Analysis of power losses for instantaneous compensation of three-phase four-wire systems

This paper deals with the effect that the instantaneous compensation in three-phase four-wire systems, including or not the compensation of the neutral current, has on the supply line power losses. Thus, for three-phase circuits, the instantaneous compensation criterion has been established based on the instantaneous power theory. According to the instantaneous value concept the noninstantaneous power current is reduced, without altering the instantaneous active power. Two approaches are marked in this paper for instantaneous compensation: the first one is for eliminating the total noninstantaneous power current but the neutral current can still flow. The second one for eliminating the modified noninstantaneous power current, thus the neutral current component is compensated. It demonstrates that, in common situations of medium and low relative-values of the zero-sequence voltage, the total losses (line and neutral losses) obtained with the second approach are lower than those obtained with the first approach. The same results are obtained when a criterion based on the average value concept is used. Simulated and experimental results are obtained to confirm the theoretical properties and to show the compensator performance.     

新型三相三线制并联有源滤波器的滑模控制方法

为了提高有源滤波器的谐波补偿效果,设计了一种新型滑模控制器,用于三相三线制并联有源滤波器的参考电流跟踪控制.谐波电流检测方法采用基于瞬时无功功率理论的谐波电流检测方法,能快速、准确的检测出负载电流中的谐波分量.直流侧电压控制方法采用PI控制方法实现.Simulink仿真结果显示,与传统的滞环比较控制方法相比,所设计的新型滑模控制方法能够有效的降低跟踪误差,提高有源滤波器的谐波补偿效果.     

基于瞬时无功功率理论的谐波和无功电流检测

介绍了基于瞬时无功功率的谐波和无功电流实时检测理论。该理论突破了传统的平均值功率定义,系统的定义了瞬时无功功率、瞬时有功功率。可实时的检测电力系统中的谐波和无功电流。讨论了瞬时无功功率理论,得出基于瞬时无功功率理论的谐波和无功电流检测算法。结果表明,这种检测法能为抑制谐波和无功补偿提供可靠的谐波及无功分量。     

An instantaneous active and reactive current component method foractive filters

A shunt active filter based on the instantaneous active and reactive current component i_d-i_q method is proposed. This new control method aims to compensate harmonics and first harmonic unbalance. To evaluate its relative performance, it is compared with the instantaneous active and reactive power p-q method under various mains voltage conditions and for different harmonic injection high-pass filters. Both methods are completely frequency-independent, however under distorted mains voltages the proposed method presents a better harmonic compensation performance. The system synthesis and implementation are performed. Simulation and experimental results are presented     

选择性有源滤波器治理12脉波整流器的谐波

文章介绍12脉波整流器应用选择性有源滤波器抑制谐波电流和补偿无功,采用基于瞬时功率理论的谐波和无功电流检测方法。对有源滤波器和负荷系统进行仿真,并对仿真结果进行详细分析。仿真结果表明：基于瞬时功率理论的谐波和无功电流检测方法可以准确、实时地检测出三相电流中的任意次谐波及无功电流,有源滤波器抑制11次和13次谐波电流,并补偿无功。     

有源电力滤波器新型控制策略

基于瞬时无功功率理论和预测控制算法，提出了一种新型有源电力滤波器控制方法，该方法消除了电源电流在负载电流发生突变处产生的锯齿抖动。实时检测负载电流的二阶导数，判断负载电流是否发生突变。发生突变则采用预测控制程序模块进行补偿电流控制。这种方法可以应用在单相、三相电力系统的滤波电路中。仿真结果证明了这种算法的有效性。     

New hybrid active power filter for harmonic current suppression and reactive power compensation

In the case of undistorted and balanced grid voltages, low ratio shunt active power filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt APF. A new method for alleviating the negative effects of a nonideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field-programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance result of the proposed HAPF system is tested and presented under nonideal supply voltage conditions.     

Three-phase reactive power compensation using a single-phase AC/ACconverter

A new control strategy and topology for VAr compensation is presented and analyzed. It treats a three-phase power system as two energy ports and uses one single-phase bidirectional AC/AC power converter to transfer reactive energy between the two ports to produce three-phase reactive power. The compensated reactive power can be leading or lagging. Hysteresis control is investigated as a means of current modulation. The system has fast transient response capability, and one unit of AC/AC converter power generates 2.412 units of reactive power. The characteristics of the topology and predicted results are verified experimentally     

Application of a three-level NPC inverter as a three-phase four-wire power quality compensator by generalized 3DSVM

A two-level four-leg inverter has been developed for the three-phase four-wire power quality compensators. When it is applied to medium and large capacity compensators, the voltage stress across each switch is so high that the corresponding dv/dt causes large electromagnetic interference. The multilevel voltage source inverter topologies are good substitutes, since they can reduce voltage stress and improves output harmonic contents. The existing three-level neutral point clamped (NPC) inverter in three-phase three-wire systems can be used in three-phase four-wire systems also, because the split dc capacitors provide a neutral connection. This paper presents a comparison study between the three-level four-leg NPC inverter and the three-level NPC inverter. A fast and generalized applicable three-dimensional space vector modulation (3DSVM) is proposed for controlling a three-level NPC inverter in a three-phase four-wire system. The zero-sequence component of each vector is considered in order to implement the neutral current compensation. Both simulation and experimental results are given to show the effectiveness of the proposed 3DSVM control strategy. Comparisons between the 3DSVM and the 3-D hysteresis control strategy are also achieved.     

Using AC-fed PWM converters as instantaneous reactive powercompensators

A general control method that fully utilizes the inherent capability of AC-fed PWM converters to compensate for reactive and harmonic currents adsorbed by other loads is presented. For this purpose, suitable definitions of instantaneous active and reactive current and power terms are introduced. Optimum modulation laws are then derived according to a general control theory valid for PWM multiconverter systems which also results in maximum system efficiency. Simulated results demonstrate the capabilities of the proposed compensation method, which can also be implemented in existing systems as only modifications of the control section are needed     

Instantaneous power compensation in three-phase systems by using p-q-r theory

This paper proposes a novel power compensation algorithm in three-phase four-wire systems by using p-q-r theory. The p-q-r theory is compared with two previous instantaneous power theories, p-q theory and cross vector theory. The p-q-r theory provides two-degrees of freedom to control the system currents by only compensating the instantaneous imaginary power without using any energy storage element. The definition of powers maintains power conservation, and agrees well with the general understanding of power. Simulation results show the superiority of p-q-r theory both in definition and compensation.     

A three-phase active power filter operating with fixed switchingfrequency for reactive power and current harmonic compensation

The performance and dynamic characteristics of a three-phase active power filter operating with fixed switching frequency is presented and analyzed in this paper. The proposed scheme employs a PWM voltage-source inverter and has two important characteristics. First, it operates with fixed switching frequency, and second, it can compensate the reactive power and the current harmonic components of nonlinear loads. Reactive power compensation is achieved without sensing and computing the reactive component of the load current, thus simplifying the control system. Current harmonic compensation is done in time domain. The principles of operation of the proposed active power filter along with the design criteria of the power and control circuit components are discussed in detail. Finally, experimental results obtained from a 5 kVA prototype confirm the feasibility and the features of the proposed system     

基于传统功率理论谐波抑制和无功补偿方法

基于传统功率理论，提出了一种谐波抑制和无功补偿方法，根据有功功率可求等效线性负载，进一步求得该时刻补偿电流值。应用于有源电力滤波器控制中，可有效地抑制谐波电流和补偿无功功率，减小了电流信号检测中偶然误差对补偿效果的影响。这种方法可以应用在单相、三相电力系统的滤波电路中。仿真证明了这种方法的有效性。     

基于DSP的D-STATCOM硬件实现及控制算法

针对电网无功功率实现动态无功补偿的问题,采用模块化的设计方法,设计出一种基于DSP的D-STATCOM电路。根据瞬时无功功率理论计算参考电流和补偿电流,并采用直接电流控制方法产生补偿电流。建立了整个补偿过程的数学模型,分析了D-STATCOM中电流控制算法、电压控制算法以及IGBT晶闸管通断时间控制算法。结果表明:D-STATCOM完成无功补偿,达到抑制谐波的目的。     

一种单相串联混合电力有源滤波器的研究

文中对串联混合电力滤波器抑制谐波的原理进行了分析。为了检测单项系统的谐波电流,提出一种基于虚拟三相法和瞬时无功理论的谐波检测方法,并且对串联滤波逆变器的直流侧电压的控制进行了讨论。仿真结果证明了其有效性。     

Compensation-based nonactive power definition

This paper presents a new definition of nonactive current from which the definitions of instantaneous active and nonactive power are also derived. The definitions are consistent with the traditional power definitions and valid for single-phase and polyphase systems, as well as periodic and nonperiodic waveforms. The definitions are applied to a shunt compensation system. The paper elaborates on the compensation of three different cases of nonperiodic current: single-phase disturbance, three-phase subharmonics, and three-phase stochastic current. Simulation results give credibility to the applicability of the definition for a diversity of load currents. According to different compensation cases and the goals to be achieved, different averaging time intervals for the compensator are chosen which will determine the compensator's energy storage requirement and the extent of residual distortion in the source current.     

通信机房高频UPS无功就地补偿方法研究

本文在不改变UPS高频机主电路拓扑结构和配电系统结构的前提下,提出一种利用UPS高频机的PWM整流器进行无功就地补偿控制方案,应用同步旋转坐标变换和瞬时功率理论设计控制算法,在不影响UPS有功功率的前提下,利用PWM整流器进行负载侧无功补偿,提高UPS容量利用率,改善负载侧电能质量,减小高低压配电室无功补偿容量,节省成本和占地。     

三相桥式电路的谐波检测分析

本文介绍了谐波基本理论概念,在此基础上,设计了基于瞬时无功功率方法的MATLAB三相桥式电路谐波检测模型,同时利用MATLAB中POWERGUI模块中的F丌Analysis功能进行频谱分析得到谐波数据并成功分离出谐波。具有很好的理论意义及实时性。     

配电网无功补偿治理技术研究及工程应用分析

本文通过对配电网无功补偿治理现状的介绍,介绍了基于现代电力电子技术的静止无功发生装置(SVG)的工作原理,并重点分析研究了瞬时功率理论及其用于补偿无功、谐波时的检测技术.最后,结合SVG在配电网台区的实际应用,对SVG治理配网普遍存在的无功、不平衡等问题的效果进行了分析.     

An adaptive detecting method for harmonic and reactive currents

The conventional detecting methods for power system harmonic and reactive currents have various limitations. Based on adaptive interference canceling theory, a new adaptive detecting method for harmonic and reactive currents is presented, the corresponding detection system is developed, and experiments are performed which verify the feasibility of the method proposed. The new real-time detecting method is useful for dynamic compensation equipment such as active power filters, static VAr compensators, etc