Energy storage converters PCS are widely used in power systems, rail transit, military industry, petroleum machinery, new energy vehicles, wind power generation, solar photovoltaics and other fields to achieve energy in grid peak shaving and valley filling, smoothing new energy fluctuations, and energy recovery and utilization. Two-way flow, actively support the grid voltage and frequency, and improve the quality of power supply. This article will tells you what is a PCS and how does it works in a energy storage system.
A high quality PCS or right PCS is signeficant for a commercial energy storage system.
What is a PCS?——A definition of energy storage converter
As one of the important forms of large-scale energy storage systems, battery energy storage has many uses such as peak regulation, valley filling, frequency regulation, phase regulation, and emergency backup. Compared with conventional power sources, large-scale energy storage power stations can adapt to rapid changes in load, and play an important role in improving the safe and stable operation level of the power system, as well as the quality and reliability of power supply. The overall energy saving and consumption reduction of the power system can improve the overall economic benefits.
In the electrochemical energy storage system of Power Conversion System (PCS), a device connected between the battery system and the power grid (and/or load) to realize bidirectional conversion of electric energy, which can control the charging and discharging process of the battery , carry out AC-DC conversion, and can directly supply power to AC load in the absence of power grid.
PCS consists of DC/AC bidirectional converter, control unit, etc. The PCS controller receives background control commands through communication, and controls the converter to charge or discharge the battery according to the sign and size of the power command, so as to adjust the active power and reactive power of the grid. At the same time, the PCS can communicate with the BMS through the CAN interface, dry contact transmission, etc., to obtain the battery pack status information, which can realize the protective charging and discharging of the battery and ensure the safe operation of the battery.
- “Technical Regulations for Testing of Energy Storage Converters”
- “Technical Specification for Energy Storage Converter of Battery Energy Storage System”
- GB/T 14549 Power Quality Harmonics of Public Grid
- GB/T 15543 Power Quality Three-phase Voltage Unbalance
- GB/T 15945 Power Quality Power System Frequency Deviation
- GB/T 12325 Power Quality Supply Voltage Deviation
Regular PCS products
Introduction of PCS
How does PCS works
The energy storage bidirectional converter (PCS) is an AC/DC side controllable four-quadrant operation converter device, which realizes the AC-DC bidirectional conversion of electric energy. PCS can realize the two-way energy transfer between the DC battery and the AC power grid of the battery energy storage system, and realize the charge and discharge management of the battery system, the tracking of the load power on the grid side, the control of the charge and discharge power of the battery energy storage system, and the control strategy through the control strategy. Control of grid-side voltage in off-grid operation mode, etc.
Function and features
The main function of the energy storage converter is that under the condition of grid connection, the energy storage system performs constant power or constant current control according to the microgrid monitoring instructions, charges or discharges the battery, and at the same time smoothes the output of fluctuating power sources such as wind power and solar energy; the microgrid Under certain conditions, the energy storage system acts as the main power supply to provide the voltage and frequency support (V/F control) of the microgrid, and the load in the microgrid works based on this voltage and frequency. The PCS adopts double closed-loop control and SPWM pulse modulation method, which can adjust the output voltage, frequency, active and reactive power accurately and quickly.
Basic control functions
- Grid-connected constant power charge and discharge control
- Grid-connected constant voltage current limiting charging
- Off-Grid V/F Control
Reactive power regulation control
- On-grid-off-grid smooth switching control
- Anti-islanding protection function and islanding detection for mode switching function Fault ride-through control function
Basic protection functions
- Battery reverse polarity protection
- DC overvoltage protection
- DC overcurrent protection
- Grid side over/under voltage protection
- Grid side overcurrent protection
- Grid side over/under frequency protection
- IGBT module overcurrent protection
- IGBT module over temperature protection
- Transformer/Reactor Overtemperature Protection
- Lightning protection Unplanned island protection
Advantage to use the PCS
The unique mode switching smooth control technology ensures that the two modes of grid-connected and off-grid are switched without impact, ensuring the reliable operation of the converter. Ensure that the active power and reactive power are increased or decreased as required when the converter is connected to the grid; the load voltage and frequency are stabilized when operating independently.
- The integrated design of charging and discharging realizes the bidirectional flow of energy between the AC system and the DC system;
- Efficient vector control algorithm to realize active and reactive decoupling control;
- The power factor can be adjusted arbitrarily, and all reactive power can be generated within the capacity range to realize reactive power compensation;
- Under the dispatch of MEMS (Microgrid Energy Management System), actively participate in the peak regulation of the power grid to effectively relieve the pressure of the large power grid;
- Support grid-connected operation and off-grid operation; and can realize smooth and seamless switching between grid-connected and off-grid;
- Supports the operation of the micro-grid, and can provide stable voltage and frequency support for the micro-grid;
- The combination of active and passive islanding detection methods meets the UL1741 standard;
- Perfect relay protection function to effectively prevent abnormal damage to the inverter;
- Support a variety of energy storage batteries, different models only have different controller software;
- Provide CANbus, RS485, can communicate with battery management system (BMS), upper monitoring system;
- Multiple PCS can realize multi-machine parallel operation;
- Support short-term short-circuit operation mode on AC side;
- Support self-synchronization function;
- High reliability cabinet design to meet the needs of different operating areas;
- The main power loop adopts high reliability power module;
“The high efficiency of CMX energy storage system is ensured by the advanced Fe battery technology and the intelligent battery management system. CMX self-developed Fe battery system is environmental friendly and has excellent safety performance. Special designed for the CMX battery, the unique technology of CMX BMS can give smart control and protection to the system.”
Application of PCS
Energy storage converters are widely used in power systems, rail transit, military industry, petroleum machinery, new energy vehicles, wind power generation, solar photovoltaics and other fields to achieve energy in grid peak shaving and valley filling, smoothing new energy fluctuations, and energy recovery and utilization. Two-way flow, actively support the grid voltage and frequency, and improve the quality of power supply.
- It can be used in distributed power generation systems such as wind energy and solar energy to ensure the balance and continuity of distributed power supply, effectively improve its power output quality, and improve the ability to connect to the power grid.
- It can be used in power system stability. It can respond to load fluctuations through rapid electrical energy storage, absorb excess energy or supplement the lack of energy, realize dynamic adjustment of high power, and adapt to frequency adjustment and voltage power factor correction. Improve the stability of system operation.
- It can be used as an emergency power supply to provide users with electrical energy during the power outage of the large power grid or other power sources to improve the reliability of the power supply.
- It can be used for peak shaving and valley filling in the power grid, which can alleviate the contradiction between supply and demand on the user side, reduce the investment of power generation equipment, improve the utilization rate of power equipment, and reduce line losses.
- It can be used in the micro-grid as the main power supply to provide the voltage and frequency support of the micro-grid, so that wind power and photovoltaics can contribute to the micro-grid and supply power to the regional loads.
- It can be used for various types of energy storage components to realize flexible interface between energy storage and power grid, and can meet the requirements of independent or grid-connected operation.
How to select a right PCS for your commercial HV Energy storage system
From our other artic, we have already learnd what is PCS, Advantage of the PCS. Also application about PCS. In this article, we will learn baisc calculation on how to select the right PCS for the commercial energy storage system.
Energy storage converters PCS are widely used in power systems, rail transit, military industry, petroleum machinery, new energy vehicles, wind power generation, solar photovoltaics and other fields to achieve energy in grid peak shaving and valley filling, smoothing new energy fluctuations, and energy recovery and utilization. Two-way flow, actively support the grid voltage and frequency, and improve the quality of power supply. This article will take you to unlock the skills of quick selection of energy storage converters.
Quick selection method and related calculation on selecting PCS
The configuration of the energy storage converter is generally determined according to the actual load in the microgrid and the energy capacity of distributed generation. Loads are divided into important loads (computer room, office, monitoring and other loads) and non-important loads (air conditioning, lighting, boilers, door guards and other loads). The load data generally needs to be measured on site, and the time-sharing data of working days and holidays is generally measured. And excerpts from the typical time of the four seasons for a comprehensive analysis of the data.
Capacity matching of energy storage converters
The energy storage capacity is configured according to 1.2 times the load capacity. If the important load reaches 200kW, it is recommended to configure a 250kW energy storage converter. If other loads need to run off-grid, the energy storage power ratio should be increased accordingly.
Transformer ratio of energy storage converter
The transformer transformation ratio of the energy storage converter is determined by the DC voltage input range (that is, the battery voltage range). The calculation method is as follows:
Transformer transformation ratio = Ul (minimum battery voltage)/1.414. If the voltage range of the iron-lithium battery is 360~480VDC, 360/1.414=254, the transformer ratio can be determined as 200.
If the configuration without a transformer is selected, the minimum voltage of the battery must be above 540V before it can be connected to the 400V power grid.
Additional function configuration of energy storage converter
Self-synchronization function (S):
The energy storage converter can realize seamless on-grid switching without other devices. On the premise that the grid-connected switch can be controlled remotely, the energy storage converter can issue commands when it is running from on-grid to off-grid. Open the grid-connected switch, and issue an instruction to close the grid-connected switch when it is running from off-grid to grid-connected (the closing condition is judged by the converter, and cannot be closed manually);
Supercapacitor charger function (C):
When the energy storage converter is connected to the supercapacitor product, it can start charging the supercapacitor from 0 voltage, and charge and discharge when the supercapacitor voltage reaches the operating voltage, replacing the role of the traditional charger.