize the use of clean energy; when the battery is charged When the state (SOC) is less than 95%, the energy storage bidirectional converter performs charging control according to the photovoltaic output of the photovoltaic cell to smooth the DC network power curve. For example, the greater the photovoltaic output, the greater the corresponding charging power of the energy storage bidirectional converter. It can stabilize photovoltaic output fluctuations; the AC-DC bidirectional converter works in rectification mode with the DC bus voltage as the control target; when the battery state of charge (SOC) is greater than 95%, the energy storage bidirectional converter is on standby to protect the battery; AC-DC According to the photovoltaic output, when the photovoltaic output is less than the DC network load, the DC bus voltage is used as the control target to work in the rectification mode (that is, the AC power of the AC network is rectified and supplied to the DC network), when the photovoltaic output is greater than the DC network load Working in the inverter mode, the excess electric energy of the DC network is inverted to the AC network to supply power to the load of the AC network.

In the case of an accident, the substation needs to ensure the power supply of UPS load, DC load and communication load within 1h to 2h of the accident power outage; the micro-grid control platform cuts off the AC-DC bidirectional converter; the photovoltaic battery still adopts the maximum power point tracking control, Maximize the use of clean energy; according to the photovoltaic output, the energy storage bidirectional converter switches to the discharge or charging mode aimed at maintaining the stability of the DC bus voltage. That is to say, when the photovoltaic output is less than the DC network load, the energy storage bidirectional converter The inverter works in discharge mode, when the photovoltaic output is greater than the load of the DC network, the energy storage bidirectional converter is on standby or charging the battery (but the latter situation hardly occurs, because the photovoltaic output of the configured photovoltaic cells is difficult to exceed all DC network loads load.) In the event of an accident, the loads of the DC network are DC loads, communication loads, and UPS loads.

Claims (4)

1. a kind of control method of transformer station's alternating current-direct current mixing microgrid station power use system, it is characterised in that including：

Under normal circumstances, alternating current-direct current mixing microgrid station power use system is incorporated into the power networks, and the voltage of AC network, frequency are by power network branch Support；Photovoltaic cell is controlled using MPPT maximum power point tracking；When storage battery charge state is less than given threshold, energy storage Bidirectional variable-flow Device is exerted oneself carry out charge control according to the photovoltaic of photovoltaic cell；Alternating current-direct current two way convertor is using DC bus-bar voltage as control targe Work in rectification mode；

When storage battery charge state is more than given threshold, energy storage two way convertor is standby to protect battery；Alternating current-direct current is two-way Current transformer is exerted oneself according to photovoltaic, when photovoltaic is exerted oneself less than DC network load, is worked by control targe of DC bus-bar voltage In rectification mode, inverter mode is worked in when photovoltaic is exerted oneself more than DC network load, the unnecessary electric energy of DC network is inverse Change to AC network；

Under accident conditions, control platform cuts off alternating current-direct current two way convertor；Photovoltaic cell still using maximum power point with Track is controlled；Energy storage two way convertor is exerted oneself according to photovoltaic, switch to maintain DC bus-bar voltage stabilize to target electric discharge or Charge mode.

2. the control method of transformer station's alternating current-direct current mixing microgrid station power use system as claimed in claim 1, it is characterised in that

Under normal circumstances, described when storage battery charge state is less than given threshold, energy storage two way convertor is according to photovoltaic electric The photovoltaic in pond is exerted oneself carry out charge control, is specifically：

The charge power of energy storage two way convertor exerts oneself change according to the photovoltaic of photovoltaic cell and respective change is gone out with stabilizing photovoltaic Fluctuation.

3. the control method of transformer station's alternating current-direct current mixing microgrid station power use system as claimed in claim 1, it is characterised in that

Under accident conditions, the energy storage two way convertor is exerted oneself according to photovoltaic, switches to maintain DC bus-bar voltage stable Electric discharge or charge mode for target, be specifically：

When photovoltaic is exerted oneself less than DC network load, then energy storage two way convertor works in discharge mode, exerts oneself and is more than when photovoltaic DC network load, energy storage two way convertor is standby or battery is charged.

4. the control method of transformer station's alternating current-direct current mixing microgrid station power use system as claimed in claim 1, it is characterised in that

The given threshold of storage battery charge state is 95%.