Design of Permanent Magnet Synchronous Generators for Wave Power Generation

In this paper, a design method for ocean wave permanent magnet synchronous generator(PMSG)is proposed with new performance criteria to obtain better output performance at the cost of less permanent magnet material. Besides, a simple equivalent analytical geometry method is put forward to calculate the sizes of permanent magnets. Based on geometric and electromagnetic models, four types of rotor structures are compared, i.e., embedded, tangential, tile surface mount and convex surface mount structures. The designs and comparisons of machine are performed with the same permanent magnet volume. Moreover, the influences of mechanical pole-arc coefficient of tile surface mount PMSG on electrical efficiency, output power, material corrosion, core loss, and torque ripple are investigated. Finite-element analysis method is applied to verify the results using Ansoft/Maxwell.

Maximum Power Point Tracking in Variable Speed Wind Turbine Based on Permanent Magnet Synchronous Generator Using Maximum Torque Sliding Mode Control Strategy

The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy. In this strategy, first, the rotor speed is set at an optimal point for different wind speeds. As a result of which, the tip speed ratio reaches an optimal point, mechanical power coefficient is maximized, and wind turbine produces its maximum power and mechanical torque. Then, the maximum mechanical torque is tracked using electromechanical torque. In this technique, tracking error integral of maximum mechanical torque, the error, and the derivative of error are used as state variables. During changes in wind speed, sliding mode control is designed to absorb the maximum energy from the wind and minimize the response time of maximum power point tracking(MPPT). In this method, the actual control input signal is formed from a second order integral operation of the original sliding mode control input signal. The result of the second order integral in this model includes control signal integrity, full chattering attenuation, and prevention from large fluctuations in the power generator output. The simulation results, calculated by using MATLAB/m-file software, have shown the effectiveness of the proposed control strategy for wind energy systems based on the permanent magnet synchronous generator(PMSG).

Analysis of temperature field for a surface-mounted and interior permanent magnet synchronous motor adopting magnetic-thermal coupling method

Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-thermal coupling method is proposed.The magnetic-thermal coupling mechanism is analyzed.The thermal network model and finite element model are built by this method,respectively.The effects of power frequency on iron losses and temperature fields are analyzed by the magnetic-thermal coupling finite element model under the condition of rated load,and the relationship between the load and temperature field is researched under the condition of the synchronous speed.In addition,the equivalent thermal network model is used to verify the magnetic-thermal coupling method.Then the temperatures of various nodes are obtained.The results show that there are advantages in both computational efficiency and accuracy for the proposed coupling method,which can be applied to other permanent magnet motors with complex structures.

Prediction of the Inductance in a Synchronous Linear Permanent Magnet Generator

This paper presents calculations of the varying inductances profile for a synchronous linear surface mounted permanent magnet generator in an ABC reference system. Calculations are performed by utilizing the reluctance term, known from analytic calculations and finite element method simulations. With the inductance term identified, the voltage difference between the generator’s no load and load voltage can be calculated and an external circuit can be designed for optimal use of the generator. Two different operation intervals of the linear generator are considered and the results are discussed. The result indicates that time costly finite element simulations can be replaced with simple analytical calculations for a surface mounted permanent magnet linear generator.

Performance of a Wind-Diesel Hybrid Power System with STATCOM as a Reactive Power Compensator

The paper deals with automatic reactive power control of an isolated wind-diesel hybrid power system. The power is generated by diesel engine and wind turbine as prime movers with electrical power conversion by permanent-magnet synchronous generator (PMSG) and permanent-magnet induction generator (PMIG) respectively. The mathematical model of the system developed is based on reactive power flow equations. The paper investigates the dynamic performance of the hybrid system for 1% step increase in reactive power load with 1% step increase in input wind power.

A Fuzzy Logical MPPT Control Strategy for PMSG Wind Generation Systems

Making full use of wind power is one of the main purposes of the wind turbine generator control. Conventional hill climbing search （HCS） method can realize the maximum power point tracking （MPPT）. However, the step size of HCS method is constant so that it cannot consider both steady-state response and dynamic response. A fuzzy logical control （FLC） algorithm is proposed to solve this problem in this paper, which can track the maximum power point （MPP） quickly and smoothly. To evaluate MPPT algorithms, four performance indices are also proposed in this paper. They are the energy captured by wind turbine, the maximum power-point tracking time when wind speed changes slowly, the fluctuation magnitude of real power during steady state, and the energy captured by wind turbine when wind speed changes fast. Three cases are designed and simulated in MATLAB/Simulink respectively. The comparison of the three MPPT strategies concludes that the proposed fuzzy logical control algorithm is more superior to the conventional HCS algorithms.

A Novel Modified Fuzzy-predictive Control of Permanent Magnet Synchronous Generator Based Wind Energy Conversion System

A wind energy conversion system(WECS)based on a permanent magnet synchronous generator(PMSG)is an effective solution for renewable energy generation in modern power systems.The main advantages of PMSG include high performance at high and low speeds,minimal control effort owing to lower rotor inertia,self-excitation,high reliability,and simplicity of structure compared with induction generators.However,the intermittent nature of wind energy implies that maximum efficiency is not obtained from this system.Accordingly,maximum power point tracking(MPPT)in wind turbine systems has been proposed to address this problem.Traditional MPPT strategies suffer from severe output power fluctuations,low efficiency,and significant ripples in turbine rotation speed.This paper presents a novel MPPT control strategy based on fuzzy logic control(FLC)and model predictive control(MPC)to extract the maximum power from a PMSG-WECS and control the machine-side and grid-side converters.The simulation results obtained from Matlab/Simulink confirm the superiority of the control model in eliminating the output power fluctuations of the wind generators and accurately tracking the maximum power point.A comparative study between conventional MPPT and control methods is also conducted.

虚拟惯量控制对直驱风电机组载荷影响的分析及评估

针对虚拟惯量控制诱发风电机组机械载荷的问题,开展虚拟惯量控制对采用直驱永磁同步发电机(D-PMSG)的风电机组载荷影响的理论分析和仿真评估研究。从叶片、塔筒等机械结构低阶模态出发,建立虚拟惯量控制下D-PMSG线性化多体动力学模型,并通过线性化多体动力学模型分析虚拟惯量控制对机组载荷的影响机理。采用软件联合建模方法,构建涵盖永磁同步电机及其控制、电网、机械和气动特性等的D-PMSG非线性机电耦合模型。依据冲击载荷最大值、最大变化幅度百分比及等值疲劳载荷等指标,通过所建立的非线性机电耦合模型仿真分析并量化评估虚拟惯量控制对机组冲击载荷和动态疲劳载荷的影响。结果表明,D-PMSG附加虚拟惯量控制后,电网侧频率突变会使得传动轴和塔底侧向出现显著冲击载荷,且其随虚拟惯量时间常数增大而增大,在湍流风运行工况下机组传动轴和塔底侧向等值疲劳载荷较无附加虚拟惯量控制均有所减小。

航空电推进电机多层波浪形拓扑及散热设计方法

针对航空电推进电机的散热问题,提出一种基于多层波浪形散热拓扑的航空电推进电机高效散热设计方法。航空电推进电机采用多层波浪形散热拓扑,建立电机等效热网络模型,确定等效热阻、对流换热系数等重要参数,完成电机温度精确计算,并通过CFD仿真验证所建立电机等效热网络模型的准确性和有效性。以此为基础,对比分析传统散热翅和多层波浪形散热拓扑对电机功率密度的影响。基于多层波浪形散热拓扑的等效热网络模型,采用遗传学习粒子群优化(GL-PSO)算法,完成航空电推进电机高效散热优化设计。优化结果表明:相比于原始方案,优化方案的机壳质量减轻15.1%,整个电机的功率密度提升0.06 kW/kg。

计及总损耗功率的电动汽车母线电容主动快速放电方法

针对电动汽车遇到碰撞等紧急情况时,高压驱动系统母线电容电压需迅速降到安全电压(60 V),而传统基于PI控制的母线电容主动放电方法存在鲁棒性差、放电时间长和安全性低的问题,提出一种计及总损耗功率的电动汽车母线电容快速放电方法。首先,建立以永磁同步电机绕组作为泄放电阻的母线电容能量流动模型,将逆变器损耗、电机绕组铜耗、电机电感储能等损耗作为总损耗,利用扩展滑模观测器(ESMO)对总损耗功率进行估算,并通过Lyapunov稳定性理论对ESMO的稳定性进行了证明。然后,将观测的总损耗功进行前馈补偿,从而使母线电压快速降低并稳定在安全电压。仿真和实验结果表明,与现有主动放电方法相比,所提放电方法不仅显著减小了放电时间,而且提高了快速放电的鲁棒性和安全性。

船舶永磁同步推进电机的优化I/f起动控制方法

为解决高转矩与高转动惯量的船舶推进电机在开环I/f控制中转速和转矩波动大、电机易失步、效率低的问题,提出一种I/f控制改进方法。通过建立转矩角观测器,调节给定电流矢量的幅值,使其跟随负载转矩变化,提高系统鲁棒性。同时,将电机运行状态推进至接近最大转矩电流比状态,提高电机的运行效率;通过瞬时有功功率调节电流矢量的角速度,降低电磁转矩波动,加快电机的转速收敛过程。最后,在Matlab/Simulink中进行仿真实验,实验结果表明该方法可以显著提高推进电机运行效率和稳定性。

基于桨距角控制的永磁风电机组高电压穿越控制策略

为解决传统永磁风电机组高电压穿越控制策略存在超速脱网风险问题,提出一种基于桨距角控制的高电压穿越控制策略。高电压穿越期间,首先,按照并网要求向电网提供无功支撑;其次,考虑转子转速限制,当转子转速达到参考值时启动桨距角控制,抑制转子转速上升;最后,通过仿真试验,验证了所提控制策略的有效性。基于桨距角控制的永磁风电机组高电压穿越控制策略,既能向电网提供无功支撑,又能避免超速脱网。

考虑初始风速与机端故障稳态电压跌落程度的直驱风机故障响应特性分类及其判别方法研究

对电力系统进行安全分析时,往往需要对各种预想场景进行仿真。随着风电的大量接入,对风电场提出适用于预想故障分析的等值建模方法变得十分重要,而根据风机故障后的动态特性对其进行分群则是等值建模的基础。各风机在故障后的动态响应特性不仅受其控制方式的影响,还受到运行风速和故障严重程度的影响,而一般情况下风机控制的响应速度较快,可以认为在故障持续期间风机能够运行至故障稳态。基于此,提出考虑初始风速及机端故障稳态电压跌落程度的风电机组故障响应特性分类及判别方法,以此作为风机分群的依据。首先针对永磁直驱风机(direct-driven permanent magnet synchronous generator,PMSG)故障过程中无功优先控制、故障恢复期间有功斜坡恢复的控制策略,分析其在不同风速条件下故障后所有可能的响应特性,将初始风速与故障稳态电压作为分类指标,从机理上找到直驱风机进入各类响应特性的边界条件;然后,提出利用预想故障信息的风机机端故障稳态电压计算方法,在此基础上提出适用于预想故障的直驱风机分群方法;最后,通过对风电场进行详细建模仿真,验证所提分群方法的正确性。

永磁直驱型风机海上风电送出系统不对称接地及甩负荷电磁暂态研究

为明确海上风电交流送出系统过电压的特征与水平,需考虑风电机组的故障穿越特性。该文结合永磁直驱风机变流器的控制原理,提出海上风电送出系统不对称接地过电压的解析计算方法。基于PSCAD对风电机组进行精确电磁暂态建模与故障电压穿越测试,以国内某500 kV大规模海上风电工程为背景,仿真计算送出系统不对称接地及甩负荷过电压。结果表明:系统不对称接地过电压大小与风机正负序控制策略有关;海缆电网侧甩负荷将产生持续百ms的1.3 pu以上的暂态过电压,风机过电压保护动作延时越长,暂态过电压越严重。实际海上风电工程计算需紧密联系风机控制保护策略及其参数,并综合关键设备耐压水平进行评估,通过风机控制策略优化可以降低系统过电压水平。

集中绕组模块组合式定子结构对低速大功率永磁电机性能影响

针对集中绕组模块组合式定子结构对低速大功率直驱永磁同步电机性能的影响进行研究。首先介绍了模块化定子的分块规则和分块数。基于绕组函数法推导了单个定子单元模块在不同拆分方式下的绕组函数和电感表达式。基于有限元仿真先分析了仅绕组分块对电机性能影响;然后分析了冲片和绕组都分块对电机性能影响。通过对比空载和负载性能,总结出各种定子模块化拆分方案的优缺点,为大功率低速直驱永磁同步电机的模块化设计与制造建立了基础。

基于开绕组电机的电动汽车双电池集成充电系统准直接功率控制

针对基于开绕组永磁同步电机和双电池组驱动的电动汽车提出一种集成化充电拓扑,充电运行时将双逆变器和电机绕组复用为双PWM整流器及其输入侧滤波电感。在三相电压源型整流器(VSR)和开绕组永磁电机数学模型的基础上,将电网坐标系和电机坐标系相统一,分析了充电状态下的电磁转矩。实际运行时存在双电池剩余电量不相等的情况,导致充电时双通道功率不平衡,因此设计了一种准直接功率控制策略,以解决功率不平衡带来的转矩脉动问题。最后通过仿真和实验验证了该集成化充电拓扑的可行性。

基于谐波注入分段供电永磁直线同步电机变流器开路推力波动抑制

该文提出一种电流谐波注入的方法,减小长定子分段并联供电永磁直线同步电机系统的驱动变流器发生单相开路故障下电机推力波动。首先,根据动子在定子段的位置,推导出分段单元电机的电压方程,得到各个单元电机的推力表达式和系统总推力。然后,依据变流器单相开路前后的全耦合状态下单元电机基波磁动势不变的原则,构造降阶坐标变换矩阵,得到电机的电压方程和推力表达式。采用注入谐波电流、优化故障后直线电机的输出推力的方式,消除变流器单相开路故障产生的4次和6次推力谐波并消除耦合因数变化对电机推力影响;通过多变流器协同控制多单元电机,有效降低变流器单相开路故障后的推力波动,提高电机的最大输出推力。仿真和实验验证该方法的有效性。

基于反推控制的永磁同步电机稳定性单矢量控制策略

针对永磁同步电机传统单矢量控制需遍历所有基本矢量且忽略控制稳定性的问题,该文提出基于反推控制的永磁同步电机稳定性单矢量控制策略。首先,在建立dq0坐标系下永磁同步电机数学模型的基础上,推导设计常规反推控制器;其次,根据反推控制器获取的控制电压确定最优电压矢量所在扇区,并通过数学推导证明每个扇区内必有一个稳定的基本电压矢量可供选择,提出通过基本电压矢量对应Lyapunov函数导数值两两比较的最优基本电压矢量选取方法;然后,对选取包括最优基本电压矢量在内的不同基本电压矢量时的控制性能进行对比分析;最后,对提出的控制策略进行仿真和实验验证。结果表明,在驱动恒转矩、恒惯量负载和变转矩、变惯量涡簧负载的多个场景下,该文提出的控制策略均能有效追踪参考转速,并且与传统模型预测电流控制相比,所提控制策略的稳定性更强、输出量波动更小。

永磁同步风力发电系统的最大功率跟踪模糊分数阶控制

在“双碳”背景下,风电作为零碳电力和新能源发电的主力军,在助力社会全面绿色低碳转型方面发挥了关键性作用。在保证发电稳定的前提下实现风能的最大化利用,提升风力发电系统发电量至为重要。文中针对永磁同一步风力发电系统的最大功率跟踪(maximum power point tracking, MPPT)问题进行研究。首先建立了永磁同步风力发电系统的机理仿真模型,用两电平双PWM全功率换流器连接风力发电机与电网。然后基于以上模型,分别设计了整数阶PI控制器、分数阶PI"控制器、模糊分数阶PP控制器以实现MPPT控制。最后对以上控制策略进行了仿真研究。结果表明,无论在阶跃风速还是随机风速下,模糊分数阶PU控制器相较于其他两种均具有更出色的MPPT性能与更强的鲁棒性。

储能/发电机级联式供电系统功率传输控制策略

随着可再生能源渗透率的不断提升,区域电网惯性逐步降低,暂态支撑能力严重不足,给电网带来了一系列安全问题。文中提出一种储能与开绕组永磁同步发电机(open-winding permanent magnet synchronous generator,OW-PMSG)级联供电的新型分布式并网发电拓扑,在保证可再生能源消纳的前提下,重新利用原有柴油机,为电网提供功率后备以及惯量支撑。通过对OW-PMSG进行建模以及系统功率流矢量分析,设计基于源网相位差闭环控制的功率传输策略,实现发电机的稳定同步运行。基于该策略,拓扑中的储能变流器可具备同步发电机特性,实现了电网惯性和暂态支撑能力的进一步提升。仿真结果验证了所提控制策略的有效性。