CN-115441732-B - Multi-port direct current converter and control method thereof

CN115441732BCN 115441732 BCN115441732 BCN 115441732BCN-115441732-B

Abstract

The invention provides a multiport direct current converter and a control method thereof, wherein each converter controls the working state of the converter according to the voltage of a direct current bus and the deviation between the voltage of a reference bus and the corresponding deviation of the reference bus so as to keep the voltage of the direct current bus as a voltage reference value; in addition, the corresponding deviation of each converter is different, namely, the independent switching of the direct current bus voltage control right is realized through the coordinated control of each port controller, so that the system can still maintain stable operation when any port fails. The method has the advantages of centralized control and peer-to-peer control, does not need complex logic of a central controller, reduces the workload of communication, and maintains the stable operation of the system to the maximum extent on the premise of not increasing the complexity of control.

Inventors

LI YANG
DONG RUI
ZHANG YURONG
WANG XI
HE JIA
DU TAO
YANG FAN

Assignees

西安西电高压开关有限责任公司
中国西电电气股份有限公司

Dates

Publication Date: 20260505
Application Date: 20211123

Claims (8)

1. A control method of a multi-port direct current converter is characterized in that one sides of 4 converters of the multi-port direct current converter are connected through a direct current bus, the other sides of the converters are used as ports of the multi-port direct current converter to be respectively connected with a photovoltaic array, a medium-voltage direct current distribution network, a low-voltage direct current distribution network and a low-voltage alternating current distribution network, and the control method comprises the following steps: Each converter controls the working state of the converter according to the DC bus voltage and the deviation between the reference bus voltage and the corresponding reference bus voltage so as to keep the DC bus voltage as a voltage reference value; the voltage reference value is the reference bus voltage, the sum of the reference bus voltage and the corresponding deviation or the difference between the reference bus voltage and the corresponding deviation; wherein, each converter is respectively according to direct current bus voltage to and the deviation that benchmark bus voltage and each correspond, control self operating condition, so that direct current bus voltage keeps as voltage reference value, include: The photovoltaic DC/DC converter connected with the photovoltaic array controls the working state of the converter according to the direct current bus voltage and the deviation of the reference bus voltage and the first deviation so as to enable the direct current bus voltage to be kept at the voltage reference value; the photovoltaic DC/DC converter controls the working state of the converter according to the direct current bus voltage and the deviation of the reference bus voltage and the first deviation so as to enable the direct current bus voltage to be kept as the voltage reference value, and the photovoltaic DC/DC converter comprises: the feedback value of the direct current bus voltage is subtracted from the given value of the sum of the reference bus voltage and the first deviation to be used as the input of a first proportional integral regulator, wherein the output lower limit value of the first proportional integral regulator is-1; The output of the first proportional-integral regulator is connected to a first inverter; The output of the first inverter is subtracted from the feedback value of the inductance current in the photovoltaic DC/DC converter and then used as the input of a second proportional-integral regulator; And the output of the second proportional-integral regulator is subjected to PWM modulation, and PWM square waves are output and used as driving signals of all switching tubes in the photovoltaic DC/DC converter.
2. The method according to claim 1, wherein each of the converters controls its own operation state according to a dc bus voltage and a deviation of a reference bus voltage from a corresponding reference bus voltage, respectively, so as to maintain the dc bus voltage at the voltage reference value, comprising: and the bidirectional DC/DC converter connected with the low-voltage direct current distribution network controls the working state of the bidirectional DC/DC converter according to the direct current bus voltage and the second deviation of the reference bus voltage so as to keep the direct current bus voltage as the voltage reference value.
3. The method according to claim 2, wherein the bidirectional DC/DC converter controls its own operation state according to the DC bus voltage and the deviation of the reference bus voltage from the second voltage so as to maintain the DC bus voltage at the voltage reference value, comprising: The feedback value of the direct current bus voltage is subtracted from the given value of the sum of the reference bus voltage and the second deviation to be used as the input of a fourth proportional-integral regulator, wherein the output lower limit value of the fourth proportional-integral regulator is-1, and the output upper limit value of the fourth proportional-integral regulator is the value of the given value of the inductance current after passing through a third inverter; the feedback value of the direct current bus voltage is subtracted from a given value of the difference between the reference bus voltage and the second deviation to be used as the input of a fifth proportional-integral regulator, wherein the output upper limit value of the fourth proportional-integral regulator is 1; the output of the fifth proportional-integral regulator is subtracted from the feedback value of the first inductance current and then is input into a sixth proportional-integral regulator, wherein the output of the sixth proportional-integral regulator is subjected to PWM modulation and outputs PWM square waves as driving signals of a first Boost circuit corresponding to the first inductance; The output of the seventh proportional-integral regulator is subjected to PWM modulation and outputs PWM square waves as driving signals of a second Boost circuit corresponding to the second inductor; the photovoltaic DC/DC converter is of a topological structure with multiple Boost circuits connected in parallel, and comprises the first Boost circuit and the second Boost circuit.
4. The method according to claim 1, wherein each of the converters controls its own operation state according to a dc bus voltage and a deviation of a reference bus voltage from a corresponding reference bus voltage, respectively, so as to maintain the dc bus voltage at the voltage reference value, comprising: And the DC/AC converter connected with the low-voltage alternating current distribution network controls the working state of the DC/AC converter according to the voltage of the direct current bus and the deviation between the voltage of the reference bus and the third deviation so as to enable the voltage of the direct current bus to be kept at the voltage reference value.
5. The method according to claim 4, wherein the DC/AC converter controls its own operation state according to the DC bus voltage and the deviation of the reference bus voltage from the third voltage so as to maintain the DC bus voltage at the voltage reference value, comprising: The feedback value of the direct current bus voltage is subtracted from the given value of the sum of the reference bus voltage and the third deviation to be used as the input of an eighth proportional-integral regulator, wherein the output lower limit value of the eighth proportional-integral regulator is-1, and the output upper limit value of the eighth proportional-integral regulator is the value of the given value of the d-axis component of the alternating current after passing through a seventh inverter; The feedback value of the direct current bus voltage is subtracted from a given value of the difference between the reference bus voltage and the third deviation to be used as the input of a ninth proportional-integral regulator, wherein the output upper limit value of the ninth proportional-integral regulator is 1; The output of the ninth proportional-integral regulator is subtracted from the feedback value of the d-axis component of the alternating current and then input to the tenth proportional-integral regulator; the output of the tenth proportional-integral regulator is subjected to PWM modulation and is input to a dq/abc coordinate transformation unit; The given value of the alternating current q-axis component is subtracted from the feedback value of the alternating current q-axis component and then input to an eleventh proportional-integral regulator, wherein the output of the eleventh proportional-integral regulator is subjected to PWM modulation and then input to the dq/abc coordinate transformation unit; The output of the dq/abc coordinate conversion unit is subjected to PWM modulation again, and PWM square waves are output to serve as driving signals of the switching tubes in the DC/AC converter.
6. The method according to any one of claims 1 to 5, wherein each of the converters controls its own operation state according to a dc bus voltage and a deviation of a reference bus voltage from a corresponding reference bus voltage, respectively, so that the dc bus voltage is maintained at the voltage reference value, comprising: The medium-voltage DC/DC converter connected with the medium-voltage DC distribution network adopts open-loop fixed-frequency control so as to clamp the DC bus voltage to the voltage reference value when the medium-voltage DC converter operates normally.
7. The multi-port direct current converter is characterized by comprising a photovoltaic DC/DC converter, a medium-voltage direct current DC/DC converter, a bidirectional DC/DC converter and a DC/AC converter; one side of each converter is connected through a direct current bus; The other side of the photovoltaic DC/DC converter is used as a first port of the multi-port direct current converter and is connected with a photovoltaic array; the other side of the medium-voltage Direct Current (DC)/DC converter is used as a second port of the multi-port DC converter and is connected with a medium-voltage direct current distribution network; the other side of the bidirectional DC/DC converter is used as a third port of the multi-port direct current converter and is connected with a low-voltage direct current distribution network; the other side of the DC/AC converter is used as a fourth port of the multi-port direct current converter and is connected with a low-voltage alternating current distribution network; Each converter in combination implements a control method of a multi-port dc converter as claimed in any one of claims 1-6.
8. The multi-port DC converter of claim 7, wherein the DC voltage of the DC voltage source is greater than the DC voltage of the DC voltage source, The photovoltaic DC/DC converter adopts at least one path of Boost circuit; The medium voltage Direct Current (DC)/DC converter comprises at least one unidirectional resonant converter; The bidirectional DC/DC converter includes at least one bidirectional resonant converter; the DC/AC converter includes at least one three-phase inverter.

Description

Multi-port direct current converter and control method thereof Technical Field The invention belongs to the field of direct current converters and direct current converters, and particularly relates to a multi-port direct current converter and a control method thereof. Background From the aspect of energy power development, the Chinese carbon peak and carbon neutralization target are used for accelerating green low-carbon transformation, and the energy high-quality development is promoted by taking the 'optimizing structure, improving efficiency, guaranteeing safety and reducing cost' as directions. The existing photovoltaic power station mainly adopts alternating current output, but an alternating current system has the problems of voltage out-of-limit and wide-frequency-domain oscillation, and the loss of an alternating current circuit also restricts the overall efficiency and output capacity of the system. Compared with an alternating current system, the direct current system has stronger conveying capacity and smaller loss under the same voltage level, can avoid the influence of capacitive reactance and inductive reactance of the system, and has no technical problems of reactive compensation, system resonance and the like. With the development of power electronics technology, the photovoltaic medium-voltage direct current converter can solve the problem of photovoltaic direct current output. The photovoltaic medium-voltage direct-current converter and the multiport converter are combined, so that the power supply reliability and flexibility of the system can be enhanced, the access of various distributed power supplies or energy storage is facilitated, the access of various loads is facilitated, and the photovoltaic medium-voltage direct-current converter is suitable for application occasions of alternating-current and direct-current hybrid power distribution. In the prior art, according to the relation between the output voltage and the preset upper limit voltage control limit, the power of the light Fu Zhiliu converter is controlled so as to make the operation mode of the direct current converter smoothly switched. However, the application scenario of the prior art is a two-port optical Fu Zhiliu converter, the control mode only considers the coordination control between two ports, and the method cannot coordinate the operation mode switching between the ports for a three-port and more multi-port system. Disclosure of Invention In view of the above, the present invention is directed to a multi-port dc converter and a control method thereof, which are used for maintaining stable operation of the system to the maximum extent without increasing complexity of control. The application discloses a control method of a multi-port direct current converter, wherein one sides of 4 converters of the multi-port direct current converter are connected through a direct current bus, the other sides of the converters are respectively connected with a photovoltaic array, a medium-voltage direct current distribution network, a low-voltage direct current distribution network and a low-voltage alternating current distribution network as ports of the multi-port direct current converter, and the control method comprises the following steps: And each converter controls the working state of the converter according to the direct current bus voltage and the deviation between the reference bus voltage and the corresponding deviation so as to enable the direct current bus voltage to be kept as a voltage reference value, wherein the voltage reference value is the reference bus voltage, the sum of the reference bus voltage and the deviation or the difference between the reference bus voltage and the deviation, and the deviation corresponding to each converter is different. Optionally, each converter controls its own working state according to the dc bus voltage and the deviation between the reference bus voltage and the corresponding reference bus voltage, so as to keep the dc bus voltage as a voltage reference value, including: And the photovoltaic DC/DC converter connected with the photovoltaic array controls the working state of the photovoltaic DC/DC converter according to the direct current bus voltage and the deviation of the reference bus voltage and the first deviation so as to enable the direct current bus voltage to be kept at the voltage reference value. Optionally, the photovoltaic DC/DC converter controls its own working state according to the DC bus voltage and the deviation between the reference bus voltage and the first voltage, so as to maintain the DC bus voltage at the voltage reference value, including: the feedback value of the direct current bus voltage is subtracted from the given value of the sum of the reference bus voltage and the first deviation to be used as the input of a first proportional integral regulator, wherein the output lower limit value of the first proportional integral regulator is-1; The out