CN118381093B - Asynchronous generator-energy storage combined power generation system of internal combustion engine and control method thereof - Google Patents

Abstract

The invention discloses an internal combustion engine asynchronous generator-energy storage combined power generation system and a control method thereof, belonging to the technical field of emergency power supply technology. The combined power generation system comprises: an internal combustion engine power generation module, comprising a coaxially connected internal combustion engine and an asynchronous generator, the internal combustion engine is used to keep the asynchronous generator running after the asynchronous generator is started; an energy storage power generation module, comprising energy storage and a BMS, a main converter, and a secondary converter; the main converter and the secondary converter are respectively connected to the energy storage and the BMS, the secondary converter is interconnected with the asynchronous generator, the main converter and the secondary converter are used as frequency voltage sources, and the secondary converter is used to start the asynchronous generator at no load; a system controller is configured to: control the working modes of the main converter and the secondary converter, the output under the corresponding working mode and the speed of the internal combustion engine, so as to realize long-term and efficient power supply, have the ability to realize static synchronization with the power grid, and avoid resonance.

Description

Internal combustion engine asynchronous generator-energy storage combined power generation system and control method thereof

Technical Field

The present invention belongs to the technical field of emergency power supply, and in particular relates to an internal combustion engine asynchronous generator-energy storage combined power generation system and a control method thereof.

Background Art

With economic development and the improvement of people's living standards, users have higher and higher requirements for power supply reliability. To improve power supply reliability, it is necessary to ensure power supply time, power supply efficiency and power system stability.

However, existing low-voltage energy storage vehicles cannot provide power for a long time; existing internal combustion power generation vehicles are inefficient at low output power; when existing internal combustion generators based on synchronous generators are combined for energy storage and parallel power generation, if the internal combustion engine is used as the frequency voltage source, the parallel generator set is difficult to achieve static synchronization with the power grid, making it difficult to ensure the success of low-voltage grid-connected synchronization; if the energy storage vehicle is used as the frequency voltage source, resonance is prone to occur.

Therefore, it is urgent to design a generator set to solve the problems of insufficient power generation time of traditional energy storage vehicles, low efficiency of traditional internal combustion power generation vehicles, and difficulty in ensuring the stability of the power system by traditional diesel-storage combined generator sets.

Summary of the invention

The present invention provides an internal combustion engine asynchronous generator-energy storage combined power generation system and a control method thereof. An internal combustion engine-energy storage combined power generation unit is constructed based on an asynchronous generator. Not only does it use an energy storage inverter as a frequency voltage source and has the ability to achieve static synchronization with a power grid while avoiding resonance, but it also achieves long-term and efficient power supply through the combination of an energy storage inverter and an internal combustion generator.

To achieve the above object, the present invention is implemented by adopting the following technical solutions.

The present invention provides an internal combustion engine asynchronous generator-energy storage combined power generation system, comprising: an energy storage power generation module, an internal combustion engine power generation module and a control module;

The internal combustion engine power generation module comprises an internal combustion engine and an asynchronous generator connected coaxially, wherein the internal combustion engine is used to keep the asynchronous generator running after the asynchronous generator is started;

The energy storage and power generation module includes energy storage and BMS, a main converter, and a secondary converter;

The main converter and the secondary converter are connected to the energy storage and the BMS respectively, the secondary converter is interconnected with the asynchronous generator, the main converter and the secondary converter are used as frequency voltage sources, and the secondary converter is used to start the asynchronous generator at no load;

The control module includes a system controller, which is used to control the working modes of the primary converter and the secondary converter, and the output and the speed of the internal combustion engine in the corresponding working modes.

Optionally, the energy storage power generation module further includes an energy storage DC bus, a secondary converter AC bus, a secondary converter access switch, a main converter access switch, an AC main bus, an AC main bus voltage sensor, a system grid-connected switch, and a quick interface;

The energy storage and BMS DC interface is connected to the energy storage DC bus, the energy storage DC bus is connected to the DC side interfaces of the main converter and the secondary converter at the same time, the main converter AC side interface is connected to the lower end of the main converter access switch, the upper end of the main converter access switch is connected to the AC main bus, the secondary converter AC side interface is connected to the secondary converter AC bus, the secondary converter AC bus is connected to the lower end of the secondary converter access switch, the upper end of the secondary converter access switch is connected to the AC main bus, the AC main bus is connected to the upper end of the AC main bus voltage sensor and the system grid-connected switch, the lower end of the system grid-connected switch is connected to the fast interface, the AC main bus voltage sensor is used to collect the bus voltage phasor U0, and the fast interface is used to access the power grid;

The system controller is also used to control the main converter access switch, the secondary converter access switch and the system grid-connected switch to open and close.

Optionally, the internal combustion engine power generation module further includes a generator set access switch;

The secondary converter AC busbar is connected to the upper end of the generator set access switch, and the asynchronous generator AC port is connected to the lower end of the generator set access switch;

The system controller is used to control the opening and closing of the generator set access switch.

Optionally, it also includes a reactive power compensation module, a grid voltage sensor, and a grid current sensor;

The reactive power compensation module includes a reactive power compensation capacitor, which is connected to the AC port of the asynchronous generator and is used to perform reactive power compensation for the asynchronous generator startup;

The system controller is connected to a grid voltage sensor and a grid current sensor, which are used to collect the voltage phasor U0G and the current value I0M on the grid power supply side respectively.

Optionally, the mechanical power P3D of the rated output of the internal combustion engine is designed to be 1-1.5 times the rated output power P3N of the asynchronous generator, and P3N is designed to be 2 (P1N+P2N), wherein P1N is the rated power of the main converter, P2N is the rated power of the secondary converter, and P2N is designed to be the no-load starting power of the internal combustion engine and the asynchronous generator, which is not higher than 0.1 times of P3N.

In a second aspect, the present invention provides a control method, which is applied to the internal combustion engine asynchronous generator-energy storage combined power generation system according to any one of the first aspects, wherein the system controller performs the following control steps:

When the combined power generation system is in the grid parallel working mode, the main converter is controlled to generate power in constant power mode, the secondary converter is controlled to generate power in constant power mode and the asynchronous generator is started at no load in frequency/voltage control mode according to the power generation state and the remaining power of the energy storage and BMS, and the power output of the main converter, the power output and frequency/voltage output of the secondary converter and the speed of the internal combustion engine are controlled to meet the power demand of the grid;

When the combined power generation system is in the alternative grid power supply mode, the main inverter is controlled to maintain constant frequency/voltage mode support according to the power generation status and the remaining energy storage capacity of the energy storage and BMS. The secondary inverter generates electricity in power control mode and starts the asynchronous generator at no load in frequency/voltage control mode, and controls the frequency/voltage output of the main inverter, the power output and frequency/voltage output of the secondary inverter, and the speed of the internal combustion engine to meet the power demand of the grid.

Optionally, when the combined power generation system is in a grid parallel working mode, the system controller specifically performs the following operation control steps:

State 1: When the grid demand power P4 is not higher than the rated power P1N of the main converter, and the remaining power SOC of the energy storage and BMS is not less than 20%, the main converter and the secondary converter are controlled to discharge in power control mode, and the output power of the main converter is adjusted to P1=P1N*P4/(P1N+P2N), and the output power of the secondary converter is adjusted to P2=P2N*P4/(P1N+P2N);

State 2: When the grid demand power P4 is not higher than the rated power P1N of the main converter, and the remaining power SOC of the energy storage and BMS is lower than 20%, the secondary converter access switch is disconnected and the generator set access switch is closed. The secondary converter is controlled to soft-start the asynchronous generator to the rated speed at no load in the frequency/voltage control mode according to the reactive power compensated by the reactive compensation capacitor, and the internal combustion engine is started and controlled to run at low power in a manner to keep the asynchronous generator running at a constant speed. After the secondary converter is controlled to adjust its output voltage phasor U2 to synchronize with the voltage phasor U0 of the AC bus voltage sensor, the secondary converter is closed. When the switch is connected, the working mode of the secondary converter is changed to the power control mode, and the output power of the main converter, the output power of the secondary converter and the speed of the internal combustion engine are adjusted, so that the output power of the main converter P1=(P4-P3)*P1N/(P1N+P2N), the output power of the secondary converter P2=(P4-P3)*P2N/(P1N+P2N), and the output power of the asynchronous generator is P3≥P4. When the energy storage and BMS are charged to SOC rise to 90%, the internal combustion engine is turned off, the generator set access switch is disconnected, and the combined power generation system is controlled to resume state one operation;

State 3: When the grid demand power P4 is higher than the rated power P1N of the main converter, but does not exceed the maximum output power P1M of the main converter for 5 minutes and is gradually increasing, the secondary converter access switch is disconnected and the generator set access switch is closed. The secondary converter is controlled to soft-start the asynchronous generator to the rated speed at no load in the frequency/voltage control mode according to the reactive power compensated by the reactive compensation capacitor, and the internal combustion engine is started and controlled to run at low power in a manner to keep the asynchronous generator running at a constant speed. The secondary converter is controlled to adjust its output voltage phasor U2 and the voltage phasor U of the AC bus voltage sensor. 0 After synchronization, close the secondary converter access switch and change the working mode of the secondary converter from the frequency/voltage control mode to the power control mode. When the required power P4 is higher than P3N and not higher than P1N+P2N+P3N, adjust the output power of the main converter, the output power of the secondary converter and the speed of the internal combustion engine to make the output power P1 of the main converter = (P4-P3)*P1N/(P1N+P2N), the output power P2 of the secondary converter = (P4-P3)*P2N/(P1N+P2N), and the output power of the asynchronous generator is P3 = P3N.

Optionally, when the combined power generation system is in a grid parallel working mode, the system controller further performs the following steps:

Startup steps: connect the quick interface to the grid, close the system grid-connected switch, the main converter access switch and the secondary converter access switch, start the main converter and the secondary converter and control the main converter and the secondary converter to generate electricity in a constant power mode;

Shutdown steps: shut down the internal combustion engine, disconnect the generator set access switch, adjust the output power of the main inverter and the secondary inverter to -P1N and -P2N for charging, and when the SOC of the energy storage and BMS is charged to the set value, disconnect the secondary inverter access switch and the main inverter access switch, disconnect the system grid-connected switch, and quickly exit the grid.

Optionally, when the combined power generation system is in the alternative power grid power supply mode, the system controller specifically performs the following operation control steps:

State 1: When the grid demand power P4 is not higher than the rated power P1N of the main converter, and the remaining power SOC of the energy storage and BMS is not less than 20%, the main converter is controlled to support the system frequency and voltage in the frequency/voltage control mode, and the secondary converter is controlled to discharge in the power control mode and the real-time output power of the secondary converter is controlled to be P2N/P1N with respect to the real-time output power of the main converter;

State 2: When the grid demand power P4 is not higher than the rated power P1N of the main converter, and the remaining power SOC of the energy storage and BMS is less than 20%, the secondary converter access switch is disconnected and the generator access switch is closed. The secondary converter is controlled to soft-start the asynchronous generator to the rated speed at no load in the frequency/voltage control mode according to the reactive power compensated by the reactive compensation capacitor. The internal combustion engine is started and controlled to run at low power in a manner to keep the asynchronous generator running at a constant speed. The secondary converter is controlled to adjust its output voltage phase U2 and the AC bus voltage After the sensor voltage phasor U0 is synchronized, the secondary converter access switch is closed and the working mode of the secondary converter is changed to the power control mode. The main converter is controlled to support the system frequency and voltage in the frequency/voltage control mode. The output power of the secondary converter is adjusted to P2=(P4-P3)*P2N/(P1N+P2N). The output power of the asynchronous generator is P3≥P4. When the energy storage and BMS are charged to SOC rise to 90%, the internal combustion engine is turned off, the generator set access switch is disconnected, and the combined power generation system is controlled to resume state 1 operation.

State three: when the grid demand power P4 is higher than the rated power P1N of the main converter, but does not exceed the maximum output power P1M of the main converter for 5 minutes and is gradually increasing, the secondary converter access switch is disconnected and the generator set access switch is closed. The secondary converter is controlled to soft-start the asynchronous generator to the rated speed at no load in the frequency/voltage control mode according to the reactive power compensated by the reactive compensation capacitor, and the internal combustion engine is started and controlled to run at low power in a manner to keep the asynchronous generator running at a constant speed. After the secondary converter is controlled to adjust its output voltage phasor U2 to synchronize with the voltage phasor U0 of the AC bus voltage sensor, the secondary converter access switch is closed and the working mode of the secondary converter is changed from the frequency/voltage control mode to the power control mode. When the demand power P4 is higher than P3N and not higher than P1N+P2N+P3N, the output power of the secondary converter and the speed of the internal combustion engine are adjusted so that the output power P2 of the secondary converter is P2=(P4-P3)*P2N/(P1N+P2N), and the output power of the asynchronous generator is P3=P3N.

Optionally, when the combined power generation system is in the alternative power grid power supply mode, the system controller further performs the following control steps:

Startup steps: connect the quick interface to the grid, close the system grid-connected switch, the main converter access switch and the secondary converter access switch, start the main converter and the secondary converter, control the main converter and the secondary converter to generate electricity in constant power mode, increase the output power P1 of the main converter and the output power P2 of the secondary converter, until the grid current sensor detects that the grid current amplitude I0M is lower than I0ML, then open the grid section switch, and after the AC total bus voltage sensor detects that the bus voltage amplitude U0M is less than U0ML, change the working mode from constant power mode generation to constant frequency/voltage mode support, where I0ML is determined according to the detection accuracy of the grid current sensor, the control accuracy of the main converter and the rated current of the on-site line, and U0ML is set to 0.5-1 times of the rated voltage amplitude U0MN;

Shutdown steps: adjust the voltage phasor of the main converter so that the amplitude and phase of each phase of U0 and the grid voltage phasor U0G detected by the grid voltage sensor are the same, close the grid section switch, and when the system controller detects that the grid-side current I0M is greater than I0ML through the grid current sensor, control the main converter to change the working mode from constant frequency/voltage mode support to constant power mode power generation, turn off the internal combustion engine, disconnect the generator set access switch, adjust the output power of the main converter and the secondary converter to -P1N and -P2N for charging, charge the energy storage and BMS SOC to the set value, disconnect the secondary converter access switch and the main converter access switch, disconnect the system grid-connected switch, and quickly exit the grid through the interface.

Compared with the prior art, the beneficial effects achieved by the present invention are as follows: an internal combustion engine driven asynchronous motor and energy storage combined generator set architecture is proposed, which has the ability to achieve static synchronization with the power grid while avoiding resonance, and a primary-secondary energy storage inverter combination is proposed, and the secondary energy storage inverter is reused as the startup and merging network controller of the asynchronous generator for frequent soft starting of the asynchronous motor under isolated power generation. The energy storage inverter is used as a frequency voltage source to drive the asynchronous generator set to rotate, solving the problem that the asynchronous generator set needs excitation and soft starting before grid connection, and a large amount of reactive power is required under isolated power generation. Without increasing the engine inertia, the internal combustion engine cylinder pressure is increased, and fuels that are not easy to burn stably, such as ammonia, are compatible; a reactive compensation system and control method based on the remaining capacity of the energy storage inverter and the capacitor are also proposed to reduce the reactive output of the inverter and improve the power generation efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the structure of a combined power generation system in an embodiment of the present invention.

In the figure: 101, system controller; 201, energy storage and BMS; 202, main converter; 203, secondary converter; 204, energy storage DC bus; 301, internal combustion engine; 302, asynchronous generator; 303, generator set access switch; 304, secondary converter AC bus; 305, secondary converter access switch; 306, main converter access switch; 307, AC main bus voltage sensor; 308, AC main bus; 309, system grid-connected switch; 310, quick interface; 311, grid voltage sensor; 312, grid current sensor; 401, capacitor for reactive power compensation.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

Example 1

This embodiment proposes an internal combustion engine asynchronous generator-energy storage combined power generation system, including: an energy storage power generation module, an internal combustion engine power generation module and a control module;

The internal combustion engine power generation module comprises an internal combustion engine 301 and an asynchronous generator 302 connected coaxially, wherein the internal combustion engine 301 is used to keep the asynchronous generator 302 running after the asynchronous generator 302 is started;

The energy storage and power generation module includes energy storage and BMS 201, a main converter 202, and a secondary converter 203;

The main converter 202 and the secondary converter 203 are connected to the energy storage and the BMS 201 respectively, the secondary converter 203 is interconnected with the asynchronous generator 302, the main converter 202 and the secondary converter 203 are used as frequency voltage sources, and the secondary converter 203 is used to start the asynchronous generator 302 at no load;

The control module includes a system controller 101;

The system controller 101 is configured to control the working modes of the main inverter 202 and the secondary inverter 203, the output in the corresponding working mode and the speed of the internal combustion engine 301 according to the working mode of the combined power generation system, the required power and the energy storage and the remaining energy storage capacity of the BMS 201.

Example 2

Based on Example 1, this example also makes the following design.

As shown in FIG1 , the system consists of a system controller 101, energy storage and BMS 201, a main converter 202, a secondary converter 203, an energy storage DC bus 204, an internal combustion engine 301, an asynchronous generator 302, a generator set access switch 303, a secondary converter AC bus 304, a secondary converter access switch 305, a main converter access switch 306, an AC bus voltage sensor 307, an AC bus 308, a system grid-connected switch 309, a quick interface 310, and a capacitor 401 for reactive power compensation.

The DC interface of the energy storage and BMS 201 is connected to the energy storage DC bus 204, and the energy storage DC bus 204 is also connected to the DC side interfaces of the main converter 202 and the secondary converter 203. The AC side interface of the main converter 202 is connected to the lower end of the main converter access switch 306, and the upper end of the main converter access switch 306 is connected to the AC bus 308. The AC side interface of the secondary converter 203 is connected to the secondary converter AC bus 304, and the secondary converter AC bus 304 is also connected to the secondary converter access switch 305. The lower end and the upper end of the generator set access switch 303, the upper end of the secondary converter access switch 305 is connected to the AC main bus 308, the internal combustion engine 301 is coaxially connected to the asynchronous generator 302, the AC port of the asynchronous generator 302 is connected to the lower end of the generator set access switch 303 and the capacitor 401 for reactive power compensation, the AC main bus 308 is also connected to the AC main bus voltage sensor 307 and the upper end of the system grid-connected switch 309, and the lower end of the system grid-connected switch 309 is connected to the quick interface 310.

At the same time, the control circuits of the main converter 202 and the secondary converter 203 are connected to the AC bus voltage sensor 307 to collect the bus voltage phasor U0. The system is connected by the control circuit of the system controller 101 with the control circuits of the main converter 202, the secondary converter 203, the energy storage and the BMS201 and the internal combustion engine 301, which are respectively used to control the working mode and frequency/voltage or power output of the main converter 202 and the secondary converter 203, collect the remaining energy storage of the energy storage and the BMS201, and control the speed of the internal combustion engine 301; the control circuit of the system controller 101 is also connected to the control circuits of the system grid-connected switch 309, the generator set access switch 303, the secondary converter access switch 305, and the main converter access switch 306 to control the opening and closing of the switch group; the system controller is also connected to the grid voltage sensor 311 and the grid current sensor 312 to collect the voltage phasor and current value on the grid power supply side.

The rated output mechanical power P3D of the internal combustion engine 301 is usually 1.2 times the rated output power P3N of the asynchronous generator 302. Usually P3N is designed to be 2 times P1N+P2N, where P1N is the rated power of the main converter 202 and P2N is the rated power of the secondary converter 203. P2N is usually designed to be the no-load starting power of the internal combustion engine 301 and the asynchronous generator 302, and is usually not higher than 0.1 times P3N.

Example 3

This embodiment provides a control method, which is applied to the internal combustion engine asynchronous generator-energy storage combined power generation system described in Example 2. The combined power generation system used for power supply vehicles and power generation vehicles mainly has two working modes, one is "grid parallel working mode" and the other is "alternative grid power supply mode".

1. In the grid parallel working mode, the combined generator set and the grid jointly supply power to the load, and the combined generator set is in a power output state. Therefore, the startup process, operation control and shutdown process of the combined generator set are as follows.

The startup process connects the quick interface 310 to the grid, and under the control of the system controller 101, closes the system grid-connected switch 309, closes the main converter access switch 306 and the secondary converter access switch 305, starts the main converter 202 and the secondary converter 203, and the main converter 202 and the secondary converter 203 generate electricity in a constant power mode.

During operation control, the system controller 101 performs control according to the power generation state.

State 1: When the power demanded by the grid or load/the output power of the combined generator set P4 is not higher than the rated output power P1N of the main converter, and the remaining power SOC of the energy storage and BMS201 is not less than 20%, the demanded power is shared by the main converter 202 and the secondary converter 203 according to the rated power, that is, the output power P1 of the main converter 202 = P1N*P4/(P1N+P2N), and the output power P2 of the secondary converter 203 = P2N*P4/(P1N+P2N).

State 2: When the power demand P4 of the power grid or load is not higher than the rated output power P1N of the main converter, and the remaining power SOC of the energy storage and BMS201 is less than 20%, the joint generator set must start the internal combustion engine 301, and use the asynchronous generator 302 to generate electricity for the power grid while replenishing the power for the energy storage and BMS201. Disconnect the secondary converter access switch 305, the required power P4 is fully met by the main converter 202, the secondary converter 203 is shut down, and the generator set access switch 303 is closed. Combined with the reactive power compensated by the reactive power compensation capacitor 401, the secondary converter 203 is controlled to compensate the remaining required reactive power in a frequency-voltage control mode to soft-start the no-load asynchronous generator 302 to the rated speed, start the internal combustion engine 301 and run it at a low power in a way that keeps the asynchronous generator 302 running at a constant speed. After the secondary converter 203 adjusts the output voltage phasor U2 to synchronize with the voltage phasor U0 of the AC bus voltage sensor 307, The secondary converter access switch 305 is closed and the working mode of the secondary converter 203 is changed from the frequency-voltage control mode to the power control mode. The output power of the main converter 202 and the secondary converter 203 and the speed of the internal combustion engine 301 are adjusted so that the output power P1 of the main converter 202 is P4-P3*P1N/(P1N+P2N), and the output power P2 of the secondary converter 203 is P4-P3*P2N/(P1N+P2N). At this time, both P1 and P2 are negative values, the energy storage and BMS201 are in the charging state, and the output power of the asynchronous generator 302 is P3=P4. When the SOC rises to 90%, the internal combustion engine 301 is turned off, the generator set access switch 303 is disconnected, and the unit resumes state 1 operation.

State 3: When the power demand P4 of the power grid or load is higher than the rated output power P1N of the main converter, but does not exceed the maximum output power P1M of the main converter for 5 minutes and is gradually increasing, the internal combustion generator is started in the manner described in state 2. When the power demand P4 is higher than P3N but not higher than P1N+P2N+P3N, the output power of the main converter 202 and the secondary converter 203 and the speed of the internal combustion engine 301 are adjusted to make the output power P1 of the main converter 202 = (P4-P3)*P1N/(P1N+P2N), and the output power P2 of the secondary converter 203 = (P4-P3)*P2N/(P1N+P2N). At this time, both P1 and P2 are positive values, the energy storage and BMS201 are in a discharging state, and the output power of the asynchronous generator 302 is P3=P3N.

In the shutdown process, under the control of the system controller 101, the internal combustion engine 301 is shut down, the generator set access switch 303 is disconnected, the output power of the main inverter 202 and the secondary inverter 203 is adjusted to -P1N and -P2N for charging, and the SOC of the energy storage and BMS201 is charged to the set value, which is usually 90%. The secondary inverter access switch 305 and the main inverter access switch 306 are disconnected, the system grid-connected switch 309 is disconnected, and the quick interface 310 exits the power grid.

In the alternative grid power supply mode, the combined generator set replaces the grid to supply power to the load, and the combined generator set is in a constant frequency-voltage output state. Therefore, the startup process, operation control and shutdown process of the combined generator set are as follows.

The startup process connects the quick interface 310 to the grid. Under the control of the system controller 101, the system grid-connected switch 309 is closed, the main converter access switch 306 and the secondary converter access switch 305 are closed, and the main converter 202 and the secondary converter 203 are started. The main converter 202 and the secondary converter 203 generate electricity in a constant power mode. P1 and P2 are increased until the grid current sensor 312 detects that the amplitude I0M of the grid current I0 is lower than I0ML. Then the grid section switch is manually opened. I0ML is usually determined according to the detection accuracy of the grid current sensor 312, the control accuracy of the main converter and the rated current of the on-site line, and is usually not more than 5A. After the main converter 202 detects that the bus voltage amplitude U0M is less than U0ML, the working mode is changed from constant power mode generation to constant frequency-voltage support. Usually, U0ML is set to 0.8 times the rated voltage amplitude U0MN.

During operation control, the system controller 101 performs control according to the power generation state, the main converter 202 maintains a constant frequency-voltage output mode, and the rest is consistent with state 1, state 2 and state 3 in the grid parallel working mode.

In the shutdown process, under the control of the system controller 101, the voltage phasor of the main converter 202 is adjusted so that the amplitude and phase of each phase of the grid voltage phasor U0G detected by the grid voltage sensor 311 are the same, and the grid segment switch is manually closed. When the system controller 101 detects that the grid-side current I0M is greater than I0ML through the grid current sensor 312, the main converter 202 changes the working mode from constant frequency-voltage support to constant power mode power generation. The internal combustion engine 301 is turned off, the generator set access switch 303 is disconnected, the output power of the main converter 202 and the secondary converter 203 is adjusted to -P1N and -P2N for charging, and the SOC of the energy storage and BMS201 is charged to the set value, which is usually 90%. The secondary converter access switch 305 and the main converter access switch 306 are disconnected, the system grid-connected switch 309 is disconnected, and the quick interface 310 exits the grid.

Example 4

Taking the 400V low-voltage power supply vehicle supplying power to the low-voltage branch box as an example, the combined power generation system and its control process are as follows.

The rated capacity of the energy storage and BMS201 is 200kW/100kWh, the rated power of the main converter 202 is P1N=160kW, the maximum operating power P1M for 5 minutes is 192kW, the rated power of the secondary converter 203 is P2N=40kW, the rated power of the asynchronous generator 302 is P3N=400kW, the rated power of the internal combustion engine 301 is P3D=500kW, the asynchronous generator 302 adopts a 3-pole design, a rated speed of 800 rpm, a squirrel cage rotor, and the internal combustion engine 301 adopts a diesel-liquid ammonia engine with a stable combustion speed of 800 rpm.

1. In the grid parallel working mode, after the required power P4=150kW lasts for 1 hour, P4 is increased to 300kW and lasts for 1 hour to end the work. The initial SOC of the vehicle energy storage and BMS201 is 90%.

1. Connect the quick interface 310 to the quick interface of the low-voltage branch box, close the system grid-connected switch 309, and close the main converter access switch 306 and the secondary converter access switch 305;

2. Start the main converter 202 and the secondary converter 203. The main converter 202 and the secondary converter 203 generate electricity in a constant power mode. The P1 target value is set to 120 kW, and the P2 target value is set to 30 kW.

3. When the energy storage and BMS 201 are discharged for about 25 minutes, the SOC drops to 20%, the P1 target value is set to 150kW, and the P2 target value is set to 0kW. The secondary converter 203 is stopped, and the secondary converter access switch 305 is disconnected;

4. Close the generator set access switch 303, and the secondary converter 203 soft-starts the asynchronous generator 302 with no load in a frequency-voltage control mode until the speed reaches 800 rpm. At this time, the frequency of the secondary converter 203 is about 55 Hz, and the voltage amplitude is about 420 V;

5. Start the internal combustion engine 301, and after the combustion is stable, reduce the frequency of the secondary inverter 203 to 50 Hz and simultaneously reduce the speed of the internal combustion engine 301 to make the power P2 of the secondary inverter 203 = 0 kW, at which time the speed is about 760 rpm;

6. The secondary converter 203 adjusts the output voltage phasor U2 to be synchronized with the voltage phasor U0 of the AC bus voltage sensor 307;

7. Close the secondary converter access switch 305 and change the working mode of the secondary converter 203 from the frequency-voltage control mode to the power control mode;

8. Adjust the speed of the internal combustion engine 301 so that the output power of the asynchronous generator 302 is P3 = 350kW, and at the same time, the target value of P1 is set to -150kW, the target value of P2 is set to -50kW, and the output power of the combined generator set P4 is kept at 150kW unchanged, while the energy storage and BMS201 are charged;

9. After the energy storage and BMS 201 are charged for about 25 minutes, the energy storage SOC rises to 90%, the internal combustion engine 301 is turned off, the generator set access switch 303 is disconnected, the P1 target value is set to 120kW, the P2 target value is set to 30kW, and the combined generator set output power P4 is kept unchanged at 150kW;

10. When the power generation operation is carried out for 1 hour, the required power P4 increases to 300kW;

11. The target value of P1 is set to 150 kW, and the target value of P2 is set to 0 kW. The operation of the secondary converter 203 is stopped, and the secondary converter access switch 305 is disconnected.

12. Close the generator set access switch 303, and the secondary converter 203 soft-starts the asynchronous generator 302 with no load in a frequency-voltage control mode until the speed reaches 800 rpm. At this time, the frequency of the secondary converter 203 is about 55 Hz, and the voltage amplitude is about 420 V;

13. Start the internal combustion engine 301, and after the combustion is stable, reduce the frequency of the secondary inverter 203 to 50 Hz and simultaneously reduce the speed of the internal combustion engine 301 to make the power P2 of the secondary inverter 203 = 0 kW, at which time the speed is about 760 rpm;

14. The secondary converter 203 adjusts the output voltage phasor U2 to be synchronized with the voltage phasor U0 of the AC bus voltage sensor 307;

15. Close the secondary converter access switch 305 and change the working mode of the secondary converter 203 from the frequency-voltage control mode to the power control mode;

16. Adjust the speed of the internal combustion engine 301 so that the asynchronous generator 302 outputs power P3=400kW, and at the same time, the target value of P1 is set to -75kW, the target value of P2 is set to -25kW, and the output power P4 of the combined generator set is 300kW. At the same time, the energy storage and BMS201 are charged;

17. When the SOC rises to 90% after the energy storage and BMS 201 are charged for about 10 minutes, the speed of the internal combustion engine 301 is adjusted so that the output power of the asynchronous generator 302 is P3 = 300 kW, and the target values of P1 and P2 are set to 0 kW.

18. After the power generation operation has been carried out for 2 hours, the internal combustion engine 301 is turned off, the generator set access switch 303 is disconnected, the main converter 202 and the secondary converter 203 are turned off, the secondary converter access switch 305 and the main converter access switch 306 are disconnected, the system grid-connected switch 309 is disconnected, and the quick interface 310 is disconnected from the power grid.

2. In power supply mode, after the required power P4 is no higher than 150kW for 1 hour, P4 is increased to no less than 200kW but no higher than 300kW for 1 hour, and the initial SOC of the vehicle energy storage and BMS201 is 90%.

1. Connect the quick interface 310 to the quick interface of the low-voltage branch box, close the system grid-connected switch 309, and close the main converter access switch 306 and the secondary converter access switch 305;

2. Start the main converter 202 and the secondary converter 203. The main converter 202 and the secondary converter 203 generate electricity in a constant power mode, increase P1 and P2 at a ratio of 4:1, and detect the bus current I0M at the same time, set I0ML=2A, when I0M is less than 2A, manually open the grid section switch, and at the same time the bus voltage U0M begins to drop, the main converter 202 detects U0M in real time, sets U0ML=300V, when U0M drops to 300V, the main converter 202 changes the working mode from constant power mode generation to constant frequency-voltage support, and adjusts the frequency to 50Hz, and the voltage to 380V, and at the same time the target value of the output power P2 of the secondary converter 203 is tracked in real time as 0.25 times of P1;

3. When the energy storage and BMS 201 are discharged to a SOC value of 20%, the secondary converter 203 is stopped and the secondary converter access switch 305 is disconnected;

4. Close the generator set access switch 303, and the secondary converter 203 soft-starts the asynchronous generator 302 with no load in a frequency-voltage control mode until the speed reaches 800 rpm. At this time, the frequency of the secondary converter 203 is about 55 Hz, and the voltage amplitude is about 420 V;

5. Start the internal combustion engine 301, and after the combustion is stable, reduce the frequency of the secondary inverter 203 to 50 Hz and simultaneously reduce the engine speed to make the power P2 of the secondary inverter 203 = 0 kW, at which time the speed is about 760 rpm;

6. The secondary converter 203 adjusts the output voltage phasor U2 to be synchronized with the voltage phasor U0 of the AC bus voltage sensor 307;

7. Close the secondary converter access switch 305 and change the working mode of the secondary converter 203 from the frequency-voltage control mode to the power control mode;

8. Adjust the speed of the internal combustion engine 301 so that the asynchronous generator 302 outputs power P3=P4+200kW, and the target value of P2 is set to -50kW. The main converter supports the system frequency and voltage, and the energy storage and BMS201 are charged;

9. After the energy storage and BMS 201 SOC rise to 90%, shut down the internal combustion engine 301, disconnect the generator set access switch 303, set the P2 target value to 0.25 times of P1, and maintain the combined generator set output power P4;

10. When the power generation operation is carried out for 1 hour, the required power P4 is increased to not less than 200kW but not more than 300kW;

11. The P2 target value is set to 0 kW, the secondary converter 203 is stopped, and the secondary converter access switch 305 is disconnected;

12. Close the generator set access switch 303, and the secondary converter 203 soft-starts the asynchronous generator 302 with no load in a frequency-voltage control mode until the speed reaches 800 rpm. At this time, the frequency of the secondary converter 203 is about 55 Hz, and the voltage amplitude is about 420 V;

13. Start the internal combustion engine 301, and after the combustion is stable, reduce the frequency of the secondary inverter 203 to 50 Hz and simultaneously reduce the engine speed to make the power P2 of the secondary inverter 203 = 0 kW, at which time the speed is about 760 rpm;

14. The secondary converter 203 adjusts the output voltage phasor U2 to be synchronized with the voltage phasor U0 of the AC bus voltage sensor 307;

15. Close the secondary converter access switch 305 and change the working mode of the secondary converter 203 from the frequency-voltage control mode to the power control mode;

16. Adjust the speed of the internal combustion engine 301 so that the asynchronous generator 302 outputs power P3 = 350kW, and the P2 target value is set to -50kW. At the same time, the energy storage and BMS 201 are charged;

17. When the SOC rises to 90% after the energy storage and BMS 201 are charged for about 10 minutes, the speed of the internal combustion engine 301 is adjusted so that the output power of the asynchronous generator 302 is P3=P4, and the target value of P2 is set to 0kW.

18. After the power generation operation has been carried out for 2 hours, the internal combustion engine 301 is turned off, the generator set access switch 303 is disconnected, the main converter 202 and the secondary converter 203 are turned off, the secondary converter access switch 305 and the main converter access switch 306 are disconnected, the system grid-connected switch 309 is disconnected, and the quick interface 310 is disconnected from the power grid.

The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims (9)

1. An internal combustion engine asynchronous generator-energy storage combined power generation system, characterized by comprising: an energy storage power generation module, an internal combustion engine power generation module and a control module;

The internal combustion engine power generation module comprises an internal combustion engine (301) and an asynchronous generator (302) which are coaxially connected, wherein the internal combustion engine (301) is used for keeping the asynchronous generator (302) running after the asynchronous generator (302) is started;

the energy storage power generation module comprises an energy storage battery (201), a BMS (battery management system), a main converter (202) and a secondary converter (203);

The main current transformer (202) and the secondary current transformer (203) are respectively connected into an energy storage system (BMS) (201), the secondary current transformer (203) is interconnected with the asynchronous generator (302), the main current transformer (202) and the secondary current transformer (203) are used as frequency voltage sources, and the secondary current transformer (203) is used for starting the asynchronous generator (302) in an idle mode;

the control module comprises a system controller (101), wherein the system controller (101) is used for controlling the working modes of the main converter (202) and the secondary converter (203) and corresponds to the output in the working modes and the rotating speed of the internal combustion engine (301);

The energy storage power generation module further comprises an energy storage direct current bus (204), a secondary converter alternating current bus (304), a secondary converter access switch (305), a main converter access switch (306), an alternating current total bus (308), an alternating current total bus voltage sensor (307), a system grid-connected switch (309) and a quick interface (310);

The energy storage and BMS (201) direct current interface is connected with an energy storage direct current bus (204), the energy storage direct current bus (204) is simultaneously connected with direct current side interfaces of a main converter (202) and a secondary converter (203), an alternating current side interface of the main converter (202) is connected with the lower end of a main converter access switch (306), the upper end of the main converter access switch (306) is connected with an alternating current total bus (308), an alternating current side interface of the secondary converter (203) is connected with an alternating current bus (304) of the secondary converter, the alternating current bus (304) of the secondary converter is connected with the lower end of the secondary converter access switch (305), the upper end of the secondary converter access switch (305) is connected with an alternating current total bus (308), the alternating current total bus (308) is connected with the upper ends of an alternating current total bus voltage sensor (307) and a system grid-connected switch (309), the lower end of the system grid-connected switch (309) is connected with a quick interface (310), and the alternating current total bus voltage sensor (307) is used for collecting bus voltage phasor U0, and the quick interface (310) is used for being connected with a power grid;

the system controller (101) is also used for controlling the switching of the primary converter access switch (306), the secondary converter access switch (305) and the system grid-connected switch (309).

2. The internal combustion engine asynchronous generator-energy storage cogeneration system of claim 1, wherein said internal combustion engine power generation module further comprises a genset access switch (303);

the secondary converter alternating current bus (304) is connected with the upper end of the generator set access switch (303), and an alternating current port of the asynchronous generator (302) is connected with the lower end of the generator set access switch (303);

the system controller (101) is used for controlling the generator set access switch (303) to be opened and closed.

3. The internal combustion engine asynchronous generator-energy storage combined power generation system according to claim 2, further comprising a reactive compensation module and a grid voltage sensor (311) and a grid current sensor (312);

the reactive compensation module comprises a capacitor (401) for reactive compensation, wherein the capacitor (401) for reactive compensation is connected to an alternating current port of the asynchronous generator (302) and is used for reactive compensation for starting the asynchronous generator (302);

The system controller (101) is connected to a power grid voltage sensor (311) and a power grid current sensor (312) and is used for collecting voltage phasors U0G and current values I0M on the power grid power supply side respectively.

4. The internal combustion engine asynchronous generator-energy storage combined power generation system according to claim 1, characterized in that the mechanical power P3D of the rated output of the internal combustion engine (301) is designed to be 1-1.5 times the rated output power P3N of the asynchronous generator (302), and p3n=2 (p1n+p2n) is designed, wherein P1N is the rated power of the main converter (202), P2N is the rated power of the sub-converter (203), and P2N is designed to be P3N which is not higher than 0.1 times the no-load starting power of the internal combustion engine (301) and the asynchronous generator (302).

5. A control method applied to the internal combustion engine asynchronous generator-energy storage combined power generation system according to any one of claims 1 to 4, characterized in that the system controller (101) performs the control steps of:

When the combined power generation system is in a power grid parallel operation mode, the main converter (202) is controlled to generate power in a constant power mode according to a power generation state and the energy storage residual quantity of the energy storage and BMS (201), the secondary converter (203) generates power in a power mode and starts an asynchronous generator (302) in a frequency/voltage control mode in an idle mode, and the power output of the main converter (202), the power output and frequency/voltage output of the secondary converter (203) and the rotating speed of the internal combustion engine (301) are controlled to meet the power demand of the power grid;

When the combined power generation system is in a power supply mode of a substituted power grid, the main converter (202) is controlled to maintain constant frequency/voltage mode support according to a power generation state and the energy storage residual quantity of the energy storage and BMS (201), the secondary converter (203) generates power in a power control mode, starts an asynchronous generator (302) in a frequency/voltage control mode in an idle mode, controls the frequency/voltage output of the main converter (202), and controls the power output and the frequency/voltage output of the secondary converter (203) and the rotating speed of the internal combustion engine (301) so as to meet the power demand of the power grid.

6. The control method according to claim 5, wherein the system controller (101) specifically performs the following operation control steps when the combined power generation system is in a grid parallel operation mode:

state one: when the power grid demand power P4 is not higher than the rated power P1N of the main converter (202) and the residual capacity SOC of the energy storage and BMS (201) is not lower than 20%, the main converter (202) and the secondary converter (203) are controlled to discharge in a power control mode, the output power P1=P1N of the main converter (202) is adjusted to be P4/(P1N+P2N), and the output power P2=P2N of the secondary converter (203) is adjusted to be P4/(P1N+P2N);

State two: when the power grid demand power P4 is not higher than the rated power P1N of the main converter (202), and the residual capacity SOC of the energy storage and BMS (201) is lower than 20%, the secondary converter access switch (305) is opened, the generator set access switch (303) is closed, the secondary converter (203) is controlled to idle the asynchronous generator (302) to the rated rotation speed in a frequency/voltage control mode according to the reactive power compensated by the reactive power compensation capacitor (401), the internal combustion engine (301) is started and controlled to operate in a low power mode of keeping the asynchronous generator (302) to operate at a constant speed, and after the secondary converter (203) is controlled to adjust the output voltage phasor U2 of the secondary converter to be synchronous with the voltage phasor U0 of the alternating current total bus voltage sensor (307), the working mode of the secondary converter (203) is changed into a power control mode while the secondary converter access switch (305) is closed, the output power of the main converter (202) is regulated, the output power of the secondary converter (203) and the rotating speed of the internal combustion engine (301) are regulated, so that the output power P1= (P4-P3) P1N/(P1N+P2N) of the main converter (202), the output power P2= (P4-P3) P2N/(P1N+P2N) of the secondary converter (203) and the output power of the asynchronous generator (302) are equal to or more than P4, when the energy storage and BMS (201) is charged to the state that the SOC is increased to 90%, the internal combustion engine (301) is closed, the generator set access switch (303) is opened, controlling the combined power generation system to recover the first operation;

State three: when the grid demand power P4 is higher than the rated power P1N of the main converter (202), but does not exceed the maximum output power P1M of the main converter (202) for 5 minutes, and when the grid demand power is increased gradually, the secondary converter is opened to switch on the switch (305) and the generator set to switch on the switch (303), the secondary converter (203) is controlled to carry out no-load soft start of the asynchronous generator (302) to the rated rotation speed in a frequency/voltage control mode according to reactive power compensated by the reactive compensation capacitor (401), the internal combustion engine (301) is started and controlled to operate in a low power mode in a constant speed operation mode of the asynchronous generator (302), the secondary converter (203) is controlled to adjust the output voltage phasor U2 of the secondary converter to be synchronous with the voltage phasor U0 of the alternating current total bus voltage sensor (307), the secondary converter is switched on to switch on the switch (305) from the frequency/voltage control mode to the power control mode, when the demand power P4 is higher than P3N and is not higher than P1N+P2N+P3N, the output power of the secondary converter (202) is adjusted to be equal to the rated rotation speed P1, and the output power of the secondary converter (202) and the output power of the internal combustion engine (202) is equal to P2P 1 and P2/(P2) is equal to P1.

7. The control method according to claim 6, wherein the system controller (101) further performs the following steps when the cogeneration system is in grid parallel operation mode:

The starting step: the method comprises the steps of connecting a quick interface (310) to a power grid, closing a system grid-connected switch (309), connecting a main converter to a switch (306) and connecting a sub-converter to a switch (305), starting the main converter (202) and the sub-converter (203) and controlling the main converter (202) and the sub-converter (203) to generate power in a constant power mode;

Closing: the internal combustion engine (301) is closed, the generator set access switch (303) is disconnected, the output power of the main converter (202) and the secondary converter (203) is adjusted to be-P1N and-P2N for charging, when the SOC of the energy storage and BMS (201) is charged to a set value, the secondary converter access switch (305) and the main converter access switch (306) are disconnected, the system grid-connected switch (309) is disconnected, and the quick interface (310) exits the power grid.

8. The control method according to claim 5, wherein the system controller (101) specifically performs the following operation control steps when the cogeneration system is in an alternative grid power mode:

state one: when the power grid demand power P4 is not higher than the rated power P1N of the main converter (202) and the residual capacity SOC of the energy storage and BMS (201) is not lower than 20%, controlling the main converter (202) to support the system frequency and voltage in a frequency/voltage control mode, controlling the secondary converter (203) to discharge in a power control mode and controlling the ratio of the real-time output power of the secondary converter (203) to the real-time output power of the main converter (202) to be P2N/P1N;

State two: when the power grid demand power P4 is not higher than the rated power P1N of the main converter (202), and the residual electric quantity SOC of the energy storage and BMS (201) is lower than 20%, the secondary converter access switch (305) is opened, the generator set access switch (303) is closed, the secondary converter (203) is controlled to carry out no-load soft start on the asynchronous generator (302) to the rated rotation speed according to reactive power compensated by the reactive compensation capacitor (401) in a frequency/voltage control mode, the internal combustion engine (301) is started and controlled to operate in a low power mode of keeping the asynchronous generator (302) operating at a constant speed, the secondary converter (203) is controlled to adjust the output voltage phasor U2 of the secondary converter and the voltage phasor U0 of the AC total bus voltage sensor (307), the secondary converter access switch (305) is closed, the working mode of the secondary converter (203) is changed into a power control mode, the main converter (202) is controlled to support the system frequency and the voltage in a frequency/voltage control mode, the output power P2 of the secondary converter (203) is adjusted to be equal to or more than (P4-P3) in a frequency/voltage control mode, the output power P2N/(P1 N+P2N), the output power of the secondary converter (203) is controlled to operate at a state of the asynchronous generator (302) at a constant speed, and the power of the power generator (201) is switched off when the power is equal to or more than 90% of the power system is switched off, and the power of the power generator is switched off, and the power system is switched off to the power system (301) and is switched to a state of the power mode;

State three: when the grid demand power P4 is higher than the rated power P1N of the main converter (202), but does not exceed the maximum output power P1M of the main converter (202) for 5 minutes, and the generator set is connected with the switch (305) in a gradually increasing mode, the secondary converter (203) is controlled to be in idle soft start with the asynchronous generator (302) to the rated rotating speed according to reactive power compensated by the reactive compensation capacitor (401), the internal combustion engine (301) is started and controlled to operate at low power in a mode of keeping the asynchronous generator (302) to operate at constant speed, after the secondary converter (203) is controlled to adjust the output voltage phasor U2 of the secondary converter to be synchronous with the voltage phasor U0 of the alternating current total bus voltage sensor (307), the secondary converter is connected with the switch (305) in a gradually increasing mode, the working mode of the secondary converter (203) is changed from the frequency/voltage control mode to the power control mode, when the demand power P4 is higher than P3N and not higher than P1N+P2N+P3N, the output power of the secondary converter (203) and the rotating speed of the internal combustion engine (301) are adjusted to enable the output power of the secondary converter (203) to be equal to P2 = P2P 2 to P3.

9. The control method according to claim 8, wherein the system controller (101) further performs the control step of, when the cogeneration system is in an alternative grid power mode:

The starting step: the method comprises the steps of switching in a quick interface (310) to a power grid, closing a grid-connected switch (309) of a system, switching in a switch (306) of a main converter and a switch (305) of a secondary converter, starting the main converter (202) and the secondary converter (203), controlling the main converter (202) and the secondary converter (203) to generate power in a constant power mode, improving the output power P1 of the main converter (202) and the output power P2 of the secondary converter (203), opening a grid sectionalizing switch until a grid current sensor (312) detects that the grid current amplitude I0M is lower than I0ML, changing a working mode from a constant power mode to a constant frequency/voltage mode to support after an alternating current total bus voltage sensor (307) detects that the bus voltage amplitude U0M is lower than U0ML, wherein U0ML is set to be 0.5-1 times of a rated voltage amplitude U0MN according to the detection precision of the grid current sensor (312), the control precision of the main converter (202) and the rated line current in the field;

Closing: and (3) adjusting the voltage phasor of the main converter (202) to enable the amplitude and the phase of each phase of the power grid voltage phasor U0G detected by the power grid voltage sensor (311), closing the power grid sectionalizing switch, controlling the main converter (202) to change the working mode from a constant frequency/voltage mode to a constant power mode for power generation when the system controller (101) detects that the power grid side current I0M is larger than I0ML through the power grid current sensor (312), closing the internal combustion engine (301), disconnecting the generator set access switch (303), adjusting the output power of the main converter (202) and the secondary converter (203) to be-P1N and-P2N for charging, charging the SOC of the energy storage and the BMS (201) to a set value, disconnecting the secondary converter access switch (305) and the main converter access switch (306), disconnecting the system grid-connected switch (309), and enabling the quick interface (310) to exit the power grid.