CN116613774A - Network-structured converter interface power supply frequency response system - Google Patents

Abstract

The invention discloses a frequency response system of a network-type converter interface power supply, which includes the following steps: Step 1: According to the grid-connected mode of the distributed power supply, the distributed power supply can be divided into a motor directly connected to the grid and a power supply through a converter There are two types of grid-connected type, and the fault current characteristics of the motor directly connected to the grid-connected distributed power supply depend on the motor; the system of the present invention can fully consider the impact of system operating state changes, improve the power response speed and dynamic performance, and affect the power supply in the circuit. Sensitive loads have a more favorable impact, effectively avoiding the current traditional grid-type converter interface power supply frequency is preset, without considering the impact of system operating state changes, which will reduce power response speed and dynamic performance. Problems that adversely affect sensitive loads in electrical circuits.

Description

A Frequency Response System of Networked Converter Interface Power Supply

technical field

The invention relates to the technical field of converters, in particular to a frequency response system for a networked converter interface power supply.

Background technique

A converter is an electrical device that changes the voltage, frequency, number of phases, and other quantities or characteristics of a power system.

In practical applications, some occasions need to change the AC power supply into a DC power supply, which is the rectifier circuit. In other occasions, it is necessary to change the DC power supply into an AC power supply. This reverse process corresponding to rectification is defined as an inverter circuit. Under certain conditions, a set of thyristor circuits can be used as both a rectifier circuit and an inverter circuit. This device is called a converter. Including rectifier (AC to DC <AC/DC>), inverter (DC to AC <DC/AC>), AC converter (AC inverter <AC/AC>) and DC converter (DC chopper <DCChopper>).

At present, the frequency of the interface power supply of the traditional network-type converter is preset, without considering the impact of system operating state changes, which will reduce the power response speed and dynamic performance, and have an adverse impact on sensitive loads in the circuit.

Contents of the invention

The purpose of the present invention is to overcome the current traditional grid-type converter interface power supply frequency that is pre-set in the prior art, without considering the impact of system operating state changes, which will reduce the power response speed and dynamic performance. In order to solve the problem of adverse effects on sensitive loads in the circuit, a frequency response system for the interface power supply of networked converters is provided. It can improve the power response speed and dynamic performance, and have a more favorable effect on the sensitive load in the circuit.

In order to achieve the above object, the present invention provides the following technical solution: a frequency response system for the interface power supply of a network-type converter, comprising the following steps:

Step 1: According to the grid-connected mode of the distributed power supply, the distributed power supply can be divided into two types: the motor directly connected to the grid and the converter connected to the grid. The fault current characteristics of the motor directly connected to the grid depends on the motor;

Step 2: From the perspective of active power flow control of distributed power generation, the control methods of distributed power generation mainly include maximum power point tracking control, constant power control and droop characteristic control, etc.;

Step 3: Droop characteristic control is mainly applied to distributed power sources in microgrids. In the maximum power point tracking control mode, the grid-connected power changes with the maximum available power of renewable energy sources such as wind and solar;

Step 4: When a short-circuit fault occurs in the power grid, the current output by the converter may increase sharply, and the main circuit components may experience severe overcurrent; in addition, affected by the decline in active power during the short-circuit period, the power transmission between various links in the distributed power supply The balance may be damaged, resulting in a sudden rise in DC voltage. Therefore, the grid-connected converter of the distributed power supply must be designed with corresponding voltage limiting and current limiting measures;

Step 5: The short-circuit current characteristics of the distributed power supply depend on the circuit topology and control strategy of the grid-connected inverter. The main circuit of the distributed power grid-connected inverter generally adopts a voltage source converter structure based on PWM control technology;

Step 6: Inverter control usually includes outer loop target control and inner loop current control. Outer loop control realizes distributed power flow control or AC/DC voltage control, and inner loop control realizes current control or current-limited operation. Current-limited operation It is to limit the output current of distributed power generation within the allowable value through control as much as possible in the case of grid failure;

Step 7: In order to realize the current limiting function, the current inner loop control is often introduced on the basis of the outer loop target control. The vector decoupling control is a kind of current inner loop control. First, according to the active power/DC voltage and reactive power/ The deviation between the set value and the actual value of the AC voltage is generated by the target control regulator to generate the active component and reactive component reference value of the VSC AC current, and then the current regulator generates the VSC output voltage reference signal on the d-q axis according to the current tracking control requirements Finally, according to the PWM modulation strategy, the IGBT drive signal is generated.

Preferably, in the first step, although there are many types of converter-type distributed power sources, including distributed power generation and distributed energy storage, and distributed power generation includes wind power generation, photovoltaic power generation, etc., they usually have the same or a similar system structure.

Preferably, in step 3, in order to achieve this goal, the power generation link and the DC conversion link realize maximum power tracking according to the current distributed energy conditions, and convert as much natural energy as possible into DC electric energy, while the inverter link uses DC Voltage stability control realizes power balance, and transmits all the generated electric energy to the grid at any time.

Preferably, in the step five, the DC voltage limiting function is usually realized by the power generation link and the DC conversion link, while the AC current limiting function is completed by the inverter link. Therefore, the converter-type distributed power supply pair The current response characteristics of grid short-circuit mainly depend on the control characteristics of the inverter.

Preferably, in the fifth step, no matter what circuit topology the VSC adopts, it is equivalent to an AC voltage source with the same phase as the grid voltage and continuously controllable amplitude from the perspective of the fundamental wave, and the VSC must be filtered in series The reactor is connected to the grid, so that the active component and reactive component of the output current of the grid-connected inverter can be adjusted respectively by controlling the amplitude and phase of the inverter voltage relative to the power supply voltage, and then the active power exchanged between the distributed power supply and the grid can be controlled. power and reactive power.

Preferably, in the sixth step, obviously, the fault current response characteristic of the distributed power supply is closely related to its current control strategy.

Compared with the prior art, the present invention provides a network-type converter interface power supply frequency response system, which has the following beneficial effects:

The system of the present invention can fully consider the impact of system operating state changes, improve power response speed and dynamic performance, and have a more favorable impact on sensitive loads in the circuit, effectively avoiding the current traditional network-type converter interface The power frequency is pre-set, without considering the impact of system operating state changes, which will reduce the power response speed and dynamic performance, and adversely affect the sensitive load in the circuit;

The parts not involved in the device are the same as the prior art or can be realized by adopting the prior art. The present invention has scientific and reasonable structure, safe and convenient use, and provides great help to people.

Detailed ways

In the description of the present invention, it should be noted that, unless otherwise specified and limited, the terms "installed", "set with", "connected", etc. should be understood in a broad sense, such as "connected", which may be a fixed connection , can also be a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

The present invention provides a technical solution: a frequency response system for an interface power supply of a network-type converter, comprising the following steps:

Step 1: According to the grid-connected mode of the distributed power supply, the distributed power supply can be divided into two types: the motor directly connected to the grid and the converter connected to the grid. The fault current characteristics of the motor directly connected to the grid depends on the motor;

Step 2: From the perspective of active power flow control of distributed power generation, the control methods of distributed power generation mainly include maximum power point tracking control, constant power control and droop characteristic control, etc.;

Step 3: Droop characteristic control is mainly applied to distributed power sources in microgrids. In the maximum power point tracking control mode, the grid-connected power changes with the maximum available power of renewable energy sources such as wind and solar;

Step 4: When a short-circuit fault occurs in the power grid, the current output by the converter may increase sharply, and the main circuit components may experience severe overcurrent; in addition, affected by the decline in active power during the short-circuit period, the power transmission between various links in the distributed power supply The balance may be damaged, resulting in a sudden rise in DC voltage. Therefore, the grid-connected converter of the distributed power supply must be designed with corresponding voltage limiting and current limiting measures;

Step 5: The short-circuit current characteristics of the distributed power supply depend on the circuit topology and control strategy of the grid-connected inverter. The main circuit of the distributed power grid-connected inverter generally adopts a voltage source converter structure based on PWM control technology;

Step 6: Inverter control usually includes outer loop target control and inner loop current control. Outer loop control realizes distributed power flow control or AC/DC voltage control, and inner loop control realizes current control or current-limited operation. Current-limited operation It is to limit the output current of distributed power generation within the allowable value through control as much as possible in the case of grid failure;

Step 7: In order to realize the current limiting function, the current inner loop control is often introduced on the basis of the outer loop target control. The vector decoupling control is a kind of current inner loop control. First, according to the active power/DC voltage and reactive power/ The deviation between the set value and the actual value of the AC voltage is generated by the target control regulator to generate the active component and reactive component reference value of the VSC AC current, and then the current regulator generates the VSC output voltage reference signal on the d-q axis according to the current tracking control requirements Finally, according to the PWM modulation strategy, the IGBT drive signal is generated.

In the present invention, preferably, in step 1, although there are many types of converter-type distributed power sources, including distributed power generation and distributed energy storage, distributed power generation includes wind power generation, photovoltaic power generation, etc., but they usually have the same or similar system structure.

Preferably, in step 3, in order to achieve this goal, the power generation link and the DC conversion link realize maximum power tracking according to the current distributed energy conditions, and convert as much natural energy into DC power as possible, and the inverter link stabilizes the DC voltage through the The control realizes power balance, and transmits all the generated electric energy to the grid at any time.

Preferably, in step five, the DC voltage limiting function is usually realized by the power generation link and the DC conversion link, while the AC current limiting function is completed by the inverter link. The current response characteristics of the short circuit mainly depend on the control characteristics of the inverter.

Preferably, in step five, no matter what circuit topology the VSC adopts, it is equivalent to an AC voltage source with the same phase as the grid voltage and continuously controllable amplitude from the perspective of the fundamental wave, and the VSC must pass through a series filter reactor Connected to the power grid, so that the active component and reactive component of the output current of the grid-connected inverter can be adjusted respectively by controlling the amplitude and phase of the inverter voltage relative to the power supply voltage, and then control the active power and power exchanged between the distributed power supply and the grid. reactive power.

Preferably, in step six, obviously, the fault current response characteristic of the distributed power supply is closely related to its current control strategy.

The preferred embodiments of the present invention have been described in detail above, however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (6)

1. A frequency response system for a network-type converter interface power supply, characterized in that: comprising the following steps: Step 1: According to the grid-connected mode of the distributed power supply, the distributed power supply can be divided into two types: the motor directly connected to the grid and the converter connected to the grid. The fault current characteristics of the motor directly connected to the grid depends on the motor; Step 2: From the perspective of active power flow control of distributed power generation, the control methods of distributed power generation mainly include maximum power point tracking control, constant power control and droop characteristic control, etc.; Step 3: Droop characteristic control is mainly applied to distributed power sources in microgrids. In the maximum power point tracking control mode, the grid-connected power changes with the maximum available power of renewable energy sources such as wind and solar; Step 4: When a short-circuit fault occurs in the power grid, the current output by the converter may increase sharply, and the main circuit components may experience severe overcurrent; in addition, affected by the decline in active power during the short-circuit period, the power transmission between various links in the distributed power supply The balance may be damaged, resulting in a sudden rise in DC voltage. Therefore, the grid-connected converter of the distributed power supply must be designed with corresponding voltage limiting and current limiting measures; Step 5: The short-circuit current characteristics of the distributed power supply depend on the circuit topology and control strategy of the grid-connected inverter. The main circuit of the distributed power grid-connected inverter generally adopts a voltage source converter structure based on PWM control technology; Step 6: Inverter control usually includes outer loop target control and inner loop current control. Outer loop control realizes distributed power flow control or AC/DC voltage control, and inner loop control realizes current control or current-limited operation. Current-limited operation It is to limit the output current of distributed power generation within the allowable value through control as much as possible in the case of grid failure; Step 7: In order to realize the current limiting function, the current inner loop control is often introduced on the basis of the outer loop target control. The vector decoupling control is a kind of current inner loop control. First, according to the active power/DC voltage and reactive power/ The deviation between the set value and the actual value of the AC voltage is generated by the target control regulator to generate the active component and reactive component reference value of the VSC AC current, and then the current regulator generates the VSC output voltage reference signal on the d-q axis according to the current tracking control requirements Finally, according to the PWM modulation strategy, the IGBT drive signal is generated. 2. The frequency response system of network-type converter interface power supply according to claim 1, characterized in that, in the first step, although there are many types of converter-type distributed power sources, there are distributed power generation and distributed In terms of energy storage, distributed power generation includes wind power generation, photovoltaic power generation, etc., but they usually have the same or similar system structure. 3. The network-type converter interface power supply frequency response system according to claim 1, characterized in that, in the third step, in order to achieve this purpose, the power generation link and the DC conversion link are realized according to the current distributed energy conditions Maximum power tracking converts natural energy into DC power as much as possible, and the inverter link realizes power balance through DC voltage stability control, and transmits all the generated power to the grid at any time. 4. The network-type converter interface power supply frequency response system according to claim 1, characterized in that, in the fifth step, the DC voltage limiting function is usually realized by the power generation link and the DC conversion link, while the AC The current limiting function is completed by the inverter link. Therefore, the current response characteristics of the converter-type distributed power supply to the short circuit of the distribution network mainly depend on the control characteristics of the inverter. 5. The network-based converter interface power supply frequency response system according to claim 1, characterized in that, in the fifth step, no matter what circuit topology the VSC adopts, it is equivalent to An AC voltage source with the same phase as the grid voltage and continuously controllable amplitude, the VSC must be connected to the grid through a series filter reactor, so that the grid-connected inverter can be adjusted separately by controlling the amplitude and phase of the inverter voltage relative to the power supply voltage. The active component and reactive component of the output current of the transformer, and then control the active power and reactive power exchanged between the distributed power supply and the grid. 6. The frequency response system of networked converter interface power supply according to claim 1, characterized in that in the sixth step, it is obvious that the fault current response characteristics of the distributed power supply are closely related to its current control strategy.