CN202309538U - Standard converting device of electric automobile and distributed power source - Google Patents

Abstract

The utility model discloses a standardized converter device for an electric vehicle and a distributed power supply. 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 utility model is composed of a 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 They are respectively transmitted to the grid-side power module, user-side power module and electric vehicle charging and discharging module, and the controller communicates with a background server through Ethernet. The utility model 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

A standardized converter device for electric vehicles and distributed power sources

technical field

The utility model relates to the field of power supply and utilization, in particular to a standardized converter device for an electric vehicle and a distributed power supply. the

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". the

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 sources in traditional power systems 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. the

(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. the

(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. the

(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. the

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. the

(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. the

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. . the

Utility model content

The utility model provides a standardized converter device for an electric vehicle and a distributed power supply, which realizes the effective isolation of the distributed power supply and the power grid, so as to ensure the power quality requirements of high-end users and prevent heavily polluted power users from injecting power into the power grid. And ensure that the distributed generation system is properly utilized. the

For this reason, the utility model 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, and a user-side power module connected to the user CSM and the electric vehicle charging and discharging module EVM for energy storage, the user side power module CSM and the electric vehicle charging and discharging module EVM are connected 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, 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. the

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

The control strategy of the standardized converter device for the above-mentioned electric vehicles and distributed power sources 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

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

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

The utility model 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 The power supply of distributed energy solves the problem of natural fluctuation of distributed energy power, and realizes the two-way controllable flow of power between the public distribution network and the user side; 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 electricity price adjustments, and can also sell power battery power to the grid to obtain certain economic benefits. Benefits; for the power grid, it can also play a role in peak shaving and valley filling, increasing load rate and reducing the total installed capacity of the system. the

The utility model will be described in further detail below in conjunction with the accompanying drawings and specific embodiments of the description. the

Description of drawings

Fig. 1 is the structural diagram of the standardized converter device of the utility model (in the figure 1 represents active power exchange, 2 represents reactive power exchange, 3 represents public connection point, 4 represents user AC system, 5 represents load, 6 represents distributed power supply, 7 represents the public power distribution network, and 8 represents the electric vehicle power battery). the

Fig. 2 is a schematic circuit diagram of the standardized converter device of the present invention (in the figure, 5 represents a load, 6 represents a distributed power supply, 7 represents a public power distribution network, and 8 represents an electric vehicle power battery). the

Fig. 3 is a schematic diagram of the main circuit of the utility model USM. the

Fig. 4 is a schematic diagram of the USM closed-loop control of the utility model. the

Fig. 5 is a schematic diagram of the main circuit of the utility model CSM. the

6 is a schematic diagram of the main circuit of the utility model EVM. the

Fig. 7 is the control schematic diagram of the utility model (in the figure, 1 represents active power exchange, 2 represents reactive power exchange, 3 represents public connection point, 4 represents user AC system, 5 represents load, 6 represents distributed power supply, 7 represents public distribution Power grid, 8 means electric vehicle power battery, 9 means grid data, 10 means battery data, 11 means controller, 12-Ethernet, 13-background monitoring software module, 14-LCD display unit). the

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

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 the connection between the intermediate DC bus and the distributed power supply. Bidirectional control of active and 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

The circuit structures of USM and CSM are basically the same, and 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. the

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. the

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. the

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

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. the

2. Customer side power module (CSM)

CSM operates as a fundamental sinusoidal voltage source in this utility model, so the control of CSM is a kind of voltage control, by controlling its three-phase output voltage to be a symmetrical sinusoidal voltage, so as to realize the CSM system for the load terminal under non-ideal load conditions Voltage requirements, that is, the output voltage always maintains a symmetrical rated sinusoidal voltage. For the 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 . the

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

The utility model 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 Figure 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. the

3. Electric vehicle charging and discharging module (EVM)

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. the

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. the

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. the

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

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. the

As shown in Figure 7, the controller collects the grid data of the public distribution network and distributed power, 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. the

Claims (4)

1. A standardized converter device for electric vehicles and distributed power sources, 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 an electric vehicle charger for energy storage The discharge module EVM, the user side power module CSM and the electric vehicle charging and discharging module EVM are connected in parallel and then connected in series with the grid side power module USM; 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 power distribution network and the distributed power supply, and the controller communicates with a background server through Ethernet. 2. The standardized converter device for electric vehicles and distributed power sources according to claim 1, characterized in that the grid-side power module USM is composed of controllable devices to form a three-phase full-bridge rectifier circuit, connected through a transformer or directly public distribution network. 3. The standardized converter device for electric vehicles and distributed power sources according to claim 1 or 2, characterized in that the user-side power module CSM is composed of controllable devices to form a three-phase full-bridge inverter circuit, through a transformer or Directly connected to the user-side distributed power supply. 4. The standardized converter device for electric vehicles and distributed power sources according to claim 3, characterized in that the electric vehicle charging and discharging module EVM is a buck-boost chopper circuit composed of controllable devices, and electric vehicle power battery interface. the

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