CN102029926A - Standardized current conversion device of electric vehicle and distributed power source - Google Patents

Abstract

The invention discloses a standardized converter device suitable for connecting electric vehicles and distributed power sources to public distribution networks. The current distributed power generation cannot be effectively isolated from the power grid, and cannot guarantee the power quality requirements of high-end users, nor can it prevent heavy polluting power users from injecting power into the power grid. The invention consists of a power grid side module, a user side module, an electric vehicle charging and discharging module, and a controller. The user side power module is connected in parallel with the electric vehicle charging and discharging module and then connected in series with the grid side power module. The trigger pulse signal generated by the controller passes through the optical fiber respectively. The data is transmitted to the grid-side power module, the user-side power module, and the electric vehicle charging and discharging module. The controller communicates with a background server through Ethernet, and the background server is equipped with a background monitoring software module. The invention can realize the effective isolation of the distributed power supply and the power grid, and can also take into account the functions of dynamic reactive power compensation, fault current limitation, power quality control and the like.

Description

Standardized converters for electric vehicles and distributed power

technical field

The invention relates to the field of power supply and utilization, in particular to a standardized converter device for electric vehicles and distributed power sources.

Background technique

With the continuous expansion of the grid scale, the disadvantages of large-scale power systems are becoming more and more prominent, such as high cost, inflexible operation control, difficulty in adapting to the increasingly high reliability requirements of users, inability to flexibly track load changes and diversified electric energy Quality needs. Scholars began to study the development model of the future power system. Obviously, simply expanding the scale of the power grid cannot meet the requirements. Therefore, European and American power experts proposed a distributed power grid with less pollution, high reliability, low investment, flexible power generation methods, and compatibility with the environment. The way of joint operation of power generation and large power grid. For example, the European Union has implemented the project "Integrated Application of Renewable Energy and Distributed Power Generation in European Power Grid", and the United States has proposed projects such as "Smart Grid" and "Advanced Distribution Automation".

With my country's strong support for renewable energy, distributed power generation has emerged as an emerging power generation model. This small-capacity generator set provides power near the distribution network users and becomes a supplement to centralized power generation. Common distributed power sources include small internal combustion engines, solar photovoltaics, and micro fans. However, the introduction of distributed power in the traditional power system has brought many problems to the security and stability of the power grid, mainly including:

(1) Operation control: The scheduling and operation of distributed power sources are controlled by the property owners of the power sources, which cannot be effectively regulated.

(2) Output power fluctuations: The active input of distributed power sources using wind energy and solar energy has natural volatility, so the output power of distributed power sources fluctuates greatly, with a high degree of uncertainty, which is likely to cause flicker due to grid voltage fluctuations.

(3) Harmonic pollution: Distributed power sources often use rectification and inverter devices to connect to the power grid, which will output a large number of multiple harmonic currents to the power grid.

(4) Reactive power: Most wind turbines use asynchronous motors. When the speed of the wind turbine decreases, it needs to absorb a large amount of reactive power from the grid.

With the upgrading of my country's industry, electric energy, as a commodity, is becoming more and more refined, and more and more power users have higher and higher requirements for power quality, which are specifically reflected in:

(1) Loads sensitive to power quality: such as semiconductor production plants, paper mills, etc., if the voltage drops for tens of milliseconds, the production equipment will not work normally and a large amount of waste products will appear.

(2) The load itself is a source of pollution: With the development of metallurgical industry, chemical industry and electrified railway in our province, nonlinear loads (silicon rectifier equipment, electric locomotives, electrolytic equipment) and impact loads (electric arc furnace, Rolling mill) makes the harmonic pollution, asymmetry (negative sequence) and volatility of the power grid increasingly serious.

Therefore, in order to ensure the safety and reliability of the power grid, it is very urgent and necessary to remotely schedule the output power of distributed power generation and strengthen supervision. Therefore, it is very necessary to develop a general-purpose access control technology to ensure the power quality requirements of high-end users, prevent heavily polluted power users from injecting power into the grid, and ensure the rational use of distributed power generation systems. .

Contents of the invention

The invention provides a standardized converter device for electric vehicles and distributed power sources, which can effectively isolate distributed power sources from the power grid to ensure high-end users' demand for power quality, prevent heavily polluted power users from injecting power into the power grid, and Ensure that the distributed generation system is properly utilized.

To this end, the present invention adopts the following technical solution: a standardized converter device for electric vehicles and distributed power sources, which is characterized in that it includes a grid-side power module USM connected to the public distribution network, a user-side power module CSM connected to users, and For the electric vehicle charging and discharging module EVM for energy storage, the user side power module CSM is connected in parallel with the electric vehicle charging and discharging module EVM and then connected in series with the grid side power module USM;

The grid-side power module USM is composed of controllable devices to form a three-phase full-bridge rectifier circuit, which can be connected to the public distribution network through a transformer or directly, and can operate in four quadrants to realize bidirectional control of active power and reactive power with the public distribution network ; The user-side power module CSM is composed of controllable devices to form a three-phase full-bridge inverter circuit, which can be connected to the user-side distributed power supply through a transformer or directly, and can run in four quadrants to realize active power between the intermediate DC bus and the distributed power supply. , two-way control of reactive power; the electric vehicle charging and discharging module EVM is a buck-boost chopper circuit composed of controllable devices, which interfaces with the electric vehicle power battery to charge or discharge the power battery, and the USM and CSM are each composed of 6 Composed of two controllable devices (such as IGBT), it is a voltage source converter with the same structure;

The trigger pulse signal generated by the controller is respectively transmitted to the grid-side power module USM, the user-side power module CSM, and the electric vehicle charging and discharging module EVM through optical fibers, and the controller communicates with a liquid crystal display unit and an electric vehicle power battery management system BMS respectively. , the controller collects the grid data of the public distribution network and the distributed power supply, the controller communicates with a background server through Ethernet, and the background server is equipped with a background monitoring software module.

If the user does not install a distributed power supply or the installed capacity of the distributed power supply on the user side is smaller than the load, the AC power on the public distribution network side is rectified by the USM and converted into DC power, part of which is used to charge the power battery of the electric vehicle through the EVM, and part of which is reversed through the CSM. become AC power supply load. If the installed capacity of the user-side distributed power supply is greater than the load, the excess electricity will be rectified into direct current through CSM, part of it will be charged to the power battery of electric vehicles through EVM, and part will be converted into alternating current through USM and sold to the public distribution network. If the public distribution network fails and the power is cut off, the electricity in the power battery of the electric vehicle is supplied to the user through the EVM and the CSM, which can maintain uninterrupted power supply for a period of time. If the installed capacity of the user-side distributed power is less than the load or the user-side distributed power is temporarily unable to generate power due to natural conditions, but it is desired to keep the output power of the user-side distributed power constant for a period of time, the electricity in the power battery will pass through the EVM and The USM feeds the public distribution network and keeps the output power constant. If the user's AC system is exporting electric energy to the public distribution network and wants to reduce the electric energy output by the user, the output power of the USM can be directly and remotely controlled through the background monitoring software module.

The control strategy of the standardized converter device for the above-mentioned electric vehicle and distributed power supply is as follows:

The grid-side module USM adopts a control strategy for stabilizing DC voltage. When the battery is charging or powering user loads from the public distribution network, the USM works in the rectification state to maintain the stability of the DC side voltage; when the battery or user AC system supplies power to the public distribution network When the grid injects active power, the USM works in the inverter state to maintain the stability of the DC side voltage; when the USM outputs reactive power, it also stabilizes the DC bus voltage through closed-loop control of the active component.

The user-side module CSM adopts a control strategy of constant frequency and constant AC voltage amplitude to maintain the user-side voltage amplitude and frequency within the required range, and the voltage phase and frequency of the user-side distributed power supply and CSM are kept in sync.

The electric vehicle charging and discharging module EVM uses a constant DC current control strategy to maintain a constant DC output current on the battery side, realizes constant current charging or constant current discharging of the battery and has a constant current and voltage limiting function, that is, when the battery charging voltage is higher than the upper limit or discharge voltage When it is lower than the lower limit, it will automatically switch to stable voltage operation.

The invention can realize the effective isolation of the distributed power supply and the power grid, and can also take into account functions such as dynamic reactive power compensation, fault current limitation, and power quality control; through the power exchange between the distributed power supply and the power battery of the electric vehicle, and the power battery's load Power supply solves the problem of natural fluctuations in distributed energy power, and realizes the two-way controllable flow of power between the public distribution network and the user side; the user AC system can be softly connected to the grid, softly disconnected under the control of the dispatcher, and even in the Connected to the grid when it is not synchronized with the public distribution network; users can use distributed power sources or grid power to charge electric vehicle power batteries according to peak and valley power price adjustments, and can also sell power battery power to the grid to obtain certain economic benefits ; For the power grid, it can also play the role of peak shaving and valley filling, increasing load rate and reducing the total installed capacity of the system.

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a structural diagram of a standardized converter device of the present invention.

Fig. 2 is a schematic circuit diagram of the standardized converter device of the present invention.

Fig. 3 is a schematic diagram of the main circuit of the USM of the present invention.

Fig. 4 is a schematic diagram of the USM closed-loop control of the present invention.

Fig. 5 is a schematic diagram of the main circuit of the CSM of the present invention.

FIG. 6 is a schematic diagram of the main circuit of the EVM of the present invention.

Fig. 7 is a control schematic diagram of the present invention.

Detailed ways

As shown in Figure 1-2, the standardized converter device for electric vehicles and distributed power supplies consists of a grid-side power module USM connected to the public distribution network, a user-side power module CSM connected to users, and an electric vehicle for energy storage The charging and discharging module EVM is composed of the user side power module CSM and the electric vehicle charging and discharging module EVM in parallel and then connected in series with the grid side power module USM.

The grid-side power module USM is composed of controllable devices to form a three-phase full-bridge rectifier circuit, which can be connected to the public distribution network through a transformer or directly, and can operate in four quadrants to realize bidirectional control of active power and reactive power with the public distribution network ; The user-side power module CSM is composed of controllable devices to form a three-phase full-bridge inverter circuit, which can be connected to the user-side distributed power supply through a transformer or directly, and can run in four quadrants to realize active power between the intermediate DC bus and the distributed power supply. . Two-way control of reactive power; the electric vehicle charging and discharging module EVM is a buck-boost chopper circuit composed of controllable devices, which interfaces with the electric vehicle power battery to charge or discharge the power battery.

The circuit structures of USM and CSM are basically the same, both are composed of IGBT three-phase full-bridge circuit, LC filter unit and switchgear. EVM is composed of DC/DC step-up and step-down chopper circuit, LC filter circuit and switchgear, etc., which will be described in detail below. 1. Grid side power module (USM)

The schematic diagram of the USM main circuit is shown in Figure 3. Before starting the device, first manually close the AC side incoming line switch K1, then close the soft start contactor K3, the AC power supply charges the DC side capacitor through the resistance, and close the main contactor K2 when the DC side voltage reaches the set value, and the main circuit is completed Power-on. Then the trigger pulse can be turned on, and the device enters closed-loop grid-connected operation.

USM can operate in four quadrants, adopts active/reactive component decoupling control technology, can output both inductive reactive power and capacitive reactive power, can output continuously adjustable reactive power according to grid requirements, and participates in the voltage/reactive power of the grid Reactive power control: It can output active power and absorb active power, and provide a channel for two-way exchange of active power between the subsequent CSM and EVM and the grid. At the same time, USM adopts active power factor correction technology, the power factor of the grid side can reach more than 0.99, and the current harmonic distortion rate is less than 5%, which will not cause harmonic and reactive power pollution to the grid.

There are many control schemes for the three-phase grid-connected converter. The present invention adopts the vector control technology based on the rotating coordinate system, and the closed-loop control block diagram is shown in FIG. 4 . Due to the coupling between the d-axis and the q-axis of the system under the rotating d, q coordinate system, this coupling caused by the rotation 3/2 transformation will greatly affect the dynamic performance of the system. The present invention adopts a method based on the rotation d , The state feedback decoupling control scheme of the q coordinate system, which introduces the current state of the d axis and the q axis in the two-phase rotating coordinate system, and realizes the decoupling between the d axis and the q axis in real time through the state feedback matrix process.

In the rotating coordinate system, the component of the output current on the d-axis represents the active current component, and the component on the q-axis represents the reactive current component. Through the decoupling control between the d and q axes, its output is realized Independent control of active and reactive currents. Among them, the setting of reactive current can be adjusted according to the needs of scheduling or system, while the setting of active current needs to be generated by the closed-loop regulator of DC side voltage. The USM realizes the balance of power exchange between the AC side and the DC side through the stable control of the DC bus voltage.

2. Customer side power module (CSM)

CSM operates as a fundamental sinusoidal voltage source in the present invention, so the control of CSM is a kind of voltage control, by controlling its three-phase output voltage to be a symmetrical sinusoidal voltage, thereby realizing the CSM system for the load terminal voltage under non-ideal load conditions Requirements, that is, the output voltage always maintains a symmetrical rated sinusoidal voltage. For a three-phase four-wire voltage source converter, the key to its voltage control technology is how to overcome the influence of load imbalance and nonlinearity on the output voltage of the converter, and maintain the output voltage of the converter as the desired symmetrical sinusoidal voltage .

In practical applications, the user-side power system is generally a three-phase four-wire system, and the three-phase load may have serious imbalances. Since the three-phase three-wire inverter cannot provide a neutral line, the unbalanced operation will have a serious impact on the quality of its output voltage waveform. There are many schemes for the three-phase four-wire inverter power supply system. The commonly used scheme is to add a bridge arm to form the midpoint, and connect the common point of the three-phase output (that is, the neutral point) to the bridge arm to form a four-phase inverter. Bridge arm structure. The added bridge arm in the three-phase four-leg inverter can directly control the neutral point voltage, and generate a neutral point current to flow into the load, which adds a degree of freedom, so that the three-phase four-leg inverter power supply has three independent The controllable voltage of the three-phase output voltage is completely decoupled, so that it has the ability to maintain the symmetrical output of the three-phase voltage under unbalanced load.

The present invention adopts the scheme of adding a Dyn11 power frequency isolation transformer to the output of the three-phase three-wire inverter, and provides a neutral line through the transformer. The circuit schematic diagram is shown in FIG. 5 . The CSM interfaces with the user-side distributed power system and can operate in four quadrants. It can output both inductive reactive power and capacitive reactive power, and can output continuously adjustable reactive power according to the requirements of the user-side power grid. The CSM works in the inverter state, which can output active power and absorb active power. When the active power on the user side is insufficient, the power of the DC bus can be inverted and provided to the load on the user side, and when the power on the user side is excessive, the power can also be fed back to the bus on the DC side. CSM adopts SPWM technology and voltage waveform control technology, which can provide stable and high-quality electric energy for the user grid.

3. Electric vehicle charging and discharging module (EVW)

The interface between EVM and electric vehicle power battery can control the charging or discharging of the battery. It can not only store the grid power or user-side excess power in the battery, but also release the battery energy to the grid or user-side power grid. Its main circuit As shown in Figure 6.

Before the device is started, the relay K1 is first closed, the battery side capacitor is charged through the soft-start resistor, and the contactor K2 is closed when the voltage is established. After the main circuit is powered on, it can enter charging/discharging/standby operation.

When the EVM is working in the charging state, S2 is blocked. At this time, S2 is equivalent to a diode. The main circuit in Figure 6 is equivalent to a step-down chopper circuit. By adjusting the duty cycle of the PWM pulse of S1, the output of the step-down chopper circuit can be adjusted. Voltage, so as to maintain a constant charging current, when the charging is completed, it will enter the constant voltage operation mode.

When the EVM is working in the discharge state, S1 is blocked. At this time, S1 is equivalent to a diode. The main circuit in Figure 6 is equivalent to a boost chopper circuit. By adjusting the duty cycle of the PWM pulse of S2, the boost chopper circuit can be adjusted. Output voltage, so as to maintain a constant discharge current, when the discharge is completed, it will enter the standby mode.

The closed-loop control of EVM adopts the classic PID regulator. In the constant current section, the battery charging/discharging current is used as the control quantity, and in the constant voltage section, the output voltage is used as the control quantity. The output of the PID regulator is compared with the triangular carrier to generate a trigger pulse signal.

As shown in Figure 7, the controller collects the grid data of the public distribution network and distributed power generation, and the trigger pulse signal generated by the controller is transmitted to the grid-side power module USM, user-side power module CSM, and electric vehicle charging and discharging module through optical fibers. EVM. The controller adopts RS232 liquid crystal display unit communication to realize the interactive function of man-machine interface; adopts CAN interface to communicate with BMS, the management system of electric vehicle power battery, to exchange battery data; communicates with the background server through Ethernet, and the background server is equipped with background monitoring software The module realizes the control function of remote scheduling through the background monitoring software module.

Claims (9)

1. the normalisation current converter of electronlmobil and distributed power source, it is characterized in that it comprise the grid side power model USM that connects public distributing net, connect the user user side power model CSM, be used for electronlmobil charge-discharge modules EVM, controller and the background monitoring software module of energy storage, connect with grid side power model USM after user side power model CSM and the electronlmobil charge-discharge modules EVM parallel connection;

Described grid side power model USM forms three-phase bridge rectification circuit by controllable devices, by voltage transformer or directly insert public distributing net, can four quadrant running, and realize meritorious, idle two-way control with public distributing net; Described user side power model CSM forms the three phase full bridge inverter circuit by controllable devices, by voltage transformer or directly insert the user side distributed power source, can four quadrant running, and realize two-way control meritorious, idle between intermediate dc bus and the distributed power source; The stepping-up/stepping-down chopper circuit that described electronlmobil charge-discharge modules EVM is made up of controllable devices with the electric automobile power battery interface, carries out charge or discharge to electrokinetic cell;

The start pulse signal that controller produces is transferred to grid side power model USM, user side power model CSM and electronlmobil charge-discharge modules EVM respectively by optical fiber, controller respectively with the management system BMS communication of a liquid crystal display and an electric automobile power battery, controller is gathered the electric network data of public distributing net and distributed power source, controller is equipped with the background monitoring software module by an ethernet and a background server communication in the background server.

2. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, it is characterized in that if the generating capacity that the user does not install distributed power source or distributed power source during less than load, the alternating current of public distributing net side is transformed to direct current (DC) through after the rectification of USM, part is given electric automobile power battery charging by EVM, and part is that alternating current is supplied with load by the CSM inversion.

3. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, it is characterized in that if user side distributed power source generating capacity greater than when load, the redundance electricity is a direct current (DC) by the CSM rectification then, part is given electric automobile power battery charging by EVM, and part is that alternating current is sold to public distributing net by the USM inversion.

4. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, it is characterized in that if public distributing net et out of order and when cutting off the power supply, electricity in the electric automobile power battery is supplied with the user by EVM and CSM, can keep the uninterrupted power supply in a period of time.

5. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, the generating capacity of user side distributed power source it is characterized in that if temporarily can't generate electricity owing to natural conditions limit less than load or user side distributed power source, but wish that user side distributed power source horsepower output keeps the constant of a period of time, then the electricity in the electrokinetic cell is supplied with public distributing net by EVM and USM, keeps horsepower output constant.

6. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, it is characterized in that if user's AC system is exported electric energy to public distributing net, and wish to reduce the electric energy that the user exports, then pass through the horsepower output of the direct Long-distance Control USM of background monitoring software module.

7. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, it is characterized in that described grid side module USM adopts the control policy of stable DC voltage, when battery charge or from public distributing net is customer charge when power supply, and USM is operated in rectification state to keep the stable of dc voltage; When battery or user's AC system when public distributing net injects active volt-amperes, USM is operated in inverter mode to keep the stable of dc voltage; Also come the stable DC bus voltage during USM output reactive volt-amperes by closed loop control to active component.

8. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, it is characterized in that described user side module CSM adopts decides the control policy that frequency is decided the alternating-current voltage/AC voltage amplitude, keep user side voltage magnitude and frequency in claimed range, the voltage-phase of user side distributed power source and CSM and frequency keep synchronously.

9. the normalisation current converter of electronlmobil according to claim 1 and distributed power source, to keep electrokinetic cell side average anode current constant with deciding the DC current control policy to it is characterized in that described electronlmobil charge-discharge modules EVM, realization is to the constant-current charge or the constant current discharge of storage battery and possess constant current pressure limiting function, promptly is lower than and changes voltage regulation operation down in limited time automatically over to when battery charging voltage is higher than the upper limit or sparking voltage.

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