41 REACTIVE POWER COMPENSATION FOR RENEWABLE ENERGY SYSTEM WITH
COMPENSATING DEVICE: A REVIEW
Rohit Kumar Singh
Stream: Power System Engineering, University: KK University, Biharsharif Nalanda Mr. Amit Kumar
Assistant Prof., KK University, Biharsharif Nalanda
Abstract- This article introduces various aspects of the problem of reactive power control in wind farms. The first part provides some background information on the control of reactive power in wind farms. This includes motivations and applicable methods for using wind farms. In general, there are active (wind power generators, compensators) and passive methods (L, C) for static VAR compensation. In the proposed method, a wind power plant model (wind turbine, clover circuit, battery storage, transformer, cable route between the wind power plant and PCC, a model of a dual power induction generator (DFIG) based on a control system) is used.
In a wind power plant, as the low voltage rises, the clover protection changes from an ineffective power supply to an ineffective power load, which in turn increases the load on the residual current system.
Based on the Static Compensator, STATCOM synchronizes with the wind energy system and grid. STATCOM exchanges perceptible reactive power for capacitive reactive power. This limits system voltage fluctuations and maintains system voltage stability in the event of a failure. Wind turbine and STATCOM control and reactive power control strategies were explained with the help of basic operating principles and related models, and simulation of the actual system was performed with the help of PSCAD. Simulation results show that system maintenance with STATCOM improves wind turbine voltage.
Keywords: DFIG; bar; malfunction; reactive power coordination control; RTCCS.
1. INTRODUCTION
Wind energy is a renewable energy source generated from air currents flowing on the surface of the earth. Wind turbines can extract this kinetic energy and convert it into usable energy to power small (residential) or large (utility) homes, farms, schools, or business applications.
Wind energy is one of the fastest growing power sources in the world today and one of the fastest growing markets. These growth trends can be combined with the multifaceted benefits of wind energy, such as green power and sustainable and affordable economic development. Power factor is defined as the ratio of actual power to apparent power. This definition is often mathematically expressed as kW/kVA, where the molecule is active power (active power) and the denominator is (active power + reactive power) or
apparent power. Reactive power means that in an AC system, when voltage and current rise and fall at the same time, only active power is transferred, and when there is a time lag between voltage and current, both active power and reactive power are transferred. However, when you calculate the time average, there is an average active power that causes a net energy flow from one point to another, regardless of the grid or state of the system, but the average reactive power is zero.
For reactive power, as shown in Figure 1, the amount of energy flowing in one direction is equal to the amount of energy flowing in the opposite direction (or replacing capacitors, different parts of the inductor, reactive power). This means that no reactive power is generated or
42 consumed. Reactive power (vars) is
required to maintain the voltage to supply the actual power (watts) over the transmission line. Motor loads and other loads require reactive power to convert the flow of electrons into useful work. If the reactive power is too low, the voltage will drop and the power needed by the consumer will not be able to flow to the transmission line. Transformers, transmission lines, and motors require reactive power the schematic shows the reactive power requirement for a constant PF of 0.85 for two months.
Figure 1 Real, Reactive and complex power
In the event of a wind turbine failure, the wind turbine must maintain grid- connected operation within a certain voltage and time range. If not, you will need to shut down a large capacity wind farm. Failure to do so will significantly impair the functionality of the error system and may even lead to failure.
Double-fed induction generators (DFIGs) are widely used in China, most of which are fitted with a bar, a type of low voltage drive-through protector. Currently, research on clover devices and low-voltage
ride-through technologies focuses on two main aspects.
On the other hand, attention is paid to clover. The paper suggests that the key points for the DFIG wind turbine to maintain continuous grid connection operation in the event of a failure are the normal rotor current and the upper limit of the rotor connection bypass resistance from the clover to the stator current.
Reactive power can be provided at time.
On the other hand, in addition to clover protection, measures have been taken to improve the stability of low voltage passages. One solution is to limit the AC component of the rotor current caused by the stator current by improving the excitation current control strategy in the event of a system failure.
Alternatively, you can combine grid fault excitation control with regular wind power tracking control to get the generator up and running quickly again, improving the post-failure stability of the entire power system.
2 DFIG CHARACTERISTICS
Under normal operating conditions, the Double Feb induction generator (DFIG) can output reactive power, allowing the wind power plant to operate as a reactive power source to supply the reactive power of the power system. Therefore, DFIG operates with a kind of power control.
That is, reactive power is generated according to the system timetable. In the event of a power system failure, the voltage at the grid connection points drops rapidly, intervening with DFIG's clover protection, making the aforementioned power control modes difficult. Next, the rotor side of the DFIG is shortened by a protection circuit to become a winding induction generator that can supply reactive power to the system.
If a error occurs, the voltage drops rapidly. When the rotor current or DC bus voltage exceeds the critical value, DFIG's
43 low voltage ride-through begins. To
protect the converter, the clover conducts, all IGBTs (Insulated Gate Bipolar Transistors) on the rotor converter side are turned off, and the rotor current is shifted to the clover. DFIG is a winding induction generator that not only supplies reactive power to the system, but also needs to draw reactive power from the system to maintain normal operation. In addition, wind farms are converted from reactive power sources to reactive power loads, and if effective compensation control strategies are not implemented, the faulty system will need to be heavily loaded.
The STATCOM compensation unit built into the newspaper's RTCCS has this capability. When a power system failure occurs and protection is enabled, RTCCS controls the compensation unit to supply reactive power to the wind farm and failure system, quickly and continuously increasing the voltage level at the grid connection points. Allows DFIG to process quickly. It returns to the normal operating state. If protection is ineffective, RT CCS controls the compensation unit to provide reactive power support to faulty systems and wind farms, prevent protection effects and keep wind farms in normal grid connection operation
3 REACTIVE POWER CONTROL STRATEGY
Static VAR compensation using capacitor banks or inductors is ineffective and inaccurate, but is still widespread today.
In most cases, only the inductors found in the PCC are used. As a result, the power factor of wind farms is always inductive, but the rates are low. Therefore, active compensation was investigated to allow for more accurate control of reactive power. The main purpose of the compensation method is to operate the wind farm with a variable power factor (using PCC) within a specified range.
Wind farms equipped with such control
systems can participate in grid regulations. The
RTCCS provides static power compensation between wind farms, compensation units, and grid-connected systems through tuned real-time control.
A complete RTCCS consists of a control strategy for normal behavior and a control strategy for faulty behavior. The former is already mature. This white paper only discusses error condition control strategies.
STATCOM is connected to the low voltage side of the transformer in a wind farm. RTCCS controls wind farms and compensation units according to information collected from wind farms, STATCOMs, grid connection points, and power systems.
Without error, RTCCS runs in power control mode according to the system's reactive power instructions. If an error occurs, RTCCS adjusts the control strategy based on the clover's operational status. Wind farms can provide reactive power even if clover protection does not work. After that, RTCCS remains in power control mode, the compensation unit and the wind farm guarantee the voltage level of the grid connection points and disable power support to the fault system to keep the wind power plant in normal grid connection operation. After clover protection, the wind turbine will no longer be able to supply reactive power. The main control objective in that case is to maintain the grid-connected operation of the wind farm. The RTCCS goes into voltage regulation mode and the compensation unit is controlled to maximize the voltage level of the grid connection points in order to maintain and resume the grid connection operation of the wind turbine.
4 CONCLUSION
This article proposes a new RTCCS by combining the STATCOM Compensation Module with RTCCS. The new RTCCS
44 controls STATCOM to compensate for
DFIG's reactive power through the clover circuit. Filters are also used to compensate for reactive power on the grid side, increasing the voltage level of the system. This allows the wind farm to operate more stably thanks to the low voltage.
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