CN-115189374-B - Three-phase unbalance management system and method for optical storage power supply and dynamic power adjustment

CN115189374BCN 115189374 BCN115189374 BCN 115189374BCN-115189374-B

Abstract

The invention relates to a three-phase imbalance management system and method for optical storage power supply and dynamic power adjustment. The power grid side and the live wire of the load side of the grid-connected point are respectively provided with a current transmitter, the live wire of the load side is respectively provided with a voltage transmitter, two current transmitters and voltage transmitters on each phase of live wire are connected with an analog-digital converter, the analog-digital converter is connected with a PLC, the PLC is connected with an inversion system through an RS485 concentrator, the output end of the inversion system is connected with the live wire, the input end of the inversion system is connected with a photovoltaic cell charging controller, and the photovoltaic cell charging controller is connected with a storage battery and a photovoltaic panel. The invention dynamically adapts to the three-phase unbalanced load while the distributed photovoltaic power supply is connected with the grid for generating power, and independently controls the output power of each phase of the photovoltaic to compensate and treat the three-phase unbalanced load, thereby improving the new energy absorbing capacity and the flexible and economic operation degree of the photovoltaic system and achieving the purposes of improving the electric energy quality and reducing the energy consumption.

Inventors

WANG LIDI
PENG YIWEN
YANG YANG
ZHANG LIUYANG
DUAN JIALIN
WANG XINYAO
LI GUANGPENG
Qu Haowei
Fang Jiankai

Assignees

沈阳农业大学

Dates

Publication Date: 20260512
Application Date: 20220804

Claims (7)

1. The three-phase unbalance management system for light storage power supply and dynamic power regulation is characterized in that current transmitters are respectively arranged on a power grid side and a live wire of a load side of a grid-connected point, voltage transmitters are respectively arranged on the live wire of the load side, two current transmitters and voltage transmitters on each phase of the live wire are connected with an analog-to-digital converter, the analog-to-digital converter is connected with a PLC (programmable logic controller), the PLC is connected with an inversion system through an RS485 concentrator, the output end of the inversion system is connected with the live wire, the input end of the inversion system is connected with a photovoltaic cell charging controller, the photovoltaic cell charging controller is connected with a storage battery and a photovoltaic panel, and the inversion system comprises an A-phase inverter, B-phase inverter and C-phase inverter, A-phase inverter, The output ends of the B-phase inverter and the C-phase inverter are respectively connected with a first alternating current contactor and then connected to a grid connection point, the input end of a control coil of the first alternating current contactor is connected with a PLC, a first current transducer and a fourth current transducer are arranged on a phase A live wire, a second current transducer and a fifth current transducer are arranged on a phase B live wire, a third current transducer and a sixth current transducer are arranged on a phase C live wire, the first current transducer and the fourth current transducer are connected with a first analog-to-digital converter, the second current transducer and the fifth current transducer are connected with a second analog-to-digital converter, the third current transducer and the sixth current transducer are connected with a third analog-to-digital converter, the first analog-to-digital converter is connected with a third voltage transducer, the third voltage transducer is connected with a phase A live wire at a load side, the second analog-to-digital converter is connected with a second voltage transducer, the second voltage transducer is connected with a phase B live wire at the load side, the third analog-to-digital converter is connected with a first voltage transducer, the first voltage transducer is connected with a phase C at the load side, the voltage transducer is connected with a phase C-to-digital converter, and the three-phase voltage transducer is connected with the grid connection point transducer the three-phase current of the grid side and the three-phase current of the load side are transmitted to the PLC after analog-digital conversion, and the three-phase power of the grid side of the grid-connected point is obtained, The PLC judges whether the load side three-phase power and the respective load unbalance degree are larger than a set value, if the load side three-phase power unbalance degree is smaller than the set value, the PLC starts the balanced distribution of the three-phase output power of the photovoltaic grid-connected mode, the PLC sends data to an inversion system to change the output power of the inverter, three inverters simultaneously send the same power to a power grid, the value of the three-phase power is one third of the capacity of a photovoltaic cell, if the load side three-phase power unbalance degree is larger than the set value, the PLC judges whether the power grid side unbalance degree is larger than the set value, if the load side three-phase power unbalance degree is smaller than the set value, the PLC judges that the current system has ensured three-phase power balance in an optimal mode, the grid-connected state and the output power of the inverter are maintained, if the power grid side unbalance degree is still larger than the set value, the system is still unbalanced, the output power is regulated, and when the power grid side unbalance degree is larger than the set value, the output power is regulated, the maximum power phase of the load side is judged, The maximum power phase at the load side is alpha phase, the intermediate power phase is beta phase and the minimum power phase is gamma phase, then the inverter outputting power to the maximum phase is alpha phase inverter, the inverter outputting power to the intermediate phase is beta phase inverter, the inverter outputting power to the minimum phase is gamma phase inverter, delta = alpha phase and beta phase difference value is calculated, epsilon = alpha phase and gamma phase difference value, and zeta = beta phase and gamma phase difference value.
2. The system for controlling three-phase unbalance of light storage power supply and dynamic power regulation according to claim 1, wherein a second alternating current contactor is arranged between the photovoltaic cell charging controller and the photovoltaic panel, and the control coil input end of the second alternating current contactor is connected with the PLC.
3. The system for controlling three-phase unbalance of light storage power supply and dynamic power regulation according to claim 1, wherein a third alternating current contactor is arranged between the photovoltaic cell charging controller and the storage battery, and the input end of a control coil of the third alternating current contactor is connected with the PLC.
4. The three-phase imbalance management system for light storage power supply and dynamic power adjustment according to claim 1, wherein a fourth alternating current contactor is arranged between the photovoltaic cell charging controller and the inversion system, and the control coil input end of the fourth alternating current contactor is connected with the PLC.
5. The system for harnessing three-phase imbalance between optical storage and power supply and dynamic power adjustment according to claim 1,2, 3 or 4, wherein said PLC model is FX3U48MR.
6. The method for managing the three-phase imbalance management system for light storage power supply and dynamic power adjustment according to claim 1, wherein the method comprises the following steps: if delta is more than or equal to S, namely the difference value between the maximum phase power and the intermediate phase power at the load side is more than or equal to the capacity of the photovoltaic cell, the PLC sends data to the inverter, the output power of the alpha-phase inverter is changed into the capacity of the photovoltaic cell, and the inversion power of the beta-phase inverter and the gamma-phase inverter is 0; If delta is less than S, namely the difference value of the maximum phase power and the intermediate phase power is less than the capacity of the photovoltaic cell, judging the sizes of epsilon+zeta and S; If epsilon+ζ is more than or equal to S, the PLC sends data to the inverter, the inversion power of the alpha-phase inverter is changed to be delta, the residual available capacity is RES1=S-delta, the PLC sends data to the inverter, the residual available capacity RES1 is averagely distributed to the alpha-phase inverter and the beta-phase inverter, namely, the alpha-phase inverter is delta+RES1/2, the beta-phase inverter inverts power RES1/2, and the gamma-phase inverter inverts power to be 0; If ε+ζ < S, PLC sends data to inverter, changing β -phase inverter output power to ζ, α -phase inverter power to ε, then remaining available capacity to RES1=S- (ε+ζ), PLC sends data to inverter, and the remaining available capacity RES1 is evenly distributed to A-phase inverter, B-phase inverter and C-phase inverter, that is, each phase increases inverter power RES1/3, that is, α -phase inverter is ε+RES1/3, β -phase inverter power is ζ+RES1/3, γ -phase inverter power is RES1/3.
7. The method for controlling the three-phase imbalance control system for light-storage power supply and dynamic power adjustment according to claim 6, wherein the three inverters are used for carrying out timing waiting after simultaneously transmitting the same power to the power grid, and waiting for entering the next PLC again to judge whether the load side three-phase power imbalance is larger than a set value.

Description

Three-phase unbalance management system and method for optical storage power supply and dynamic power adjustment Technical Field The invention relates to a grid-connected three-phase imbalance treatment system and method, in particular to a light storage power supply and dynamic power adjustment three-phase imbalance treatment system and method. Background The Low-voltage distribution network (LVDN: low-Voltage DistributionNetwork) in China adopts a three-phase four-wire system wiring mode, and the problems of asymmetric parameters, unbalanced load three phases and the like exist due to imperfect management of LVDN and lack of prospective planning. Along with the improvement of the living standard of people, the load demand is gradually increased, meanwhile, the single-phase distributed photovoltaic is widely connected, the three-phase unbalance degree of LVDN is further increased, various challenges are brought to the voltage quality and line loss management of the power distribution network, and the operation safety of LVDN is even affected. The corresponding measures against the three-phase imbalance of LVDN can now be classified into 2 classes. The method has the advantages that the load side is controlled, the phase sequence distribution is carried out through an algorithm, the phase inversion is carried out by combining a phase inversion device, the uniform distribution of the load is realized, the load of a low-voltage station area is numerous, more phase inversion switches are needed, the investment is large, in addition, the voltage flicker problem is inevitably generated in the phase inversion process, the load power failure is caused due to the phase inversion failure, and the user equipment and the electricity utilization experience are negatively influenced. The other type of measure is system side control, which is mainly to coordinate control LVDN by methods of regulating on-load voltage regulating transformer, load reconstruction, power control of photovoltaic inverter, etc. The grid-connected efficiency of the photovoltaic power generation unit reaches the maximum when the three-phase load is balanced, namely, the generated power can be injected into a power grid with balanced three-phase power, and the grid-connected efficiency when the three-phase load is unbalanced can not be completely utilized by the photovoltaic power generation unit due to the existence of the exchange power, so that the grid-connected power generation efficiency is reduced. Disclosure of Invention The invention provides a three-phase unbalance management system and a method for optical storage power supply and dynamic power adjustment, aiming at improving the three-phase load unbalance condition of a low-voltage power network by utilizing a mode of respectively independently controllable phase-to-phase parallel network injection power. In order to achieve the purpose, the three-phase unbalance management system for optical storage power supply and dynamic power regulation is characterized in that current transmitters are respectively arranged on a power grid side and a live wire on a load side of a grid-connected point, voltage transmitters are respectively arranged on the live wire on the load side, two current transmitters and voltage transmitters on each phase of live wire are connected with an analog-to-digital converter, the analog-to-digital converter is connected with a PLC (programmable logic controller), the PLC is connected with an inversion system through an RS485 concentrator, the output end of the inversion system is connected with the live wire, the input end of the inversion system is connected with a photovoltaic cell charging controller, and the photovoltaic cell charging controller is connected with a storage battery and a photovoltaic panel. The inversion system comprises an A-phase inverter, a B-phase inverter and a C-phase inverter, wherein the output ends of the A-phase inverter, the B-phase inverter and the C-phase inverter are respectively connected with a first alternating current contactor and then connected to a grid connection point, and the input end of a control coil of the first alternating current contactor is connected with a PLC. And a second alternating current contactor is arranged between the photovoltaic cell charging controller and the photovoltaic panel, and the input end of a control coil of the second alternating current contactor is connected with the PLC. And a third alternating current contactor is arranged between the photovoltaic cell charging controller and the storage battery, and the input end of a control coil of the third alternating current contactor is connected with the PLC. A fourth alternating current contactor is arranged between the photovoltaic cell charging controller and the inversion system, and the input end of a control coil of the fourth alternating current contactor is connected with the PLC. The model of the PLC is FX3U48MR. The phase A live wire is