CN-121983940-A - DC collecting system

CN121983940ACN 121983940 ACN121983940 ACN 121983940ACN-121983940-A

Abstract

The application relates to the technical field of power electronics, in particular to a direct current collection system, which aims to solve the problem of decoupling control on bus voltage stability and midpoint voltage balance of a photovoltaic direct current collection system. Therefore, in the direct current collecting system, the first converter module coupled with two ends of any one of the first capacitor and the second capacitor is independently arranged and used for carrying out balance control on midpoint potential between the first capacitor and the second capacitor, meanwhile, the second converter module is used for controlling stable output of the direct current bus, and the busbar voltage and the midpoint potential of the capacitor are respectively regulated by different control channels, so that the busbar voltage and the midpoint potential of the capacitor respectively correspond to independent feedback targets, the problem that a power output path is influenced when the midpoint potential is disturbed or the midpoint is regulated when the busbar voltage is regulated in the traditional system is avoided, and the decoupling control between the busbar voltage stability and the midpoint voltage balance is facilitated.

Inventors

WU LIXIN
HUO QUNHAI
YIN JINGYUAN
HAN LIBO
YANG JIE

Assignees

中国科学院电工研究所

Dates

Publication Date: 20260505
Application Date: 20260409

Claims (9)

1. The direct current collection system is characterized by comprising a first capacitor, a second capacitor, a first converter module and a second converter module; the first capacitor and the second capacitor are connected in series between the direct current buses at the input side; the input end of the first converter module is coupled with two ends of any one of the first capacitor and the second capacitor, and is used for carrying out balance control on midpoint potential between the first capacitor and the second capacitor; the input end of the second converter module is coupled with the direct current bus and used for controlling the direct current bus to stably output, wherein the second converter module comprises a second direct current-direct current converter and a second regulating circuit; the input end of the second direct current-direct current converter is coupled with the direct current bus; The second regulating circuit is used for generating a second control signal based on the actually measured bus output voltage, the reference bus output voltage and a second actually measured inductor current output by the second direct current-direct current converter so as to drive and control the second direct current-direct current converter based on the second control signal.
2. The dc pooling system of claim 1, wherein the first converter module includes a first dc-dc converter and a first regulation circuit; An input end of the first DC-DC converter is coupled with two ends of any one of the first capacitor and the second capacitor; the first regulating circuit is used for generating a first control signal at least based on the actually measured midpoint potential, the target midpoint potential and a first actually measured inductor current output by the first direct current-direct current converter so as to drive and control the first direct current-direct current converter based on the first control signal.
3. The direct current sink system of claim 2, wherein the first regulation circuit comprises a subtractor, a first voltage loop PI regulator, and a first current loop PI regulator; The subtracter is used for determining midpoint potential offset according to the actually measured midpoint potential and the target midpoint potential; The first voltage loop PI regulator is used for determining a first reference inductance current based on the midpoint potential offset; the first current loop PI regulator is configured to generate the first control signal based on the first reference inductor current and an offset of the first measured inductor current.
4. The direct current collection system according to claim 2, wherein the first adjusting circuit employs a model predictive controller based on state space modeling, and the model predictive controller takes the measured midpoint potential, the first measured inductor current, the target midpoint potential, and a sampling time duty ratio as inputs to output a first control signal to balance the midpoint potential.
5. The direct current sink system of claim 1, wherein the second regulation circuit comprises a second voltage loop PI regulator and a second current loop PI regulator; the second voltage loop PI regulator is used for determining a second reference inductance current based on the measured bus output voltage and the offset of the reference bus output voltage; the second current loop PI regulator is configured to generate the second control signal based on the second reference inductor current and an offset of the second measured inductor current.
6. The direct current collector system according to claim 1, wherein one of the first converter modules and one of the second converter modules are used as a set of double converter modules, and the direct current collector system can be provided with a plurality of sets of double converter modules which are connected in parallel to the output side of the direct current bus.
7. The direct current collection system of claim 6, wherein each set of dual inverter modules is preconfigured with a priority, wherein a first inverter module of each set of dual inverter modules is further configured to determine whether a master inverter module takes over based on an offset of the measured bus output voltage and the reference bus output voltage and a bus current change speed, and if so, send a take over request to the master inverter module, wherein the master inverter module is a highest priority dual inverter module of the plurality of sets of dual inverter modules.
8. The direct current collection system of claim 7, wherein a next highest priority dual converter module of the plurality of sets of dual converter modules is further configured to upgrade autonomously when no heartbeat frame sent by the master converter module is received within a preset time.
9. The direct current collection system of claim 7, wherein the reference bus output voltage corresponding to the master converter module is greater than the reference bus output voltages corresponding to the remaining converter modules in the plurality of sets of dual converter modules.

Description

DC collecting system Technical Field The application relates to the technical field of power electronics, and particularly provides a direct current collection system. Background With the rapid development of distributed new energy systems, photovoltaic (PV) power generation systems are widely used in smart grids and micro grids. To improve energy transfer efficiency, photovoltaic outputs are typically connected to a common direct current Bus (DC Bus) through a DCDC (direct current-direct current) converter and further concentrated to a direct current distribution network (DC Grid). However, due to uncertainty of the photovoltaic power supply and dynamic change of the load, fluctuation of the voltage of the direct current bus is easy to occur, and stable operation of the system is affected. In addition, when the voltage division capacitor structure is used in the process of collecting the photovoltaic, a midpoint drifting phenomenon is easy to occur, so that uneven capacitor stress, unbalanced voltage distribution and asymmetric system operation are caused. Traditional capacitive midpoint potential balancing methods typically rely on the introduction of zero sequence components in the modulated signal or on the coupling of multiple legs in the topology to indirectly adjust the midpoint potential. These methods essentially take the midpoint potential adjustment as a byproduct of the master control target (such as bus voltage or output current) adjustment process, so that the adjustment speed is limited, the control response is limited to the bandwidth of the master control variable, and independent adjustment of midpoint offset is difficult under complex disturbance. Meanwhile, coupling interference exists between two targets of bus voltage stabilization and midpoint voltage balance, and effective decoupling between the bus voltage stabilization and midpoint voltage balance is difficult to achieve, so that control accuracy is reduced or dynamic performance of a system is insufficient. Disclosure of Invention The application aims to solve the technical problems, namely the problems of decoupling control on bus voltage stability and midpoint voltage balance of a photovoltaic direct current collection system. In a first aspect, the present application provides a dc sink system comprising a first capacitor, a second capacitor, a first converter module, and a second converter module; the first capacitor and the second capacitor are connected in series between the direct current buses at the input side; the input end of the first converter module is coupled with two ends of any one of the first capacitor and the second capacitor, and is used for carrying out balance control on midpoint potential between the first capacitor and the second capacitor; the input end of the second converter module is coupled with the direct current bus and used for controlling the direct current bus to stably output. In some embodiments, the first converter module includes a first dc-dc converter and a first regulation circuit; An input end of the first DC-DC converter is coupled with two ends of any one of the first capacitor and the second capacitor; the first regulating circuit is used for generating a first control signal based on at least the actually measured midpoint potential, the target midpoint potential and a first actually measured inductance current output by the first DC-DC converter so as to drive and control the first DC-DC converter based on the first control signal, wherein the second converter module comprises a second DC-DC converter and a second regulating circuit; the input end of the second direct current-direct current converter is coupled with the direct current bus; The second regulating circuit is used for generating a second control signal based on the actually measured bus output voltage, the reference bus output voltage and a second actually measured inductor current output by the second direct current-direct current converter so as to drive and control the second direct current-direct current converter based on the second control signal. In some embodiments, the first regulation circuit includes a subtractor, a first voltage loop PI regulator, and a first current loop PI regulator; The subtracter is used for determining midpoint potential offset according to the actually measured midpoint potential and the target midpoint potential; The first voltage loop PI regulator is used for determining a first reference inductance current based on the midpoint potential offset; the first current loop PI regulator is configured to generate the first control signal based on the first reference inductor current and an offset of the first measured inductor current. In some embodiments, the first adjusting circuit uses a model predictive controller based on state space modeling, and the model predictive controller takes the measured midpoint potential, the first measured inductor current, the target midpoint potential an