CN106532766A - Distributed photovoltaic power generation grid-connected measuring and controlling device - Google Patents

Abstract

A distributed photovoltaic power generation grid-connected measurement and control device includes a PLC module, a communication module, a data acquisition module, a switch, a power supply module and a human-computer interaction interface. The first data acquisition module is connected to the first communication management module through the RS485 interface, the second data acquisition module is connected to the second communication management module through the RJ45 interface, the PLC module is connected to the switch through the RJ45 interface, and the switch communicates with the man-machine interface through the RJ45 interface It is connected with the wireless communication module, and the power module is connected with the PLC module, switch, and man-machine interface to provide 24V DC power for the PLC module, switch, and man-machine interface.

Description

A distributed photovoltaic power generation grid-connected measurement and control device

technical field

The invention relates to a distributed photovoltaic power generation grid-connected measurement and control device.

Background technique

Compared with the centralized photovoltaic power generation system, the distributed photovoltaic power generation system is generally small in scale (from hundreds of kilowatts to several megawatts), and the location of the power generation devices is scattered. A large number of distributed photovoltaic power plants connected to the grid can cause power fluctuations in the grid and affect the stable operation of the grid. Therefore, it is necessary to install measurement and control devices to monitor them in real time and accept grid dispatch.

The distributed photovoltaic grid-connected measurement and control device that has been demonstrated includes a CPU module, a data acquisition module, a communication module, and a display interface, but it does not have the voltage control function of the grid-connected point.

Although some photovoltaic grid-connected inverter products have the dispatchable function of active power and reactive power and can support the grid voltage, they generally require the grid dispatching agency to issue instructions, and the delay is too long, so it is not operable in a weak grid. At present, the measurement and control device does not have the function of local voltage control, and the centralized monitoring system cannot realize fast real-time control. Therefore, this subject develops an integrated distributed grid-connected measurement and control device. The reactive power output calculation for voltage stabilization is performed locally at the grid-connected point, reducing the calculation pressure on the upper level and making the entire system more intelligent.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of existing measurement and control devices that do not have local voltage control functions and cannot solve the problem of voltage rise caused by distributed power grid connection, and propose a distributed photovoltaic power generation grid connection measurement and control device.

The invention includes a PLC module, a communication management module, a data acquisition module, a switch, a power supply module, a man-machine interaction interface and a wireless communication module. The first data acquisition module is connected to the first communication management module through the RS485 interface, the second data acquisition module is connected to the second communication management module through the RJ45 interface, the PLC module is connected to the switch through the RJ45 interface, and the switch communicates with the man-machine interface through the RJ45 interface It is connected with the wireless communication module, and the power module is connected with the PLC module, switch, and man-machine interface to provide 24V DC power for the PLC module, switch, and man-machine interface.

The PLC module is the computing and control core of the integrated distributed photovoltaic power generation grid-connected measurement and control device, and performs power generation measurement and control, load measurement and control, inverter Start-stop control, grid-connected voltage control, and remote communication.

The data collection module realizes parameter collection, the first data collection module collects the power parameters of the grid-connected point, and the second data collection module collects the load side power parameters. The data acquisition module has the functions of power parameter monitoring, power quality monitoring, energy bidirectional metering, and fault recording, etc., and transmits the collected information to the PLC module through the communication management module.

The human-computer interaction module realizes data display, storage and local control functions. It can not only visually view the grid and inverter data and curve information, but also issue inverter start-stop control and grid-connected voltage upper limit commands to the PLC module. The PLC module issues a start-stop control command or an inverter output power command to the inverter through the second communication management module. The setting of the upper limit of the grid-connected point voltage should meet the requirement that the photovoltaic grid-connected point voltage should not exceed 7% of the rated voltage stipulated in my country's national standard GB/T.19964 and national standard GB/T.12325.

The communication management module, the first data acquisition module and the second data acquisition module communicate with the first communication management module through RS485 communication; the inverter is connected with the second communication management module through RS485 communication, and the two communication modules are synchronized and parallel Work, realize the unified collection of monitoring data, and complete the access of different types and models of equipment from different manufacturers without secondary development.

The switch transmits the information in the PLC module one way to the remote data center, and the other way to the human-computer interaction interface.

The power module provides 24V DC power for the PLC module and the man-machine interface.

The first data acquisition module collects the grid-connected point and load-side data information through voltage and current sensors, realizes energy bidirectional metering, power quality monitoring, and fault recording, and transmits the data information of the grid-connected point and load side through the first communication management module to PLC module; the inverter transmits the information of the inverter group, such as the inverter in the inverter room, the combiner box, and the environmental information measured by the weather station outside the inverter room, to the PLC module through the second communication management module. As the core of the integrated distributed photovoltaic power generation grid-connected measurement and control device, the PLC module analyzes and processes the collected information, and transmits it to the human-machine interface through Ethernet communication to realize two-way communication with the human-machine interface. All the way through the switch, the collected data is transmitted to the remote terminal through the VPN protocol network to realize two-way communication with the upper data center. The man-machine interface and the remote data center can view the status of the grid-connected point in real time based on the data information uploaded from the PLC module, such as voltage and current, power information, power quality information, photovoltaic power generation, etc., and the status of the load side: such as voltage and current, power information, load consumption Power, etc., inverter status: power generation, operation mode, fault type, power quality information, etc., and operation logs, etc. In addition, the PLC module receives the control commands issued by the human-computer interface or the remote data center, such as the upper limit of the grid-connected point voltage and the dispatch value of active and reactive power, and performs calculation and processing to realize the start-up and stop of the inverter and the voltage control of the grid-connected point.

in;

The data acquisition module realizes the acquisition of grid-connected point and load side parameters, energy bidirectional metering, power quality monitoring, and fault recording, and transmits the collected information to the PLC module;

The first data acquisition module records the amount of photovoltaic power generation at the grid-connected point and the remaining amount of grid connection, and the second data acquisition module records the power supply amount of the grid and the power consumption of the load to realize two-way energy metering;

The first data acquisition module collects and records the energy quality information of the grid-connected point, and the second data acquisition module collects and records the power quality information of the load side; such as voltage and current unbalance, voltage and current total harmonic distortion rate and voltage and current harmonic information, etc. Power quality information to realize power quality monitoring;

When power quality events such as voltage drop and voltage surge occur at the grid-connected point, the first data acquisition module records the time when the event occurs and the trigger condition for generating the event, so as to facilitate the determination of the fault type of the power grid and record the fault wave.

The PLC module realizes two-way communication with the remote data center through the network. On the one hand, the on-site data is transmitted to the remote data center for data analysis and processing; on the other hand, the voltage control command issued by the remote data center is received to control the reactive power output of the inverter.

Distributed photovoltaic power generation has randomness and volatility. The change of power generation directly leads to the fluctuation of the grid voltage at the access point. higher than the line front end voltage. When the power of photovoltaic power generation on the line is higher than that required by the load, the voltage at the grid connection point may exceed the upper limit. In order to avoid the voltage limit of the grid-connected point, the PLC module can independently manage the voltage of the grid-connected point, and can also accept the power scheduling command from the superior to avoid the voltage limit of the grid-connected point:

The first data acquisition module collects the voltage value of the grid-connected point in real time, and transmits the voltage value of the grid-connected point to the PLC module through the first communication management module. The PLC module determines the reactive power output of the inverter through the feedback mechanism and PI control. The reactive power output expression is:

Among them, Q _n is the output power of the inverter, Q _n+1 is the output power of the inverter at the next moment, V _meas is the real-time voltage of the grid, V _set is the set value of the upper limit of the grid voltage, k is the proportional integral operator, In practical applications, the value of k is properly selected according to the power level and control effect of the system.

The specific algorithm implementation process is as follows:

The first data acquisition module collects the grid-connected point voltage V _meas in real time, and transmits the grid-connected point voltage V _meas upwards to the PLC module; the human-computer interaction interface and the remote data center set the grid-connected voltage upper limit V _set according to the site conditions or scheduling instructions, and set The grid-connected voltage upper limit V _set is passed down to the PLC module. The PLC module compares the grid-connected point voltage V _meas with the grid-connected point voltage upper limit V _set . When V _meas > V _set , the grid-connected point voltage does not exceed the upper limit, and the inverter Output reactive power Q _n ; when V _meas < V _set , the grid-connected point voltage exceeds the upper limit, and the inverter output reactive power is Q _n -k(V _meas -V _set ).

The distributed photovoltaic power generation grid-connected measurement and control device of the present invention realizes the data monitoring, data processing and remote communication of the grid-connected system, and also realizes the data statistics of the power consumption on the load side, meeting the requirements of bidirectional billing and power analysis of future smart grid electric energy It also has the function of regulating the grid-connected point voltage. The application of the device's integrated distributed photovoltaic power generation grid-connected measurement and control device enables the photovoltaic system to be connected to the grid friendly, and provides technical support and technical means for the flexible grid-connection of distributed photovoltaic power generation.

Description of drawings

Figure 1 is a diagram of the installation location of the integrated distributed photovoltaic power generation grid-connected measurement and control device;

Figure 2 is a structural diagram of the integrated distributed photovoltaic power generation grid-connected measurement and control device;

Figure 3 is a working block diagram of grid-connected voltage control function.

detailed description

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

As shown in Figure 1, the first data acquisition module in the distributed photovoltaic power generation grid-connected measurement and control device of the present invention is installed at the switch of the common connection point between the distributed photovoltaic power station and the power grid. Distributed photovoltaic power generation grid-connected voltage levels are divided into 10kV and 380V. For users with 10kV grid-connected voltage level, they are generally installed at 10kV photovoltaic grid-connected points; Installed on the user incoming line side.

As shown in Figure 2, the distributed photovoltaic power generation grid-connected measurement and control device of the present invention includes a PLC module, a communication module, a data acquisition module, a switch, a power module, a man-machine interface, and a wireless communication module. The first data acquisition module is connected to the first communication management module through the RS485 interface, the second data acquisition module is connected to the second communication management module through the RS485 interface, the PLC module is connected to the switch through the RJ45 interface, and the switch is connected to the man-machine interface through the RJ45 interface and wireless communication module. The distributed photovoltaic power generation grid-connected measurement and control device realizes modular and compact design, adopts the design method of integral panel, fully enclosed 3U chassis, and strong and weak current isolation.

The first data acquisition module collects grid-connected point and load side data information through voltage and current sensors, and then transmits it to the PLC module through the first communication management module 3; the inverter sends inverter group information, such as the inverter in the inverter room , the combiner box, and the environmental information measured by the weather station outside the inverter room, etc., are transmitted to the PLC module through the second communication management module 4 . As the core of the integrated distributed photovoltaic power generation grid-connected measurement and control device, the PLC module analyzes and processes the collected information, and then transmits the analyzed and processed information to the human-machine interface through Ethernet communication to realize communication with human The two-way communication of the machine interface, and the other way through the switch to transmit the collected data to the remote terminal through the VPN protocol network, so as to realize the two-way communication with the upper data center. The man-machine interface and the remote data center can view the status of the grid-connected point in real time based on the data information uploaded from the PLC module: such as the voltage and current of the grid-connected point, power information, and power quality information, and check the status of the grid-connected point according to the load-side voltage and current, power information, and load power consumption information etc., real-time monitoring of load-side status, monitoring of inverter status based on power generation, operation mode, fault type, power quality information, etc., and checking of voltage changes at grid-connected points before and after a fault based on fault recording information; in addition, the receiver of the PLC module Control instructions issued by the machine interface or remote data center, such as the upper limit of the grid-connected point and the dispatch value of active and reactive power, are calculated and processed to control the start-up and stop of the inverter and the output power of the inverter, so as to realize the voltage control of the grid-connected point .

Figure 3 shows the working block diagram of grid-connected control function. When the power of photovoltaic power generation on the line is higher than that required by the load, the voltage at the grid connection point may exceed the upper limit. In order to avoid the grid-connected point voltage exceeding the limit, the present invention can not only manage the grid-connected point voltage independently, but also accept the superior power dispatching instruction to avoid the grid-connected point voltage exceeding the limit. Its implementation is as follows:

The first data acquisition module collects the voltage value of the grid connection point in real time, and transmits the voltage value of the grid connection point to the PLC module through the first communication management module. For reactive power output, the reactive power value of the inverter is transmitted to the inverter through the second communication management module, and the reactive power output expression of the inverter is:

Among them, Q _n is the output power of the inverter, Q _n+1 is the output power of the inverter at the next moment, V _meas is the real-time voltage of the grid, V _set is the set value of the upper limit of the grid voltage, k is the proportional integral operator, In practical applications, the value of k is properly selected according to the power level and control effect of the system. The specific algorithm implementation process is as follows:

The first data acquisition module collects the grid-connected point voltage V _meas in real time, and transmits the grid-connected point voltage V _meas upwards to the PLC module; the human-computer interaction interface and the remote data center set the grid-connected voltage upper limit V _set according to the site conditions or scheduling instructions, and set The grid-connected voltage upper limit V _set is passed down to the PLC module. The PLC module compares the grid-connected point voltage V _meas with the grid-connected point voltage upper limit V _set . When V _meas > V _set , the grid-connected point voltage does not exceed the upper limit, and the inverter Output reactive power Q _n ; when V _meas < V _set , the grid-connected point voltage exceeds the upper limit, and the inverter output reactive power is Q _n -k(V _meas -V _set ).

Claims (6)

1. the grid-connected measure and control device of a kind of distributed photovoltaic power generation, it is characterised in that：The grid-connected observing and controlling of described distributed photovoltaic power generation Device includes PLC module, communication module, data acquisition module, switch, power module and human-computer interaction interface；First data Acquisition module is connected with the first communication management module by RS485 interfaces, and the second data acquisition module passes through RJ45 interfaces and the Two communication management module connections, PLC module are connected to switch through RJ45 interfaces, and switch passes through RJ45 interfaces and man-machine boundary Face communicates and wireless communication module connection, and power module is connected with PLC module, switch, man-machine interface, is PLC module, is exchanged Machine, man-machine interface provide 24V dc sources.

2. the grid-connected measure and control device of distributed photovoltaic power generation according to claim 1, it is characterised in that：Described PLC module Grid entry point, load side according to collection, inverter information carry out generating observing and controlling, measure and control of load, inverter on off control, grid-connected electricity Voltage-controlled system, telecommunication；

Described data acquisition module realizes electric parameter acquisition, the grid-connected point data of the first data collecting module collected, the second number Load side data is gathered according to acquisition module：Line voltage, line current, phase voltage, phase current, power monitoring, electric energy quality monitoring, energy Amount bidirectional measuring, and failure wave-recording；

Human-computer interaction module realizes display, storage and the local control function of data, assigns inverter on off control and grid-connected electricity PLC module is arrived in pressure upper limit instruction, and PLC module assigns on off control instruction or inversion to inverter by the second communication management module Device power output is instructed；

Communication management module realizes that the first data acquisition module and the second data acquisition module pass through RS485 communication modes and first Communication management module communication；Inverter is connected with the second communication management module by RS485 communication modes, two communication modules it Between simultaneously and concurrently work, realize Monitoring Data unification collection；

Information in PLC module is sent to remote data center by switch all the way, and another road is delivered to human-computer interaction interface；

Power module is that PLC and human-computer interaction interface provide 24V dc sources.

3. the grid-connected measure and control device of distributed photovoltaic power generation according to claim 1, it is characterised in that：Described data acquisition Module realizes grid entry point and load side parameter acquisition, energy bidirectional measuring, electric energy quality monitoring, failure wave-recording, and by collection Information transmission is to PLC module；First data acquisition module records grid entry point photovoltaic power generation quantity and surplus online amount；Second data are adopted Collection module record electrical network delivery and load power consumption, realize the bidirectional measuring of energy；

First data collecting module collected records grid entry point energy quality information, the second data collecting module collected record load side electricity Can quality information；Such as voltage, current unbalance factor, the electric energy such as voltage, current total harmonic distortion rate and voltage, current harmonics information Quality information, realizes electric energy quality monitoring；

Grid entry point occur Voltage Drop, voltage jump etc. the quality of power supply event when, the first data acquisition module record event is sent out Raw time and the trigger condition of generation event, it is convenient to determine electric network fault type, carry out failure wave-recording.

4. the grid-connected measure and control device of distributed photovoltaic power generation according to claim 1, it is characterised in that：Described PLC module By real-time performance and the both-way communication of remote data center；On the one hand field data is sent to into remote data center, is carried out Data analysis and process；On the other hand the voltage control command that remote data center is issued is received, inverter reactive power is controlled Output.

5. the grid-connected measure and control device of distributed photovoltaic power generation according to claim 1, it is characterised in that：The first described data Grid entry point magnitude of voltage is delivered to PLC module by the first communication management module by acquisition module, PLC module by feedback mechanism and PI is controlled, and determines the reactive power output of inverter；Inverter reactive power exports expression formula：

$Q_{n+1}=\left\{\begin{array}{cc}{Q}_n-k(V_{meas}-V_{set})& V_{meas}<V_{set}\\ Q_n& V_{meas}>V_{set}\end{array}\right.$

Wherein, Q_nFor the power output of inverter, Q_n+1For the power output at inverter lower a moment, V_measFor electrical network real-time voltage, V_setFor line voltage upper limit set value, k is proportional integral operator.

6. the grid-connected measure and control device of distributed photovoltaic power generation according to claim 1, it is characterised in that：The first described data The grid-connected point voltage V of acquisition module Real-time Collection_meas, and by grid-connected point voltage V_measIt is passed up to PLC module；Man-machine interaction circle Face, remote data center are according to field condition or dispatch command setting grid-connected voltage upper limit V_set, by grid-connected voltage upper limit V_set Pass down to PLC module, PLC module is by grid-connected point voltage V_measWith grid entry point upper voltage limit value V_setRelatively, work as V_meas＞ V_set When, grid-connected point voltage does not get over the upper limit, inverter output reactive power Q_n；Work as V_meas＜ V_setWhen, grid entry point Over High-Limit Voltage is inverse Become device output reactive power into Q_n-k(V_meas-V_set)。